Valve Glossary J to R

Jacketed Pipe - a double-walled pipe in which liquids that are too viscous for pipeline transport at normal temperatures flow through the inner pipe that is surrounded by a pipe circulating hot fluids.

Jacketed Valve - Jacketed Valve - a valve body cast with a double wall or provided with a double wall by welding

material around the body so as to form a passage for a heating or cooling medium. Also refers to valves which are enclosed in split metal jackets having internal heat passageways or electric heaters. Also referred to as Steam Jacketed or Vacuum Jacketed. In a vacuum jacketed valve, a vacuum is created in the space between the body and secondary outer wall to reduce the transfer of heat by convection from the atmosphere to the internal process fluid, usually cryogenic.

Jacketed Valve - this valve design incorporates a jacket around the valve body. Steam is introduced into the jacket to keep the fluids being controlled at the required temperature.

Jacketed Valve - this valve design incorporates a so-called jacket around the valve body. Steam is introduced into the jacket to keep the fluids being controlled at the required temperature.

Jackscrew - a screw which can be turned to adjust the position of an object into which it fits. Jam Nut - see Locknut JDA - Joint Development Area Jewel - a bearing lining of soft metal JFS - Joint Feasibility Study Jig - a device used to position and hold parts for machining operations and to guide the cutting

tool. Jig Grinder - a precision grinding machine used to locate and grind holes to size, especially in

hardened steels and carbides. JIT - see Just-In-Time Job Shop - a manufacturing facility that generates variety of products in relatively low numbers

and in batch lots. Joggle - 1) a small projection on a piece of metal fitting into a corresponding recess in another

piece, to prevent lateral movement; 2) a lap joint in which one plate is slightly cranked so as to allow the inner edges of the two plates to form a continuous surface.

Joint Ring - a pipe-joint flange whose outside diameter is less than the diameter of the circle containing the connecting bolts and thus fits inside the bolts.

Jointer - a pipe of random length made from two joined, relatively short lengths. Jominy Test - Jominy Test - a hardenability test in which a standard test piece, 4 in. long and 1 in. diameter,

gets heated to a predetermined temperature, rapidly transferred to a jig fixture and quenched, under standard conditions, but a jet of water impinging at one end. When the specimen is cool, determinations of hardness are done along the specimen from the quenched end. The diagram relating hardness to distance from the quenched end of the specimen is termed as a hardenability curve.

Jominy Test - a test which is used for determining the relative hardenability of steels in which one end of a heated cylindrical specimen gets quenched, the resulting hardness decrease towards the unquenched end giving a measure of improved hardness; also called End Quench Test.

Joule - Joule - a unit of work or energy, equal to the work done when a force of one Newton moves

through a distance of one meter in the direction of the force. Joule - a unit of work, energy and heat. It may be defined as the work done when a force of one

Newton moves through a distance of one meter. Joule - the unit of energy or work in the meter-kilogram-second system of units, equal to the work

done by a force of 1 Newton magnitude when the point at which the force is applied is displaced 1 meter in the direction of the force; symbolized J; also known as Newton-Meter of Energy.

Journal -

Journal - that part of a shaft or crank which is supported by and turns in a bearing. Journal - That part of the shaft that rides in a plain cylindrical bearing. Journal - the part of a rotating shaft that rests on and is supported by bearings. Journal - the part of a shaft which is in contact with and supported by a bearing. Journal Bearing - a cylindrical bearing which supports a rotating cylindrical shaft. Journal Box - a metal housing for a journal bearing. Journal Friction - friction of the axle in a journal bearing arising mainly from viscous sliding

friction between journal and lubricant. Junction Box - a protective enclosure into which wires or cables are led and connected to form

joints; also known as J Box. Just In Time - a systems approach to developing and operating a manufacturing system so that

the least amount of resources is expended in producing the final products.

K - Potassium Kalrez® - Kalrez® - a carbon-black filled compound with good mechanical properties and excellent

chemical resistance, manufactured by DuPont. A maximum intermittent operating temperature of 366° C is recommended. It is used as a gasket material in high temperature applications.

Kalrez® - a fluorinated elastomer used for high temperature / high purity or highly aggressive applications. Kalrez® is a trademark of DuPont Dow Elastomers.

KBD - Thousand Barrels per Day KEL-F - a polymer with high thermal stability, resistance to chemical corrosion, high dielectric

strength, and high impact and tensile strengths. It is used for gaskets and seals. Kellering - three-dimensional machining of a contoured surface by tracer-milling the die block or

punch; the cutter path is controlled by a tracer that follows the contours on a die model.

Kelvin Scale - the temperature scale using absolute zero as the zero point and divisions that are the same size as centigrade degrees.

Kennison Nozzle - a specially shaped nozzle designed for measuring flow through partially filled pipes; because of its self-scouring, nonclogging design, it is especially useful for measuring flow of liquids containing suspended solids or debris and at low flow rates or widely varying flow rates.

Kerf - a cut made in wood, metal, or other material by a saw or cutting torch. Kerosene - a light fuel oil obtained by distilling petroleum; also called Paraffin Oil. KeV - Kilo-electronvolt (a unit of x-ray energy) Key - Key - 1) the relative roughness of a surface; 2) a pin or wedge for fixing (holding stationary)

something. Key - a piece inserted between a shaft and a hub to prevent relative rotation. It fits in a way

parallel with the shaft axis, in one or both members, the commonest form being the parallel key, or rectangular section.

Key - a piece of iron or steel which is inserted between a shaft and a hub to prevent relative rotation and fitting into a keyway parallel with the shaft axis.

Key - a projecting portion that serves to prevent movement of parts at a construction joint. Key Bed - a keyway Key Boss - Key Boss - a local thickening of a hub at a point where a keyway has been cut to compensate for

loss of strength due to the cut. Key Boss - a local thickening up of a boss or hub at the point at which a key way is cut, to

compensate for loss of strength due to the cut. Key Seat - see Keyway Keyhole - a hole or a slot for receiving a key. Keyseater - a machine for milling beds or grooves in mechanical parts which receive keys. Keyway - Keyway - a groove or channel for a key in any mechanical part; also known as Key Seat. Keyway - a shallow longitudinal slot which is cut in a shaft or a hub for receiving a key; also

called Key Seating. Keyway - a slot cut in a part of a machine or electrical connector, to ensure correct orientation

with another part which is fitted with a key. Killed Steel - Killed Steel - steel deoxidized with certain deoxidizing elements, such as aluminum, silicon, etc.

The term "killed" is used because such additions cause the steel to lie quietly in the molds during solidification.

Killed Steel - steel that has been fully deoxidized before casting by the addition of manganese, silicon and sometimes aluminum. There is practically no evolution of gas from the reaction between carbon and iron oxide during solidification, and therefore soundingots are obtained.

Killed Steel - steels that have been deoxidized up to the maximum extent to enable them to be used in machine tools. Deoxidation is carried out by the addition of aluminum and

silicon. These steels are known as killed steels. During solidification a cavity is formed at the upper portion of the ingot due to shrinkage. It is reduced by making the top portion of the ingot a little bigger than the remaining mold and making a refractory top.

Kiln - a heated enclosure used for drying, burning, or firing materials such as ore or ceramics. Kinetic Energy - Kinetic Energy - the energy possessed by a moving body because of its weight and motion. Kinetic Energy - the energy that a substance has while it is in motion. Kinetic Head - refers to the energy of flowing water due to its speed. Kinetic Theory - a theory of matter that assumes that the molecules of matter are in constant

motion. Kingston Valve - a sea valve fitted to a ship’s side for the purpose of admitting water to

circulating pumps, or flooding or blowing out ballast tanks. Kip - a 1000-pound (453.6-kilogram) load. Kish - solid graphite which has separated from and floats on the top of a molten bath of cast iron

or pig iron which is high in carbon. Kiss-Roll Coating - procedure for coating a substrate web in which the coating roll carries a

metered film of coating material; part of the film transfers to the web, part remains on the roll.

Knife Coating - procedure for coating a continuous-web substrate in which coating thickness is controlled by the distance between the substrate and a movable knife or bar.

Knife Gate Valve - a gate valve design that is distinguished from the standard design by use of a simple metal plate for the gate and the absence of a bonnet; also called a Slide Valve.

Knock Off - a device that causes automatic stopping. Knockout Vessel - a vessel, drum, or trap used to remove fluid droplets from flowing gases. Knoop Hardness Test - a hardness test using an indenter in the form of a four-sided pyramid

whose indentation is a parallelogram with the longer diagonal about seven times that of the shorter.

Knurl - to provide a surface, usually a metal, with small ridges or knobs to ensure a firm grip oras a decorative feature.

KSB - Kemaman Supply Base Ksi - pounds per inch x 1000 Kynar® - a brand of Polyvinylidene Fluoride (PVDF). A dense, high-purity plastic that is used in

critical applications, such as semiconductor manufacturing. Kynar is a trademark ofAtofina.

L - Low L / D - Length / Diameter Lack of Fusion - in welding, incomplete fusion; fusion that is not complete. Lack of Penetration - in welding, if the depth of fusion up to which the weld metal penetrates is

insufficient, the weld is weaker at the weldment. The joint must allow entry of the electrode and permit unrestricted manipulation. It requires proper design of joints with respect to size and type of electrodes. Use of electrodes of wrong classification may not give correct penetration. The most common cause of lack of penetration is use of too low welding currents. When DC is used, wrong polarity also causes lack of penetration. Improper technique of welder, bad incorporation of tack welds and inadequate deslagging also result in lack of penetration; also called Incomplete Fusion or Lack of Fusion.

Laden - heavily loaded or weighed down Lading - the cargo that a ship or plane carries. Ladle Metallurgy Furnace (LMF) - an intermediate steel processing unit that further refines the

chemistry and temperature of molten steel while it is still in the ladle. The ladle metallurgy step comes after the steel is melted and refined in the electric arc or basic oxygen furnace, but before the steel is sent to the continuous caster.

Lamella - a thin sheet or plate, usually made of many thin layers. Laminate - 1) to cover with a thin layer of protective or strengthening material; 2) to beat metal

into thin sheets. Land Installation - an installation located at sufficient distance from open saliferous water to

minimize the effects of a salt laden atmosphere. Lantern Pinion - a pinion with bars (between parallel disks) instead of teeth. Lantern Ring - Lantern Ring - a metal spacer ring placed in a stem packing set so that it lines up with a leakoff

connection in the bonnet. It divides the packing into an upper set and a lower set; see Leakoff Connection.

Lantern Ring - a rigid spacer assembled in the packing box with packing normally above and below it and designed to allow lubrication of the packing or access for a leak off connection.

Lantern Ring - a rigid spacer used in the packing with packing above and below it. The lantern ring is used to allow lubrication to the packing or allow access to a leak off connection. On some of the new fugitive emission packing systems, it also acts as a stem guide.

Lantern Ring - a ring or sleeve around a rotating shaft; an opening in the ring provides for forced feeding of oil or grease to bearing surfaces; particularly effective for pumps handling liquids.

Lantern Ring - a spacing ring inserted in the stuffing box to form a pressure relief or condensing chamber.

Lantern Ring - a spacing ring inserted in the valve stuffing box to form a pressure relief or condensing chamber.

Lantern Ring - a spacing ring which is inserted in a stuffing box of a valve to form a pressure relief or condensing chamber.

Lantern Wheel - a cylindrical gearwheel Lap - Lap - a rotating abrasive disc for polishing metal. Lap - a surface defect appearing as a seam caused by folding over hot metal, fins, or sharp

corners and then rolling or forging them into the surface but not welding them. Lap Joint - Lap Joint - a connection between two parts made by overlapping members at the junction and

welding, riveting or bolting them together. Lap Joint - a riveted or welded joint in which one member overlaps the other. Lap Joint - a simple joint between two members made by overlapping the ends and fastening

them together with bolts, rivets, or welding. Lapped In - a term that describes a procedure for reducing the leakage rate on metal-to-metal

seated valves and regulators. The plug and seat are lapped together with the aid of

an abrasive compound in an effort to establish a better seating surface than would normally be achieved by means of machining.

Lapping - Lapping - a finishing operation used to produce an extremely smooth and flat surface on

mechanical seal faces. Lapping - an abrading process for refining the surface finish and the geometrical accuracy of a

surface. Large Dyne - see Newton Laser Beam Welding - Laser Beam Welding - a welding process in which heat is obtained from the application of a

concentrated coherent light beam impinging upon the surfaces to be joined. Concentrated energy is available with the development of “Light Amplified Stimulated Emission Radiation”. A laser beam is a coherent light having identical and parallel waves. It is based on the principle of concentrating and amplifying the very divergent radiation from an intense source of light into a finely focused beam of light. It is done by using a laser crystal. The crystal consists of ruby or a specially constituted glass. In the apparatus a man-made cylindrical ruby crystal is used. Ruby is aluminum oxide with chromium dispersed through it. The ends of the crystal are silvered to from mirrors internally, while one end has a tiny hole in the silver layer, through which the laser beam emerges. Around the crystal is placed a flash tube containing the inert gas xenon. The flash tube converts electrical energy into light energy and is designed for operation at a rate of thousands of flashes per second. When electrical discharges from the capacitor are supplied to the xenon, it converts high proportions of electrical energy into white light flashes. The ruby crystal converts the white light flashes into red fluorescent light. This light is amplified by the crystal which is concentrated on the workpiece to be welded through a focusing lens. The electrons in the ruby rod are stimulated by this light source, and in returning to their normal energy level, release energy at a constant wavelength. A laser beam is a high-energy beam suitable for both cutting and welding of metals. This is used for connecting leads for small electronic components, to weld high melting point metals like stainless steel, tungsten, molybdenum, columbium, titanium, zirconium, and tantalum. It is also used for welding wire-to-wire, sheet-to-sheet, tube to sheet in aeronautical and ship building industry. It is also used to weld lead wires without removing the polyurethane insulation. In using this method care is needed that operator’s eyes do not come in contact with either the direct or indirect laser rays.

Laser Beam Welding - welding using a laser as the heat source. Latent Defect - a flaw or other imperfection in any article which is discovered after delivery;

usually, latent defects are inherent weakness which normally are not detected by examination or routine tests, but which are present at time or manufacture and are aggravated by use.

Lathe - a machine for shaping a work piece by gripping it in a holding device and rotating it under power.

Lattice - a regular repeated three-dimensional arrangement of atoms, ions or molecules that forms the structure of a metal or other crystalline solid.

Lay Up - production of reinforced plastics by positioning the reinforcing material (such as glass fabric) in the mold prior to impregnation with resin.

Lazy Jack - a device that accommodates changes in length of a pipeline or similar structure through the motion of two-linked bell cranks.

LBF - Foot Pound LBM - Laser Beam Welding LCB - a Low Temperature Cast Carbon Steel LCC - a Low Temperature Cast Carbon Steel LCL - Loose Cargo Load LCOT - Labuan Crude Oil Terminal LCS - Local Control Station LD - Liquidated Damages LDPC - Level Displacer Chamber

LE - Large End Lead - the distance that a screw will advance or move into a nut in one complete turn. Lead (Pb) - Lead (Pb) - a soft, heavy, bluish-gray, highly toxic metallic element that is resistant to corrosion. Lead Joint - a pipe joint made by caulking with lead wool or molten lead. Lead Screw - a threaded shaft used to convert rotation to longitudinal motion; in a lathe it moves

the tool carriage when cutting threads. Lead Time - Lead Time - 1) the time between the conception or design of a product and its actual production

or completion; 2) the time between the ordering and delivery of goods. Lead Time - the time allowed or required to initiate and develop a piece of equipment that must

be ready for use at a given time. Leaf - one of the two halves of a cavity wall. Leak Detection - the establishment by various detection methods that a leak is present and

significant to system performance. Mass spectrometer helium leak detectors, offering sensitivity to about 5 x 10-10 Torr l/sec or better, are excellent for this purpose. NOTE: Teflon is permeable to helium, so care must be exercised to avoid saturating the Teflon tape used with thermocouple tubes. This permeation can sharply curtail the usefulness of a helium mass spectrometer.

Leak Detector - an instrument used for finding small holes or cracks in the walls of a vessel; the helium mass spectrometer is an example.

Leak Off - a term used to describe a threaded connection located on the bonnet of a valve that allows for the detection of leakage of the process fluid past the packing area.

Leak Off Gland - a packing box with packing above and below the lantern ring so as to provide a sealed low pressure leak collection point for fluid leaking past the primary seal (lower packing).

Leakage - Leakage - the amount of fluid passing through a valve when it is off. It is usually expressed in

units of volume/time at a given pressure and temperature. Leakage - the quantity of fluid passing through a valve when the valve is in the full closed position

under stated closure forces, with the pressure differential and temperature as specified. Leakage is usually expressed as a percentage of the valve capacity at full rated travel.

Leakage - undesired and gradual escape or entry of a quantity. Leakage Classification - a term used to describe certain standardized testing procedures for

control valves with a flow coefficient greater then 0.1 (Cv). These procedures are outlined in ANSI Standard B16.104-1976, which gives specific tests and tolerances for six seat leakage classifications. It should be remembered that these tests are used to establish uniform acceptance standards for manufacturing quality and are not meant to be used to estimate leakage under actual working conditions. Nor should anyone expect these leakage rates to be maintained after a valve is placed in service. There is no standard test for self contained regulators at this time. Note - you will see many instances where regulators are specified using the above criteria.

Leakage Rate - Leakage Rate - 1) the maximum rate at which a fluid is permitted or determined to leak through a

seal. NOTE: The type of fluid, the differential pressure across the seal, the direction of leakage and the location of the seal must be specified; 2) the amount of leakage across a boundary per unit of time; see also Bubble-Tight.

Leakage Rate - the rate at which a fluid (either gas or liquid) passes a barrier. Total leakage rate includes the amounts that diffuse or permeate through the material of the barrier as well as the amount that escapes around it.

Leakoff Connection - a threaded hole through a valve bonnet wall in the area of the stuffing box. It is used to collect leakage past a lower packing set or to inject lubricant into the stuffing box.

Ledeberite - the eutectic mixture of iron and carbon. Ledoux Bell Meter - a type of manometer used to measure the difference in pressure between

two points generated by any one of several types of flow measurement devices

such as pitot tube; it is equipped with a shaped plug which makes the reading of the meter directly proportional to the flow rate.

Left Hand Screw - a screw that advances when turned counterclockwise. LEGR - Level Gauge Reflex LEGT - Level Gauge Through Vision Leo - a unit of acceleration, equal to 10 meters per second per second; it has rarely been

employed. LER - Local Equipment Room Less Than Carload - too light to fill a freight car and therefore not eligible for carload rate.

Abbreviated LCL. Leveling Line - a process to flatten any shape deficiencies (wavy edges and buckles) in the

sheet, prior to final shipment. Most cold-rolled sheet initially has a crowned cross-section that, if such a shape is undesirable to the customer, it must be flattened in the leveling line.

Lever - a handle type operating device for quarter-turn valves. Lever and Spring Loaded - in which the load is applied to the valve head by a spring acting

through a lever and fulcrum. Lever Limiting Guide - the guide in which the lever works and which limits its travel. Lever Valve - a valve operated by a lever which travels through a maximum arc of 180 degrees. LH - Left Hand Life Expectancy - the predicted useful service life of an item of equipment. Life Test - Life Test - a destructive test in which a device is operated under conditions that simulate a

lifetime of use. Life Test - a laboratory procedure used to determine the amount and duration of resistance of an

article to a specific set of destructive forces or conditions. Lift - the actual travel of the disc away from closed position when a valve is relieving. Lift Check - this non-return valve design incorporates a piston to damp the disk during operation. Lift Check Valve - Lift Check Valve - a mechanism incorporating a disc, piston or ball which lifts along an axis of the

body seat. Lift Check Valve - a non-return valve in which the non-return mechanism incorporates a disc,

piston or ball which lifts along an axis in line with the axis of the body seat. Lift Check Valve - a type of check valve in which the flow control element moves parallel to the

direction of fluid flow. The force of the fluid lifts the flow control element off its seat. Lift Check Valve - a type of check valve in which the non-return mechanism incorporates a disc

piston or ball which lifts along an axis in line with the axis of the body seat. The three sub-categories of lift check valves are disc check, piston check and ball check.

Lift Valve - Lift Valve - a valve in which the disc, ball, plate, etc., lifts or is lifted vertically, to allow the

passage of a fluid. Lift Valve - a valve that moves perpendicularly to the plane of the valve seat. Lifting Device - a device to manually open a pressure relief valve by decreasing the spring

loading in order to determine if the valve is in working order. Light Alloys - the general term for alloys of aluminum, which are used for structural purpose;

alloys of magnesium are also in use and are even lighter. Light Coated Electrode - a filler metal electrode used in arc welding, consisting of metal wire

and a light coating of flux. Light Crude - crude oil rich in low viscosity hydrocarbons of low molecular weight. Light Gauge Steel - a very thin steel sheet that has been temper-rolled or passed through a

cold-reduction mill. Light gauge steel normally is plated with tin or chrome for use in food containers.

Light Gauge Steel - usually refers to structural members such as metal decking or metal studs fabricated from sheets less than one-quarter inches thick. The design and specification standard for such members is in the ‘Light Gauge Cold-Formed Steel Design Manual’ published by the American Iron and Steel Institute.

Light Running - the running of mechanisms, e.g., shafting, under no load and with a minimum of friction.

Lime - Calcium Oxide. Produced from limestone (common mineral) and extensively used as a slag forming agent in the steel industry.

Limestone - a mineral substance. It contains calcium carbonate, silica, aluminum etc. On heating, limestone breaks up into lime and carbon dioxide. This lime then combines with the oxides of impurities in an ore to form a fusible substance called slag. Slag = impurities + flux; limestone is also known as Flux.

Limit Control - in machine-tool operation, a sensing device which terminates motion of the work piece or tool at prescribed points.

Limit Gauging - a method of measurement to ensure the fitting of two pieces together within specified clearance limits and thus permitting inter-changeability.

Limit of Elasticity - see Elastic Limit Limit of Proportionality - Limit of Proportionality - the point on the stress-strain curve at which the strain ceases to the

proportional to the stress; also called Creep Limit. Limit of Proportionality - the stress, or load divided by original cross-sectional area of the test

piece, at which the strain-elongation per unit of gauge length ceases to be proportional to the corresponding stress. It is determined by inspecting a load-elongation diagram, obtained by plotting extensometer reading and is the stress at which the load elongation line ceases to be straight.

Limit Switch - Limit Switch - an electrical cutoff switch, usually for safety purposes, installed on cranes and

similar moving equipment to cut off power at the end of a run in the event the operator does not do so. They are usually mechanically activated by arm on the moving part.

Limit Switch - electrical switches which may be applied to manual or automated valves to signal that the valve cycle has been completed. When applied to manual or pneumatically actuated valves, it is most common to provide two switches in a Nema Rated Enclosure. Each switch is activated by an adjustable tripping device driven by the actuator or valve system. Normally one switch is adjusted to trip in the open position and one is adjusted to trip in the closed position. Optional additional switches are available to perform other functions; i.e., pump start-up or shut-down. All electric actuators have Open/Close limit switches.

Limiting Link - 1) the component attached to the spring loading bolt and to the loading and easing lever to limit the travel of the latter; 2) the component attached to the spring loading bolt and the body to prevent overloading.

Limiting Temperature - the maximum permissible temperature for apparatus or parts. It is determined by: (a) the danger of ignition of the explosive atmosphere, or (b) the thermal stability of the materials used. The lesser of these temperatures is the limiting temperature.

Line - a tube, pipe, or hose that is used as a conductor of fluid. Line Blind - Line Blind - a pipeline shut-off device, in which a flat disk is forced between two flanges. Line

blinds are less expensive than valves, but require much more time to operate. Line Blind - a pipeline shut-off device, whereby a flat disk is forced between two flanges. Line Blind Valve - a pipeline shut off device which uses a plate arranged to rotate between two

flanges; sometimes referred to as a Spectacle or Goggle valve. Line Class Valve - a valve qualified by its design characteristics to be used as the first valve off

the process line. Line Loss - the quantity of gas that is lost in a distribution system or pipeline. Line Pack - the actual amount of gas in a pipeline or distribution system. Line Pipe - pipe used in the surface transmission of oil, natural gas and other fluids. Linear - Linear - a straight line relationship between two variables. Linear - having an output that varies in direct proportion to the input. Linear Expansion - expansion in any one linear dimension or the average of all linear

dimensions. Linear Strain - the ratio of the change in the length of a body to its initial length; also known as

Longitudinal Strain. Linear Valve - Linear Valve - another name for a globe valve. It refers to the linear or straight-line movement of

the plug and stem. Linear Valve - see Multi-Turn Lined Butterfly Valve - a design of a butterfly valve that has a body liner and a disc whose axis

of rotation passes through the seating surfaces of the disc and body (generally referred to as a “conventional” disc).

Lined Valve Body - a valve body to which a protective coating or liner has been applied to internal surfaces of pressure containing parts or to the surfaces exposed to the fluid.

Liner - a non-metallic covering applied to the inside of the body of a valve. Liners are mostly used on butterfly, plug, and diaphragm valves for corrosion resistance.

Liner Bushing - a bushing, provided with or without a head that is permanently installed in a jigto receive the renewable wearing bushings; also known as Master Bushing.

Link - a connecting piece in the moving parts of a machine. Liquefied Natural Gas - natural gas in the liquid state, consisting mainly of methane, used as a

domestic fuel. Liquefied Petroleum Gas (LPG) - butane, propane, or pentane in the liquid form, used as a

portable fuel, as in cigarette lighters and camping stoves. Liquefied Petroleum Gas (LPG) - Liquefied Petroleum Gas (LPG) - propane, butane or similar hydrocarbon gas, usually

compressed to liquid form. Liquid - a form of matter that has a definite volume but takes the shape of its container. Liquid Penetrant Inspection - a nondestructive method of detecting the presence of surface

cracks and imperfections through use of a special dye. Abbreviated as LPI or PT. Liquid Penetrant Test - a penetrant method of nondestructive testing used to locate defects

open to the surface of nonporous materials; penetrating liquid is applied to the surface, and after 1-30 minutes excess liquid is removed, and a developer is applied to draw the penetrant out of defects, thus showing their location, shape, and size.

List - to lean to one side, or deviate from the vertical. Live Load - a moving load or a load of variable force acting upon a structure, in addition to its

own weight. Live Loaded Valve - to live-load the packing gland by installing springs under the bolt nut of the

gland flange. These springs help maintain packing compression after cycling and aging of the packing.

LL - Low Low LM - 1) Licensed Manufacturer; 2) Large Male Face LME - Liquid Metal Embrittlement LMU - Length Measuring Unit LMW - Licensed Manufacturing Warehouse LNG - Liquefied Natural Gas LO - Lube Oil LOA - Letter Of Award Load - Load - 1) the power demand on an electrical distribution system; 2) the amount of power needed

to start or maintain motion in a power driven machine; 3) in a physical structure, the externally applied force, or the sum of external forces and the weight of the structure borne by a single member or by the entire structure.

Load - a term that can denote force or pressure. Load - mechanical force that is applied to a body. Load - the power output of an engine or power plant under given circumstances. Load - the power that is being delivered by any power-producing device. The equipment that

uses the power from the power-producing device.

Load Full Torque - the torque the load demands on the shaft-end of a motor when the torque of the driven machine is at its full value.

Load Starting Torque - the torque required by the load over the starting period from zero speed to load speed. The starting torque includes, if applicable, compression torque and bearing friction torque.

Loading and Easing Lever - the lever to which the spring is attached by means of which the load is applied to the valve head and by which the valve head may be manually eased off its seat.

Loading Lever - that component which transmits the load to the spindle. Lobe - Lobe - a projection on a cam wheel or a noncircular gear wheel. Lobe - a rounded projection or cam Local Heating - in welding, heating only a specific portion of a workpiece. Local Panel - the operating panel located close to the mechanical valve to be operated. Location Fit - the characteristic wherein mechanical sizes of mating parts are such that, when

assembled, the parts are accurately positioned in relation to each other. Lock Bolt - 1) a bolt equipped with a locking collar instead of a nut; 2) a bolt for adjusting and

securing parts of a machine. Lock Up Valve - a special type of regulator that is installed between the valve positioner and the

valve actuator, where it senses the supply air pressure. If that pressure falls below a certain level, it locks or traps the air loaded into the actuator causing the valve to fail in place.

Lock Washer - Lock Washer - a solid or split washer placed underneath a nut or screw that prevents loosening

by exerting pressure. Lock Washer - a washer which is designed to prevent loosening of a nut or bolt head. Lock Washer - a washer with tongue and prongs to hold a locknut in place. Locked In Liner - in a butterfly valve body, a liner retained in the body bore by a key ring or other

means. Locked Rotor Current - the maximum measured steady-state root-mean-square (RMS) current

taken from the line with the motor held at rest, with rated voltage and frequency applied. (Note: maximum relates to the angular position of the locked rotor.)

Locked Rotor Torque - the minimum measured torque the motor develops at its shaft-end with the rotor locked and rated voltage and frequency applied.

Locking Device - Locking Device - a part or an arrangement of parts providing a means to secure a valve in the

open or closed position. Locking Device - a part or an arrangement of parts providing a means to secure a valve in the

open or closed position. Locking Device - any valve attachment whose purpose is to prevent the operation of the valve by

unauthorized persons. Locking Fastener - a fastening used to prevent loosening of a threaded fastener in service, for

example, a seating lock, spring stop nut, interference wedge, blind or quick release.Locknut - Locknut - 1) an auxiliary (thin) nut which is used in conjunction with another to prevent it from

loosening under vibration; 2) a nut which is designed to obviate accidental loosening; it may have a plastic insert, or be of a special shape, so that one part of a nut locks against another, or a lock wire or pin can get inserted.

Locknut - 1) a nut screwed down on another to keep it tight; 2) a nut designed so that once tightened, it cannot be accidentally loosened.

Locknut - a nut screwed down firmly against another or against a washer to prevent loosening; also known as Jam Nut.

Locknut - a nut used in combination with a lock washer to hold a bearing in place on a shaft. Locknut - a specially designed nut used with screws or bolts to prevent their working loose from

the pieces joined. LOFC - List of Operations of Fabrication and Control Logy - sluggish, low snap or recovery of a material.

