A Block Flow Diagram
Oct 05, 2015
A Block Flow Diagram - BFD, is a schematic illustration of the major process. The block or rectangles used represent a unit operation. The blocks are connected by straight lines which represent the process flow streams which flow between the units. These process flow streams may be mixtures of liquids, gases and solids flowing in pipes or ducts, or solids.
In order to prepare block flow diagrams a number of rules should be followed:
unit operations such as mixers, separators, reactors, distillation columns and heat exchangers are usually denoted by a simple block or rectangle.groups of unit operations may be noted by a single block or rectangle. process flow streams flowing into and out of the blocks are represented by neatly drawn straight lines. These lines should either be horizontal or vertical. the direction of flow of each of the process flow streams must be clearly indicated by arrows.flow streams should be numbered sequentially in a logical order.unit operations (i.e., blocks) should be labelled.where possible the diagram should be arranged so that the process material flows from left to right, with upstream units on the left and downstream units on the rightPipe classification:Iron pipe size (approximate internal dia.)Manufacturers weight: NPS +STDXSXXSSchedule number: NPS +5, 5s, 10, 10s, 20, 20s, 30, 40, 40s, 60, 80, 80s, 100, 120, 140, 160SCH 1000 P/SNPS 12, OD NPSNPS 14, OD = NPSNPS 10, SCH 40 = STDNPS 8, SCH 80 = XSLight wall = light gage = 5, 5s, 10, 10sAPI designationA25, A, B, X42, X46, X52, X60, X65, X70X(AA), AA = Allowable stressPressure-Temperature Ratings150, 300, 400, 600, 900, 1500, 2500Pipe:NPS:1/8, , 3/8, , , 1, 1 , 2, 3, 4, 6, 8, 10,12, 14, 16, 18, 20, 24, 28, 30, 32, 36, 40,44, 48 52, 56, 60NPS1 , 2 , 3 , 5 not used
Pipe is supplied inRandom length (17 to 25 ft)Double random length (38 to 48 ft)Pipe end:BE (bevel end)PE (plain end)T& C (treaded and coupled, rating of coupling shall be specifiedTube:Specify by two ofOutside diameterInside diameterThousandths of inchGauge numberAmerican wire gaugeSteel wire gaugeBirmingham wire gaugeWhen gauge numbers are given without reference to a system (BWG) is implied
General GuidelinesFollowing sketch (sketch-1) shows a portion of a typical plot plan with few Equipment's, pipe rack etc shown. For equipment spacing pl refer, plant layout and piping specification number P-GS-PL-003, GE Gap guidelines, and/or OISD 118.
Pump Piping Layout superimposed in a plot plan
Pump location will affect the piping routing and supporting. Pumps carrying hydrocarbons and materials above 230 degree C shall not be located below pipe racks, structures, air fin coolers and vessels. Those in non-flammable service may be located beneath the pipe rack without obstructing the access bay, other maintenance requirements of the respective process unit.
Pumps shall be located as close to the source of suction in order to minimize pressure drop in the system. The line size and temperature will be the determining factors in piping layout.A preliminary piping layout ( study layout ) shall be made to determine the requirement of spacing between pumps especially in case of side suction/ side discharge, top suction/ top discharge pumps where straight length requirement / platform / CPS requirement etc have to be considered.
Reducers in pump suction lines shall be as close as possible to the pump suction/discharge nozzles.
Eccentric reducers in pump suction lines shall be flat on top in order to prevent any entrained vapours in the liquid from accumulating in the high point ( if installed bottom flat ) and thus causing cavitation in the pump. Pumps in boiler feed water service operating close to vapour pressure of the liquid are susceptible to this type of problems.
Reducers in pump discharge should be concentric in most cases. Eccentric reducers may be used in both suction and discharge piping for top suction/top discharge pumps in order to obtain clearance between suction and discharge piping.
Consideration must be given to lube oil and seal oil systems and any cooling water requirements. Care must be exercised not to block access to the pump seals and bearings when routing these lines.. The pump data sheet should always be reviewed to make sure these requirements are not missed. For very large pumps these may be separate on skids.
When developing an equipment layout in pump areas, the layout designer must envision potential obstructions around the pumps (e.g. large block valves, steam turbine piping, and tee-type pipe supports from grade). As per Oil Industry Safety Directorate stipulation ( OISD 118 ) 1 mtr (1000mm ) is the minimum accepted spacing between pumps.