LOI - Letter Of Intent Long Products - classification of steel products that includes bar, rod and structural products,

that are "long", rather than "flat". Long Stand Still Service - a valve in open or closed position for more than one week. Long Term Storage - materials and equipment to be preserved in storage yards for a period of

more than 12 months. Long Time Creep Test - long time tests are carried out with a Martene type extensometer. The

test is based upon observations of test pieces at constant stress and temperatures. A series of tests are carried out at a single temperature and limited creep stress is estimated for a certain arbitrary rate of creep, and a factor of safety is used in design.

LONGIT - Longitudinal Longitudinal - running lengthwise; relating to length Longitudinal Bead Test - refers to a test for weldability in which a welded test piece has been

bent double; if the parent metal or the weld metal gets cracked then neither has been weldable.

Longitudinal Strain - see Linear Strain Looping - laying a parallel pipeline along another, or along just a section of it, to increase

capacity. Loose Cargo Load - one or more different shipments combined together. Loose Fit - a fit with enough clearance to allow free play of the joint members. Lost Motion - the delay between the movement of a driver and the movement of a follower. Low Alloy Steel - Low Alloy Steel - 1) steel with a total alloying element content of less than about 5%, but more

than specified for carbon steel; 2) steels from 0.5% up to 9% chromium with 1% molybdenum, or steels from 0.5% up to 9% nickel.

Low Alloy Steel - an iron-carbon alloy which contains up to about 1% C, and less than 5% by weight of additional elements.

Low Alloy Steel - steel containing less than 5% alloying elements, or less than 11% chromium. Low Carbon Steel - Low Carbon Steel - an iron-carbon alloy containing about 0.05 to 0.25% C, and up to about 0.7%

Mn. Low Carbon Steel - steel having 0.04 to 0.25% of carbon. Low Carbon Steel - steel with less than 0.005% carbon is more ductile (malleable). It is capable

of being drawn out or rolled thin for use in automotive body applications. Carbon is removed from the steel bath through vacuum degassing.

Low Leakage Rate Service - a valve which has an allowed leakage in the closed position. Low Pressure Area - the point in a bearing where the pressure is the least and the area or

space for a lubricant is the greatest. Low Recovery Valve - a valve design that dissipates a considerable amount of flow stream

energy due to turbulence created by the contours of the flow path. Consequently, pressure downstream of the valve vena contracta recovers to a lesser percentage of its inlet value than a valve with a more streamlined flow path. The conventional globe style control valve is in this category.

Low Temperature Flexibility - the ability of a rubber product to be flexed, bent, or bowed at a low temperature without cracking.

Low Voltage (LV) - a voltage not exceeding 1,000 volts Lowenhertz Thread - a screw that differs from U.S. Standard form in that the angle between that

flanks measured on an axial plane is 538 degrees 8’; height equals 0.75 times the pitch, and width of flats at top and bottom equals 0.125 times the pitch.

Lower Critical Temperatures - in ferrous metals, the temperatures at which austenite begins to form during heating or at which the transformation of austenite is completed during cooling.

Lower Spreader - in a double disc gate valve, the component complementary to the upper spreader.

LPG - Liquefied Petroleum Gas LR - Long Radius (R = 1.5 D)

LS - LS - Low Sulfur LS - Lube / Seal oil LSS - Long Stand Still service LT - Low Temperature LTCS - Low Temperature Carbon Steel Lubricant Check Valve - a check valve fitted to a lubricated plug valve to prevent leakage of line

fluid through the lubricant feed. Lubricant Ring - nonstandard valve term; see Lantern Ring. Lubricant Screw - a screw fitted to a lubricated plug valve to force the lubricant to the working

parts of the valve. Lubricated Packing Box - a packing arrangement consisting of a lantern ring with packing rings

above and below with provision to lubricate the packing. Lubricator - Lubricator - a device that adds controlled or metered amounts of lubricant into a fluid power

system. Lubricator - a device used to add lubricants into a fluid power system. Lubricator Isolating Valve - in a control valve, an isolating valve is a small hand operated valve

located between the packing lubricator assembly and the packing box assembly. It shuts off the fluid pressure from the lubricator assembly.

Lug - Lug - a projection or head on a metal part to serve as a cap, handle, support, or fitting

connection. Lug - a protruding part on something that acts as a kind of handle, allowing the object to be

carried or turned; sometimes called a Boss. Lug - any projection, like an ear, used for supporting or grasping. Lug Body - a valve body that does not have ends but has lugs (bosses), with threaded holes

around its perimeter for fastening to pipe flanges. Lug Bolt - a bolt with a flat extension or hook instead of a head. Lump Sum - a fixed price for a specified amount of work, as opposed to a Unit Cost. LV - Low Voltage LVO - Last Valves Off

M - Monitor Machinability - the ability of a metal to be easily cut by a tool. Grey cast iron, mild steel etc. are

machinable, while high carbon steel, white cast iron etc. are not machinable. Machinable - material capable of being finished by tools or cutters in or on a machine tool. Machine - Machine - a combination of rigid or resistant bodies having definite motions and capable of

performing useful work. Machine - a device for transforming or transferring energy. Machine - any apparatus which is used to overcome one force by applying another force. Simple

machines include the lever, the screw, the wheel, and the tackle and lifting jack. Machine - any device capable of performing useful work, especially a device for producing

controlled motion or for regulating the effect of a given force. Machine Bolt - Machine Bolt - a small, thick, round bar of metal with a screw thread, used with a nut to fasten

things together. A head is attached on the end opposite where the nut screws on; compare with Stud Bolt

Machine Bolt - a heavy-weight bolt with a square, hexagonal, or flat head used in the automotive, aircraft, and machinery fields.

Machine Element - any of the elementary mechanical parts, such as gears, bearings, fasteners, screws, pipes, springs, and bolts used as essentially standardized components for most devices, apparatus, and machinery.

Machine Key - a piece inserted between a shaft and a hub to prevent relative rotation; also known as Key.

Machine Oxygen Cutting - oxygen cutting of metal with cutting equipment that performs the cutting with the help of a machine.

Machine Screw - a blunt ended screw with a standardized thread and a head that may be flat, round, fillister, or oval, and may be slotted, or constructed for wrenching; used to fasten machine parts together.

Machine Stop - a workshop in which work, metal or other material is machined to specified size and assembled.

Machine Tight - the extent of the tightening of a screwed fitting that can be accomplished without damaging or stripping the thread.

Machine Tool - any machine which is used for cutting metal, such as boring machine, drill grinder, planning machine, hobber, sharper or lathe.

Machining - performing various cutting or grinding operations on a piece of work. Machining Center - manufacturing equipment that removes metal under computer numerical

control by making use of several axes and a variety of tools and operations. Macor - a machinable glass-ceramic manufactured by Corning, which retains the usual hardness

and strength of ordinary ceramics without needing to be fired after machining. Magnetic Crack Detection - the part to be examined is magnetized either by passing a heavy

current through it or by making it the core of a coil through which a heavy current ispassed. Small cracks, or non-magnetic phases such as inclusions, make the magnetic flux break the surface thus forming small magnets. If the part gets sprayed with a suspension of iron oxide particles in paraffin, the particles cling to the small magnets and thereby reveal defects.

Magnetic Hardness Comparator - Magnetic Hardness Comparator - a device for checking the hardness of steel parts by placing a

unit of known proper hardness within an induction coil; the unit to be tested is then placed within a similar induction coil, and the behavior of the induction coils compared; if the standard and test units have the same magnetic properties, the hardness of the two units is considered to be the same.

Magnetic Hardness Comparator - a device for determining hardness of a steel part by comparing its response to electromagnetic induction with the response of a similar part of known hardness.

Magnetic Particle Inspection - see Magnetic Particle Testing Magnetic Particle Testing - Magnetic Particle Testing - a nondestructive method of detecting the presence of surface cracks

and imperfections through use of fine iron particles in an electrical field. Abbreviated as MPI or MT.

Magnetic Particle Testing - a test for defects in metal and welded joints. The metal to be tested is magnetized and sprayed with a white paint, then a dark magnetic powder is oversprayed and the powder collects on both sides of a crack, acting as a defect indicator.

Magnetite - a shiny, black magnetic mineral which consists of an oxide of iron, and is an important form of iron ore.

Main - a duct or pipe that supplies or drains ancillary branches. Maintenance - the upkeep of industrial facilities and equipment. Maintenance Painting - periodic painting (repair / touch up of corroded areas or deteriorated

paintwork) after initial painting. Major Defect - defect which causes serious malfunctioning of a product. Major Diameter - the largest diameter of a screw thread, measured at the crest for an external

(male) thread and at the root for an internal (female) thread. Major Repair - repair work on items of material or equipment that need complete overhaul or

substantial replacement of parts, or that require special tools. Malleability - Malleability - it is the ability to undergo large permanent deformation in compression, or property

which enables a material to be beaten or rolled into thin sheets. Malleability - the ability of a metal to be hammered or rolled into thin sheets without breaking.

Most metals are malleable. Instead of being smashed into splinters when struck by a hammer, a piece of metal is flattened into a sheet or a foil.

Malleability - this is the term used when plastic deformation occurs as the result of applying a compressive load. A malleable material combines the properties of plasticity and compressibility, so that it can be squeezed to shape by such processes as forging and rolling.

Malleable - able to be hammered or pressed into shape without breaking or cracking. Malleable Cast Iron - see Malleable Iron and Cast Iron Malleable Iron - Malleable Iron - a cast iron of such composition that it solidifies as white iron, which upon proper

heat treatment is converted to a metallic matrix with nodules of temper carbon. Malleable Iron - a somewhat ductile form of cast iron made by heat treating white cast iron to

convert the carbon containing phase from iron carbide to nodular graphite. Malleable Iron - an iron casting which is heat treated by being packed in an oxidizing agent and

held for about four days at a temperature of 800° C. Its average tensile strength is approximately double that of ordinary cast iron.

Malleable Iron - it is made by transforming white-iron castings by heat treatment that converts it into a matrix of ferrite containing nodules of temper carbon, and thus it becomes tough and ductile, resistant to impact, and easily machinable.

Malleable Iron - it is tougher and less brittle than either white or ordinary grey cast iron and is made by heat treatment of grey cast iron of suitable composition. Under this treatment, the flakes of graphite coalesce into globular particles, which because of their small cross-sectional area, weaken the ferrite less than do flakes. Cast iron is the cheapest form of iron, but its usefulness is limited by its low strength. A great amount is converted into steel, and a smaller amount into wrought iron.

Malleable, Ferritic - a ferrous alloy that is cast as white is converted by an appropriate heat treatment to a microstructure of temper carbon embedded in a ferritic matrix essentially free of pearlite and carbide.

Malleable, Pearlitic - a ferrous alloy that is cast as white iron but which is converted by an appropriate heat treatment to a microstructure of temper carbon embedded in a matrix containing a controlled quantity, form, and distribution of pearlite or tempered martensite.

Malleableize - to convert white iron into malleable iron through an appropriate graphitizing heat treatment.

Mandrel - Mandrel - a cylindrical metal rod or bar used as a core around which metal or other material is

cast, molded, forged or shaped. Mandrel - an accurately turned rod over which metal is forged, drawn or shaped during working

so as to create or preserve a desired axial cavity. A tapered mandrel is also used for holding and locating a bored component so that external diameters can be machined true to the bore; in USA it is spelled Mandril; also known as Arbor.

Mandrel - the core around which continuous strands of impregnated reinforcement materials are wound to fabricate hollow objects made of composite materials.

Mandrel Press - a press for driving mandrels into holes. Manganese (Mn) - Manganese (Mn) - a hard, brittle, pinkish-gray metallic element. It is used to make alloys that

are very hard and resistant to wear. Manganese (Mn) - contributes to strength and hardness in steel, but to a lesser degree than

carbon. The amount of increase in these properties is dependent upon the carbon content. i.e., higher carbon steels are affected more by manganese than lower carbon. Manganese tends to increase the rate of carbon penetration during carburizing.

Manganese (Mn) - it increases hardenability and beyond certain limits increases the liability to quenching cracks. All the commercial steels contain 0.3 to 0.8% manganese, to reduce oxides and to counteract the harmful effects of sulphur. Any manganese in excess of these requirements partially dissolves in iron and partly forms Mn3C which occurs with Fe3C. Manganese lowers Ac1 and Ac3 and quite small quantities increase hardenability. Manganese also acts as a cheaper substitute for nickel. Steels with 0.3 to 0.4% carbon, 1.3 to 1.6% manganese and 0.3% molybdenum have replaced 3% nickel steel for some purposes. Non-shrinking tool steel contains 0.8 to 0.9% carbon and 2% manganese. Steels with 5 to 12% manganese are martensitic after slow cooling and have little commercial use. Hatfield’s manganese steel contains 12 to 14% Mn and 1% carbon. It is characterized by a great resistance to wear and therefore used for railway points, rock drills and stone crushers.

Manganese Steel - steel having about 1% manganese and up to 0.4% molybdenum is used for railway points and crossing, dredger components and similar heavily stressed parts. Austenitic manganese steel having about 14% manganese and 1% carbon gives extremely high resistance to abrasion.

Mangle Gearing - gearing for producing reciprocating motion; a pinion rotating in a single direction drives a rack with teeth at the ends and on both sides.

Manifold - Manifold - a fluid conductor that has provisions for multiple connections to it. Manifold - a pipe or header for collecting a fluid from, or the distributing of a fluid to a number of

pipes or tubes. Manifold - a pipe with one inlet and several outlets, or with one outlet and several inlets, for

conducting flow. Manifold - a type of fluid conductor that provides multiple connections ports. Manifold Valve - a multiple valve comprising of 2 or more valves in one body. Manifold valves of

through-valve or fire-valve combination are often connected to differential pressure instruments or orifice flanges.

Manifolding - the gathering of multiple-line fluid inputs into a single intake chamber (intake manifold), or the division of a single fluid supply into several outlet streams (distribution manifold).

Manifolds - set of pipes and valves directing fluid. Manipulator - a device to which work has been clamped during welding so that all welds can be

done in the download position. Manometer - Manometer - a differential pressure gauge in which pressure is indicated by the height of a liquid

column of known density. Pressure is equal to the difference in vertical height between two connected columns multiplied by the density of the manometer liquid. Some forms of manometers are U tube, inclined tube, well, and bell types.

Manometer - a double-leg liquid-column gauge that is used to measure the difference between two fluid pressures.

Manual Gas Shutoff Valve - a manually operated valve in a gas line for the purpose of completely turning on or shutting off the gas supply.

Manual Gate Valve - block valves that are operated manually, placed in check valve segments periodically to provide more positive isolation than can be provided by check valves.

Manual Oil Shutoff Valve - a manually operated valve in the oil line for the purpose of completely turning on or shutting off the oil supply to the burner.

Manual Override - Manual Override - a device to manually impart motion in either one or two directions to the valve

stem. It may be used as a limit stop; see also Handjack and/or Handwheel. Manual Override - any mechanical device by which an automated valve may be manually

operated. On smaller actuators, this may simply be wrench flats on the output shaft of the actuator. Larger actuators may require a more sophisticated system, such as declutchable handwheels, manual gears, or jack screws, or hydraulic hand pump over-ride.

Manual Reset Safety Shutoff Valve - a manually opened, electrically latched, electrically operated safety shutoff valve designed to automatically shutoff fuel when de energized.

Manufactured Gas - fuel gas manufactured from coal, oil, etc., as differentiated from natural gas.Manufacturer - the firms or persons involved in some or all phases of manufacturing or

assembly of components. Manufacturer’s Part Number - identification number or symbol assigned by the manufacturer to

a part, subassembly, or assembly. Maraging - Maraging - a heat treatment, (martensite ageing), used to harden alloy steels (commonly those

containing 18% nickel) involving precipitation of intermetallic compounds in a carbon free martensite. These include nickel-iron martensites with high toughness and resistance to shock and saline corrosion.

Maraging - a precipitation hardening treatment applied to a special group of iron base alloys to precipitate one or more intermetallic compounds in a matrix of essentially carbon-free martensite.

Margin of Safety - a design criterion, usually the ratio between the load that would cause failure of a member or structure and the load that is imposed upon it in service.

Marine Environment - offshore and coastal areas Martensite - Martensite - 1) a very hard, brittle solid solution of carbon in iron (or the carbide of iron, Fe3C),

into which hot steel turns when suddenly chilled by cold water. It is the main constituent of hardened steel; 2) a supersaturated solid solution of carbon in iron characterized by an acicular (needle-like) microstructure.

Martensite - obtained by the sudden cooling of high carbon steels from the austenitic range. It is the hardest constituent obtained in steels and has a hardness of around 750 VPN.It is magnetic and brittle. It shows a needle-like structure under a microscope.

Martensitic Stainless Steel - Martensitic Stainless Steel - a small category of stainless steel characterized by the use of heat

treatment for hardening and strengthening. Martensitic stainless steels are plain chromium steels with no significant nickel content. They are utilized in equipment for the chemical and oil industries and in surgical instruments. The most popular martensitic stainless steel is type 410 (a grade appropriate for non-severe corrosion environments requiring high strength).

Martensitic Stainless Steel - a steel in which a microstructure of martensite can be attained by quenching at a cooling rate fast enough to avoid the formation of other microstructures. Martensitic stainless steels are capable of being heat treated in such a way that martensite is the prime constituent.

Martensitic Stainless Steel - this contains 12.5% chromium. It is very hard, magnetic and used for making cutlery and surgical instruments and chemical plants.

Mash Seam Welding - an electrical resistance welding process in which the slightly overlapping edges of the workpiece are forged together during welding by broad-faced, flat electrodes.

Mash Weld - it is a seam weld in which the finished weld is only slightly thicker than the sheets,

and the lap disappears. Mass Effect - the tendency for hardened steel to decrease in hardness from the surface to the

center, as a result of the variation in cooling throughout the section becoming less marked as the rate of cooling required for hardening decreases, i.e. as hardenability of the steel imparted by the content of alloying elements increases.

Mass Flowmeter - an instrument that measures the mass of fluid that flows through a pipe, duct, or open channel in a unit time.

Master Bushing - see Liner Bushing Master Valve - the lowermost valve on the vertical bore of the Christmas tree. It is used to

completely shut in the well. Mastic - 1) a gum used in making varnish; 2) any of various waterproof, putty-like pastes used

as joint sealers or fillers. Masticate - to process rubber on a machine to make it softer and more pliable before mixing with

other substances. Matched-Metal Molding - forming of reinforced-plastic articles between two close-fitting metal

molds mounted in a hydraulic press. Material Take Off - a general, not fully specific list of materials needed. Material Test Reports - certificates provided by the steel manufacturer indicating the chemical

analysis and mechanical properties of a specific batch of steel traced by sequentially assigned heat numbers or codes.

Matte - 1) having a dull surface, without gloss or shine or finish; 2) an impure product of smelting of suphide ores, particularly those of copper or nickel.

MAV - Motor Actuated Valve MAWP - Maximum Allowable Working Pressure Maximum Design Metal Temperature - the temperature used to determine the allowable stress

for the material when calculating equipment wall thickness required for pressure containment.

Maximum Operating Pressure Differential (MOPD) - Maximum Operating Pressure Differential (MOPD) - the maximum difference between the

pressure upstream of a valve and the pressure downstream when measured at specific locations.

Maximum Operating Pressure Differential (MOPD) - the maximum difference in pressure, measured in Pounds per Square Inch between the valve inlet and outlet at which the solenoid can safely operate the valve.

Maximum Operating Temperature - the highest temperature which can be attained by the process fluid, including but not limited to, the highest operating temperature in one of the applicable heat and material balance streams, and the highest operating temperature encountered during start-up, shut-down, recycling, cleaning or purging.

May - indicates an option or possible course of action acceptable to the buyer. Mbd - Million Barrels a Day MBG - Manual Bleed Valve with Gauge MBV - Manual Bleed Valve MC - Management Committee MCC - Motor Control Center MDMT - Minimum Design Metal Temperature Mean Average Boiling Point - pseudo boiling point for a hydrocarbon mixture; calculated from

the American Society for Testing and Materials (ASTM) distillation curve’s volumetric average boiling point.

Mechanical - referring to tools or machinery Mechanical Advantage - the ratio of the resisting weight to the acting force. The ratio of the

distance through which the force is exerted divided by the distance the weight is raised.

Mechanical Galvanizing - a batch process used to produce a zinc coating on manufactured steel items by shot peening. Small iron and steel parts are coated with zinc by drum-tumbling with a mixture of promoter chemicals, zinc powder, and glass beads. The tumbling action peens the zinc powder onto the part.

Mechanical Hysteresis - the dependence of the strain of a material not only on the

instantaneous value on the stress but also on the previous history of the stress; for example, the elongation is less at a given value of tension when the tension is increasing than when it is decreasing.

Mechanical Limit Stop - a mechanical device to limit the valve stem travel. Mechanical Limit Switch - any limit switch, usually plunger or lever type, which is mechanically

activated by the tripping mechanism making physical contact with the switch, and are normally used for remote valve position indication.

Mechanical Properties - such as hardness, ductility, malleability, strength etc. Mechanical Seal - mechanical assembly that forms a leak proof seal between flat, rotating

surfaces to prevent high pressure leakage. Mechanism - that part of a machine which contains two or more pieces so arranged that the

motion of one compels the motion of the others. Mechatronics - the term is a blend of mechanics and electronics. A cross-disciplinary

combination of mechanics, electronics, electrical engineering and computing - in essence the use of microelectronics to control mechanical devices.

Media - Media - the material flowing through the valve. Media - the material that passes through the valve, i.e. air, gases, water, hydraulic fluids,

petroleum products, corrosive and non-corrosive liquids and gases. Medium Carbon Steel - Medium Carbon Steel - an alloy of iron and carbon containing about 0.25 to 0.6% C, and up to

about 0.7% Mn. Medium Carbon Steel - iron containing 0.3 to 0.55% carbon MEK - Methyl Ethyl Ketone Melt - the total molten metal produced in a single heat. Melting Rate - the weight or length of a welding electrode melted in a unit of time. Member - one component of a complex structure Membrane - a thin, pliable sheetlike structure acting as a boundary, lining or partition. Memory - tendency of a material to return to its original shape after deformation. Mercaptan - molecules containing sulfur, very light because of low molecular weight. Merchant Bar - a group of commodity steel shapes that consist of rounds, squares, flats, strips,

angles, and channels, which fabricators, steel service centers and manufacturers cut, bend and shape into products. Merchant products require more specialized processing than reinforcing bar.

Merchant Pig Iron - pig iron produced for commercial sale to foundries. MESC - Material and Equipment, Standards and Code Mesh - Mesh - engagement of a gear with its mating pinion or rack. Mesh - engagement or working contact of teeth of gears or of a gear and a rack. Metal - a chemical element that is crystalline in the solid state, exhibits relatively high thermal

and electrical conductivity, and has a generally lustrous or reflective surface appearance.

Metal Arc Cutting - severing metal pieces carried out with the heat of an arc between a metal electrode and the base metal.

Metal Arc Welding - Metal Arc Welding - a welding process in which the heat to form a molten pool of metal is

produced by an electric arc. The process uses either AC or DC for striking the arc between the electrode and the work piece. One terminal is connected to the electrode and the other to the work piece and the circuit is completed through an air gap between the electrode and the work piece. Depending upon the current and voltage, the air gap is between 3mm and 6mm. The temperature of the arc varies between 3500° and 4000° C. A coated electrode that is of nearly the same composition as that of the metal is used in metal arc welding. Coated electrodes may either be lightly or heavily coated by a suitable flux to prevent oxidation of the weld.

Metal Arc Welding - an arc welding process in which the metal acts as a filler material. Metal Arc Welding - this is the most commonly used method of welding. In this process the arc is

struck between the workpieces to be welded and a metallic rod, which form the two terminals of the arc. Bare electrode has nearly the same composition as that of the base metal. Bare electrodes have the disadvantage that their surfaces may be subjected to oxidation. Coated electrodes may either be lightly or heavy coated by a suitable flux to prevent oxidation of the weld. When a coated metal electrode is used, this process is called Shielded Metal Arc Welding. The shielding is done due to production of gas by the decomposition of the electrode coating. Both AC or DC currents may be used. For currents above 750 ampere, AC equipment is preferred as it has high efficiency, negligible loss at no load and minimum maintenance and initial cost. When a bare electrode is used, the process is called Bare Metal Arc Welding as no shielding of gas is obtained. While using DC the work or base metal is connected to a positive pole because the heat generated at this pole is more than that at the other pole. This type of welding is called welding with Straight Polarity. Bare electrodes are generally used for welding non-ferrous metals. If the electrode is connected to the positive pole and the workpiece to the negative pole, then it is called Reverse Polarity. Reverse Polarity arc is used with covered electrodes for welding ferrous metals. The temperature produced by the arc is nearly 3,500° C, which is concentrated on a small area, and sufficient to form a pool of metal.

Metal Dip Brazing - a dip brazing process in which the filler metal is obtained from the molten metal bath.

Metal Electrode - a metallic wire used in arc welding, with or without covering or coating. Metal Electrode Arc Welding - various arc welding processes carried out with suitable

electrodes. Metal Fiber Welding - it is used for making lap joints and can be said to be an extension of

resistance spot welding process. The equipment used is the same as for resistance spot welding. In this process a small piece of metallic sheet (material used is the same as for parent metal) is introduced between the pieces to be joined. The pieces are held between the electrodes and welding is completed under low pressure.

Metal Foil Welding - this process is used for butt welding of sheet metal. The equipment consists of two wheel type electrodes similar to wheels used in seam welding. The sheets to be welded are butted together and a thin foil of sheet is placed over and below the joint. The sheet used is less than 0.20mm thickness and of the same material as the parent metal. The sheets to be joined are placed between the rolls and operation is similar to seam welding.

Metal Inert Gas (MIG) Welding - Metal Inert Gas (MIG) Welding - recent developments in MIG welding is the introduction of semi-

automatic processes. It reduces cost of high diving operations. Automatic feeding of feeler wires does automatic operation or flux cored wires. MIG welding is faster than TIG welding. MIG dry welding is preferred over MIG wet welding for better results.

Metal Inert Gas Arc Welding - this process involves welding of metals in an inert gas atmosphere using a consumable metal electrode. The inert gas generally used is argon or helium. The electrode, made of the parent metal, is made in the form of consumable wire and is continuously fed into the arc by an adjustable electric speed motor. The speed of feeding is the same at which the rod is being melted and deposited in the weld. The arc is struck between the consumable electrode and the workpiece. The electrode holder used is specially designed to enable passage of inert gases in addition to movement of the consumable electrode; abbreviated MIG Welding.

Metal Oxide - rust Metal Piston Type Seal - in a butterfly valve, a self expandable metal seal ring installed in a

groove on the disk circumference to block the clearance between the disk outer diameter and the liner bore with the disk in closed position.

Metal to Metal Seal - a seal effected by very smooth finishes on mating metal parts. Metallizing - a process used to produce a zinc coating on manufactured steel items by metal

spraying. Zinc metal wire or powder is fed into a spray gun where it is melted and sprayed onto the part to be coated. Melting is accomplished either by combustion in an oxygen-fuel gas flame or an electric arc. Combustion gases and/or auxiliary

compressed air provide the necessary velocity to spray the liquid metal onto the part.

Metallurgy - the science concerned with the production, purification and properties of metals and their application.

Meter - a device for measuring the value of a quantity under observation; the term is usually applied to an indicating instrument alone.

Meter In - to regulate the amount of fluid into a system or an actuator. Meter Out - to regulate the flow of fluid from a system or actuator. Meter Stop - a valve installed in a water service pipe for control of the flow of water to a building. Metering - Metering - 1) regulating the flow of a fluid so that only a measured amount is permitted to flow

past a given point in the system; 2) measuring any variable (flow rate, electrical power, etc.)

Metering - an adjustable pin that regulates the flow of media over a specified path; placed as a restriction in the media path.

Methane (CH4) - a hydrocarbon compound that is the primary component of natural gas. It is a colorless, odorless, flammable gas, used in the manufacture of organic chemicals and heating fuel. It is formed naturally by the decomposition of vegetable matter, as in marshes and mines, or produced artificially by heating carbon monoxide and hydrogen. It is reported separately from the category of gases called Volatile Organic Compounds (VOCs).

Methylethyl Ketone (MEK) - a common solvent Metric Screw Thread - a standard screw-thread in which the diameter and pitch are specified in

millimeters with a 60 degree angle. Meyer Hardness Number - a number which is obtained by the same test as for the Brinell

hardness number; it refers to the ratio of the load divided by the projected area of the indentation.

MFC - Multivariable Controller MFD - Mechanical Flow Diagram Mg - Magnesium MHS - Medical / Health Services MI - Mineral Insulated (cables) Micrometer - Micrometer - a caliper for making precise measurements; a spindle is moved by a screw thread

so that it touches the object to be measured; the dimension can then be read on a scale; also known as Micrometer Caliper.

Micrometer Gauge - a U-shaped length gauge in which the gap between the measuring faces is adjustable by an accurate screw whose end forms one face. The gap is read off a scale uncovered by a thimble carried by the screw, and by a circular scale which is engraved on the thimble; commonly called Micrometer.

Micron - Micron - a millionth of a meter or about 0.00004 inch. Micron - one-thousandth of a millimeter Microstructure - Microstructure - the fine crystalline structure in a metal, which is visible under a microscope. Microstructure - the structure of a metal as revealed by microscopic examination of a suitably

prepared specimen. MIG - Gas Metal Arc Welding MIG Welding - MIG Welding - metal-inert gas welding; see Gas Metal Arc Welding Mild Steel - Mild Steel - an alloy of iron containing less than 0.03% carbon. Mild Steel - steel which contains from 0.15 to 0.25% carbon. Because of its low carbon content it

cannot get hardened by quenching, but it is more ductile than high carbon steel. Mill - Mill - a building that houses machinery for manufacturing processes.

Mill - machine which is used for grinding or crushing material, such as a hammer mill, a ball mill or a pug mill.

Mill - to cut or shape metal with a rotating tool. Mill Certificate - chemical and physical analysis Mill Scale - black iron oxide which gets formed on steel sections during rolling. This scale should

always be removed before painting. Mill Shearing - a defect in metal which can be described as a feathering type light surface lap. Mill Test Report - Material Test Report Millibar - a unit of pressure equal to one-thousandth of a bar; abbreviated mb; also known as

Vac. Milling - Milling - a machine process which is used for the removal of metal shavings from a surface by

passing it under a rotating toothed cutter. Milling - shaping of metal pieces by removing metal with a revolving multi-tooth cutter to produce

flat and profiled surfaces, slots and grooves. Milling Machine - a machine for the removal of metal by feeding a work piece through the

periphery of a rotating circular cutter; also known as Miller. Mineral Oil - Mineral Oil - a colorless, odorless, oily liquid obtained from petroleum. Mineral Oil - petroleum and the oils derived from it, or other oils obtained from underground

mineral deposits. Mini Mills - normally defined as steel mills that melt scrap metal to produce commodity products.

Although the mini-mills are subject to the same steel processing requirements after the caster as the integrated steel companies, they differ greatly in regard to their minimum efficient size, labor relations, product markets and management style.

Minimum Design Metal Temperature - the temperature used to select materials with appropriate toughness properties.

Minimum Metal Condition - the condition corresponding to the removal of the greatest amount of material permissible in a machined part.

Minimum Operating Temperature - the lowest temperature which can be attained by the process fluid, including but not limited to, the lowest operating temperature in one of the applicable heat and material balance streams, and the lowest operating temperature encountered during start-up, shut-down, de-pressurizing, repeated start-up and de-pressurizing, cleaning or purging.

Minor Detect - a defect which reduces the effectiveness of the product, without causing serious malfunctioning.

Mirror Finish - a bright, polished surface. Mismatch - unsymmetrical seal caused by dissimilar cavities in mating mold sections. Miter Bend - a pipe bend made by mitering (angle cutting) and joining pipe ends. Miter Gear - a bevel gear whose bevels are in 1:1 ratio. Miter Valve - Miter Valve - a safety valve having the annular seating cut at an angle of 45 degrees; also

spelled Mitre Valve. Miter Valve - a valve in which a disk fits in a seat making a 45 degree angle with the axis of the

valve. Miter Valve - a valve in which the disc is at an angle of approximately 45 degrees to the axis of

the valve body. MITI - Ministry of International Trade and Industry Mixing - to flow into both ends (of a 3 way, 2 port valve) and out the side. Mixing Chamber - a portion of a gas welding torch in which gases are mixed for combustion. Mixing Valve - Mixing Valve - a valve having more than one inlet but only one outlet port; it is used to blend two

or more fluids to give a mixture of predetermined composition. Mixing Valve - multi-inlet valve used to mix two or more fluid intakes to give a mixed product of

desired composition. MLD - Million Liters per Day

mm Hg - millimeters of mercury. In vacuum work, this is a measure of absolute pressure, being the height of a column of mercury that the air or other gas will support. Standard atmospheric pressure will support a mercury column 760 mm high (760 mmHg). Any value less than this represents some degree of vacuum.

Mmboe - Million Barrels of Oil Equivalent MMCFD - Million Cubic Feet per Day MMS - Maintenance Management System MMSCFD - abbreviation for million standard cubic feet per day; usually refers to gas flow. MMSCFH - abbreviation for million standard cubic feet per hour; usually refers to gas flow. MMSCFM - abbreviation for million standard cubic feet per minute; usually refers to gas flow. Mn - Manganese MN - Meganewton Mo - Molybdenum MOD - MODification Instructions Modification - a major or minor change in the design of an item, effected in order to correct a

deficiency, to facilitate production, or to improve operational effectiveness. Modified Parabolic - a flow characteristic that lies somewhere between linear and equal

percentage. It provides fine throttling at low flow capacity and an approximately linear characteristic at higher flow capacities.

Modulating - the actions to keep a quantity or quality in proper measure or proportion; see alsoThrottling.

Modulating Service - when the valve is being used to throttle or regulate the rate of flow by being positioned at varying positions between open and closed.

Modulation - the action of a control valve to regulate fluid flow by varying the position of the closure component.

Modulus - Modulus - a quantity expressing the response of a sample of material to an external stimulus,

such as mechanical stress. The response is usually expressed as a fractional change in the physical quantity being affected.

Modulus - tensile stress at a specified elongation. (Usually 100% elongation for elastomers). Modulus of Elasticity - Modulus of Elasticity - generally termed as Young’s modulus (E), this is the ratio between the

stress and the strain of a material under load. Some common values of E in millions of lb/in2 have been steel, 30; aluminum alloys 10; magnesium alloys, 6.5: concrete loaded over a long period, 2, and over a short period, 6.

Modulus Of Elasticity - in any solid, the slope of the stress-strain curve within the elastic region; for most materials, the value is nearly constant up to some limiting value of stress known as the elastic limit; modulus of elasticity can be measured in tension, compression, torsion or shear; the tension modulus is often referred to as Young's modulus.

Modulus of Elasticity - it is the ratio of stress to strain within the elastic limit. It is a measure of stiffness.

Modulus of Elasticity - one of the several measurements of stiffness or resistance to deformation, but often incorrectly used to indicate specifically static tension modulus.

Modulus of Elasticity - the rate of change of unit tensile stress to unit tensile strain for uniaxial stress with the elastic limit. It is also called Young's Modulus.

Modulus of Elasticity (E) - it is the constant which expresses the ratio of unit stress to unit deformation for all values unit stress not exceeding the proportional limit of material. Modulus of elasticity in shear is sometimes known as the Modulus of Rigidity.

MOF - Ministry Of Finance Mold - a hollow cavity, frequently in packed sand, for giving a desired shape to a material in a

molten or plastic shape. Mold Cavity - a hollow space or cavity in the mold which is used to impart the desired form to the

product being molded. Mold Finish - the uninterrupted surface produced by intimate contact of rubber with the surface

of the mold at vulcanization. Mold Lubricant - a material usually sprayed onto the mold cavity surface prior to the introduction

of the uncured rubber to facilitate the easy removal of the molded rubber parts. Mold Marks - indentations or ridges embossed into the skin of the molded product by

irregularities in the mold cavity surface. Mold Register - accuracy of alignment or fit of molded sections. Molding Sand - the freshly prepared refractory sand used for making a mold cavity. It contains

various constituents such as silica, clay binders, moisture, etc. in appropriate proportions to get the desired results. It surrounds the pattern while making the mold.

Mole (mol) - the SI unit of amount of substance equal to the quantity containing as many elementary units, including molecules, atoms or ions, as there are atoms in 12 grams of pure carbon-12.

Molecular Attrition - see Fretting Molecule - a small natural particle of matter composed of two or more atoms. Molten - melted; made liquid by heat Molybdenum (Mo) - Molybdenum (Mo) - 3% can be added to low chromium steel to improve impact properties. Molybdenum (Mo) - a hard, brittle, silvery-white metallic element, used as a hardening agent in

steel and other alloys. Molybdenum (Mo) - a metallic element the influence of which on steel is closely related to that of

chromium and tungsten. Molybdenum may replace tungsten in high speed steel, being twice as effective weight for weight. When added to low alloy steels it has a marked effect in reducing temper brittleness. In solid solution, molybdenum is able to increase strength and toughness, improving resistance to creep at high temperature.

Molybdenum (Mo) - an alloying element used as a raw material for some classes of stainless steel. Molybdenum in the presence of chromium enhances the corrosion resistance of stainless steel.

Molybdenum (Mo) - molybdenum is soluble both in a- and y-iron and in the presence of carbon forms complex carbides (Fe Mo)6C, Fe2, Mo2 C6, Mo2C. Molybdenum is similar to chromium in its effect but up to 0.5% carbon retards pearlitic formation and increases bainitic formation. 0.5% molybdenum increases the strength of steels at boiler temperature of 400° C. Generally, molybdenum is used in combination with other alloying elements. Ni-Cr-Mo steels are widely used for ordnance components, turbine rotors and other large components, since molybdenum tends to minimize temper brittleness and reduces mass effect. Molybdenum is also used as a cheaper substitute for tungsten in high speed steels. It is also used in magnet steels, heat resisting and corrosion resisting steels.

Molybdenum (Mo) - promotes hardenability in steel, and is useful where close hardenability-control is essential. It increases depth-hardness and widens the range of effective heat-treating temperatures.

MOM - Minutes Of Meeting Moment - Moment - 1) of force, the effectiveness of a force in producing rotation about an axis; it equals

the product of the radius perpendicular to the axis of rotation that passes through the point of force application and the tangential component of force perpendicular to the plane defined by the radius and axis of rotation; 2) of inertia, the resistance of a body at rest or in motion to changes in its angular velocity.

Moment - a turning effect (torque) produced by a force on an object. Moment - static moment of some quantity, except in the term “moment of inertia”. Moment Load - load which acts eccentrically on a body, such as a bearing, producing a motion

or rotation about a point or axis. Moment Of Force - see Torque Moment Of Inertia - the sum of the products formed by multiplying the mass (or sometimes, the

area) of each element of a figure by the square of its distance from a specified line; also known as Rotational Inertia.

Monel® - Monel® - a high strength, corrosion resistant steel used in valve trim, made with 65% nickel and

30% copper.

Monel® - a series of International Nickel Co. high nickel, high copper alloys used for their corrosion resistant properties to certain conditions.

Monitor - an optional inspection point. Work is not to be held up if an inspection is not available. Monkey Wrench - a wrench having one jaw fixed and the other adjustable, both of which are

perpendicular to a straight handle. Monomer - a simple molecule that can be joined to many others to form a much larger molecule

known as a polymer. Mooney Scorch - the measurement of the rate at which a rubber compound will cure or set up

by means of the Mooney Viscometer test instrument. Mooney Viscosity - the measurement of the plasticity or viscosity of an uncompounded or

compounded, unvulcanized, elastomeric seal material by means of the Mooney Shearing Disk Viscometer.

MOP - Maximum Operating Pressure Mortise - a groove or slot in a timber for holding a tenon. Mortise and Tenon - a type of joint, principally used for wood, in which a hole, slot, or groove

(mortise) in one member is fitted with a projection (tenon) form the second member.MOS - Maintenance Override Switch MOT - Means Of Transportation Motion - a continuous change of position of a body. Motive - having to do with motion Motor - a device that converts power into mechanical force and motion. It usually provides rotary

mechanical motion. Motor Driven Reset Safety Shutoff Valve - an electrically operated safety shutoff valve

designed to automatically shut off fuel flow upon being de energized. The valve is opened and reset automatically by integral motor device only.

Motor Operated Valve (MOV) - an isolation valve which, due to its size and / or pressure rating, is fitted with a motorized (electric) actuator to facilitate ease of operation. These valves are not utilized as SDVs (Shutdown Valves); compare with Blowdown Valve and Shutdown Valve.

Motor, Cage Induction - an induction motor with secondary cage (squirrel cage) winding(s). Motor, Fixed-Displacement - a motor in which the displacement per unit of output motion

cannot be varied. Motor, Linear - Motor, Linear - see Cylinder Motor, Linear - some cylinder manufacturers use this term to describe cylinders. Motor, Rotary - a motor capable of continuous rotary motion. Motor, Rotary Limited - a rotary motor having limited motion. Motor, Variable-Displacement - a motor in which the displacement per unit of output motion can

be varied. Mottled Cast Iron - see Mottled Iron Mottled Iron - Mottled Iron - a cast iron containing a mixed structure of gray iron and white iron of variable

proportions. The fracture has a mottled appearance. Mottled Iron - cast iron containing the structure of free cementite, free graphite and pearlite. Mottled Iron - when cast iron is melted and then subjected to normal cooling, mottled cast iron is

obtained. Its composition is 93.5% iron, 1.75% graphite, 1.75% combined carbon and remaining other impurities. As carbon is present in the mottled cast iron partly in the combined form and partly in the free form, its color as well as its properties are in between those of grey and white cast iron. Its resistance to corrosion is more than that of the grey variety. It is hard and brittle and its fluidity is good and is therefore, a good material for casting. It is mainly used for making main-hole cover, fire plugs, lamp posts etc.

MOU - Memorandum Of Understanding Mounce - a unit of mass, equal to 25 grams; also known as Metric Ounce. Mounting Flange - a flange or pad formed on the exterior of the body for the attachment of the

valve operating mechanism. Mounting Position - the location and orientation of an actuator or auxiliary component relative to

a valve. This can apply to the valve itself relative to the piping. MOV - Motor Operated Valve Mpa - Megapascal MPI - Magnetic Particle Inspection MPT - Magnetic Particle Testing MRI - see Magnetic Resonance Imaging MRIC - Pressure Instrument connection on meter run MRO - Maintenance, Repair and Overhaul MRP - see Material Requirements Planning MRTD - see Minimum Resolvable Temperature Difference MS - 1) Malaysian Standard; 2) Management System Ms - see Megasound ms - see Millisecond MSBF - Monoflange Single Block Ball MSCF - Thousand (Milli-) Square Cubic Feet MSDS - Materials Safety Data Sheet MSE - Malaysian Shipyard and Engineering MSIR - Minimum Source Inspection Requirements MSL - Mean Sea Level MSNF - Monoflange Single Block Needle MSS - Manufacturers Standardization Society (of the Valve and Fittings Industry) MT - 1) Magnetic Particle Examination (Test); 2) Metal Seat MTJDA - Malaysia – Thailand Joint Development Area MTO - 1) Material Take Off; 2) Multimodal Transport Operator MTR - 1) Material and Test Report; 2) Mill Test Report; 3) Manual Bleed Valve with Thermal

Relief MTRR - Meter Run Mud - mud is drilling fluid. Mud consists mainly as a mixture of water, or oil distillate, and 'heavy'

minerals such as Bentonite or Barites. Mud is pumped into a well at densities calculated to provide a hydrostatic pressure sufficient to overcome down hole formation pressures such as gas kick. The mud is continuously circulated down to the bit, and returns in the annular space outside the drill-string, bringing with it rock cuttings for inspection and keeping the well clean. Mud is also engineered to maintain a thin protective layer of filter-cake on the bore hole wall, but without excessive weight which would decrease the weight on the bit and hence penetration (see Drill String). Wrongly configured mud could also possibly lead to differential sticking and formation damage. Mud is pumped from the mud pit / tank into the drill stem. On return from down hole the mud is recovered and the shale shakers remove rock cuttings, it can then be re-circulated.

Mud Valve - Mud Valve - provide resilient sealing in harsh applications. They are purposely made for mud,

cement, fracturing and water service. Mud valves are particularly suited to abrasive applications

Mud Valve - a valve that acts under the same principles as the gate valve. The mud valve is specifically suitable to abrasive applications such as the control of mud.

Mull - to mix thoroughly or grind. Multi Port Valve - Multi Port Valve - a ball valve or a plug valve with more than two ends that is used for changing

flow direction. Multi Ported - multi-ported valves include additional inlet / outlet ports, to allow fluids to be

directed. The ball and plug valve types are ideally suited to multi-port designs. Multi Turn - Multi Turn - a category of valves (such as gate, globe, needle) which require multiple turns of the

stem to move the valve from the fully open to the fully closed positions. Also known as linear valves.

Multi Turn - category of valves (such as gate, globe, needle) which require multiple turns of the

stem to move the valve from the fully open to the fully closed position; also known as Linear Valves; see also Quarter-Turn.

Multiple Sampling - a plan for quality control in which a given number of samples from a group are inspected, and the group is either accepted, resampled, or rejected, depending on the number of failures found in the samples.

Multistage - functioning or occurring in separate steps. Muntz Metal - a filler material generally used for braze welding, consisting of 60% copper and

40% zinc. Muskhelishvili’s Method - a method of solving problems concerning the elastic deformation of a

planar body that involves using methods from the theory of functions of a complex variable to calculate analytic functions which determine the plane strain of the body.

MVC - Measurement Validation Comparison Technology MW - see Megawatt mW - see Miliwatt

N - 1) Nitrogen; 2) Newton Na - Sodium NAB - No As-Built work required NACE - National Association of Corrosion Engineers NAMAS - National Measurements Accreditation Service. Naphtha - 1) the feedstock used to make ethylene and propylene, the basic building blocks for

the chemical industry; 2) hydrocarbon distillate used as solvent and washing agent.NATA - National Association of Testing Authorities (Australia) National Electrical Code (NEC) - a set of regulations governing construction and installation of

electrical wiring and apparatus, established by the National Fire Protection Association. It is widely used by state and local authorities within the United States.

National Electrical Manufacturers Association (NEMA) - used in valve terminology to define the level of external resistance an enclosure or solenoid coil is suited for. e.g.: NEMA 1 is dust tight; NEMA 9 is explosion proof, etc.

National Institute for Certification in Engineering Technologies (NICET) - provides certification in "Industrial Instrumentation Engineering Technology Technician."

National Pipe Taper - see National Pipe Thread National Pipe Thread (NPT) - National Pipe Thread (NPT) - a specification for tapered pipe threads from ANSI (American

National Standards Institute). Actually taken from American National Standard Taper Pipe Threads. When listed as NPT-F, it indicates female ends.

National Pipe Thread (NPT) - a standard tapered thread for pressure pipe and components. Requirements are defined in ASME B1.20.1.

Natural - describes resins, frequently PP or PVDF, that have not had colorants, fibers, or other components added prior to processing. Sometimes mistakenly interchanged with "Virgin."

Natural Gas (NG) - Natural Gas (NG) - a mixture of gaseous hydrocarbons trapped in rock formations below the

earth's surface. The mixture consists chiefly of methane and ethane, with smaller amounts of other low molecular weight combustible gases, and sometimes noncombustible gases such as nitrogen, carbon dioxide, helium and H2S called Sour Gas.

Natural Gas (NG) - a mixture of gaseous hydrocarbons, chiefly methane, occurring naturally under the ground or seabed in petroleum-bearing regions, and piped to cities, etc. to be used as a fuel.

Natural Gas and Gas Products (NG&GP) - includes the gathering, processing, distribution and marketing of natural gas and natural gas liquids.

Natural Gasoline Plant - compression, distillation, and absorption process facility used to remove natural gasoline (mostly butanes and heavier components) from natural gas.

Nb - Niobium NB - Take Note (from Latin - Nota Bene) NBR - 1) Nitrile (Acrylonitrile Butadiene); 2) Nitrile Rubber (Buna – N) NC - describes the resting (non-activated) position of a valve. In this case the valve is Normally

Closed. NCR - Non-Conformance Report NDE - Non-Destructive Examination NDT - Non-Destructive Testing Ne - Neon NE - Normally Energized NEC - National Electric Code Necking - tensile testing involves the application of load onto a specimen and physically

stretching it under an increasing load, measuring the extension of the metal and the reduction of the cross-sectional area until fracture occurs, often referred to as Necking.

Need Date - the date within which documents are to be transmitted to purchaser for review, comments and approval or to be available for review at vendor’s premises.

Needle Bearing - a roller-type bearing with long rollers of small diameter; the rollers are retained in a flanged cup, have no retainer, and bear directly on the shaft.

Needle Point Valve - see Needle Valve Needle Valve - Needle Valve - a screw-down stop valve which has the body ends in line or at right-angles to

each other or may be of the oblique type with the disc in the form of a needle point. Needle valves are usually restricted to small sizes.

Needle Valve - a form of screw–down stop valve, generally restricted to small sizes, which may have the body ends in line or at right angles with each other or may be of the oblique type. The disc is in the form of a needle point.

Needle Valve - a form of screw-down stop valve, generally restricted to small sizes, which may have the body ends in line or at right angles with each other, or may be of the oblique type. The disc is in the form of a needle point.

Needle Valve - a small globe valve without a separate disc, but with a stem with an integral conical seating surface.

Needle Valve - a small valve in which the moving sealing element is small and sharply tapered or needle shaped.

Needle Valve - a type of metering valve used chiefly for precisely controlling flow. Its essential design feature is a slender tapered rodlike control element which fits into a circular or conoidal seat. Operating the valve causes the rod to move into or out of the seat, gradually changing the effective cross sectional area of the gap between the rod and its seat.

Needle Valve - a type of valve having a needle point plug. Needle Valve - a type of valve which has a needle point plug and a small seat orifice for metering

low flows. Needle Valve - a valve closed by a thin tapering part. Needle Valve - a volume-control valve that restricts flow in small lines. The fluid going through

the valve turns 90 degrees and passes through an orifice that is the seat for a rod with a cone-shaped tip. The size of the orifice is changed by positioning the cone in relation to the seat.

Needle Valve - cone-shaped valve terminating in a sharp point, which finds use in controlling the flow to a water turbine.

Needle Valve - this multi-turn valve derives its name from the needle-shaped closing element. The design resembles that of the globe valve. Typically available in smaller sizes, they are often used on secondary systems for on / off applications, sampling, etc.

Needle Valve - this multi-turn valve derives its name from the needle-shaped closing element. The design resembles that of the globe valve. Typically available in smaller sizes, they are often used on secondary systems for delicate control and shut off, e.g. with analyzers.

Negative Position - the installation position of a multi-port valve such that fluid inlet pressure can be into a closed body opening, thereby retarding valve sealing; compare withPositive Position.

Negative Rake - the orientation of a cutting tool whose cutting edge lags the surface of the tooth face.

Negatoscope - a box containing a source of light with one face of the box acting as a translucent screen for examination of transparencies or films.

NEMA - National Electrical Manufacturer Association Nema 4 - weather-proof enclosure suitable for indoor/outdoor applications to protect from

windblown dust, rain or hose-directed water. Nema 4x - offers the same protection as Nema 4 with the addition of corrosion resistance. Nema 6 - enclosure that may be submerged up to six feet for 30 minutes. Nema 7 - enclosure for hazardous locations, must be capable of withstanding an internal

explosion of gases so as not to ignite an external gas-air mixture. Nema Rating - National Electrical Code Ratings for electrical component enclosures. Neoprene - Neoprene - a non-metallic material used as a valve trim. It is an elastomer also known as

chloroprene rubber. It has excellent abrasion resistance and compression-set

resistance and very good resilience. The addition of carbon black increases its tear resistance. It is used for butterfly valve liners and for diaphragm valve linings and diaphragms.

Neoprene - a synthetic rubber highly resistant to oil, light, heat, and oxidation. Neoprene - a synthetic rubber made by polymerization of chloroprene (2 chlorobutadiene 1,3).

Its color varies from amber to silver to cream. It exhibits excellent resistance to weathering, ozone, flames, various chemicals and oils.

Neoprene Washers - washers made from neoprene, usually to provide insulating protection such as to prevent galvanic corrosion between dissimilar materials, as between a steel screw fastening an aluminum sheet.

Nett - no more additions to the price – includes tax, shipping, etc. Neutral Flame - a gas welding flame having neither oxidizing nor reducing characteristics. Neutralization Number - a measure of the total acidity or basicity of an oil; this includes organic

or inorganic acids or bases or a combination of them. Newton - Newton - a unit of force equivalent to that which gives a one kilogram mass an acceleration of

one second every second. Newton - metric unit for force Newton - the force required to accelerate a mass of one kilogram at one meter per second

squared; abbreviated N. Newton - the unit of force in the meter-kilogram-second system, equal to the force which will

impart an acceleration of 1 meter per second squared to the International Prototype Kilogram mass: symbolized N; formerly known as Large Dyne.

Newton’s First Law - the law that a particle not subjected to external forces remains at rest or moves with constant speed in a straight line; also known as First Law of Motion; Galileo’s Law of Inertia.

Newton’s Laws of Motion - three fundamental principles (called Newton’s first, second, and third laws) which form the basis of classical, or Newtonian, mechanical problems not involving speeds comparable with the speed of light and not involving atomic or subatomic particles.

Newton’s Second Law - the law that the acceleration of a particle is directly proportional to the resultant external force acting on the particle and is inversely proportional to the mass of the particle; also known as Second Law of Motion.

Newton’s Third Law - the law that, if two particles interact, the force exerted by the first particle on the second particle (called the action force) is equal in magnitude and opposite in direction to the force exerted by the second particle on the first particle (called the reaction force); also known as Law of Action and Reaction.

NFPA - National Fire Protection Association NG - Natural Gas NG & GP - Natural Gas And Gas Products NGL - Natural Gas Liquids; includes ethane, propane, butane and condensate. Ni - Nickel Nib - a small projecting point. Nickel (Ni) - Nickel (Ni) - a grayish-white, malleable metal element used especially in steels, alloys, and for

plating. Nickel (Ni) - added to steel to improve strength Nickel (Ni) - an alloying element used as a raw material for certain classes of stainless steel.

Nickel provides high degrees of ductility (ability to change shape without fracture) as well as resistance to corrosion. Approximately 65% of all nickel is used in the making of stainless steel.

Nickel (Ni) - in behavior, nickel is very similar to manganese and both lower the critical temperatures. Eutectoid temperature is lowered progressively with the increase of nickel (approximately 10° C for 1% of nickel) on heating, but the lowering of the change on cooling is greater and irregular. The addition of nickel acts similarly to increasing the rate of cooling of a carbon steel. With a constant rate of cooling, 5 to 8% nickel steels become troostitic; at 8 to 10% nickel, where a drop in cooling rate

appears, the structure is martensitic, while above 24% nickel the critical point is depressed below room temperature and austenite remains. In mechanical properties, much change takes place with the increase in the nickel content. Steels with 0 to 5% nickel are similar to carbon steel, but are stronger on account of the finer pearlite formed and the presence of nickel in solution in the ferrite. When 10% nickel is exceeded, the steels have a high tensile strength and great hardness, but are brittle. When the nickel is sufficient to produce austenite, the steels become non-magnetic, ductile, tough and workable, with a drop in strength and elastic limit. Steels containing 0.1% carbon and 2 to 5% nickel are used for case hardening, but the principal pearlitic nickel steels in commercial use are those containing 0.25 to 0.40% carbon with 3 to 3.75% nickel. They are used for crankshafts, axles and connecting rods. By quenching and tempering, nickel steels give superior properties. Since Ac3 point is lowered, a lower hardening temperature than for carbon steels is permissible and also a wider range of hardening temperatures above Ac3 without excessive grain growth, which is hindered by the slow rate of diffusion of the nickel. Martensitic nickel steels are not utilized and the austenitic alloys cannot compete with similar manganese steels owing to the higher cost. High nickel steels are used only for special purposes, owing to the marked influence of nickel on the coefficient of expansion of the metal. Steel containing 0.2% carbon, 36% nickel and 0.5% manganese has practically zero coefficient of expansion between 0° and 100° C. The alloy is called invar and is used in clocks. Binary alloy, known as Permalloy, contains 78.5% nickel and 21.5% iron (the alloy is free from carbon) and has high permeability in small magnetic fields. This alloy is annealed at 900° C followed by air cooling at 600° C.

Nickel (Ni) - it occurs with iron in meteorites. Its principal ores are niccolite NiAs, millerite NoS and pentlandite (NiFe)S. The metal is produced as an alloy containing iron and other elements by roasting the ore and reducing with carbon. In the purification of nickel by Mond process the compound nickel carbonye (Ni(CO)4) is manufactured and then decomposed. The ore is reduced with hydrogen to metallic nickel under conditions so that iron oxide is not reduced. Carbon monoxide is then passed through the reduced ore at room temperature; it combines with the nickel to form nickel carbonye, a gas. It is then passed into a decomposer, and heated to 150° C. The gas decomposer, depositing pure metallic nickel and the liberated carbon monoxide is returned to be used again. Nickel is white metal, with a faint tinge of yellow. It is used in making alloys including the copper-nickel alloy (75% copper, 25% nickel) used in coinage. Iron objects are plated with nickel by electrolysis. The metal is still less reactive than cobalt and displaces hydrogen only very slowly from acids.

Nickel (Ni) - provides properties in steel such as improved toughness at low temperatures, good resistance to corrosion when used in conjunction with chromium in stainless grades, deep hardening, and ready response to conventional methods of heat treating.

Nickel Silver - an alloy of copper, zinc and nickel, that looks like silver. Nickel Steel - it generally contains 4% nickel. The addition of nickel increases elasticity,

hardness and resistance to fatigue. It is generally used for making precision instruments.

Niobium (Nb) - a rare, relatively unreactive, soft, bluish-gray metallic element with a brilliant luster, resistant to corrosion, and formerly known as Columbium.

Nipple - Nipple - 1) a small drilled bush or tubular nut; 2) a short length of externally threaded pipe. Nipple - a short piece of pipe or tube, usually with an external thread at each end. Nipple - A short piece of pipe threaded on both ends. Nipple - a short piece of tubing, usually with an internal or external thread at each end, used to

couple pipes: also know as Bushing. Nipple - any small projection with a hole through it, which a flow is regulated or machine parts

lubricated. Nitric Acid (HNO3) - a colorless corrosive poisonous liquid Nitride - a nitride coating is a very hard coating that will increase the hardness and thus wear life

of a surface. Useful when abrasive substances come into contact with equipment, e.g. mud valves.

Nitriding - Nitriding - a case-hardening process whereby nitrogen is introduced into the surface of metallic

materials (most commonly ferrous alloys). Typical processes include, but are not limited to, liquid nitriding, gas nitriding, and ion or plasma nitriding.

Nitriding - a type of case hardening in which the steel materials are heated in an atmosphere of ammonia (NH3) for a prolonged period and then cooled slowly. The heating temperature for nitriding ranges from 480° to 550° C. In this process of case-hardening the case is saturated with the nitrogen of ammonia. Besides increasing surface hardness and wear resistance, nitriding provides a very good resistances to corrosion due to atmospheric air, water, steam, etc.

Nitriding - case hardening of steel by holding it at a temperature of about 500° Celsius for approximately two and a half days in an atmosphere of ammonia, with the object of introducing nitrogen into the surface of the metal.

Nitrile Seals - nitride has excellent resistance to mineral oils and is specially formulated to give low temperature flexibility coupled with resistance to most oil well fluids.

Nitrogen (N) - an element which is the colorless, odorless and tasteless gas making up four-fifths of the air we breathe.

Nitrogen Oxides (NOX) - a general term for nitrogen oxide gases, produced by combustion. Nm - Newton meter NO - describes the resting (non-activated) position of a valve. In this case the valve is Normally

Closed. No. 1 Heavy Melt - obsolete steel scrap grade, at least one-quarter inch in thickness and in

sections no larger than five feet by two feet. Much of the metal comes from demolished buildings, truck frames and heavy duty springs. Mini-mills are primary consumers of No. 1 heavy scrap.

Noble Metals - Noble Metals - metals such as gold, silver, platinum, etc. which have a relatively positive

electrode potential, and which do not enter readily into chemical combination with non-metals. They have a high resistance to corrosive attack by acids and other agents, and resist atmospheric oxidation.

Noble Metals - metals, such as gold, silver or platinum that are highly unreactive and resist attack by acids, and so do not easily tarnish on exposure to air, and do not corrode; (opposite of Base Metal).

NOC - National Oil Companies Nodular Cast Iron - see Cast Iron Nodularity - the volumetric proportion of spheroidal or nodular graphite to total graphite in a

ductile iron or a compacted graphite iron matrix. Nodularity, Degree of - the volumetric proportion of spheroidal or nodular graphite to total

graphite in a ductile iron matrix. Nodulizing Alloy - an alloy added to molten iron for the primary purpose of causing the

formation of spheroidal graphite during solidification. No-Go-Gauge - a limit gauge designed not to fit a part being tested; usually employed with a go

gauge to set the acceptable maximum and minimum dimension limits of the part. Noise Sources, Control Valve - control valve noise can be caused by the following: a) turbulent

flow of liquid, b) aerodynamic flow, c) liquid cavitation flow, d) mechanical vibration. Nominal Dimension - nearest fractional equivalent to actual decimal dimension. Nominal Pipe Size (NPS) - a dimensionless number used to indicate sizes of pressure pipe and

valves; used interchangeably with valve size in inches. Nominal Size - Nominal Size - 1) the standard dimension closest to the central value of a toleranced dimension;

2) size used for general identification. Nominal Size - size used for purposes of general identification. The actual size of a part will be

approximately the same as the nominal size but need not be exactly the same. For example, a rod may be referred to as ¼ inch, although the actual dimension on this drawing is 0.2495 inch, and in this case ¼ inch is the nominal size.

Non Blooming - the absence of bloom. Non Destructive Testing -

Non Destructive Testing - a means of testing the quality of materials without breaking or otherwise damaging them. Example of non-destructive includes Dye Penetrant Testing, Magnetic Particle Testing, Ultrasonic Testing and X-Ray Inspection.

Non Destructive Testing - any form of testing which is used to verify the integrity and expected full service life of an item, which does not itself reduce longevity of that item.

Non Destructive Testing - any testing method which does not damage or destroy the sample. Usually, it consists of stimulating the sample with electricity, magnetism, electromagnetic radiation or ultrasound, and measuring the sample's response.

Non Destructive Testing - any testing method which does not involve damaging or destroying the test sample; includes use of x-rays, ultrasonic, radiography, magnetic flux, and so on.

Non Destructive Testing - methods of inspecting materials and products without affecting their subsequent properties and performance.

Non Ferrous Materials - those which do not contain iron as principal constituent e.g., aluminum, copper, zinc etc.

Non Ferrous Metal - Non Ferrous Metal - a metal in which the major constituent is one other than iron. Non Flashing - fluid state that does not change to a vapor phase at any normal operating

condition or temperature. Non Hazardous Area - an area in which an explosive gas mixture is not expected in a quantity

such as to require special precautions for the construction and use of electrical apparatus, cables and accessories.

Non Metallic Materials - plastics have low cost, light weight, good resistance to shock and vibration, self-lubrication, ease of fabrication. However, these have low strength, high thermal expansion, low heat resistance, high creep and deformation under load and embrittlement at low temperature.

Non Pressure Thermit Welding - a thermit welding process carried out by superheated liquid. The heat is generated by the chemical reaction of metal oxide and aluminum.

Non Pressure Welding - a welding operation carried out without external mechanical pressure. Non Return Mechanism - the term for the part or assembly of parts operated by the flow of fluid.Non Return Valve - Non Return Valve - a valve which prevents reversal of flow by means of the non – return

mechanism, the valve being opened by the flow of fluid and closed by the weight of the non – return mechanism when the flow ceases, or by back pressure; also variously called Check Valve, Reflux valve, Retention Valve, Clack valve, Back-Pressure Valve.

Non Return Valve - see Check Valve Non Return Valve - see Stop Check Valve Non Sparking Apparatus - apparatus meeting the requirements of a recognized standard for

industrial equipment, which in normal service does not arc or spark or produce ignition-capable hot surfaces.

Non Transferred Arc Process - a plasma arc welding process in which the arc is formed between the electrode and the water cooled constructing nozzle. The arc is independent of the workpiece. The main advantage of this process is that the arc flame can be moved from one place to another and can be better controlled.

Nonhazardous Area - an area in which explosive gas/air mixtures are not expected to be present so that special precautions for the construction and use of electrical apparatus are not required.

Nonincendive - equipment and wiring which in its normal operating condition is incapable of igniting a specific hazardous atmosphere or hazardous dust layer. Equipment and wiring having exposed blanketed surface temperatures above 80 percent of the ignition temperature in degrees centigrade of the specific hazardous dust layer are NOT classed as nonincendive. The blanketed surface temperature shall be determined at the outside surface of the enclosure beneath the surface of a dust accumulation 0.2 inch or more thickness.

NON-IS - Non Intrinsically Safe Nonreclosing Pressure Relief Device - Nonreclosing Pressure Relief Device - a device for relieving internal pressure which remains

open when actuated and must be replaced or reset before it can actuate again. Nonreclosing Pressure Relief Device - a device which remains open after relieving pressure and

must be reset before it can operate again. Nordel 1070 - an ethylene propylene rubber by E. I. du Pont de Nemours Co. Nordel® - see EPT Normal Operation - intrinsically safe electrical apparatus or associated electrical apparatus is in

normal operation when it complies electrically and mechanically with the requirements of its design specification and is used within the limits specified by the manufacturer.

Normal Operational Conditions - equipment is in normal operational conditions when it conforms electrically and mechanically with its design specifications and is used within the limits specified by the manufacturer. This includes: a) supply voltage, current, and frequency, b) environmental conditions (including process interface), c) all tool removable parts in place, (e.g., covers), d) all operator accessible adjustments at their most unfavorable settings, and e) opening, shorting, or grounding of nonincendive field wiring.

Normalizing - Normalizing - 1) to heat steel in order to refine the crystal structure and to relieve internal stress

and improve strength; 2) heating a ferrous metal to a suitable temperature above the transformation range (austenitizing), holding at temperature for a suitable time, and then cooling in still air or protective atmosphere to a temperature substantially below the transformation range.

Normalizing - a general type of annealing that usually involves air cooling of ferrous metals after first heating to a specific temperature for a designated period of time. It is generally done to soften and increase ductibility but not to as great a degree as full annealing. The process is sometimes carried out on large or thick parts as a preliminary step in a multistage heat-treating procedure.

Normalizing - a heat treatment applied to steel. It involves heating above the critical range, followed by cooling in air, performed to refine the crystal structure and eliminate internal stress.

Normalizing - heating a ferrous alloy to a suitable temperature above the transformation range and then cooling in air to a temperature substantially below the transformation range.

Normalizing - in heat treating ferrous alloys, to heat 50° to 100° F above the upper transformation temperature, then cool in still air.

Normalizing - the process of normalizing is similar to that of annealing except that cooling is done in air instead of cooling inside a furnace. The purpose is to refine the grains or to reduce the size of the crystals and to remove all internal strains caused by cold working. In normalizing, steels are heated to 40° to 50° C above the upper critical temperature, soaked at the temperature for short period of time and then cooled slowly in still open air. Normalized low carbon steels contain ferrite and pearlite. Normalized medium carbon steel contains pearlite and cementite.

Normally Closed - a condition of no flow through a valve or other system when there is no input signal.

Normally Closed - see Air To Open Normally Closed (NC) - Normally Closed (NC) - 1) a switch position where the usual arrangement of contacts permits the

flow of electricity in the circuit; 2) in a solenoid valve, an arrangement in which the disk or plug is seated when the solenoid is deenergized; 3) a field contact that is closed for a normal process condition and open when the process condition is abnormal; 4) a valve with means provided to move to and/or hold in its closed position without actuator energy supply; 5) relay contacts that are closed when the coil is not energized; see also Field Contact.

Normally Closed (NC) - describes a valve that is "fail-safe" to the closed position. This is usually accomplished by a spring built into the valve.

Normally Closed (NC) Valve - a valve with means provided to move to and/or hold in its closed position without actuator energy supply; see Fail Close.

Normally Open (NO) -

Normally Open (NO) - 1) in a solenoid valve, an arrangement in which the disk or plug is seated when the solenoid is energized; 2) a valve with means provided to move to and/or hold wide open position without actuator energy supply.

Normally Open (NO) - a valve or other device which allows fluid flow when there is no input signal. An input action must be applied to close the valve.

Normally Open (NO) - describes a valve that is "fail-safe" to the open position. This is usually accomplished by a spring built into the valve.

Normally Open (NO) - see Air To Close Normally Open (NO) Valve - a valve with means provided to move to and/or hold in its wide open

position without actuator energy supply; see Fail Open. Normally Open Solenoid Valve - a valve in which the inlet port is open when the solenoid coil is

de-energized. NOT - Notational As-Built Not Closed Position - a position that is more than zero percent open. A device that is not

closed may or may not be open. Notch Brittleness - the brittle property of a material causing fracture with small absorption of

energy in an Izod or Charpy test. Notched-Bar Test - subjecting a notched metal test-piece to a sudden blow by a striker which is

performed by a pendulum or falling weight by which the energy of fracture is measured; also called Impact Test or Izod Test.

Nox - Nitrogen Oxides NPS - NPS - Nominal Pipe Size NPS - Nominal Pipe Size (inches) NPS - Nominal Pipe Size in inches. NPT - 1) National Pipe Threads; 2) Nominal Pipe Thread; 3) National Standard Pipe Thread

Taper NPTF - National Pipe Thread - Female NR - Natural Rubber NRM - Not Required for this Material specification NRO - Not Required for this Purchase Order NRS - Non-Rising Stem NS - Nominal Size (metric) NTP - Normal Temperature and Pressure NTS - Not To Scale Nugget - a welding bead Nut - Nut - a small, usually hexagonal, piece of metal with a threaded hole through it, for screwing on

the end of a bolt. Nut - an internally threaded fastener for bolts and screws. Nut - the mating part of screwed members which get rotated to tighten their hold. The heads may

have various shapes, (square, hexagonal, etc.), to fit the wrenches used to rotate them.

O - 1) Oxygen; 2) Original O Ring - O Ring - a flat ring made from synthetic rubber, used as an airtight seal or a seal against high

pressures. O Ring - a gasket in the form of a ring with a circular cross section. O Ring - a toroidal (doughnut shaped) sealing ring made of synthetic rubber or similar material.

The cross section through the torus is usually round or oval, but may be rectangular or some other shape.

O Ring - a toroidal ring of circular cross-section which is made of rubber, neoprene or similar material usually fitting into a carefully machined groove to provide a sealing between two making parts; sometimes called O-Seal.

O Ring - a torus; a circle of material with a round cross section which effects a seal through squeeze and pressure.

O Ring - a type of seal. An O-ring is a round elastomeric ring, ideally suited to be a compressed, static seal between non moving parts. O-rings can be used as a face seal on a valve, and used on rotating shafts inside a valve.

O Ring - an elastomeric or synthetic seal ring of circular cross section. O Ring - an elastomeric sealing ring with an O-shaped (circular) cross section. It may be used as

a secondary seal or as a gasket. O Ring Groove - space into which an O-ring is inserted and retained. O Ring Seal - the combination of a gland and an o-ring providing a fluid-tight closure. (Some

designs may permit momentary or minimum leakage). a) Moving (dynamic) – an o-ring seal in which there is relative motion between some gland parts and the o-ring-oscillating, reciprocating, or rotary motion; b) Non-moving (static) – an o-ring seal in which there is no motion between any part of the gland and the o-ring (distortion from fluid pressure or swell from fluid immersion is excluded).

OBF - Oil Based Fuels Oblique Valve - Oblique Valve - a screw-down stop-valve having a casing or body of spherical shape. The axis of

the stem is oblique to the body ends, which are in line with each other. Oblique Valve - a type of globe valve having an inclined orifice that serves to reduce the

disruption of the flow pattern of the working fluid. Oblique Valve - a valve having generally a spherical body in which the body ends are in line with

each other and in which the axis of the stem is oblique (not at a right angle) to that of the body ends.

Oblique Valve - a valve having generally a spherical body in which the body ends are in line with each other and in which the axis of stem is oblique to that of the body ends.

Obsolescence - decreasing value of functional and physical assets or value of a product or facility from technological changes rather than deterioration.

Obsolescent - Obsolescent - lower in physical or functional value due to changes in technology rather than to

deterioration. Obsolete - Obsolete - no longer satisfactory for the purpose for which obtained, due to improvements or

revised requirements. Obsolete - no longer suitable for the intended use because of changes in technology or

requirements. Occlusion - a) the mechanical process by which vapors, gases, liquids, or solids are entrapped

within the folds of a given substance during working or solidification; b) the materials so trapped.

OCTG - Oil Country Tubular Goods Octoid - pertaining to a gear tooth form used to generate the teeth in bevel gears; the octoid

form closely resembles the involutes form. OD - OD - 1) Outside Diameter; 2) Optical Density OD - the measurement of the Outside Diameter of a circular part. ODC - Over Dimension Cargo

OEM - Original Equipment Manufacturer Off - designating the inoperative state of a device, or one of two possible conditions (the other

being “on”) in a circuit. Off Line - 1) a borehole that has deviated from its intended course; 2) a state in which

equipment or a subsystem is in standby, maintenance, or mode of operation other than on-line.

Off Register - misalignment of mold halves causing out-of-round o-ring cross section. Off the Shelf - available for immediate shipment. Offset - Offset - the amount by which something is out of line. Offset - the steady-state difference between the desired control point and that actually obtained in

a process control system. The value of strain between the initial linear portion of the stress-strain curve and a parallel line that intersects the stress-strain curve of an arbitrary value of strain; used as an index of yield stress; a value of 0.2% is common.

Offset Yield Strength - that stress at which the strain surpasses by a specific amount (called the offset) an extension of the initial proportional portion of the stress-strain curve; usually expressed in pounds per square inch.

Offshore Installation - an installation located in open saliferous water, at a location remote from the nearest land.

OFW - Oxy Fuel Gas Welding Ohm - the metric unit for electrical resistance; it is the resistance (or impedance) of a conductor

such that an electrical potential of one volt exists across the ends of the conductor when it carries a current of one ampere.

OI - Operating Instructions Oil Bath - oil, in which a piece of apparatus is submerged. Oil Country Tubular Goods (OCTG) - a label applied to the pipe products used by petroleum

exploration customers. Includes casing, drill pipe and oil well tubing, which, depending on their use, may be formed through welded or seamless processes.

Oil Dilution Valve - a valve used to mix gasoline with engine oil to permit easier starting of the gasoline engine is cold weather.

Oil Fired Furnaces - these are normally used for castings of non-ferrous materials. Oil Groove - one of the grooves in a bearing which distribute and collect lubricating oil. Oil Hardening - Oil Hardening - the hardening of cutting tools of high carbon content by heating and then

quenching in oil, which cools it less suddenly than in water. Oil Hardening - the hardening of steels of medium and high carbon content by heating to the

austenitic condition, followed by quenching into a bath of oil, resulting in a cooling less sudden than is effected by water, and consequently a reduced risk of cracking.

Oil Hardening Steel - any alloy steel which will harden when cooled in oil instead of in water. The limiting diameter or cross section which will harden fully in this manner must also be stated, since this depends on the alloy composition and transformation characteristics of the steel.

Oil Hole - a small hole for injecting oil for a bearing. Oil Lift - hydrostatic lubrication of a journal bearing by using oil at high pressure in the area

between the bottom of the journal and the bearing itself so that the shaft is raised and supported by an oil film whether it is rotating or not.

Oil Quench - the immersion of hot metal in oil, for purpose of tempering. Oil Ring - a ring on a journal, dipping into an oil bath for lubrication. Oil Ring Lubricated Bearing - a bearing in which a ring, encircling the journal and rotated by it,

raises the oil to lubricate the bearing from a reservoir into which the ring dips. Oil Swell - the change in volume of a rubber article due to absorption of oil or other fluid. Oiliness - the effect of a lubricant to reduce friction between two solid surfaces in contact; the

effect is more than can be accounted for by viscosity alone. Oiliness Bearing - a self-lubricating bearing containing solid or liquid lubricants in its material. OIM - Offshore Installation Manager Olefins - a group of chemicals characterized by their straight or branched structure. Includes

ethylene, the largest volume petrochemical, and butadiene and propylene. On - designating the operating state of a device or one of two possible conditions (the other

being “off”) in a circuit. On Off Control - On Off Control - a simple control system in which the device being controlled is either full on or

full off, with no intermediate operating positions; also known as On-Off System. On Off Control - a system of control in which the final control element has only two positions from

which to choose; also known as Two-Position Control. On Off Service - when the valve is being used to start or stop flow by being cycled to the full

open or full closed position. On Off System - see On-Off Control On Stream - of a plant or process-operations unit, being in operation. On Stream Factor - the ratio of the number of operating days to the number of calendar days per

year. On Stream Time - in plant or process operations, the actual time that a unit is operating and

producing product. One Barrel - 42 gallons One Piece Body Ball Valve - a ball valve which utilizes a one-piece body incorporating body

ends. There are five main variants of the construction: a) axial entry, b) top entry, c) bottom entry, d) side entry, e) sealed.

One Piece Element Clamp - a one piece element clamp or pinch valve is a valve consisting of a one piece flexible element or liner installed in a body with the element or liner extending over the flange faces and acting as gaskets between the valve and connecting piping; compare with Two Piece Element Clamp; see Pinch Valve.

One Piece Gland - One Piece Gland - a bolted design in which the gland is integral with the gland flange. One Piece Gland - a bolted design in which the gland of a valve is integral with the gland flange. One-Sided Acceptance Sampling Test - a test against a single specification only, in which

permissible values in one direction are not limited. OP - Operator OPEC - Organization of Petroleum Exporting Countries Open Circuit Voltage - in welding, voltage across the terminals of a power source when no

current is flowing in the circuit. Open Hearth Furnace - a broad, shallow hearth to refine pig iron and scrap into steel. Heat is

supplied from a large, luminous flame over the surface, and the refining takes seven to nine hours. Open Hearths, at one time the most abundant steelmaking furnaces among integrated companies, have been replaced by the basic oxygen furnace.

Operating Temperature - the nominal or average temperature of a fluid in a system. Operation - a job, usually performed in one location, and consisting of one or more work

elements. Operational Maintenance - the cleaning, servicing, preservation, lubrication, inspection, and

adjustment of equipment; it includes the minor replacement of parts not requiring high technical skill, internal alignment, or special locative training.

Operator - Operator - a mechanical device used to reduce the force required to operate a valve manually;

also called an Actuator. Operator - a person whose duties include the operation, adjustment, and maintenance of a piece

of equipment. Operator Training - the process to prepare the employee to make his expected contribution to

his employer, usually involving the teaching of specialized skills. Optimum Cure - Optimum Cure - the degree of vulcanization at which maximum desired property is reached. Optimum Cure - the state of vulcanization at which the most desirable combination of properties

is attained. OPU - Operating Units Ordinary Lift Safety Valve - a valve in which the valve head lifts automatically at least D/24,

where D = bore of valve seat. These valves may be a) direct spring loaded, b)

direct weight loaded, c) weight and lever loaded, d) lever and spring loaded, e) ramsbottom valve.

Ordinary Safety Valve Direct Spring Loaded - pop safety valve ORF - Onshore Receiving Facility ORFS - Orifice Flange Set Organization Chart - graphic representation of the interrelationships within an organization,

depicting lines of authority and responsibility and provisions for control. ORIC - Pressure Instrument connection on orifice flanges Orifice - an opening inside the valve that can be either open or closed to control the passage of

media. Orifice Meter - an instrument that measures fluid flow by recording differential pressure across a

restriction placed in the flow stream and the static or actual pressure acting on the system.

Orifice Plate - a disk, with a hole, placed in a pipeline to measure flow. Orthogonal - a term meaning at right angles. Orthophosphoric Acid - see Phosphoric Acid Orthotropic - the description applied to the elastic properties of material such as timber, which

has considerable variations of strength in two more directions at right angles to one another.

OS&Y - Outside Screw and Yoke OSFAM - Offshore Structure Fabricators Association of Malaysia Osmium (Os) - a hard, dense, silvery-white metallic element, used in alloys and as a catalyst. OSS - Optical Sensing System Ounce - a unit of mass in avoirdupois measure equal to 1 over 16 pound or to approximately

0.0283495 kilogram. Abbreviated oz. Ouncedal - a unit of force equal to the force which will impart an acceleration of 1 foot per

second per second to a mass of 1 ounce; equal to 0.0086409346485 Newton. Outgassing - a vacuum phenomenon in which a substance spontaneously releases volatile

constituents in the form of vapors or gases. In rubber compounds, these constituents may include water vapor, plasticizers, air, inhibitors, etc.

Outlet Port - a tubular opening through a chamber wall, usually flanged, permitting access for pumping or the extraction of components from the chamber.

Output Power - the useful mechanical power measured at the shaft-end of a motor. Output Shaft - the shaft that transfers motion from the prime mover to the driven machine. Outside Diameter - the outer diameter of a pipe, including the wall thickness; usually measured

with calipers; abbreviated OD. Outside Screw - Outside Screw - in which the actuating thread of the stem is exterior to the bonnet. This may

take three forms: a) outside screw, stem rising with hand wheel. Where the hand wheel is attached directly to the stem and rises with it when the valve is opened, b) outside screw, stem rising through handwheel. Where the handwheel is attached to a yoke sleeve or bridge sleeve which revolves in the yoke or bridge and through which the stem rises when the valve is opened, c) outside screw, non-rising spindle, rising stem. Where the handwheel is attached to a non-rising spindle and the stem rises when the valve is opened.

Outside Screw - where the actuating thread of the valve stem is exterior to the bonnet; comparewith Inside Screw

Outside Screw and Yoke (OS&Y) - Outside Screw and Yoke (OS&Y) - a stem design in which the threaded portion of the stem is

outside the pressure boundary of the valve. It must be used with a bonnet having a yoke, which holds a yoke nut to allow valve operation.

Outside Screw and Yoke (OS&Y) - a valve design in which the stem threads are above the packing gland or outside the valve body and there is a yoke to support the top or outer end of the stem.

OVA - Organic Vapor Analyzer Oven - a heated enclosure for baking, heating, or drying. Over Center Locking - a gate valve mechanical feature which ensures that the valve will remain

closed in the event of loss of either air pressure or electrical power. Over Cure - Over Cure - a condition resulting from vulcanizing longer than necessary to achieve full

development of physical strength; causes softness or brittleness and impaired age-resisting quality of the material.

Over Cure - a degree of cure greater than the optimum causing some desirable properties to be degraded.

Overhaul - Overhaul - a maintenance procedure for machinery involving disassembly, the inspecting,

refinishing, adjusting, and replacing of parts, and reassembly and testing. Overhaul - to thoroughly examine and repair as necessary. Overhead Position - a welding operation carried out from the underside of the joint. Overlay - a covering; something that is laid over something else. Overpressure - a pressure increase over the set pressure of a pressure relief valve. It is usually

expressed as a percentage of set pressure. Override - to cancel the influence of an automatic control by means of a manual control. Overshoot - the exceeding or surpassing of a target value as operating conditions change. Overstrain - the result of stressing an elastic material beyond its yield point. Overtravel Stop - on a butterfly valve, a lug that prevents the disc from rotating too far. OWG - Oil, Water & Gas; see CWP Oxidation - Oxidation - the addition of oxygen to a substance. The oxygen of air oxidizes silicon of iron ore. Oxidation - the process by which oxygen unites with some other substance, causing rust or

corrosion. Oxidation - the reaction of oxygen on a compound, usually detected by a change in the

appearance or fell of the surface, or by a change in physical properties, or both. Oxidation - this take places when any substance reacts chemically with oxygen. The rate at

which oxidation takes place depends on several factors, the most important being temperature. Oxidation may be rapid, as in the case of uncontrolled combustion or burning. Flame cutting relies on rapid combustion. The oxidation or rusting of steel on the other hand is a relatively slow process. The rapid reaction of oxygen with another substance can be dangerous and damaging, or it may be extremely useful.

Oxide - Oxide - a compound of oxygen with another element or group. Oxide - chemical compound of an element, usually metal, with oxygen. Oxidize - 1) to become rusty; 2) a chemical reaction with oxygen. Oxidizing Flame - a gas welding flame having an oxidizing effect. Oxy Acetylene Cutting - Oxy Acetylene Cutting - severing metal by means of chemical reaction of oxygen with the base

metal at elevated temperatures. The heat necessary for high temperature is obtained from gas flames by combustion of acetylene.

Oxy Acetylene Cutting - the flame cutting of ferrous metals in which the preheating of the metal is accomplished with a flame produced by an oxyacetylene torch; also known as Acetylene Cutting.

Oxy Acetylene Welding - Oxy Acetylene Welding - various gas combinations like oxy-hydrogen, oxy-benzene, oxy-propane

and oxy-acetylene are used for welding of metals. The selection of combustible gas depends on many factors, such as a) temperature of the flame required, b) cost of gases, c) material to be welded. Oxy-acetylene flame is most commonly used as it produces a very high temperature of 3500° C at its hottest portion and is most suitable for welding. However, an oxy-hydrogen mixture can be used for welding metals of low melting point like magnesium, aluminum, lead, tin, zinc and their alloys. In gas welding, care is needed that the gases used are highly pure, so that the high temperature of the flame can be obtained. Even small amounts of impurities like nitrogen, argon and water vapor have a marked effect on the flame temperatures. Gas welding can be used for preheating the area of the section being welded. This is not possible in arc welding. The flame temperature is also

lower than the arc. The flame can be adjusted to make it neutral, reducing or oxidizing. An oxidizing flame is used for welding brasses and bronzes, reducing flame for nickel alloys and hard-facing materials and neutral flame for welding low-carbon steels.

Oxy Acetylene Welding - a process of joining metals by heating with a gas flame. The heat is obtained by the combustion of acetylene and oxygen.

Oxy Acetylene Welding - the welding of steel is performed without any flux, while fluxes are necessary for welding particularly all other metals. Oxygen cutting is used for wrought iron, steel and cast iron.

Oxy Arc Cutting - severing metal carried out by chemical reaction between the metal and oxygen. The heat necessary is supplied by the arc between the electrode and the base metal.

Oxy Hydrogen Cutting - severing metal, effected by means of the chemical reaction of oxygen with the base metal at an elevated temperature. The heat required for carrying out the process is obtained by the combustion of hydrogen and oxygen.

Oxy Hydrogen Welding - a welding process carried out by the heat produced by the combustion of hydrogen and oxygen.

Oxyacetylene Flame - flame which is obtained from the combustion of oxygen and acetylene, fed from separate steel cylinders. It is used for cutting metals.

Oxyacetylene Torch - a torch that mixes acetylene and oxygen to produce a hot flame for the welding or cutting of metal; also known as Acetylene Torch.

Oxygen Bomb - a chamber capable of holding oxygen at an elevated pressure which can be heated to an elevated temperature. Used for an accelerated aging test.

Oxygen Bomb Aging - a means of accelerating the change in physical properties of rubber compounds by exposing them to the action of oxygen at an elevated temperature and pressure.

Oxygen Cutting - Oxygen Cutting - any of several types of cutting processes in which metal is removed with or

without a flux by a chemical reaction of the base metal with oxygen at high temperatures.

Oxygen Cutting - severing metal at elevated temperature, effected by means of the chemical reaction of oxygen with the base metal.

Oxygen Lance - a length of cutting torch used in conveying oxygen to the point of cutting. Oxygen Service - solenoid valves specified for oxygen service require special cleaning, handling

and packaging and are generally furnished free of any oils or contaminants. Ozone Resistance - ability to withstand the deteriorating effect of ozone (which generally causes

cracking).

P - 1) Phosphorus; 2) Preliminary; 3) liquid hydrocarbon, non corrosive; 4) hydrocarbon, liquid, sweet

P&ID - Piping and Instrument Diagram P1 - used to designate Inlet Pressure P2 - used to designate Outlet Pressure PA - 1) Price Agreement; 2) Public Address; 3) Pascal Pack Hardening - a form of case-hardening. It uses a solid carburizing medium which is packed

around the low carbon steel objects and the whole object is then heated for such a time and such a temperature so as to allow carbon to diffuse into the surface to the desired depth.

Packing - Packing - 1) a sealing system consisting of deformable material of one or more mating and

deformable elements contained in a packing box which may have an adjustable compression means to obtain or maintain an effective pressure seal; 2) a method of sealing a mechanical joint in a fluid system. A material such as oakum or treated asbestos is compressed into the sealing area (known as a "packing box" or "stuffing box") by a threaded seal ring.

Packing - a class of seal that is used to provide a seal between two parts of a unit which move in relation to each other.

Packing - a deformable sealing material inserted into a valve stuffing box which when compressed by the gland provides a tight seal about the stem.

Packing - a device used to seal a valve or other components. It consists of a deformable material or deformable mating element.

Packing - a flexible device used to retain fluids under pressure or seal out foreign matter; it normally refers to a dynamic seal.

Packing - a sealing system that normally consists of a deformable material such as TFE, graphite, asbestos, etc. It is usually in the form of solid or split rings contained in a packing box that are compressed so as to provide an effective pressure seal.

Packing - any variety of materials such as carbon, cotton, hemp, or synthetic materials fit into a seal chamber. The packing material is used to make sealing contact with the shaft by adjustment of a gland which compresses the material against face and bore of the seal chamber.

Packing - deformable non-metallic material formed into rings, used to form a seal between the shell and the valve stem or shaft.

Packing - material which is inserted in the stuffing box of a pump to provide water tightness. Packing - see Stuffing Packing Box - Packing Box - the chamber located in the bonnet which surrounds the stem and contains the

packing and other stem-sealing components. Packing Box - the chamber, in the bonnet, surrounding the stem and containing packing and

other stem sealing parts. Packing Box, Purged - a packing arrangement consisting of a lantern ring inside the packing

rings to permit introduction of a purge fluid to continually flush the space between the stem and body.

Packing Chamber - see Stuffing Box Packing Follower - Packing Follower - a part that transfers a mechanical load to the packing from the packing flange

or nut. Packing Follower - a ring shaped device that is installed on top of the packing to hold it in place.

It may also be used to adjust the pressure on the packing. Packing Gland - a separate part from the gland flange, used to prevent uneven load distribution

against the packing. Packing Nut - Packing Nut - (usually associated only with small relatively low-pressure valves) a nut which itself

contains and compresses the packing in cases where a gland and stuffing box are not used.

Packing Nut - a nut similar to a gland nut, but which itself contains and compresses the packing

in cases where a gland and stuffing box are not used; usually associated only with small, relatively low-pressure valves.

Packline - oil flow that completely fills a pipeline. Pad - 1) a layer of material used as a cushion for protection; 2) a projection of excess metal on a

casting forging, or welded part. Paint - in the general sense, includes primers, enamels, varnishes, emulsions, catalyzed

coatings, bituminous coatings, and other organic coatings. Inorganic coatings which are applied in the same manner as paints are included in this definition.

Painting - used to protect large areas of steel, particularly on structures where other methods would be impractical: one could hardly paint dip a super tanker. The painting of steel not only protects against rusting but also enhances the appearance. Although painting appears to be a simple process, unless carried out correctly it will fail to give prolonged protection.

Painting System - a term intended to include, with equal emphasis, not only the well accepted components of a system such as surface preparation and paint materials, but also the application, inspection, and safety functions.

Pallet - a tray or platform used in conjunction with a fork lift for lifting and moving materials. PAMI - Positive Alloy Material Identification Pan Bolt - a bolt with a head resembling an upside-down pan. Pane - one of the sides on a nut or on the head of a bolt. PAPA - Prepare to Abandon Platform Alarm Parallel Gate Valve - double disc (gate) valve. Parallel Slide Valve - Parallel Slide Valve - a gate valve having one or two discs sliding between parallel body seats

without a spreading mechanism as in a double disc (gate) valve. The pressure of the fluid forcing the downstream disc face against its mating body seat obtains the effective closure.

Parallel Slide Valve - a gate valve in which the gate disc or discs are parallel to the seat or seats, and closure is dependent on the mass of fluid holding the disc against the seat. This type of valve is distinguishable by its stem, which runs between parallel guides.

Parallel Slide Valve - a valve in which the gate consists of one or two discs, without spreading mechanism, which slide between parallel body seats, effective closure being obtained by the pressure of the fluid forcing the downstream disc face against its mating body seat.

Parent Metal - see Base Metal Particulate Matter (PM) - finely divided liquid and solid material in gaseous emissions that result

from combustion or refining. Parting Line - in casting, the dividing line between the two molding flasks that make up the sand

mold. It is also the dividing line between the two halves of the pattern. PAS - Platform Automated System Pascal - Pascal - a unit of pressure equal to the pressure resulting form a force of 1 Newton acting

uniformly over an area of 1 square meter; symbolized Pa. Pascal - a unit of pressure, equal to a force of one Newton per square meter. Pascal - a unit of pressure, which equals 1 N/m2; abbreviated Pa. Pascal - metric unit for pressure or stress Pascal’s Law - Pascal’s Law - a pressure applied to a confined fluid at rest is transmitted with equal intensity

throughout the fluid. Pascal’s Law - in hydrostatics, a law which states that in a perfect fluid the pressure exerted on it

anywhere gets transmitted undiminished in all directions. Pascal’s Law - it states that when a pressure is applied to a fluid enclosed in a container it is

transmitted to every portion of the fluid and walls of the container. Pass - in metal rolling, the passage in one direction of metal deformed between rolls. Passivate - Passivate - a process for the treatment of stainless steel in which the material is subjected to the

action of an oxidizing solution which augments and strengthens the normal

protective oxide film providing added resistance to corrosive attack. Passivate - to treat a metal in order to form a protective coating on its surface and reduce its

chemical activity. Passivation of Metal - the chemical treatment of a metal to improve its resistance to corrosion. Passive - 1) resistant to corrosion; 2) unreactive because of a thin inert surface layer of oxide. Passive Metal - a metal which has a natural or artificially produced surface film that makes it

resistant to electrochemical corrosion. Patch Bolt - a bolt with a countersunk head having a square knob that twists off when the bolt is

screwed in tightly; used to repair boilers and steel ship hulls. Path Line - it is the path followed by a fluid particle in motion. Pattern - Pattern - a duplicate made of wood or metal of a part to be cast. It is used to form the mold into

which the molten metal is poured. Pattern - in casting, the replica of the final object to be made with some modifications. The cavity

in the mold is made with the help of a pattern. Pattern - pattern is a model of an object to form a cavity of a sand mould for casting. Materials

used for pattern making are: wood, metals (brass, aluminum, etc.), plaster, plastic compounds, wax, etc.

PAW - see Plasma Arc Welding. Pb - Lead PBE - Plain Both Ends PC - 1) Piece; 2) liquid hydrocarbon, Corrosive, onshore or offshore PCN - Personnel Certification in Non-destructive Testing (British National Scheme) PCTFE - Poly-Choro-Tri-Fluoro-Ethylene PDA - Petroleum Development Act PE - Plain End Pearlite - Pearlite - a finely laminated mixture of ferrite and cementite present in cast iron and steel; also

spelled Perlite. Pearlite - a mixture of iron and cementite, which crystallizes during the slow cooling of high-

temperature steel and cast iron. Pearlite - the eutectoid mixture of ferrite and cementite. It consists of alternate layers of ferrite

and cementite in its grains. It is very strong, tough and possesses about 0.8% carbon. It is stable below the critical temperatures. Its hardness is about 180 VPN.

Pectee - Ethylene-Chlorotrifluoroethylene. a Halar brand, for some external valve components; it is also a valve body material for high temperature / high purity applications.

PEEK - PEEK - (polyether-etherketone) a non-metallic material used as valve trim. It is a thermoplastic

suited for high temperatures and up to 450 psi. It is used for ball and butterfly valve seats.

PEEK - Polyether-etherketone Peel Test - a test to determine the adhesive strength of bonded strips of metals by peeling or

pulling the metal strips back and recording the adherence values. PEFS - Process Engineering Flow Scheme Penalty Clause - a clause sometimes put into a construction contract indicating the amount to be

paid as a penalty for non-fulfillment of a provision of the contract. It usually refers to a penalty for each day’s delay beyond a specified completion date.

Penetration - in welding, the distance from the original surfaces of the base metal to that point at which fusion ceases; also know as Depth of Fusion.

Peninsular Gas Utilization (PGU) - in Malaysia, an infrastructure development to process and transmit natural gas fed from the fields offshore Terengganu to end-users in the power, industrial and commercial sectors.

Penstock - a valve or sluice gate for regulating water or sewage flow. Penstock Valve - Penstock Valve - a type of simple gate valve, used to contain fluids in open channels. Often

found in waste water treatment plants.

Penstock Valve - a type of simple gate valve, used to contain fluids in open channels. Often found in waste water treatment plants.

Penstock Valve - a vertically sliding gate usually in an open fluid channel, which seals against abutments on the end walls of the downstream channel.

Percussion Welding - Percussion Welding - a resistance welding process in which coalescence is produced over the

entire area of abutting surfaces, by the heat obtained by the arc from stored electrical energy.

Percussion Welding - a resistance welding process in which coalescence is produced from the heat of the arc by a rapid discharge of stored electrical energy followed by impact to complete the weld. Since electrostatic capacitors are used in this process, it is also known as electrostatic stored energy system or process of welding. It differs from other welding processes, as in those processes a transformer is used, while in this system discharge from a condenser is applied directly to the weld. The workpieces to be welded are cleaned from grease, oil, dust, or rust. The workpieces are then clamped into machine clamps or fixtures. The ends of the two pieces are brought near to each other by application of light force. An arc between the workpieces is struck. Then the welding force is applied. It extinguishes the arc and holds the parts together while the weld cools. The welding force is then released and the workpieces are unclamped. This process is suitable for welding copper and its alloys, aluminum alloys, nickel alloys, low carbon steels, medium carbon steels, stainless steels and high carbon steels. This process is advantageous as there is complete absence of flash or upset. Heat treated and cold drawn metals can also be welded. This process is limited to weld joints only.

Percussion Welding - a welding procedure in which heat is produced simultaneously over the entire area of abutting surfaces from an arc produced by a rapid discharge of stored electric energy, followed immediately by the application of pressure.

Perfect Lubrication - a complete, unbroken film of liquid formed over each of two metal surfaces moving relatively to one another with no contact.

Periphery - the outside surface, especially that of a rounded object or body. Perlite - see Pearlite Permafrost - any rock or soil material that has remained below 32½° F continuously for two or

more years. Permanent Gas - a gas at a pressure and temperature far from its liquid state. Permanent Pressure Drop - the unrecoverable reduction in pressure that occurs when a fluid

passes through a nozzle, orifice or other throttling device. Permanent Set - Permanent Set - 1) the extension which is remaining after removal of a load from a test piece

when the elastic limit has been exceeded; 2) the permanent deflection of any structure after having been subjected to a load.

Permanent Set - an extension which remains in a test piece after the load has been removed, the elastic limit of the material having been exceeded.

Permanent Set - permanent plastic deformation of a structure or a test piece after removal of the applied load; also known as Set.

Permanent Set - the deformation remaining after a specimen has been stresses in tension for a definite period.

Permeability - Permeability - in casting, metal is poured in the mold at high temperatures. Heat from casting

causes evolution of steam and hot gases. As such, the mold must be permeable, i.e., porous so that the gases can escape easily through it.

Permeability - in high vacuum devices, the degree of vacuum that can be maintained depends, in part, upon the quantity of gas passing through (permeating) the wall or gasket from outside the chamber. Materials used for gaskets and chamber walls should be of low permeability.

Permeability - the rate at which a liquid or gas under pressure passes through a solid material by diffusion and solution. In rubber terminology, it is the rate of gas flow expressed in atmospheric cubic centimeters per second through an elastomeric material one centimeter square and one centimeter thick (atm cc/cm2/cm/sec).

Perpendicular - vertical; at a right angle to something PET - Polyethylene Terephthalate. Used on certain housings. (PETRA is a brand name of this

material). Peter Out - to fail gradually in size, quantity, or quality; for example, a mine may be said to have

petered out. PETRA - see PET Petrochemicals - chemicals derived from petroleum :.i.e. feedstock for the manufacture of

plastics and synthetic rubber etc. petrochemicals include benzene, toluene, xylem, styrene, and methanol.

Petroleum - means ‘Stone Oil’ from the Latin petroleum, an inflammable liquid varying in color (yellow-black), consisting mainly of hydrocarbons. Petroleum is found in sedimentary strata of the Earth’s crust.

Petroleum Engineering - the application of almost all types of engineering to the drilling for and production of oil, gas, and liquefiable hydrocarbons.

Petroleum Processing - the recovery and processing of various usable fractions from the complex crude oils; usable fractions include gasoline, kerosene, diesel oil, fuel oil, and asphalt; also known as Petroleum Refining.

PFA - Perfluoroalkoxy (a thermoplastic) PFD - Process Flow Diagram PFP - Passive Fire Protection PFS - Process Flow Scheme PGU - Peninsular Gas Utilization PH - the logarithm to the base ten of the reciprocal of the concentration of hydrogen ions in an

aqueous solution. Phase - the type of state of a system, such as solid, liquid, or gas. Phase Structure - Most metallic materials in general use are alloys since this allows their

properties to be manipulated for the most appropriate performance in use. Although alloys are mixtures of identifiable individual metals, their combination can precipitate quite complex intermetallic compounds. In a solution of metals, after cooling and solidification, it may be possible to identify the original pure element constituents, or there may be new combinations with two metals yielding a new solid solution, or one identifiable metal may be suspended in a new solution. All of these variants are individually identifiable to a metallurgist, and they are called Phases. The formation of different but identifiable phases is controlled by the temperature the metals are heated to and their rate of cooling as well as the relative proportions of the original constituents used in the mixture. Atoms diffuse through metals at different rates at different temperatures and this rate of movement is arrested when the cooling process starts. Consequently, the final Phase Structure is determined by the rate of cooling. This is why subsequent heat treatments to metals have to be carefully controlled. Phase structures can be altered and this will affect the strength and other properties of the metal. This explains why welding is such a critical process and has to follow precise standards.

Philips Screw - a screw having in its head a recess in the shape of a cross; it is inserted or removed with a Philips screwdriver that automatically centers itself in the screw.

Phosphating - a method for applying a thin layer of phosphate on a metal surface. Phosphor Bronze - a hard copper-tin alloy, deoxidized with phosphorus, and sometimes

containing lead to enhance its machinability. Phosphoric Acid - a transparent, crystalline, water-soluble compound used in rust removers and

for forming a corrosion resistant layer on iron and steel; also called Orthophosphoric acid.

Phosphorus - Phosphorus - in appreciable amounts, it increases strength and hardness in steel, but at the

sacrifice of ductility and impact toughness, particularly in higher carbon steels that are quenched and tempered. Consequently. for most applications phosphorus is maintained below a specified maximum.

Phosphorus - phosphorus has a powerful tendency to segregate. Hence, steels with an average phosphorus content of 0.05% have a few areas that contain 0.1%, which then becomes dangerous. The phosphorus content should be kept at 0.02 to 0.05%.

Phosphorus forms Fe3P which dissolves in iron up to 1.7%, but in the presence of 3.5% carbon its solubility is reduced to 0.3% and the excess forms the brittle eutectic found in cast iron.

Phosphorus - up to 0.15% (by weight) can harden steels, to aid accurate machining. Physical Properties - such as shape, size, color, specific gravity, melting point, atomic structure

etc. PIC - Project Inspection Coordinator Pickling - Pickling - a process of removing a coating of scale, oxide, tarnish, etc. from metal objects, in

order to obtain a chemically clean surface. It is usually accomplished by immersing the metal in an acid bath. Acid pickling is a more convenient method of scale removal in many cases than mechanical cleaning and sand blasting.

Pickling - preferential removal of oxide scale from the surface of metal by immersion in a strong alkaline or inhibited acid solution.

Pickling - the process of chemically removing scale or oxide from metal objects to get a chemically clean surface prior to galvanizing or painting. This is usually done by immersion in an acid bath.

Pickling - the removal of scale, grease, or salt water deposits by dipping in a suitable dilute acid circulating bath. It is done before bounding metals with high-grade adhesive.

Pieze - a unit of pressure equal to 1 sthene per square meter, or to 1000 Pascal; abbreviated pz.Piezometer - an instrument for measuring fluid pressure, such as a gauge attached to a pipe

containing a gas or liquid. Pig - Pig - 1) an in line scraper for removing scale and deposits from the inside surface of a pipeline; a

holder containing brushes, blades, cutters, swabs, or a combination is forced through the pipe by fluid pressure; 2) a crude metal casting, usually of primary refined metal intended for remelting to make alloys.

Pig - a device which fits snugly inside an oil or gas pipeline, and is sent through it to clean or test the inside, or to act as a barrier.

Pig - a handleable mass of metal (e.g. cast iron, copper or lead), cast in a simple shape for transportation or storage, and subsequently remelted for purification, alloying, casting into final shapes, or into ingots for rolling.

Pig - an in-line scraper (brush, blade cutter, or swab) forced through pipelines by fluid pressure; used to remove scale, sand, water, and other foreign matter from the interior surfaces of the pipe.

Pig Iron - Pig Iron - a semi-refined iron with approximately 4% (by weight) of carbon, and also containing

unwanted elements such as silicon, manganese, sulphur and phosphorus. Pig iron needs to be further refined to reduce the carbon content and the other undesirable elements.

Pig Iron - crude iron produced by reducing iron ore in a blast furnace and casting it into pigs for subsequent use in making steel, cast iron or wrought iron. Principal impurities are carbon from 2.5 to 5%, and varying amounts of silicon, manganese, sulphur and phosphorus.

Pig Iron - it is manufactured by smelting iron ore in a blast furnace along with coke, limestone and hot air. Iron ore is a mineral substance. It contains iron oxide )Fe2O3) along with silicon, manganese, sulphur, phosphorus as impurities. Iron ore used in India for the extraction of iron contains at least 60% iron.

Pig Iron - the high carbon iron product obtained by the reduction of iron ores, typically in a blast furnace or an electric furnace, and cast into uniform shapes having physical and chemical characteristics suitable for end as foundry melting stock.

Pig Iron - the name for the melted iron produced in a blast furnace, containing a large quantity of carbon (above 1.5%). Named long ago when molten iron was poured through a trench in the ground to flow into shallow earthen holes, the arrangement looked like newborn pigs suckling. The central channel became known as the "sow," and the molds were "pigs."

Pigment - a solid coloring agent in paint. Pillar / Bonnet Connection - (obsolete term) the bosses or flange on the bonnet to which the

pillars are secured. Pillar Nuts - nuts used to secure the pillars to a valve bridge or to the bonnet. Pillars - Pillars - (obsolete term) distance pieces connecting the bridge to the cover; also formerly called

Columns. Pillars - distance pieces connecting the bridge to a valve bonnet. Pillars - the lower half of a journal bearing. Pillars Nuts - (obsolete term) nuts used to secure the pillars to the bridge or to the bonnet. Pilot Hole - a small hole drilled ahead of a larger borehole. Pilot Tube - an instrument that measures the stagnation pressure of a flowing fluid, consisting of

an open tube pointing into the fluid and connected to a pressure-indicating device; also known as Impact Tube.

Pilot Valve - Pilot Valve - a device acting between the source pressure and the actuator that directs (controls)

flow. Pilot Valve - a small valve requiring little power which is used to operate a larger valve. Pilot Valve - a valve used to operate another valve or control. PIM - Pre-Inspection Meeting Pin - a cylindrical fastener made of wood, metal, or other material used to join two members or

parts with freedom of angular movement at the joint. Pin Joint - a joint made with a pin hinge which has a removable pin. Pinch Point - on a ball valve, the area of the seat insert that experiences an increased velocity

when the valve is seated closed and unseated open. This is where the seat seal experiences the most wear.

Pinch Valve - Pinch Valve - a valve consisting of a flexible elastomeric tubular member connected to two rigid

flow path ends in which modulation and/or shut off of flow is accomplished by squeezing the flexible member into eventual tight sealing contact.

Pinch Valve - a valve consisting of a flexible elastomeric tubular member connected to two rigid flow path ends in which modulation and/or shut off of flow is accomplished by squeezing the flexible member into eventual tight sealing contact. The flexible member may or may not be reinforced. The flexible member may or may not be surrounded by a pressure retaining boundary consisting of a metal housing with stem packing box. Squeezing of the flexible member may be accomplished by: a) single stem and leverage acting from both sides so that the total collapse and sealing occurs along the horizontal center line of the flexible member; b) double stem action involving two separate actuator assemblies diametrically opposed, or c) a separate source of fluid pressure applied to an annulus surrounding the flexible member. A Clamp Valve is a pinch valve but with clamps and shaped inserts used to provide stress relief in the creased area of the tubular member; see One Piece Element Clamp, Two Piece Element Clamp.

Pinch Valve - a valve in which a flexible hose is pinched between one or two moving external elements to stop the flow. This valve is often used in slurry and mining applications, as its operation is not affected by solid matter in the medium. It is also used with certain gases, as the absence of possible leak paths to the atmosphere ensures good emission control.

Pinch Valve - a valve in which a flexible hose is pinched between one or two moving external elements to stop the flow. This valve is often used in slurry and mining applications, as its operation is not affected by solid matter in the medium.

Pinch Valve - a valve with a flexible flow tube, usually rubber, which is flattened to close the tube and stop the flow.

Pinch Valve - particularly suited for applications of slurries or liquids with large amounts of suspended solids. It seals by means of one or more flexible elements, such as a rubber tube, that can be pinched to shut off flow.

Pinholes - Pinholes - a fault in a casting or coating resulting from small blisters that have burst or from small

voids that formed during plating.

Pinholes - numerous small gas holes at the surface or just below the surface of castings, generally occurring in the thicker parts of the casting as a reduction in the solubility of gases in the metal as the metal cools.

Pinholes - numerous very small holes revealed on a casting surface after shot blasting. They are caused due to a) high moisture content, b) faulty metal, c) dissolved gases in metal, and d) sand containing gas-producing ingredients.

Pinion - Pinion - 1) a small wheel in gear with a much larger one; 2) a small gear wheel meshing with a

rack. Pinion - a small, toothed gear that engages with a larger wheel or rack. Pinion - the smaller of a pair of gear wheels or the smallest wheel of a gear train. Pinion - the smaller of two gear wheels, or the smallest gear in a gear train. Pinion Leaf - a tooth of a pinion Pinion Shaft - the external input shaft of certain gear operators which drive the internal reduction

gearing. Pintle - Pintle - a pin or bolt upon which some other part pivots or turns. Pintle - a vertical pivot pin, as on a rudder or a gun carriage. Pipe - Pipe - a tube made of metal, clay, plastic, wood, or concrete and used to conduct a fluid, gas, or

finely divided solid. Pipe - a type of fluid line whose dimensions are designated by nominal (approximate) inside

diameter and wall thickness. Pipe - technically a tube used to transport fluids or gases. However, pipe and tube are often

used interchangeably in steel lexicon, with a given label applied primarily as a matter of historical use.

Pipe - used to carry liquids, gases, or solids suspended in liquid, and is manufactured in a wide range of materials, some of which are better suited than others for specific uses. Pipe is roughly classified as either pressure pile, which can be subjected to internal pressure such as for water supply system or drainage pipe, which is also called non-pressure or gravity pipe and is used primarily for drainage, waste lines and venting. Pipe is specified in terms of its internal diameter as opposed to tubing, which is specified by the outside diameter. The term ‘class’ refers to pressure pipes and indicates pressure-resisting characteristics; the term schedule refers to wall thickness.

Pipe Elbow Meter - a variable head for measuring flow around the bend in a pipe. Pipe Fitting - a piece, such as couplings, unions, nipples, tees, and elbows for connecting

lengths of pipes. Pipe Flange - a round, collar-like plate around the end of a pipe, used to join sections of pipe

together by bolting a matching flange on one pipe to another flange on the other pipe. A blind flange is one without a hole for passage of liquids, used to close the end of the pipe.

Pipe Run - the path followed by a piping system. Pipe Scale - rust and corrosion products adhering to the inner surfaces of pipes; it decreases

ability to transfer heat and increases the pressure drop for flowing fluids. Pipe Still - a petroleum-refinery still in which heat is applied to the oil while it is being pumped

through a coil or pipe arranged in a firebox, the oil then running to a fractionator with continuous removal of overhead vapor and liquid bottoms.

Pipe Tap - a small threaded hole or entry made into the wall of a pipe; used for sampling of pipe contents, or connection of control devices or pressure drop measurement devices.

Pipe Tee - a T-shaped pipe fitting with two outlets, one at 90 degrees to the connection to the main line.

Pipe Thread - most commonly, a 60 degrees thread used on pipes and tubes, characterized by flat crests and roots and cut with three quarter inch taper per foot (about 1.9 centimeters per 30 centimeters); also known as Taper Pipe Thread.

Pipe Wrench - a wrench with slightly curved, serrated jaws, designed to tighten the grip on the pipe as the handle is turned; also called Stillson Wrench.

Pipeline - Pipeline - a line of pipe connected to valves and other control devices, for conducting fluids,

gases, or finely divided solids. Pipeline - a pipe laid across country, either on the surface or in a trench which is later filled in, to

transport oil, natural gas and many other substances over long distances. Pipework - see Piping Piping - Piping - a system of pipes provided to carry a fluid; also known as Pipework. Piping - can occur during the solidification of a steel in a slightly tapered ingot mold, placed

narrow end uppermost. Firstly, a layer of solid metal forms around the ingot walls and contraction in liquid metal takes place that results in the fall of the level of liquid. In this way, the successive layers of solid are formed, each accompanied by a fall in the liquid metal that results in the formation of primary piping. When an ingot is used with the narrow end up, a conical volume of steel still remains liquid, though metal at the top has solidified. Solidification of this metal produces further cavity known as secondary piping. Secondary piping can be prevented by using the wide end of the mold upward. In this case, the shrinkage is counteracted by feeding down the molten metal from the top, the region last to solidify. A brick-lined top at the mold also helps in reducing primary piping. Though forging eliminates a lot of piping, there are chances that the material may not weld properly during forging. Piping or sinking also takes place in shaped castings. It is minimized by placing feeders, risers, or reservoirs of molten metal to compensate for solidification shrinkage. Some exothermic materials are also added at the top of the risers to delay cooling at the top and compensate for shrinkage of metal during solidification. Chills are also used to accelerate cooling at thick sections.

Piping And Instrumentation Drawing (P&ID) - 1) shows the interconnection of process equipment and the instrumentation used to control the process. In the process industry, a standard set of symbols is used to prepare drawings of processes. The instrument symbols used in these drawings are generally based on Instrument Society of America (ISA) Standard S5.1; 2) the primary schematic drawing used for laying out a process control installation.

Piston - Piston - a disc or short cylinder fitting closely within a tube in which it moves up and down, as in a

pump. Piston - that part of the non-return mechanism of a piston non-return valve which works in the

dashpot cylinder. Piston Check Valve - a type of lift check valve in which a dashpot is incorporated, consisting of a

piston and cylinder, which provides a cushioning effect during operation. Piston Non Return Valve - Piston Non Return Valve - a disc non-return valve in which is incorporated a dashpot, consisting

of a piston and cylinder, which provides a cushion effect during operation. Piston Non Return Valve - dashpot valve Piston Rod - in a linear actuator, a rod attached to the piston to transfer the piston’s motion to

the valve stem via the stem adapter. Piston Valve - a cylindrical type of steam engine slide valve for admission and exhaust of steam.Pit - Pit - a circular depression, usually small; also called Pock Mark. Pit - a hollow or indentation in a surface. Pit - a small surface cavity in a metal part or coating usually caused by corrosion or formed

during electroplating. Pitch - Pitch - a product of coal tar. It is used up to 3% in the form of ground powder. Pitch is used

along with clay and sulphite binder for making cores. Pitch provides hot strength to the core in the presence of molten metal around the core.

Pitch - the distance between similar elements arranged in a pattern or between two points of mechanical part, as the distance between the peaks of two successive grooves on a screw.

Pitch Circle - in toothed gears, an imaginary circle concentric with the gear axis which is defined

at the thickest point on the teeth and along which the tooth pitch is measured. Pitch Cone - a cone representing the pitch surface of a bevel gear. Pitch Cylinder - a cylinder representing the pitch surface of a spur gear. Pitch Diameter - the diameter of the pitch circle of a gear. Pitting Corrosion - Pitting Corrosion - a concentrated attack by oxygen or other corrosive chemicals in a boiler,

producing a localized depression in the metal surface. Pitting Corrosion - passive metals have been resistant to a wide variety of corrosive media but

under certain conditions breakdown of the passive film may take place at various points. Depending on conditions, this may lead to complete breakdown of the passive film or the attack may concentrate at these initial areas, leading to rapid failure by pitting.

Plain Carbon Steel - steels containing iron and carbon only. Plane Strain - a deformation of a body in which the displacement of all points in the body are

parallel to a given plane, and the values of these displacements do not depend on the distance perpendicular to the plane.

Planishing - smoothing the surface of a metal by a rapid series of overlapping, light hammer like blows or by rolling in a planishing mill.

Plasma Arc Cutting - metal cutting by melting a localized area with an arc followed by removal of metal by high-velocity, high-temperature ionized gas.

Plasma Arc Welding (PAW) - a welding process in which coalescence is produced by the heat obtained from a concentrated arc set up between a tungsten electrode and a water cooled nozzle. Arc plasma is the temporary state of a gas. The process employs two inert gases. One gas forms the arc plasma and the second shields the arc plasma. In plasma arc welding the arc is constructed with the help of a water-cooled small diameter nozzle. The nozzle increases the gas pressure, intensely raises the temperature, improves arc stability and arc shape. When electric current is passed through a gas, the gas gets ionized. The ionized gas consists of electrons and ions. Arc plasma is the temporary state of a gas. The energy on arc plasma depends upon the electrical power used to create the arc plasma. The temperature obtained by arc plasma is as high as 20000° C as compared to 3600° to 4000° C by the ordinary arc. Depending upon the nature of the arc, plasma arc welding can be divided into 2 categories: 1) non -transferred arc process, and 2) transferred arc process.

Plasma Arc Welding (PAW) - Plasma Arc Welding (PAW) - metals are heated with a constricted arc between an electrode and

the workpiece (transferred arc), or the electrode and the constricting nozzle (nontransferred arc). Shielding is obtained from the hot, ionized gas issuing from the orifice which may be supplemented by an auxiliary source of shielding gas.

Plasma Torch - a torch in which temperatures as high as 50,000° Celsius are achieved by injecting a plasma gas tangentially into an electric arc formed between electrodes in a chamber; the resulting vortex of hot gases emerges at very high speed through a hole in the negative electrode. To form a jet for welding, spraying of molten metal, and cutting of hard rock or hard metals.

Plastic - any of a large number of synthetic, non-metallic materials (polymeric substances) that can be molded by heat and / or pressure into any rigid or semi-rigid shape.

Plastic Collision - a collision in which one or both of the colliding bodies suffers plastic deformation and mechanical energy is dissipated.

Plastic Deformation - Plastic Deformation - deformation while a material is in a plastic state. Plastic Deformation - permanent change in shape or size of a solid body without fracture resulting

from the application of sustained stress beyond the elastic limit. Plastic Deformation - permanent deformation caused by stressing beyond the elastic limit. Plastic Fracture - refers to the breakage of a metal under tensile load when being drawn out. Plastic State - see Stress-Strain Relationship Plastic Welding - a welding process in which the pieces of metal to be joined are heated to the

plastic state and then forced together by external pressure without the addition of filler material.

Plasticate - to soften a material by heating or kneading; also known as Plastify. Plasticity - Plasticity - the ability of a material to undergo permanent deformation at a certain stage of

working. Plastic materials can be molded to any shape. Clay is a plastic material. Plasticity - the property of a solid body in which it undergoes a permanent change in shape or

size when subjected to a stress exceeding a particular value, called the yield value. Plasticity - the susceptibility of a material at a certain temperature and lading condition to exhibit

a permanent deformation after it gets induced by a stress taking it past the yield point.

Plasticity - this property is the exact opposite of elasticity. It is the state of a material which has been loaded beyond its elastic state. Under a load beyond that required to cause elastic deformation (the elastic limit) a material possessing the property of plasticity deforms permanently. It takes a permanent set and will not recover when the load is removed.

Plasticize - to soften a material to make it plastic or moldable by adding a plasticizer or by using heat.

Plasticizer - a substance, usually a heavy liquid, added to an elastomer to decrease stiffness, improve low temperature properties, and improve processing.

Plastics - a broad classification covering a variety of non-metallic, synthetic or organic materials capable of being molded or formed into desired shapes. Typical materials include nylons and tetrafluoroethylenes such as Teflon.

Plastify - see Plasticate Plastometer - an instrument for measuring the plasticity of raw or unvulcanized compounded

rubber. Plate - Plate - flat metallic materials greater than 5mm (3/16 in) thick. Plate - sheet steel with a width of more than eight inches, with a thickness ranging from one

quarter of an inch to more than one foot; see Sheet Steel. Plate - the flow control element of a wafer check valve. Platform - set of facilities used to extract oil from sea fields. The platform rises above the sea. Play - free or unimpeded motion of an object, such as the motion between poorly fitted or worn

parts of a mechanism. PLC - 1) Public Limited Company; 2) Programmable Logic Controller PLE - Plain Large End Plenum - a condition in which air pressure within an enclosed space is greater than that in the

outside atmosphere. Plug - Plug - a term sometimes used to refer to the closure component in a valve. Plug - see Closure Member Plug - that component which is turned within the body to control the flow of fluid. Plug - the flow control element of a plug valve. Plug - the moveable part of the valve that makes contact with the valve seat when the valve is

closed; and which varies the area controlling the flow. The three most common types of control valve plugs are contoured, V-port, and quick opening. A contoured plug controls flow by a shaped end. and is usually end-guided at the top or bottom (or both) of the valve body. A V-port plug has a cylinder (called a skirt) which rides up and down in the seat ring. The skirt guides the plug, and by virtue of shaped openings in the skirt, varies the flow area. Quick-opening plugs are machined to provide maximum flow quickly when the plug lifts from its seat. These plugs can be either end-guided or guided by wings riding in the seat ring.

Plug Cock - Plug Cock - a small plug valve. Plug cocks have no provision for reducing friction between the

plug and body; also called a Cock. Plug Cock - a taper-seated cock in which the plug is retained in the body by means of a washer,

screw and nut at the smaller end of the plug. Plug Cock - see Plug Valve Plug Components - those parts which are associated, but not integral, with the plug.

Plug Face - the surface of the plug or of the plug facing, which makes contact with the body seat.Plug Facing - a deposit of material, different from that of the plug, on which the plug face is

formed. Plug Fastening - comprises washer, screw and nut, or other device, to retain the plug in a plug

cock. Plug Forming - thermoforming process for plastics molding in which a plug or male mold is used

to partially preform the part before forming is completed, using vacuum or pressure.Plug Head - that part of the plug shank or stem to which the wrench or other operating device is

attached. Plug Holding Down Plate - the component, of certain compound gland cocks, which seats the

plug. Plug Holding Down Plate Fastening - comprise bolts, stud bolts, studs, set screws and nuts

used to secure the plug holding-down plate. Plug Meter - a variable-area flow-meter in which a tapered plug, located in an orifice and raised

until the resulting opening is sufficient to handle the fluid flow, is used to measure the flow rate.

Plug Packing - material inserted in a packed cock to effect a seal between the plug face and the body seat.

Plug Port - the passage-way or passage-ways through the plug. These may be a) Straight-through, b) Tee port, c) “L” or angle port, d) Double “L” or double angle port.

Plug Shank - the integral part of the plug which passes through the body or cover, and on which the plug head is formed.

Plug Valve - Plug Valve - 1) a valve with a closure member that may be cylindrical, conical or a spherical

segment in shape. It is positioned, open to closed, with rotary motion; 2) A type of shutoff valve consisting of a tapered rod with a lateral hole through it. As the rod is rotated 90 degrees about its longitudinal axis, the hole is first aligned with the direction of flow through the valve and then aligned crosswise, interrupting the flow.

Plug Valve - a form of shut-off device, having a plug which can be turned to move its port or ports relative to the body seat ports to control the flow of fluid and which incorporates design features which reduce the friction between the plug face and the body seat during turning of the plug and/or seal them against leakage.

Plug Valve - a type of valve using a cylindrical or conical flow control element with a passage through it and that rotates 90 degrees from open to closed.

Plug Valve - a valve fitted with a plug that has a hole through which fluid flows and that is rotatable through 90 degrees for operation in the open or closed position; also known as Plug Cock.

Plug Valve - a valve which is quarter turn in operation and uses either a cylindrical or conical plug as the closing member. A sealing compound is usually injected between the plug and the valve body. Lubricated plug valves have a special lubricant, which also acts as a seal, injected between the plug and the valve body. Eccentric plug valves are non-lubricated and have a cylindrical seating surface offset from the center of the valve stem. Sleeved plug valves have a ‘soft’ inset between the plug and valve body. Multi-ported valves have a special plug and body with various flow configurations.

Plug Valve - a valve with a cylindrical rotating center, through the cylinder is a hole. When the hole is correctly lined up fluid can flow through the valve. Similar to a stopcock but on a larger scale.

Plug Valve - this multi-turn valve derives its name from the rotating plug which forms the closing element. The plug may be cylindrical or truncated. In the open position, the fluid flows through a hole in the plug. Lubricated plug valves rely on a sealing compound injected between the plug and the valve body, while sleeved plug valves are fitted with a ‘soft’ insert between the plug and the body.

Plug Valve - this multi-turn valve derives its name from the rotating plug which forms the closing element. The plug may be cylindrical or truncated.

Plug Valve - used primarily for on-off service and some throttling services. It controls flow by means of a cylindrical or tapered plug with a hole in the center that lines up with the flow path of the valve to permit flow. A quarter turn in either direction blocks the

flow path. Plug Valve, Characterized Plug Configuration - plug with contoured face to provide various

flow characteristics. Plug Valve, Cylindrical Configuration Plug - plug is cylindrical, with a flow passage through it,

or is a partial cylinder. Plug Valve, Eccentric Configuration Plug - plug face is not concentric with plug stem centerline

and moves into seat when closing. Plug Valve, Eccentric Spherical Disk Configuration Plug - disk is spherical segment, not

concentric with the disk stem. Plug Valve, Lift - in which mechanical means are provided to lift the plug from the body seat

during turning of the plug. Plug Valve, Lubricated - Plug Valve, Lubricated - a design of a plug valve that uses injected sealant (lubricant) to reduce

the required operating force and achieve a tight seal against internal leakage. Plug Valve, Lubricated - a plug valve which incorporates design features in which lubricant is

injected under pressure between the plug face and body seat. Plug Valve, Non Lubricated - a plug valve which incorporates design features to reduce the

friction between the plug face and body seat during turning of the plug. Common types are lift plug and split plug.

Plug Valve, Sleeved - a plug valve design that has a non-metallic lining on the body seating surfaces.

Plug Valve, Split - in which the plug is split and mechanical means are provided to contract the plug whilst it is being turned.

Plug Valve, Tapered Configuration Plug - plug is tapered and may be lifted from seating surface before rotating to close or open.

Plug Valve, Venturi - Plug Valve, Venturi - a valve with a substantially reduced opening through the plug, in which the

transition from each full opening end to the reduced opening is well streamlined. Plug Valve, Venturi - a valve with a substantially reduced opening through the plug, in which the

transmission from each full opening end to the reduced opening is well streamlined.Plug Weld - a series of holes drilled in one plate are fillet welded to join it to another overlaping

undrilled plate. Alternatively, pins, jig pins or plugs may project from one part through holes in another to which they are then welded.

Plummet - a loose-fitting metal plug in a tapered rotameter tube which moves upward (or downward) with an increase (or decrease) in fluid flow rate upward through the tube; also known as Float.

Plunging - the formation of a barrier (plug) of solid material in a process flow system, such as a pipe or reactor.

Ply - the number of strands or layers PM - Particulate Matter PMI - Positive Material Identification PMIV - Positive Material Identification Verified PN - Pressure Nominal (Metric) Pneumatic - Pneumatic - 1) a device which converts the energy of a compressible fluid, usually air, into

motion; 2) pertaining to or operated by a gas, especially air. Pneumatic - a pneumatic valve is supplied with the pneumatic actuator alone, without a solenoid

valve; see Electro-Pneumatic. Pneumatic - operated by compressed air Pneumatic Control System - 1) a control system that uses air or gas as the energy source; 2) a

system which makes use of air for operating control valves and actuators. Pneumatic Control Valve - Pneumatic Control Valve - a spring loaded valve that regulates the area of a fluid flow opening by

changing position in response to variable pneumatic pressure opposing the spring force.

Pneumatic Control Valve - a valve in which the force of compressed air against a diaphragm is opposed by the force of a spring to control the area of the opening for a fluid

stream. Pneumatic Controller - a device activated by air pressure to mechanically position another

device, such as a valve stem; also known as Pneumatic Positioner. Pneumatic Test - Pneumatic Test - a test in which a valve is tested with air; usually a seat closure test. Pneumatic Test - pressure testing of a process vessel by the use of air pressure. Pneumatic Valve - a valve for controlling gas Pneumatics - engineering science relating to gaseous pressure and flow. PNPP - Pipe Nipple PO - Purchase Order Polishing - in petroleum refining, removal of final traces of impurities. Polishing Wheel - an abrasive wheel used for polishing. Polyether Etherketone - see PEEK Polyethylene - see Polythene Polymer - Polymer - a chemical compound or mixture consisting essentially of repeating structural units.

Polymers with special elastic properties are called elastomers. Polymer - a compound composed of one or more large molecules that are formed from repeated

units of small molecules. Polymer - a material formed by the joining together of many (poly) individual units (mer) of one or

more monomers; synonymous with elastomer. Polymer - hydrocarbon chains made from monomers. The most common include widely traded

plastics like, polypropylene, polyethylene and polystyrene. Polymeric Material - a compound formed by molecular bonding (polymerizing) of two or more

simple molecules (monomers). This material is commonly referred to as plastic. Polymide - a high molecular weight polymer with high temperature stability (up to 375° C) and

low outgassing at high temperatures. It is used for gate, bonnet, poppet and other seals. It absorbs large amounts of water when exposed to air. Thus it should be avoided in systems which are frequently cycled using room air.

Polypropylene - a lightweight plastic that offers relatively high purity characteristics at a price well below PVDF or PTFE. Impervious to many chemicals; also known as PP and PPL.

Polysulfide Treating - a petroleum refinery process used to remove elemental sulfur from refinery liquids by contacting them with a nonregenerable solution of sodium polysulfide.

Polytetrafluoroethylene - see Teflon Polythene - a waxy, translucent, easily molded thermoplastic, used for packing and insulating

materials, and to make pipes and molded articles. Polyvinyl Chloride (PVC) - a polymer used as raw material for many common products. Pop Action - the action of a safety valve as it opens under steam pressure when the valve disk

is lifted off its seat. Pop Valve - a boiler safety valve in which the head of the valve is shaped so as to cause the

steam to accelerate the rate of lift when a small lift occurs, giving rapid pressure release.

Poppet - Poppet - a gasket or O-ring carrier which moves the closure gasket or O-ring into position with

the valve seat and transfers sealing force to the gasket or O-ring to effect a leak-tight seal.

Poppet - a spring loaded ball that engages a notch. Poppet Valve - Poppet Valve - a cam-operated or spring-loaded reciprocating-engine mushroom-type valve used

for control of admission and exhaust of working fluid; the direction of movement is at right angles to the plane of its seat.

Poppet Valve - a mushroom shaped valve that controls the intake or exhaust of working fluid in a reciprocating engine; it may be cam operated or spring loaded, and its direction of movement is at right angles to the plane of its seat.

Porosity -

Porosity - a defect found in castings or welds consisting of gas bubbles or voids in the solidified metal.

Porosity - a large number of holes in a casting. In casting, porosity may result in leaking castings and reduced pressure tightness. Porosity can also occur due to a) dissolved hydrogen or sulphur dioxide, b) excessive pouring temperature, c) damp ladles, d) slow rate of solidification, and e) excessive moisture content of the mold.

Porosity - a welding defect which is the presence of gas pockets or inclusions in a weld. Gases entrapped in the weld metal cause it. When the cavities formed are in tubular shape, then the defect is known as piping or wormholes. A large associated cavity due to the same cause is known as a blowhole. Some of the major causes of porosity are the use of damp electrodes, very long arc, improper electrode, improper current intensity and defective work surface. Rust, scale, oil, grease, or galvanizing moisture on the surface promotes porosity.

Porosity - the quality or state of being porous. Port - Port - an internal or external terminus of a passage in a component. Port - openings through which the media enters and exits the valve. Port - the flow control orifice of a control valve. It is also used to refer to the inlet or outlet

openings of a valve. Port - the internal or external terminus of a passage in a component. Port - the plug opening in a plug valve; see Bore Port - this term refers to the flow-controlling opening between the seat and the disc when the

valve is wide open. It does not refer to body size or end connection size. Standard valve ports are the sizes normally used in the valves. Valves with reduced ports have flow contequal to a smaller valve with a standard port. Example: A one-inch valve with 3/4-inch reduced port size usually has the same flow-controlling area as a 3/4 inch valve with standard port size.

Port Guide - a valve plug with wings or a skirt fitted to the seat ring bore. Port Guided - a valve plug that fits inside the seat ring, which acts as a guide bushing.

Examples are Splined Plug, Hollow Skirt, and the Feather-Guide Plug. Port Size - the diameter of the hole in the ball of a ball valve or plug valve. Position Indicator - Position Indicator - a device to show whether a valve is in the open or closed position. Position Indicator - any external device which visually indicates the open and closed position of

valve. Position Switch - Position Switch - a pneumatic, hydraulic or electrical device which is linked to the valve stem to

detect a single, preset valve stem position. Position Switch - a switch that is linked to the valve stem to detect a single, preset valve stem

position. Example: Full Open or Full Closed. The switch may be pneumatic, hydraulic, or electric.

Position Transmitter - a device that is mechanically connected to the valve stem and will generate and transmit either a pneumatic or electric signal that represents the valve stem position.

Positioner - Positioner - a control accessory that accepts a varying input signal and direct air to the actuator

to position the valve for flow control. Positioner - a device used to position a valve with regard to a signal. The positioner compares

the input signal with a mechanical feed back link from the actuator. It then produces the force necessary to move the actuator output until the mechanical output position feedback corresponds with the pneumatic signal value. Positioners can also be used to modify the action of the valve (reverse acting positioner), alter the stroke or controller input signal (split range positioner), increase the pressure to the valve actuator (amplifying positioner), or alter the control valve flow characteristic (characterized positioner).

Positioner - a feedback device that aids in the accurate positioning of a valve closure or the throttling element with respect to the magnitude of the signal being received.

Positioner - a position controller, which is mechanically connected to a moving part of a final control element or its actuator, and automatically adjusts its output pressure to the actuator in order to maintain a desired position that bears a predetermined relationship to the input signal. The positioner can be used to modify the action of the valve (reversing positioner), extend the stroke/controller signal (split range positioner), increase the pressure to the valve actuator (amplifying positioner) or modify the control valve flow characteristic (characterized positioner).

Positioner - device that ensures the closing or throttling element of a valve moves to or maintains the correct position.

Positioner - devices that help control the opening and closing of valves remotely by controlling pneumatic or hydraulic elements. Positioners can be controlled by adjusting currents to its circuits or by using air. More and more positioners have feedback control options.

Positioner - instrument attached to a pneumatic valve actuator, providing accurate, automatic modulating control of the valve between the open and closed positions by increasing, decreasing, and balancing the air supply to the actuator as determined by a varying input signal generated by an external instrument source. While the operation positioners may vary, the basic function is usually either the pneumatic positioner, designed to receive a 3 to 15 PSI signal, or the electro-pneumatic, designed to receive a 4 to 20 milliamp signal.

Positive Material Identification (PMI) - Positive Material Identification (PMI) - a method for cross checking the identity of a piece of

material, often using a portable spectrometer, usually with x-rays (TN 9266, nuclear analyzer) or a welding arc (Arc Met 900, optical spectrometer).

Positive Material Identification (PMI) - a procedure used to assure that specified metallic alloy materials are properly identified as to their true elemental composition and are marked according to specific industry standards and procedures.

Positive Position - the installation position of a multi-port valve such that the valve’s flow control element is between the pressure inlet body openings and the body openings that are closed off, thereby assisting in sealing the valve; compare with Negative Position.

Post Cure - the second step in the vulcanization process for the more exotic elastomers. Provides stabilization of parts and drives off decomposition products resulting from the vulcanization process.

Post Guide - a guiding system where the valve stem is larger in the area that comes into contact with the guide bushings than in the adjacent stem area.

Post Weld Heat Treatment (PWHT) - heating and cooling a weldment in such a way as to obtain desired properties.

Postcure Bonding - a method of postcuring at elevated temperatures of parts in order to obtain higher heat-resistant properties of the adhesive bond.

Postforming - forming, bonding, or shaping of heated, flexible thermoset laminates before the final thermoset reaction has occurred; upon cooling, the formed shape is held.

Postheating - annealing or tempering a weldment to remove strain or prevent local hardening. Pot Life - Pot Life - the period of time during which paint remains useful after its original package has been

opened or after a catalyst or other additive has been incorporated; also known as Spreadable Life and Useful Life.

Pot Life - the time interval, after mixing of paint or coating materials, during which the mixture can be applied without difficulty or loss of final coating quality.

Potential Energy - the energy a substance has because of its position, its condition, or its chemical composition.

Pounds - pressure classes are frequently referred to as pounds. For instance, a class 600 valve is often called a 600 pound valve. This can be misleading, because a class 600 valve can contain an internal pressure of much more than 600 psi under some conditions, but less than 600 psi under other conditions.

Pounds Per Square Inch (PSI) - Pounds Per Square Inch (PSI) - a unit of pressure equal to the pressure resulting from a force of

1 pound applied uniformly over an area of 1 square inch; abbreviated psi.

Pounds Per Square Inch (PSI) - the force per unit area exerted against a resisting body. Pounds Per Square Inch (PSI) - used to indicate the amount of pressure in a given piping

system. Pounds Per Square Inch Absolute (PSIA) - the absolute, thermodynamic pressure, measured

by the number of pounds-force exerted on an area of 1 square inch. Pounds Per Square Inch Differential - the difference in pressure between two points in a fluid-

flow system, measured in pounds per square inch; abbreviated psid. Pour Point - the lowest temperature in which liquid will flow under specified conditions. Pouring Basin - a small funnel-shaped cavity placed at the top of a mold. Molten metal is

poured into it from a ladle. Powder Filling - an international term that describes a type of protection in which an enclosure

of electrical apparatus is filled with a material in a finely granulated state so that, in the intended conditions of service, any arc occurring within the enclosure of an electrical apparatus will not ignite the surrounding atmosphere. No ignition is allowed to be caused either by flame or by excessive temperature of the accessible surfaces of the enclosure. This type of protection is referred to by IEC as "Ex q".

Powder Metals - fabrication technology in which fine metallic powder is compacted under high pressure and then heated at a temperature slightly below the melting point tosolidify the material. Primary users of powder metal parts are auto, electronics and aerospace industries.

Power - the rate of doing work or the rate of expanding. Power Actuated Pressure Relief Valve - a pressure relief valve connected to and controlled by

a device which utilizes a separate energy source. Power Control Valve - a safety relief device operated by a power-driven mechanism rather than

by pressure. Power Factor - the relationship between air pressure and surface area of the piston in an air

cylinder. Multiply the power factor by the air pressure you intend to operate at to calculate the maximum working force of a cylinder. For example; I have a device I wish to operate at 100 psi, which has a power factor of 1.4. 100x1.4=140. The cylinder therefore has maximum force capability of 140 pounds.

Power Pack - the compact installation for the generation of the power source to serve the valve actuators.

Power Source - the medium which drives the actuators. Power Unit - A combination of pump, pump drive, controls, and conditioning components which

may be required for its application. PP - see Polypropylene PPL - see Polypropylene PQR - Procedure Qualification Record PRE - Pitting Resistance Equivalent Pre Production Meeting - a meeting convened between the purchaser and vendor, to determine

full understanding by all parties of the purchase order specifications. Pre Tension - the amount of tensile load applied to a bolt or tie-rod when it gets installed, but not

subjected to its working environment. Precipitate - a suspension of small solid particles formed in a solution as a result of chemical

reaction. Precipitation Hardening (PH) - Precipitation Hardening (PH) - a small group of stainless steels with high chromium and nickel

content, with the most common types having characteristics close to those of martensitic (plain chromium stainless class with exceptional strength) steels. Heat treatment provides this class with its very high strength and hardness. Applications for PH stainless steels include shafts for pumps and valves as well as aircraft parts.

Precipitation Hardening (PH) - hardening a ferrous metal by austenitizing and then cooling rapidly enough so that some or all of the austenite transforms to martensite.

Precision Casting - a metal die is used to make wax (Lost Wax process) or a frozen mercury (Mercast) pattern. This gets invested with refractory slurry forming a mould, which, after drying and baking, can be used for casting into. The pattern melts and runs out when the mould is warmed. Large numbers of very small accurate castings can

be made this way. The Lost Wax process is used only recently for steel. Sometimes it is known as the Cire Perdue process. It was used for bronze and precious metals by the ancient Egyptians and by Benvenuto Cellini among others.

Precision Grinding - machine grinding to specified dimensions and low tolerances. Preclude - prevent; rule out; prohibit Preheating - the application of heat to the base metal prior to a welding. Preloading - for back-pressure-control gas valves, a weight or spring device to control the gas

pressure at which the valve will open or close. PREN - Pitting Resistance Equivalent Number PRES - Pressure Press Fit - an interference or force fit assembled through the use of a press; also known as

Force Fit. Pressure - Pressure - a type of stress which is exerted uniformly in all directions; its measure is the force

exerted per unit area. Pressure - measure of applied force compared with the area over which the force is exerted. Pressure - the amount of force distributed over each unit of area, usually expressed in pounds

per square inch. Pressure Class - a pressure rating expressed as a dimensionless number. The class rating

charts give actual pounds per square inch maximum allowable pressure at a given temperature.

Pressure Containing Member - the part of a pressure relieving device which is in direct contact with the pressurized medium in the vessel being protected.

Pressure Containing Parts - Pressure Containing Parts - the valve parts whose failure to function as intended would result in a

release of retained fluid to the atmosphere such as bodies, bonnets, and stems. Pressure Containing Parts - those parts whose failure to function as intended would result in a

release of retained fluid to the atmosphere. Examples are valve bodies, bonnets, and stems.

Pressure Controlling Parts - Pressure Controlling Parts - the valve parts intended to control or regulate the movement of

pressurized fluids, such as valve bore sealing mechanisms. Pressure Controlling Parts - those parts intended to control or regulate the movement of

pressurized fluids, such as valve bore sealing mechanisms. Pressure Die Casting - the usual die casting process in which the molten metal gets forced into

highly finished moulds under heavy pressure by plungers, compressed air or combined methods.

Pressure Differential - the difference in pressure between any two points in a fluid system; also called pressure drop.

Pressure Dye Test - a leak detection method in which a pressure vessel is filled with liquid dye and is pressurized under water to make possible leakage paths visible.

Pressure Energized Seal - in a butterfly valve, a seal that is energized by interference fit between the disk groove and valve liner and also by differential pressure acting across the seal. The seal may be a solid section or have internal pressure ports.

Pressure Energized Stem Seal - a part and/or packing material deformable by fluid pressure that bears against the stem to make a tight seal.

Pressure Forming - a plastics thermoforming process using pressure to push the plastic sheet to be formed against the mold surface, as opposed to using vacuum to suck the sheet flat against the mold.

Pressure Gas Welding - a gas welding process carried out simultaneously over the entire area of abutting surfaces under pressure, without the use of filler metal.

Pressure Rating - Pressure Rating - the maximum allowable internal force per unit area of a pressure vessel, tank

or piping system during normal operation. Pressure Rating - the operating (allowable) internal pressure of a vessel, tank, or piping used to

hold or transport liquids or gases. Pressure Recovery Factor (F1) - a number used to describe the ratio between the pressure

recovery after the vena contracta and the pressure drop at the vena contracta. It is a measure of the amount of pressure recovered between the vena contracta and the valve outlet. Some manufacturers use the term Km to describe the pressure recovery factor. This number will be high (0.9) for a globe style valve with a torturous follow path and lower (0.8 to 0.6) for a rotary style valve with a streamlined flow path. On most rotary products the F1 factor will vary with the degree of opening of the valve closure member. Note! F1 does not equal Km.

Pressure Reducing Valve (PRV) - Pressure Reducing Valve (PRV) - a pressure control valve whose primary function is to limit

outlet pressure. Pressure Reducing Valve (PRV) - a self-operating valve used to reduce any excess pressure in

a system, for example, steam. The valve opens if the internal pressure exceeds that holding the valve disc onto the seat; also known as a PRV.

Pressure Reducing Valve (PRV) - a self-operating valve used to reduce any excess pressure in a system, e.g. steam. The valve opens if the internal pressure exceeds that holding the closing element onto the seat.

Pressure Reducing Valve (PRV) - a valve used to limit the outlet pressure from a source. Pressure Reducing Valve (PRV) - a valve which maintains a uniform pressure and keeps the

system full. It opens when the pressure and keeps the system full. It opens when the pressure drops under 12 psi. and closes against higher pressure.

Pressure Reducing Valve (PRV) - an automatic valve which reduces the upstream line pressure to a given level downstream and maintains the reduced pressure irrespective of upstream pressure change or variation in flow. Valves may be direct acting or pilot operated, the latter having a small direct operated pilot which controls the main valve.

Pressure Regulating Valve - Pressure Regulating Valve - a valve that can assume any position between fully open and fully

closed, or that opens or remains closed against fluid pressure on a spring loaded valve element, to release internal pressure or hold it and allow it to build up, as desired.

Pressure Regulating Valve - a valve that releases or holds process-system pressure (that is, opens or closes) either by preset spring tension or by actuation by a valve controller to assume any desired position between full open and full closed.

Pressure Regulating Valve - a valve which is the reverse acting version of the pressure reducing valve and maintains the level of upstream line pressure; sometimes called a Pressure Maintaining Valve, Surplus Valve, Pressure Retaining Valve, Pressure Sustaining Valve.

Pressure Regulator - Pressure Regulator - a valve used to automatically reduce and maintain pressure below that of a

source. Pressure Regulator - an open-close device used on the vent of a closed, gas-pressured system

to maintain the system pressure within a specified range. Pressure Relief - a valve or other mechanical device (such as a rupture disk) that eliminates

system overpressure by allowing the controlled or emergency escape of liquid or gas from a pressured system.

Pressure Relief Device - Pressure Relief Device - 1) in pressure vessels, a device designed to open in a controlled

manner to prevent the internal pressure of a component or system from increasing beyond a specified value, that is, a safety valve; 2) a spring-loaded machine part which will yield, or deflect, when a predetermined force is exceeded.

Pressure Relief Device - a mechanism that vents fluid from an internally pressurized system to counteract system overpressure; the mechanism may release all pressure and shut the system down (as does a rupture disc) or it may merely reduce the pressure in a controlled manner to return the system to a safe operating pressure (as does a spring loaded safety valve).

Pressure Relief Valve - Pressure Relief Valve - a pressure relief device which is designed to re-close and prevent the

further flow of fluid after normal conditions have been restored.

Pressure Relief Valve - a valve designed to open automatically to relieve pressure and keep it below a designated level.

Pressure Relief Valve - a valve that automatically opens at a set pressure, allows fluid to discharge, and automatically recloses when the fluid pressure drops below the set pressure.

Pressure Relief Valve - a valve which relieves pressure beyond a specified limit and recloses upon return to normal operating conditions.

Pressure Relief Valve - an automatic valve designed to automatically engage in the event that the maximum working pressure of the system is exceed; also known as a pop-off valve.

Pressure Relief Valve - an emergency type valve which bleeds water from pipes when the system pressure exceeds a set amount. It is spring operated and should be positioned where water discharge will not cause damage.

Pressure Relief Valve - designed to provide protection from over-pressure in steam, gas, air and liquid lines. The valve "lets off steam" when safe pressures are exceeded, then closes again when pressure drops to a preset level.

Pressure Retaining Member - Pressure Retaining Member - that part of a pressure beyond a specified limit and recloses upon

return to normal operating conditions. Pressure Retaining Member - that part of a pressure-relieving device loaded by the restrained

pressurized fluid. Pressure Seal - a seal used to make pressure-proof the interface (containing surfaces) between

two parts that have frequent or continual relative rotational or transnational motion. Pressure Seal Joint - a design of body-bonnet joint that uses the fluid pressure to compress a

specially designed seal ring to form a tight seal and prevent external leakage. Pressure Spike - a sudden, brief rise in pressure. Pressure Still - a continuous-flow, petroleum-refinery still in which heated oil (liquid and vapor) is

kept under pressure so that it will crack (decompose into smaller molecules) to produce lower-boiling products (pressure distillate or pressure naphtha).

Pressure Surge - a pressure spike/excursion moving through the pipeline at sonic velocity, produced by a sudden change in velocity of the moving stream that results from shutting down a pump station or pumping unit, closure of a valve or any other blockage of the moving stream.

Pressure Switch - Pressure Switch - a switch that is operated by a change in the applied pressure. Pressure Switch - an electrical switch operated by the increased decrease of fluid pressure. Pressure System - any system of pipes, vessels, tanks, reactors, and other equipment, or

interconnections of them, operating with an internal pressure greater than atmospheric.

Pressure Tap - a small perpendicular hole in the wall of a pressurized, fluid-containing pipe or vessel; used for connection of pressure-sensitive elements for the measurement of static pressures; also known as Piezometer Opening and Static Pressure Tap.

Pressure Temperature Ratings - the maximum allowable working pressures at specified temperatures. For steel valves, the ratings are defined by "Classes" and are found in ASME B16.34. For iron and bronze valves, the ratings are defined in the applicable MSS specifications.

Pressure Thermit Welding - a thermit welding process in which heat is produced by superheated liquid metal by chemical reaction of materials. The chemical reaction takes place by iron oxide and aluminum.

Pressure Transducer - an instrument component that detects a fluid pressure and produces an electrical signal related to the pressure; also known as Electrical Pressure Transducer.

Pressure Vessel - Pressure Vessel - a metal container designed to withstand a specified bursting pressure; it is

usually cylindrical with hemispherical end closures (but may be of some other shape, such as spherical) and is usually fabricated by welding.

Pressure Vessel - a metal container, generally cylindrical or spheroid, capable of withstanding bursting pressures.

Pressure Welding - any welding process where pressure is used to complete the weld. Pressure, Absolute - Pressure, Absolute - 1) the pressure measured relative to zero pressure (vacuum); 2) the

pressure above the absolute zero value of pressure that is theoretically obtained in empty space or at the absolute zero for temperature, as distinguished from gauge pressure.

Pressure, Absolute - PSIA. Sum of gauge pressure and atmospheric pressure. Pressure, Absolute - the sum of atmospheric and gauge pressures. Pressure, Absolute - the total pressure measured from an absolute vacuum. It is the sum of

gauge pressure and the prevailing atmospheric pressure measured on a barometer. The unit of pressure is the Pascal (Newton per square meter). Secondary units include dynes per square centimeter (metric), pounds per square inch (British), inches of water, millimeters of mercury.

Pressure, Absolute - true pressure above absolute zero. It takes into account barometric pressure and is the sum of such pressure and that created by other means above or below atmospheric pressure and gauge pressure.

Pressure, Atmospheric - Pressure, Atmospheric - force exerted on a unit by the weight of the atmosphere. The pressure

at seal level is 14.7 psi. Pressure, Atmospheric - pressure exerted by the atmosphere at any specific location. Pressure, Atmospheric - the barometric reading of pressure exerted by the atmosphere. At sea

level 14.7 lb per sq in. or 29.92 in. of mercury. Pressure, Atmospheric - The pressure exerted by the atmosphere. Common units are psi,

Pascals (Newtons/meter2), Bars, and Dynes/cm2. Atmospheric pressure decreases approximately exponentially with altitude.

Pressure, Back - Pressure, Back - the absolute pressure level as measured four pipe diameters downstream from

the turbine flowmeter under operating conditions, expressed in pascals. Pressure, Back - the pressure exerted on the downstream side of a valve seat. Pressure, Back - the pressure exerted on the downstream side of a valve. Pressure, Back - the pressure on the upstream side of a valve seat. Pressure, Back - the pressure uncountered by the return side of a system. Pressure, Back - the static pressure existing at the outlet of a pressure relief device due to

pressure in the discharge system. Pressure, Bearing - load on a bearing surface divided by its area; also known as Bearing

Stress. Pressure, Built Up Back - pressure existing at the outlet of a pressure relief device occasioned

by the flow through that particular device into a discharge system. Pressure, Closing - Pressure, Closing - in a safety relief valve, the static inlet pressure at the point where the disc has

zero lift off the seat. Pressure, Closing - the amount of static inlet pressure in a safety relief valve when the valve disk

has zero lift above the seat. Pressure, Cold Differential Test - the inlet static pressure at which the pressure relief valve is

adjusted to open on the test stand, expressed in pounds per square inch gage. This pressure includes the corrections for service conditions of back pressure or temperature, or both.

Pressure, Cold Working (CWP) - Pressure, Cold Working (CWP) - 1) the working pressure of a valve in psi at 100° Fahrenheit; 2)

the maximum pressure-retaining capability of a valve at ambient temperature. It is marked on the valve as CWP. It is also known as the Water Oil Gas (WOG) rating; see Water Oil Gas.

Pressure, Cold Working (CWP) - the maximum allowable pressure under non-shock conditions at ambient temperature ( -20° F to +100° F).

Pressure, Cold Working (CWP) - the maximum pressure rating of a valve or fitting coincident with ambient temperature, generally the range from -20° F to +100° F (-29° C to +38° C).

Pressure, Constant Back - back pressure which does not change appreciably under any condition of operation whether the pressure relief valve is closed or open.

Pressure, Design - Pressure, Design - the maximum allowable working pressure permitted under the rules of the

ASME Construction Code. Pressure, Design - the pressure used in the calculation of minimum thickness or design

characteristics of a boiler or pressure vessel in recognized code formulas; static head may be added where appropriate for specific parts of the structure.

Pressure, Design - the pressure used in the design of a vessel or device for the purpose of determining the minimum permissible thickness or physical characteristics of the parts for a given maximum working pressure (MWP) at a given temperature.

Pressure, Design - the pressure which is used for calculating the minimum equipment wall thickness required for pressure containment.

Pressure, Differential - Pressure, Differential - pressure difference between the inlet line and the outlet line, i.e. 100 PSI

operating pressure on inlet minus 80 PSI back pressure from outlet line = 20 PSI differential pressure.

Pressure, Differential - the difference in pressure between any two points of a system or a component.

Pressure, Differential - the difference in pressure between two points in a system (e.g. the difference between the discharge pressure and suction pressure in the pump).

Pressure, Differential Set - the pressure differential in pounds per square inch between the set pressure and the constant superimposed back pressure. It is applicable only when a conventional type safety relief valve is being used in service against constant superimposed back pressure.

Pressure, Discharge - pressure of the oil as it exits a pump station. Pressure, Gauge - Pressure, Gauge - 1) pressure measured relative to ambient pressure; 2) the difference between

the local absolute pressure of the system and the atmospheric pressure at the place of the measurement.

Pressure, Gauge - pressure above atmospheric pressure. Pressure, Gauge - pressure measured relative to ambient pressure. Pressure, Gauge - PSIG. Corrected pressure; the difference between a given pressure and that

of the atmosphere. Pressure, Gauge - the amount by which the pressure measured in a fluid exceeds that of the

atmosphere. Pressure, Gauge - the amount by which the total absolute pressure exceeds the ambient

atmospheric pressure. Pressure, Head - the pressure to the height of a column or body of fluid. It is usually expressed

in feet. Pressure, Hydrostatic - refers to the pressure in a liquid at rest; equals its depth multiplied by

its density. Pressure, Impact - the pressure of a moving fluid brought to rest that is in excess of the

pressure the fluid has when it does not flow; that is, total pressure less static pressure. Impact pressure is equal to dynamic pressure in incompressible flow, but in compressible flow, impact pressure includes the pressure change owing to the compressibility effect.

Pressure, Instrument - the output pressure from an automatic controller that is used to operate a control valve. It is the input signal to the valve.

Pressure, Leak Test - the inlet pressure used for a standard quantitative seat leakage test. Pressure, Loading - the pressure used to position a pneumatic actuator. It is the pressure that

is actually applied to the actuator diaphragm or piston. It can be the instrument pressure if a valve positioner is not used or is bypassed.

Pressure, Maximum Allowable Operating - a rating indicating the maximum pressure at which a pipeline or segment of a pipeline may be operated under the D.O.T. regulations in normal conditions; also called Pressure Rating; see Pressure, Maximum Allowable Working

Pressure, Maximum Allowable Working - Pressure, Maximum Allowable Working - the maximum gage pressure permissible in the top of a

completed vessel in its operating position for a designated temperature. This pressure is based on calculations for each element in a vessel using nominal thicknesses, exclusive of allowances for corrosion and thickness required for loadings other than pressure it is the basis for the pressure setting of the pressure-relieving devices protecting the vessel. The design pressure may be used in place of the maximum allowable working pressure in cases where calculations are not made to determine the value of the latter.

Pressure, Maximum Allowable Working - the maximum gauge pressure in a pressure vessel at a designated temperature, used for the determination of the set pressure for relief valves.

Pressure, Maximum Allowable Working - the highest gage pressure that can safely be applied to an internally pressurized system under normal operating conditions. It is usually well below the design bursting pressure and the hydrostatic test pressure for the system, and is the pressure at which relief valves are set to lift.

Pressure, Maximum Operating - the highest pressure to which pressure containing equipment is exposed during operation. It includes pressure caused by normal operation, i.e. the highest operating pressure in one of the applicable heat and material balance streams, and all normal transient conditions such as start-up, shut-down, depressurizing, pigging, cleaning, flushing and purging. It does not include pressure caused by equipment failure or incorrect operation.

Pressure, Maximum Shut Off (Delta-P) - the pressure of the media flowing into the valve against which the valve will have to close.

Pressure, Maximum Working (MWP) - the maximum total pressure permissible in a device under any circumstances during operation, at a specified temperature. It is the highest pressure to which it will be subjected in the process. It is a designed safe limit for regular use. NOTE: MWP can be arrived at by two methods: a) designed -by adequate design analysis, with a safety factor; b) tested - by rupture testing of typical samples; see Pressure, Design.

Pressure, Nominal (PN) - the maximum permissible working pressure in bar gauge at 20° C. This rating is not generally used in the petroleum and petrochemical industries.

Pressure, Operating - Pressure, Operating - the nominal or average pressure in a fluid system. Pressure, Operating - the pressure to which the vessel is usually subjected in service, expressed

in pounds per square inch gage. A vessel is usually designed for a maximum allowable working pressure, in pounds per square inch gage, which will provide a suitable margin above the operating pressure in order to prevent any undesirable operation of the relief device. (It is suggested that this margin be as great as possible consistent with economical vessel and other equipment design, system operation and the performance characteristics of the pressure relieving device.)

Pressure, Operating - the pressure which a system operates. Pressure, Operating - the system pressure at which a process is operating. Pressure, Partial - ideally, in a mixture of gases, each component exerts the pressure it would

exert if present alone at the same temperature in the total volume occupied by the mixture. The partial pressure of each component is equal to the total pressure multiplied by its mole fraction in the mixture. For an ideal gas, the mole fraction is equal to the volume fraction of the component; see Mole.

Pressure, Piping - 1) the pressure at which a safety valve opens; 2) the pressure the pipe cannot withstand without exceeding its design characteristics.

Pressure, Popping - Pressure, Popping - in compressible fluid service, the inlet pressure at which a safety valve disk

opens. Pressure, Popping - in compressible fluid systems, the inlet pressure at which a safety relief

valve opens. Pressure, Proof - the nondestructive test pressure in excess of the maximum rated operating

pressure. Pressure, Rated Working - the maximum internal pressure equipment is designed to contain,

not to be confused with test pressure. Pressure, Resealing - the inlet pressure at which fluid no longer leaks past a relief valve after it

is closed. Pressure, Rupture - the pressure, determined by test, at which a device will burst. NOTE: This

is an alternate to the design procedure for establishing maximum working pressure (MWP). The rupture pressure test consists of causing the device to burst.

Pressure, Set - Pressure, Set - the inlet pressure at which a relief valve begins to open as required by the code

or standard applicable to the pressure vessel to be protected. Pressure, Set - the inlet pressure at which the pressure relief valve is adjusted to open under

service conditions, expressed in pounds per square inch gage. In a safety or safety relief valve in gas, vapor, or steam service, the set pressure is the inlet pressure at which the valve pops under service conditions. In a relief or safety relief valve in liquid service, the set pressure is inlet pressure at which the valve starts to discharge under service conditions.

Pressure, Set - the pressure at which a pressure relief valve begins to open. It is established by adjusting the valve spring.

Pressure, Start-to-Leak - the amount of inlet pressure at which the first bubble occurs at the outlet of a safety relief valve with a resilient disk when the valve is subjected to an air test under a water seal.

Pressure, Static - the pressure in a fluid at rest. Pressure, Steam Working - the maximum working pressure capability of a valve when used with

steam, provided that the steam temperature does not exceed the maximum for the valve shell material. It is marked on the valve as S, SP, or SWP.

Pressure, Suction - pressure of the oil as it enters a pump station. Pressure, Superimposed Back - Pressure, Superimposed Back - the static pressure at the outlet of an operating pressure relief

device, resulting from pressure in the discharge system. Pressure, Superimposed Back - the static pressure existing at the outlet of a pressure relief

device at the time the device is required to operate. It is the result of pressure in the discharge system from other sources.

Pressure, Supply - Pressure, Supply - the plant air supply pressure available to operate a pneumatic actuator. Pressure, Supply - the pressure at the supply port of a device such as a controller, positioner, or

transducer. Common values of control valve supply pressures are 20 psig for a 3-15 psig output and 35 psig for a 6-30 psig output.

Pressure, Total - the gross load applied on a given surface. Pressure, Vapor - Pressure, Vapor - pressure at a given temperature below which a liquid will convert to a gas. It is

measured in pounds per square inch absolute (psia) and is a function of the temperature of the liquid.

Pressure, Vapor - the maximum pressure exerted by a liquid (or solid) heated to a given temperature in a closed container.

Pressure, Vapor - the pressure, at a given temperature, in which the liquid and gaseous phases coexist in equilibrium.

Pressure, Working - Pressure, Working - 1) the maximum pressure-retaining capability of a valve; 2) the pressure of

the fluid passing through a valve measured at the valve inlet. Fluid pressure varies as it passes through the valve and is lower at the valve outlet.

Pressure, Working - the allowable operating pressure in a pressurized vessel or conduit, usually calculated by ASME (American Society of Mechanical Engineers) or API (American Petroleum Institute) codes.

Pressure, Working - the maximum allowable operating pressure for an internally pressurized vessel, tank or piping system, usually defined by applying the ASME Boiler and Pressure Vessel Code or the API piping code.

Pressure, Working - the pressure (pounds per square inch) at which a valve is designed to operate.

Pressure, Working - the pressure at which an apparatus or engine works, as distinct from its test pressure.

Pressurization - the technique of preventing an external atmosphere, which may be ignitable, from entering an enclosure by maintaining the internal pressure of the enclosure's protective gas (with or without continuous flow) at a pressure level above that of the external atmosphere. This type of protection is referred to by IEC as "Ex p". NOTE: In the United States, pressurization is the process of supplying an enclosure in a Class II application with clean air or an inert gas, with or without continuous flow, at sufficient pressure to prevent the entrance of combustible dusts.

Presswork - the entire range of bending and drawing operations in the cold forming of sheet metal products.

Pretensioning - process of precasting concrete beams with tensioned wires embedded in them; also known as Hoyer Method of Prestressing.

PRIC - Pressure Instrument Connection on Piping Primary Carbide - carbide precipitated in cast iron during solidification. Primary Creep - see Primary Stage Creep Primary Service Rating - the working pressure class rating for a valve. Primary Stage Creep - Primary Stage Creep - in the primary stage, relatively rapid expansion takes place, but at a

slower rate. Primary stage creep is of interest to a designer since it forms part of the total extension reached in given time and may affect clearances. Thus it is of much design value to engineers.

Primary Stage Creep - the initial high strain-rate region in a material subjected to sustained stress.

Prime Mover - the source of mechanical power used to drive the pump or compressor. Priming - in a boiler, the excessive carryover of fine water particles along with the steam

because of insufficient steam space, faulty boiler design, or faulty operating conditions.

Principal - the person on behalf of whom an agent is acting; someone ultimately responsible for fulfilling an obligation.

Principal Axis of Strain - one of the three axes of body that were mutually perpendicular before deformation; also known as Strain Axis.

Principal Strain - the elongation or compression of one of the principal axes of strain relative to its original length.

Priority Valve - a valve that directs flow to one operating circuit at a fixed rate and directs excess flow to another operating circuit.

Procedure - a document that defines the purpose and scope of an activity and details how it is to be carried out.

Procedure Qualification Record (PQR) - sets out the code essential variables under which code qualification of the weld metal and weld joint properties are achieved. The PQR documents the primary weld control data from which Welding Procedure Specification production conditions are derived.

Process - Process - a series of stages which a product (such as crude oil) passes through, resulting in the

development or transformation of it. Process - a system or series of continuous or regularly occurring actions taking place in a

predetermined or planned manner to produce a desired result. Process Annealing - heating a material, like steel or aluminum in sheet or wire form, between

cold-working operations, such as stretch forming or rolling, at just below its critical temperature followed by slow cooling, to improve its structural properties.

Process Block Valve - the first valve off the process line or vessel used to isolate the measurement piping; see Line Class Valve.

Process Control System - the automatic control of a continuous operation. Process Piping - in an industrial facility, pipe work whose function is to convey the materials

used for the manufacturing processes. Processing - the act of converting material from one form into another desired form. Product - 1) an item or goods made by an industrial firm; 2) the total of such items or goods.

Product Analysis - the chemical analysis of a material done on a finished component to show compliance with the material specifications. It usually has tolerances defined for each element to allow for differences in the completed product compared to the molten metal.

Product Line - 1) the range of products offered by a firm; 2) a group of basically similarproducts, differentiated only by such characteristics as color, style or size.

Production - output, such as units made in a factory, oil from a well, or chemicals from a processing plant.

Profiled Keyway - a keyway for a straight key formed by an end-milling cutter; also known as End-Milled Keyway.

Profiling Machine - a machine used for milling irregular profiles; the cutting tool is guided by the contour of a model.

Program - an undertaking of significant scope that is enduring rather than occurring within a limited time span.

Project - a specifically defined task which is established to meet a single requirement, either stated or anticipated, for research data, an end item of material, a major component, or a technique.

Projection Welding - Projection Welding - in it, the heat for welding is derived from the localization of resistance at

predetermined points by means of projections, embossments, under adequate welding pressure.

Projection Welding - this process is a developed form of spot welding. In this process, spots at which welding operation is to be performed are located by providing projections at the desired located points on the surfaces of the workpieces. Different projections are given on the surfaces and only surfaces where welding is to take place are in contact with each other. In this case pressure is exerted mechanically, and as they come in contact, current is switched on. The pressed workpieces get welded after cooling at the projected surfaces. This method differs from spot welding, as in this case welding is completed at different points, while in spot welding the welding takes place at one spot only.

Proof - Proof - reproduction of a die impression by means of a cast. Proof - test, trial or demonstration Proof Load - Proof Load - 1) a load which is greater than the working load to which a structure or a mechanism

has been tested to ascertain whether it can withstand a like load without permanent distortion or damage; 2) the product of the limit load and the proof factor of safety; also called Test Load.

Proof Load - a predetermined test load, greater than the service load, to which a specimen is subjected before acceptance for use.

Proof Resilience - the tensile strength necessary to stretch an elastomer from zero elongation tothe breaking point, expressed in foot-pounds per cubic inch of original dimension.

Propane Deasphalting - petroleum-refinery solvent process using propane to remove and precipitate asphalt from petroleum stocks, such as for lubricating oils.

Proportional Elastic Limit - the greatest stress intensity for which stress is still proportional to strain.

Proportional Limit - the greatest stress a material can sustain without departure from linear proportionality of stress and strain.

Protective Finish - a coating applied to equipment to protect it from corrosion and wear; many substances, including metals, glass, and ceramics, are used.

Protein Binders - caseine and glue are known as protein binders. These binders harden by baking.

Proximity Limit Switch - a solid state switch is electrically tripped without mechanical contact being made. This type of switch is generally used to interface with computer or microprocessor controls.

PRT - Petroleum Revenue Tax PSB - Pressure Seal Bonnet

PSC - Production Sharing Contract PSE - Plain Small End PSFS - Process Safeguarding Flow Scheme PSI - the abbreviation for Pounds per Square Inch, the unit of pressure in the British Engineering

System. PSIA - PSIA - Pounds per Square Inch Absolute Psia - Pounds per square inch absolute PSIA - pounds per square inch, absolute. The sum of atmospheric pressure and gauge

pressure. This will vary with altitude. PSIG - PSIG - pounds per square inc, gauge. Pressure differential above or below atmospheric

pressure. Psig - Pounds per square inch gage PSIG - Pounds per Square Inch Gauge PSSB - Petronas Carigali Sdn. Bhd. PSV - Pressure Safety Valve Psychrometer - Psychrometer - a device comprising two thermometers, one a dry bulb, the other a wet or wick-

covered bulb, used in determining the moisture content or relative humidity of air or other gases; also known as Wet and Dry Bulb Thermometer.

Psychrometer - a device consisting of two thermometers, one a dry bulb, the other a wet bulb or wick-covered bulb, used to determine the moisture content or relative humidity of air or other gases.

Psychrometer - a device consisting of two thermometers, one of which is covered with a water saturated wick, used for determining relative humidity; for a given set of wet bulb and dry bulb temperature readings, relative humidity is read from a chart; also known as Wet And Dry Bulb Thermometer.

Psychrometer - an instrument with wet-bulb and dry-bulb thermometers, for measuring moisture in the air.

PT - 1) Liquid Penetrant Examination; 2) Pressure - Temperature P-T - Pressure-Temperature PTFE - PTFE - Polytetrafluoroethylene (Teflon) PTFE - Polytetrafluoroethylene; a type of fluorinated thermoplastic with outstanding chemical

resistance, low leachability, and excellent lubricity. PTFE Bellows - a sealing mechanism that is made of PTFE, formed in a bellows shape, used on

some solenoid valves. PTS - Petronas Technical Standards PTT - Petroleum Authority of Thailand PTTEP - PTT Exploration and Production Company of Thailand Pull - to produce the required propelling power. Pull In Torque - the largest steady torque with which a motor will attain normal speed after

accelerating from a standstill. Pull In Torque (of a synchronous motor) - the maximum torque against which the motor will

pull its connected load into synchronism, at rated voltage and frequency, and when the field circuit is energized, if the excitation is provided. (note: the pull-in torque depends on the total inertia of the rotating parts).

Pull Out Torque - the largest torque under which a motor can operate without sharply losing speed.

Pull Out Torque (of a synchronous motor) - the maximum torque a (synchronous) motor develops at operating temperature and at synchronous speed with rated voltage, frequency and field current.

Pull Strength - a unit in tensile testing; the bond strength in pounds per square inch. Pull Up Torque (of an AC motor) - the smallest torque the motor develops between zero and

the speed which corresponds to the breakdown torque when the motor is supplied

at the rated voltage and frequency. (note: this definition does not apply to those asynchronous motors of which the torque continually decreases with increase in speed).

Pulsation Dampening - device installed in a fluid piping system (gas or liquid) to eliminate or even out the fluid-flow pulsations caused by reciprocating compressors, pumps, and such.

Pulsation Welding - a spot, projection or seam-welding process in which the welding current is interrupted one or more times without release of pressure or change of location of electrodes.

Pump - Pump - a device that converts mechanical force and motion into hydraulic fluid power. Pump - a machine that draws a fluid into itself through an entrance port and forces the fluid out

through an exhaust port. Pump Controls - controls applied to positive-displacement variable delivery pumps to adjust

their volumetric output or direction of flow. Pump, Axial Piston - a pump having multiple pistons disposed with their axes parallel. Pump, Bucket - a pump having a bucket or piston which has valves through it for passage of the

fluid lifted. Pump, Centrifugal - a pump that produces fluid velocity and converts it to pressure head. Pump, Fixed-Displacement - a pump in which the displacement per cycle cannot be varied. Pump, Force - a pump fitted with a solid plunger and a suction valve which draws and forces a

liquid to considerable height above the valve or puts the liquid under a considerable pressure.

Pump, Radial Piston - a pump having multiple pistons disposed radially, actuated by an eccentric element.

Pump, Slush - a pump normally used to circulate drilling fluids through the drill stem into the annulus of the hole and to the surface for the purpose of removing cuttings and maintaining a hydrostatic head.

Pump, Variable-Displacement - a pump in which the volume of fluid per cycle can be varied. Pumping Station, Automatic - an installation on a pipeline that automatically provides the

proper pressure when a fluid is being transported. Pup - on a butt weld valve, a valve extension welded on in the factory, to move welding heat

further away the seat when the valve is welded into a pipeline later. After the pup is welded in the factory, the valve can be re-tested to ensure the pup welding did no seat damage.

Purify - to remove unwanted constituents from a substance. Push Down To Close - a term used to describe a linear or globe style valve that uses a direct

acting plug and stem arrangement. The plug is located above the seat ring. When the plug is pushed down, the plug contacts the seat, and the valve closes. Note:most control valves are of this type.

Push Down To Open - a term used to describe a linear or globe style valve that uses a reverse action plug and stem arrangement. The plug is located below the seat ring. When the plug is pushed down, the plug moves away from the seat, and the valve opens.

Push Fit - a hand-tight sliding fit between a shaft and a hole. Push Nipple - a short length of pipe used to connect sections of cast iron boilers. PV - Pilot Operated Valve PVC - Polyvinyl Chloride. This is the most popular material used for plastic piping systems. PVDF - Polyvinylidene Fluoride; a dense, high-purity plastic that is used in critical applications,

such as semiconductor manufacturing. Kynar PVDF is a trademark of Elf-Atochem.PVF - Pipes, Valves, Fittings. Used to describe a segment of the plastics industry, or distributors

who specialize in these products. PWHT - Post Weld Heat Treatment PXT - Plain large end X Threaded small end PXU - Plain large end X female thread small end Pyrolysis - the chemical decomposition of a substance that occurs when it is heated to a high

temperature in the absence of air.

Q + T - Quench and Tempering QA - Quality Assurance QAR - Quality Assurance Requirements QC - 1) Quality Control; 2) Quick Coupling QEV - Quick Exhaust Valve QMI - Quality Measuring Instrument QP - Quality Plan Quadrant - a frame, typically in the form of a quarter circle, enclosing a control lever. Qualification - demonstrated skill, documented training, knowledge and experience required for

personnel to properly perform the duties of a specific job. Qualified Valve - a valve that provides full conductance. Quality Assurance - a series of planned or systematic actions required to provide adequate

confidence that a product or service will satisfy given needs. Quality Control - inspection, analysis, and action applied to a portion in a manufacturing

operation to estimate overall quality of the product and determine what, if any, changes must be made to achieve or maintain the required level of quality.

Quantimet - a machine which analyses material surfaces for microstructural variables such as grain size, diameter, orientation etc. It was based originally on the optical microscope, now extended to electron optical examination.

Quarter Turn Valve - Quarter Turn Valve - a category of valves (such as ball and plug valves) which require just a 90

degree turn of the stem to move from the fully open to the fully closed positions. Quarter Turn Valve - a valve whose flow control element is rotated through 90 degrees from open

to closed. It can be a ball valve, a butterfly valve, or a plug valve. Quarter Turn Valve - category of valves (such as ball, plug, butterfly) which require just a 90

degree turn of the stem to move from the fully open to the fully closed position. Seealso multi-turn. Note: some larger valves may, for simpler manual operation, be fitted with gearboxes, giving them the appearance of a multi-turn valve.

Quench and Temper - quench hardening followed by tempering. Quenching - Quenching - a process of controlled, usually rapid, cooling of heated metal in liquid such as

water, brine, oil or molten salt, or in a gas such as air, nitrogen, hydrogen, argon or various mixtures of hydrocarbons, to effect hardening to tempering.

Quenching - a process of cooling by plunging a heated object into a fluid, with the purpose of retaining the material in a metastable state. Quenching into water gives a more rapid cooling rate than into oil. The term also applies to cooling in salt and molten metal baths or by means of an air blast. It is applied to steels heated above their upper critical temperatures in order to harden them prior to tempering and to other alloys for solution treatment prior to precipitation hardening.

Quenching - fast cooling of metal by dipping in oil. Instead of the normal crystal structure, needle-shaped crystals of martensite form, creating a great deal of stress inside the metal. Quenching is frequently followed by tempering, to reduce the internal stresses created by quenching.

Quenching - rapid cooling. When applicable, the following more specific terms should be used: Direct Quenching. Fog Quenching. Hot Quenching, Interrupted Quenching, Selective Quenching, Spray Quenching, and Time Quenching.

Quenching - shock cooling by immersing liquid or molten material into a cooling medium (liquid or gas); used in metallurgy, plastics forming, and petroleum refining.

Quenching - the dipping of heated steel into water, oil or other bath, to impart necessary hardness.

Quenching - the rapid cooling of steels from an above-critical temperature by plunging them into water, oil salt, a molten metal or a cold blast of air.

Quenching - to cool hot metal rapidly by plunging in cold liquid in order to alter its properties. Quenching Oils - oils used in heat treating. Fish oils are much used but have offensive odors.

Mineral, fish, vegetable, and animal oils are often compounded and sold under trade names.

Quick Opening Valve - a control valve with trim characteristic designed to produce large flow

capacity with small amount of valve opening. Quill - a hollow shaft into which another shaft is inserted in mechanical devices.

R - Review R / C PSC - Revenue-Over-Cost Production Sharing Contract Ra - abbreviation for "Arithmetic Average Roughness Height" - the measure of the roughness of a

surface expressed in micro inches. The higher the number, the rougher the surface. Used to designated the desired surface finish for end flange raised faces.

Rabbet - a joint formed by fitting one member into a groove, channel, or recess in the face or edge of a second member.

Rabbling - stirring a molten charge, such as metal or ore. Race - Race - 1) the inner or outer steel rings of a ball bearing or a roller bearing; 2) a straight bar or a

flat plate having a series of equi-distant teeth on one face; see also Rack and Pinion.

Race - a groove in which something (such as a ball bearing) moves or slides. Race - either of the concentric pair of steel rings of a ball bearing or roller bearing. Rack - Rack - a bar containing teeth on one face for meshing with a gear. Rack - a bar having teeth along one of its long faces for meshing with a gear. Rack - a bar with teeth which connect the teeth on a pinion to convert linear motion into rotary

motion, or vice versa. Rack and Pinion - Rack and Pinion - a method of transforming rotary into linear motion, or vice versa; it is

accomplished by a pinion or small gear wheel which engages a straight, toothed rack.

Rack and Pinion - an arrangement of a straight-toothed rack and a pinion which is used toconvert rotary into linear and reciprocal motion, generally a pinion wheel with a fixed center actuating a movable rack.

Rack and Pinion - used to convert rotary motion to linear motion. Radial - said of lines: spreading out from the center of a circle, like rays. Radial Bearing - a bearing with rolling contact in which the direction of action of the load

transmitted is radial to the axis of the shaft. Radial Force - in machining, the force acting on the cutting tool in a direction opposite to depth of

cut. Radial Load - Radial Load - a load exerted perpendicular to the axis. Radial Load - load acting in a direction perpendicular to the shaft/axis, i.e. along the radius. Radiation - an emission of varying energy content from a disturbed atom undergoing internal

change. There are two broad classifications or types: a) Corpuscular -compromising streams of particles either neutral or charged, e.g. protons, electrons, neutrons; b) Electromagnetic - compromising wave-like emissions as gamma, ultraviolet, etc.

Radiation Damage - a measure of the loss in certain physical properties of organic substances such as elastomers, due principally to ionization of the long chain molecule. It is believed that this ionization process (i.e. electron loss) results in redundant cross-linking and possible scission of the molecule. This effect is cumulative.

Radiation Dosage - the total amount of radiation energy absorbed by a substance. This value is expressed in ergs per gram, and is denoted by the following units: a) Roentgen - a quantity of gamma or x-ray radiation equal to approximately 83 ergs of absorbed energy per gram of air; b) REP (Roentgen equivalent-physical) - a quantity of ionizing radiation that causes an energy absorption of approximately 83 to 93 ergs per gram of tissue; c) REM (ROENTGEN equivalent-man) - similar to REP except used to denote biological effects; d) RAD - the unit of dosage related to elastomers. It is independent of type of radiation or specimen, and denotes an energy absorption level of 100 ergs per gram (of elastomer). The RAD is approximately equal to 1.2 Roentgens.

Radiator Valve - a valve for controlling the flow of water through a radiator. Radiographic Inspection (RT) - Radiographic Inspection (RT) - a nondestructive inspection method using x-rays to locate

internal flaws in castings, fabricated parts and welds. Radiography - the technique of examining the interior of an item by means of recorded images

(known as radiographs), which are produced by X-rays on photographic film. Radiography Technique - the use of x-rays and i-rays, in the inspection of castings and forgings

for defects like blowholes, cracks, shrinkage cavities and slag inclusions, is of primary metallurgical interest to a metallurgist. These defects are of special importance in the components designed to withstand high temperature and pressure employed in power plants, atomic reactors, chemical and pressure vessels and oil refining equipment. The principal radiography technique is based upon the principle of exposing the cast or forged metal to short wavelength radiations. Casting are exposed to x-rays (wavelength 0.001 x 10-8 cm) and i-rays (wavelength 0.005 x 10-10 cm to 3 x 10-8 cm) from suitable sources, i.e. x-ray tube and cobalt 60, respectively. These rays can penetrate opaque matter and thus are used to detect defects in the metal. The penetrating power of the x-rays is lesser as compared to the i-rays. Thus, for small thickness x-rays are used and for greater thickness i-rays are used.

Radius Rod - a rod which restricts movement of a part to a given arc. Raffinate - in solvent refining, that portion of the treated liquid mixture that remains undissolved

and is not removed by the selective solvent; also known as Good Oil to petroleum-refinery operators.

Rag Bolt - see Barb Bolt Raised Face (RF) - a flange face having a flat surface protruding 1/16 or 1/4 inch beyond the

outer flange face. Raised Face Flanged Globe-Style Angle Control Valve - a valve design in which one port is

collinear with the valve stem or actuator and the other port (usually the inlet) is at right angles to the valve stem.

Raised Faced (RF) - Raised Faced (RF) - the raised area of a flange face which is the gasket sealing surface

between mating flanges. It is defined in ASME B16.5. Class 150 and 300 valves have 0.06" RF and Classes 600 and up have a 0.25" RF.

RAL Paint - a European standard for paint colors in powder form. There are no standard paint colors available in wet form.

Ramping - in the production of parts fabricated from composite materials, a gradual and programmed sequence of changes in temperature or pressure that control curing and cooling.

Ramsbottom Valve - in which the load is applied to two coupled valve heads by a tension spring.

Rangeability - Rangeability - the range over which a control valve can control. It is the ratio of the maximum to

minimum controllable flow coefficients. This is also called Turndown, although technically it is not the same thing. There are two types of rangeability - inherent and installed. Inherent rangeability is a property of the valve alone and may be defined as the range of flow coefficients between which the gain of the valve does not deviate from a specified gain by some stated tolerance limit. Installed rangeability is the range within which the deviation from a desired installed flow characteristic does not exceed some stated tolerance limit.

Rangeability - the ratio of maximum to minimum controllable Cv (Kv). Rangeability - the ratio of the maximum controllable flow to the minimum controllable flow. For

instance, a valve with a rangeability of 50 to 1 and having a total flow capacity of 100 gal/min, fully open, will control flow accurately down as low as 2 gal/min. The valve may or may not have tight shutoff. However, for this particular valve you could not depend upon getting steady flow of, for instance, 1.5 gal/min if this were necessary to maintain stable load conditions. Generally, rangeabilities in the range of 50 to 1 or 40 to 1 are considered excellent for extreme precision of control. Valves with high rangeability are very expensive to manufacture since very close tolerances are involved between the disc and the seat. Competitively priced control valves ordinarily have rangeability of less than 30 to 1. In many cases wide rangeability compensates automatically for deviations from anticipated conditions

without loss of control. Ranking Scale - a thermometer scale based on absolute zero of the Fahrenheit scale, in which

the freezing point of water is approximately 492° R. Rat Distillate - a refinery designation for gasoline and other fuels as they come from the

condenser, before undesirable substances are removed by further processing. Ratchet and Pawl Mechanism - a cogwheel (ratchet) with which a single pivoted catch (pawl)

engages, thereby disallowing any backward turning. Rate - the speed of movement or change Rate of Flow Control Valve - see Flow Control Valve Rated Capacity - the manufacturers stated capacity rating for mechanical equipment, for

instance, the maximum continuous capacity in pounds of steam per hour for which a boiler is designed.

Rated Flow Coefficient - the flow coefficient (Cv) of the valve at rated travel. Rated Horsepower - the maximum or allowable power output of an engine, turbine or other

prime mover under normal, continuous operating conditions. Rated Load - Rated Load - the maximum design load for a machine, structure or vehicle. Rated Load - the maximum load a machine is designed to carry. Rated Output (Power) - the value of the output power included in the rating. Rated Relieving Capacity - the measured relieving capacity for which the pressure relief device

is rated in accordance with the applicable code or standard. Rated Supply Voltage - the supply voltage, or range of voltages, for which the manufacturer has

designed the equipment. Rated Torque - the torque the motor develops at its shaft-end at rated output and speed. Rating - Rating - a designation of an operating limit for a machine, apparatus, or device used under

specified conditions. Rating - the whole of the numerical values of the electrical and mechanical quantities, with their

duration and sequences, assigned to the machine by the manufacturer, the machine complying with the specified conditions. (Note: the duration may be indicated by a qualifying term).

Ratio - the value obtained by dividing one number by another, indicating their relative proportions.

Ray - any of a set of lines fanning out from a central point. RB - Reduced Bore RC - Regular Cycling Rc - Rockwell "C" RCC - Remote Control Center Re - (European rust scale) Ream - to enlarge or clean out a hole. RECB - Reducer Concentric Butt Weld Ends Receiver - a container in which gas is stored under pressure as a supply source for pneumatic

power. Recess - a surface groove or depression. Reciprocating - moving back and forth, as a piston reciprocating in a cylinder. Record Copy - a document to be retained at vendor’s premises and to be available for review

when required. This document is for record purposes and does not require purchaser’s approval.

Recrystallization - Recrystallization - 1) the change from one crystal structure to another, as occurs on heating or

cooling through a critical temperature; 2) the formation of a new, strain-free grain structure from that existing in cold worked metal, usually accomplished by heating.

Recrystallization - a nucleation and growth process in which new, strain free grains in a metal or alloy form from a distorted structure that has undergone at least a threshold amount of cold work; it occurs in a few metals at room temperature but requires annealing at elevated temperature for detectable amounts to occur in most.

Recrystallization Temperature - Recrystallization Temperature - that marking a change in crystal form at which new crystals

nucleate and grow to consume the existing structure. Range of temperature through which strain hardening disappears, approximately 0.6 tm.

Recrystallization Temperature - the minimum temperature at which a new strain-free structure is produced in cold-worked metal within a specified time.

Recrystallization Temperature - the minimum temperature at which complete recrystallization of a cold worked metal occurs in a specified time, usually one hour.

Reduce - 1) to undergo a chemical reaction in which a substance gains hydrogen or loses oxygen; 2) to make into a more concentrated form: 3) to bring into a metallic state by removing nonmetallic elements, i.e. to covert ore into metal.

Reduced Bore - Reduced Bore - a valve bore (port) found on gate valves and ball valves that is substantially

smaller than full bore, approximately one pipe size on gate valves and 60% of full bore on ball valves; compare with Full Port, Regular Port, and Venturi Port.

Reduced Bore - a valve bore opening that is smaller than the line size or the valve end connection size; also called Reduced Port.

Reduced Bore - indicates that the internal diameter of the valve is lower than the piping to which the valve is fitted.

Reduced Bore - indicates that the internal diameter of the valve is smaller than the piping to which the valve is fitted as opposed to full bore; see Full Bore.

Reduced Bore Ball Valve - a ball valve having reduced bore round ports in the body throat, body connector (s) and ball.

Reduced Opening Valve - a valve with either a venturi or other opening through the closure mechanism.

Reducer - Reducer - a fitting for connecting two pipes (or a pipe and a valve) of different sizes. Reducer - a fitting having a larger size at one end than at the other and threaded inside, unless

specifically flanged or for some special joint. Reducing Agent - either natural gas or coal can be used to remove the oxygen from iron ore in

order to produce a scrap substitute. In gas-based processes, the iron ore is heated in a vessel as reformed natural gas passes through. In coal-based processes, iron ore is combined with gasified or ground coal and heated. The oxygen in the ore combines with carbon and hydrogen in the gas or coal, producing reduced, or metallic, iron.

Reducing Coupling - a coupling used to connect a smaller pipe to a larger one. Reducing Flame - a gas welding flame which has reducing effects. Reducing Valve - Reducing Valve - a valve which is used for reducing the pressure of a fluid in a supply line. Reducing Valve - see Pressure-Reducing Valve Reduction - Reduction - 1) gain of electrons by a constituent of a chemical reaction; 2) removal of oxygen

from a chemical compound. Reduction - the removal of oxygen from an oxide. Iron oxide is reduced to metallic iron by carbon

monoxide gas. Reduction - this type of reaction may be considered as the opposite to oxidation in that its

function is to remove oxygen. The principle of reduction relies on the fact that in nature some substances combine more readily with oxygen-rich compounds. The oxygen can, under the correct conditions, be induced to change partners. A simple example of this phenomenon is when hydrogen is passed over heated copper oxide. A reaction takes place and the oxygen leaves the copper and combines with the hydrogen to leave pure copper. (hydrogen + copper oxide = copper + water : H2 + CuO = Cu + H2O). Thus copper is separated from its oxide by what is termed a reduction process. Note: the heat allows the atoms of oxygen to escape more freely. Reducing agents do not necessarily need to be gaseous, they may be solid. There are two major examples of the use of reduction processes in engineering. The first is employed in the steel industry to separate iron from iron oxide ore, and the second is the protection of steel components while they are undergoing heat

treatment. Reduction of Area - 1) commonly, the difference, expressed as a percentage of original area,

between the original cross-sectional area of a tensile test specimen and theminimum cross-sectional area measured after complete separation; 2) the difference, expressed as a percentage of original area, between original cross-sectional area and that after straining the specimen.

REEB - Reducer Eccentric Butt Weld Ends Refine - to free from impurities, as the separation of petroleum, ores, or chemical mixtures into

their component parts. Refinery - Refinery - a system of process units used to convert crude petroleum into fuels, lubricants, and

other petroleum-derived products. Refinery - plant where hydrocarbons are separated and transformed into more marketable

products. Refining - the process of converting crude oil into a more valuable commodity. Refining Residuals - by-products of petroleum refining, largely consisting of petroleum-based

sludge, spent catalysts, and nonhazardous wastes. Reflux Valve - Reflux Valve - a check valve Reflux Valve - a valve fitted on the delivery side of a pump so that the pump and its suction

system are protected against inertia surges in the delivery pipe. Refractoriness - in casting, ferrous metals and alloys are poured into molds at temperatures of

1600° to 1800° C. It requires refractory properties of sand, i.e. it must be capable of withstanding high temperatures.

Refractory Metals - a term applied to transition group elements in the periodic table which have high melting points. They include chromium, titanium, platinum, tantalum, tungsten and zirconium.

Register, Off or Uneven - see Off-register Regrind - thermoplastic that has been processed once, then is placed in a grinder to be

shredded / pelletized for re-molding. In injection molding, runners etc. are often re-ground. No thermoplastic can be successfully reground and remolded indefinitely; eventually the molecular bond begins to break down and the plastic is no longer usable.

Regular Cycling - opening or closing a valve once a week or more. Regular Pattern - having substantially full-area seats ports of rectangular or similar shape. Regular Port - a valve bore (port) found on ball valves and plug valves that is smaller than full

bore, approximately 75% to 90% of full bore on ball valves and 60% to 70% on plug valves; compare with Full Port, Reduced Port, and Venturi Port.

Regulating Valve - a valve intended for regulating purposes and which may have a clearance between the disc and the body in the closed position.

Regulating Valve - Regulating Valve - this valve type is used to regulate flows to provide a constant pressure output.Regulation - the process of holding constant a quantity such as speed, temperature, voltage, or

position by means of an electronic or other system that automatically corrects errors by feeding back into the system the condition being regulated; regulation thus is based on feedback, whereas control is not.

Regulator - Regulator - a device for controlling the supply of gases in welding. Regulator - a device that maintains a desired quantity at a predetermined value or varies it

according to a predetermined plan. Regulator - a type of control system or device that maintains the value of an output variable

constant relative to a set input value. Regulator - the device by which the operating pressure of a compressed air system is controlled.

A regulator will allow you to variably adjust the pressure from the minimum to maximum working pressure of the system.

Reinforcing Agent - material dispersed in an elastomer to improve compression, shear, or other stress properties.

Reinforcing Bar (Rebar) - a commodity-grade steel used to strengthen concrete in highway and building construction.

Relative Flow Coefficient - the ratio of the flow coefficient (Cv) at a stated travel to the flow coefficient (Cv) at rated travel.

Relative Humidity - Relative Humidity - the ratio between the weight of water vapor in the air and that in saturated air,

at the same temperature, which has the same as the corresponding ratio of the vapor pressure.

Relative Humidity - the ratio of the quantity of water vapor actually present in the atmosphere to the greatest amount possible at the given temperature.

Relaxation - Relaxation - 1) relief of stress in a strained material due to creep; 2) the lessening of elastic

resistance in an elastic medium under an applied stress resulting in permanent deformation.

Relaxation - decrease of stress with time at constant strain. Relaxation Test - a creep test in which the decrease of stress in an elastic medium under an

applied stress resulting in permanent deformation. Relay - an electrical switching device that, in response to a change in an electric circuit (such as

a small change in current), opens or closes one or more contacts in the same or another circuit.

Relief Valve - Relief Valve - a device used to protect piping and components from overpressure. Relief Valve - a direct spring loaded valve normally closed, which automatically opens in the

event of pressure reaching a predetermined maximum limit. It thus provides protection to that part of a system in which it is located.

Relief Valve - a pressure control valve whose primary function is to limit system pressure. Relief Valve - a pressure relief valve designed for use with liquids. Relief Valve - a safety device designed to open before dangerous pressure is reached. Relief Valve - a safety valve Relief Valve - a self-operated, fast acting valve which is used to bleed off excessive pressure in a

fluid system. Relief Valve - a valve which automatically discharges fluid relieve pressure. Relief Valve - an automatic pressure relieving device actuated by the static pressure upstream of

the valve, which opens in proportion to the increase in pressure over the opening pressure.

Relief Valve (Safety) - an automatic pressure relieving device actuated by the pressure upstream of the valve and characterized by opening pop action with further increase in lift with an increase in pressure over popping pressure.

Remote Gate Valve - a remotely controlled block valve for the primary purpose of protecting segments of the line in the event of a catastrophic pipeline break.

Repair - anything requiring at least partial disassembly of a valve. Representative Sample - Positive Material Identification (PMI) testing of a sample, consisting of

one or more pieces (components) selected at random from the inspection lot, which will be examined to determine acceptability of the inspection lot.

Reservoir - Reservoir - a container for storage of liquid in a fluid power system. Reservoir - a container used to store the liquid in a fluid power system. Reservoir - a place where something is kept in store. Resilience - Resilience - refers to the power of an elastically strained body to spring back on removal of load. Resilience - the capacity of a material to absorb or store energy. When a material is subjected to

external forces, it develops stress. When the stress is removed, the amount of energy that can be recovered within the elastic limit is called the Elastic Resilience. The energy stored per unit volume at the elastic limit is called the Modulus of Resilience.

Resilience - the capacity of a material to absorb or store energy. When a material is subjected to external forces, it develops stress. When the stress is removed, the amount of

energy that can be recovered within the elastic limit is called the elastic resilience. The energy stored per unit volume at the elastic limit is called the modulus of resilience.

Resilience - the stored energy of a strained or elastic material, such as on a compressed spring or in rubber dampers which have inherent damping properties.

Resilient - Resilient - able to return quickly to its original shape or position after being bent, twisted,

stretched, etc. Resilient - capable of returning to original size and shape after deformation. Resistance - Resistance - an opposition to the flow of a fluid through a device or system. A measure of the

effect of friction. Resistance - the resistance to flow in pipe or channel is expressed in ft head of water, and is

obtainable from various hydraulic formulae. Resistance Brazing - a brazing process in which heat is produced due to resistance to flow of

current. This process is carried out above 430° C. Resistance Coefficient - a measure of the resistance of a valve to fluid flow. It is determined by

the geometry of the valve. Resistance Seam Weld - overlapping plates are joined by fusion as in a spot weld with the

electric current flowing between two rotating wheels. Resistance Welding - Resistance Welding - a group of welding processes in which coalescence is produced by the

heat obtained from resistance of the work to the flow of current. Resistance Welding - a group of welding processes in which heat is obtained from resistance of

the work to electrical current in a circuit of which the work is one part. Resistance Welding - a process of electric welding in which the pieces to be welded are raised to

the required temperature by the passage of a heavy current through them while held in contact under mechanical pressure, e.g. butt welding, spot welding and seam welding.

Resistance Welding - in resistance welding, coalescence is obtained by the heat obtained from the resistance offered by the flow of electric current in a circuit of which the work is a part, and by the application of pressures.

Resistance Welding - joins metals by the simultaneous application of pressure and heat. Response Time - Response Time - the time lag between a signal input and the resulting change of output. Response Time - the time necessary for a closed valve to fully open, and for an open valve to

totally close. Voltage, pressure size and media affect response time. Typical response times for solenoid valves is 10-12 milliseconds.

Restrictor - a device that reduces the cross-sectional flow area. Restrictor, Orifice - a restrictor, the length of which is relatively small with respect to its cross-

sectional area. The orifice may be fixed or variable. Variable types are non-compensated, pressure compensated, or pressure and temperature compensated.

Retainer - Retainer - a device that holds a mechanical component in place. Retainer - a mechanical part that holds something in place. Retaining Ring - a steel ring between the races of a ball bearing to maintain the correct

distribution of the balls in the races. Retort - a vessel for heating metals such as iron and carbon to make steel. Return - a bend or turn in a piping system that causes a change in flow direction. Return Bend - a pipe fitting, equal to two ells, used to connect parallel pipes so that fluid flowing

into one will return in the opposite direction through the other. Return Line - a line used for returning fluid back into the reservoir or atmosphere. Return Valve - an overflow valve, which allows the return of fluid. Reverse Acting - this term has several different meanings depending upon the device it is

describing. A Reverse Acting Actuator is one in which the actuator stem retracts with an increase in diaphragm pressure. A Reverse Acting Valve is one with a Push Down To Open plug and seat orientation. A Reverse Acting Positioner or a

Reverse Acting Controller outputs a decrease in signal in response to an increase in set point.

Reverse Acting Controller - an air-operated controller in which the output pressure decreases as the controlled medium increases.

Reverse Acting Valve - a valve that is normally closed and which requires an increase of fluid pressure or other mechanical means to open.

Reverse Flange - a flange made by shrinking. Reverse Polarity - in welding, the arrangement of D.C. current flow in which the electrode acts

as the positive pole and the workpiece acts as the negative pole. Reversing Mill - the stand of rolls used to reduce steel sheet or plate by passing the steel back

and forth between the rolls; the gap between the rolls is reduced after each pass. Review - mandatory review point. Applies only at the final documentation stage for a sales order

item. Reynolds Number - a dimensionless criterion of the nature of flow in pipes. It is proportional to

the ratio of dynamic forces to viscous forces: the product of diameter, velocity and density, divided by absolute viscosity.

RF - Raised Face RFQ - Request For Quotation RG - Ring Groove RGS - Rigid Galvanized Steel RH - 1) Relative Humidity; 2) Right Hand Ri - (ISO rust scale) Rig - Rig - a collective term to describe the permanent equipment needed when drilling a well. It has

come to include the onshore and offshore vehicles, mobile platforms, or vessels on which the equipment is installed. Offshore platforms are often referred to as oilrigs.

Rig - a tripod, derrick, or drill machine complete with auxiliary and accessory equipment needed to drill.

Rim Pull - the force required at the edge of the handwheel to generate the required torque at the center of the handwheel.

Rimmed Steel - Rimmed Steel - a type of steel characterized by a gaseous effervescence when cooling in the

mold. This results in a relatively pure iron outer rim. Rimmed Steel - the bulk of low carbon steel produced for sheets, nails, etc., is partially oxidized

by the addition of nearby 400 gms of aluminum to 1 ton of steel. When this partial deoxidation is properly controlled, a thick rim of exceptionally pure metal solidifies. The residual liquid is enriched sufficiently in carbon and oxygen for the reaction FeO+C-> Fe+CO to occur. It forms deep-seated blowholes at a uniform depth below the surface and piping is counteracted. The central core is enriched in impurities and it corrodes more rapidly than pure iron.

Ring Joint Face - a flange face having a specially shaped groove located between the bolt holes and the flange bore.

Ring Type Joint (RTJ) - a flange connection using a specially shaped soft metal ring as a gasket. It is generally used on high pressure valves. It may be the body and bonnet connection and / or the end flange connection.

Ringbolt - an eyebolt with a ring passing through the eye. Riser - Riser - a vertical pipe on an oil or gas rig. Riser - a vertical steam, water, or gas pipe. Riser - metal contracts on cooling. A riser is a reservoir of molten metal provided in a casting so

that hot molten flows back into the mold cavity when there is reduction in volume on solidification.

RJ - Ring Joint RMS - RMS - Root Mean Square RMS - Root Mean Square Roughness Height Rockwell C Hardness (HRC) - a hardness value obtained by use of a cone-shaped diamond

indenter and a load of 150 kg, in accordance with ASTM E 18. Rockwell Hardness - a measure of hardness of a material as determined by the Rockwell

hardness test. Rockwell Hardness Test - Rockwell Hardness Test - a commercial indentation test which uses a conical indenter for hard

metals and a spherical indenter for soft metals. The indentation is directly recorded on a suitable dial after the load has been removed.

Rockwell Hardness Test - a test for determining the hardness of a material based upon the depth of penetration of a specified penetrator into the specimen under certain arbitrarily fixed conditions of test.

Rockwell Hardness Test - one of the arbitrarily defined measures of resistance of a material to indentation under static or dynamic load; depth of indentation of either a steel ball or a 120 degrees conical diamond with rounded point, 1.5875, 3.175, 6.35, 12.7 millimeters in diameter, called a brale, under prescribed load is the basis for Rockwell hardness; 60, 100, 150 kilogram load is applied with a special machine, and depth of impression under initial minor load is indicated on a dial whose graduations represent hardness number.

Rockwell Hardness Test - Rockwell hardness numbers have been based on the additional depth to which an indenter has been driven into a metal by heavy load beyond the depth to which the same indenter has been driven by a light load, the conditions under which this happens being arbitrary but definite. For the inspection of hard steel parts the sphero-conical diamond Brale penetrator has been used with a major load of 150 kg.

Rockwell Hardness Test - this machine uses different scales and loads, but B and C scales are commonly used. B scale uses a 1/16” diameter hardened steel ball loaded with 100 kg. A diamond cone having 120 degree apex angle with 150 kg load is used for the C scale. This machine simplifies the process of the Brinell testing, because in this machine, microscopic reading are not required as the depth of the indentation has been adjusted to give direct reading on the scale. As different indentors and loads are used for scales B and C, different dials are used for taking readings. Actually, the same dial is marked in two different colors to differentiate between the testings. Scale B is used for soft materials and scale C for hard materials. The penetrator is first loaded with a minor load of 10 kg to take out any slack in the machine and the indicator for measuring the depth of the impression is set to zero. Then the major load is applied and after its removal the dial gauge records the depth of the impression in terms of Rockwell numbers.

Rod - round, thin semi-finished steel length that is rolled from a billet and coiled for further processing. Rod is commonly drawn into wire products or used to make bolts and nails. Rod trains (rolling facilities) can run as fast as 20,000 feet per minute‹more than 200 miles an hour.

Rod Out - the act of pushing a specially designed rod through a valve or opening to loosen deposits.

Roentgen - see Radiation Dosage Roll - a cylinder mounted in bearings; used for such functions as shaping, crushing, moving, or

printing work passing by it. Rolled In Scale - rolled-in oxides of iron which form on the surface of hot steel. Roller Bearing - Roller Bearing - 1) a shaft bearing consisting of inner and outer steel races between which a

number of parallel or tapered steel rollers are located by a cage. It suits heavier loads than a ball bearing. 2) roller bearings have a single or double row of straight cylindrical rollers in a cage held between the two races. The rollers may be barrel-shaped, concave or tapered to make the bearing self-aligning and capable of taking greater thrust than ball bearings.

Roller Bearing - a bearing in a shaft which is composed of a number of steel rollers and located by a cage between inner and outer steel races. Roller bearings can carry heavier loads than ball bearings.

Roller Bearing - a bearing like a ball bearing but with small cylinders instead of balls. Roller Bearing - a shaft bearing characterized by parallel or tapered steel rollers confined

between outer and inner rings. Roller Bearings - hard steel cylinders in bearings which have very low frictional resistance. Rolling Diaphragm - a type of seal, also senses pressure. This is a diaphragm formed in a

convoluted shape. It gets its name because as the stem moves, the diaphragm "rolls" at the convolution. It is sometimes used in a manner similar to a U-cup; that is, to seal the gap between a linear moving shaft and the valve body.

Rolling Mill - a factory or machine for rolling steel or other metal into sheets. Room Temperature - the reduced range standard ambient (18° Celsius to 28° Celsius) stated in

footnote 5 of Table I of IEC 212. Root Mean Square Value (RMS) - 1) a statistical averaging technique where all data are

individually squared, the average of those squares taken and the square root of that average taken; 2) equal to 0.707 times the peak.

Root Valve - the first valve located in a sample line after it taps off the process. It is typically located in close proximity to the sample tap.

ROS - Required On Site Rotary Forging - rotary forging uses four mechanically driven hammers to rapidly exert force

simultaneously on four sides of the work piece. It results in spreading to take place in the desired longitudinal direction.

Rotary Valve - Rotary Valve - a valve for the admission or exhaust of working fluid, where the valve is a ported

piston or disk that turns on its axis. Rotary Valve - a valve style in which the flow closure member is rotated in the flow stream to

modify the amount of fluid passing through the valve. Rough Trim - the removal of superfluous material by pulling or picking. Usually the removal of a

small portion of the flash or sprue which remains attached to the product. Roughness - a value entering into every formula for calculating flow through pipes Round Opening Pattern - having full-bore round ports in both and plug ROV - 1) Remote Operated Valve; 2) Remote Operated Vehicle RR - Report Required RS - Rising Stem RT - 1) Radiographic Examination; 2) Radiographic Testing; 3) Run Torque; 4) Running-up

Time RTD - Resistance Temperature Detector RTFE - Reinforced Tetrafluoroethylene (Reinforced Teflon) RTJ - Ring Type Joint Rubber - Rubber - it is an excellent material for seals and diagrams for water-lubricated bearings, for parts

subjected to vibratory forces. It should be protected from high temperature, oil and sunlight.

Rubber - same as elastomer Rubber Hardness Degree, International - a measure of the depth of penetration of an indenter

into an elastomer, used to monitor the degree of cure. Rubber, Chloroprene - see Neoprene Rubber, Conductive - a rubber capable of conducting electricity. Most generally applied to

rubber products used to conduct static electricity. Rubber, Natural - raw or crude rubber obtained from vegetable sources. Rubber, Nitrile - Rubber, Nitrile - a copolymer made from acrylonitrile and butadiene, the composition depending

on use. It is widely used in solvent-resistant applications, e.g. petrol hose, brake hose.

Rubber, Nitrile - a synthetic rubber formed by random polymerization of acrylonitrile with butadiene used for gaskets and O-rings.

Rubber, Nitrile - see Buna-N Rubber, Nitrile (Buna-N) - the most commonly used elastomer for o-rings because of its

resistance to petroleum fluids, good physical properties, and useful temperature range.

Rubber, Silicone - an elastomer that retains good properties through extra wide temperature range.

Rubber, Synthetic - manufactured or man-made elastomers Run - a portion of pipe or fitting lying in a straight line in the same direction of flow as the pipe to

which it is connected. Runner - in casting, the passage in the parting plane used for regulating the flow of molten metal

to the mold cavity. Running Fit - the intentional difference in dimensions of mating mechanical parts that permits

them to move relative to each other. Running In - running a new engine, machine or mechanism under a light load and at moderate

speed, to allow time for proper clearances to become established and friction-surfaces polished.

Running Up Time (RT) - the time for a motor to complete one start with rated voltage and frequency applied and coupled to the actual load.

Runout, Shaft - same as Gyration; when expressed in inches alone or accompanied by an abbreviation "TIR" (total indicator reading), it refers to twice the radial distance between shaft axis and axis of rotation.

Rust - a product of the oxidation of iron or its alloys, due either to atmospheric attack or the electrolytic effect of cell action around impurities.

Rust Prevention - surface protection of ferrous structures or equipment to prevent formation of iron oxide; it can be by coatings, surface treatment, plating, chemicals, cathodic arrangements, or other means.

RUTQ - Regret Unable To Quote