Auxiliary piping shall be neatly routed along the base-plate and shall not extend across the operating floor. This piping shall not obstruct inspection covers, bearing caps, upper halves of casings or any other items which require access for operation or maintenance. In order to avoid a fire hazard, lubricating oil, control oil and seal oil pipes shall not be routed in the vicinity of hot process or hot utility pipes.
Typical pump suction piping at vacuum tower
Cooling water pipes to pumps and compressors shall not be less than 20NB. Pipes 25NB or less shall have the take-off connection from the top of the header in order to prevent plugging during operation.
When flexibility loops are required between pumps, it is necessary to partially run the lines over the pump and driver. Every effort must be made to minimize maintenance obstructions by running the piping either outside the area directly over the pumps or at a high enough elevation to permit the removal of the pump or driver.
The pump shall be placed in such a manner so that the suction nozzle elevation is always below the vessel/tank nozzle and suction pipe shall be routed so that there is no pockets.
Pumps in vacuum service present special problems. Since the system operates at a negative pressure and very high temperature, the pumps must be located very close to the suction source. This is often directly below the tower or immediately outside the tower support columns. Pumps located directly beneath the tower can be mounted on a special spring base as shown in sketch below.
In some rare cases one pump is installed as a common spare between two other pumps in different services. The pump must be man folded in such a way to accomplish this.
Pumps may be single-stage or multi-stage. Multi stage pumps are usually side suction side discharge. These pumps require significantly more space and faces layout problems. There is usually a straight run requirement (example, 5 pipe diameters) between the suction flange and the first elbow as shown in Sketch. Due to the heavier casing design for high pressures, allowable nozzle loads are often higher for multi-stage pumps making pipe stress problems somewhat easier to resolve.
Piping Isometric Sketch
The location of valves, strainers, spacers/blinds etc. needs special consideration. The option of placing the valves at a higher elevation and providing an operating platform has got its own advantages and disadvantages. If valves are provided at a higher elevation the accessibility for the pumps is enhanced but the operability of the valves becomes difficult.It shall be noted that even if the type of pump is same, different piping layouts may be followed. So it is not always necessary that same layout shall be followed for same type of pumps, but is governed by various factors such as temperature, requirement of vertical strainers etc
The functions of some commonly used waterworks pipes and fittings are described below:-
FittingFunction
Anti-vacuum Valvea valve in a water service that opens to admit air if the pressurewithin the water service falls below atmospheric pressure.
Ball Valvea valve that controls the entry of water into a storage cistern orflushing cistern, closing off the supply when the water level in thecistern has reached a predetermined level. It is sometimes called aball cock or float-operated valve.
Boileran enclosed vessel in which water is heated by the direct applicationof heat
Butterfly Valvea valve in which a disc is rotated about a diametric axis of a cylinderto vary the aperture. It is used where space is limited or moresophisticated control is required.
Calorifera storage vessel, not open to the atmosphere, in which a supply ofwater is heated. The vessel contains an element, such as a coil ofpipe, through which is passed a supply of hot water or steam, insuch a way that the two supplies do not mix, heat being transferredthrough the walls of the element.
Expansion Vessela closed vessel for accommodating the thermal expansion of waterin a pressurized hot water heating system
Float Switcha device incorporating a float that operates a switch in response tochanges in the level of a liquid.
Gate Valvea valve that provides a straight-through passage for the flow of fluidand in which the passage can be closed by a gate. It is used wherethe water pressure is low and on distribution pipework from astorage cistern. This valve is sometimes referred to as a fullway gatevalve because when it is fully open, there is no restriction of flowthrough the valve.
Loose Jumper TypeStopcocka screwdown pattern valve with horizontal inlet and outletconnections. It incorporates a loose jumper valve permitting flow inone direction only. It is used for isolating the supply of water in ahigh pressure pipeline. In case the supply main is shut off anddrained down for any reason, the non-return action of the loosevalve plate will stop any backflow from the service pipe.
Non-return Valvea valve that prevents reversal of flow in the pipe of a water supplyby means of the check mechanism, the valve being opened by theflow of water and closed by the action of the check mechanismwhen the flow ceases, or by back pressure. It is also known as checkvalve.
Pressure Reducing Valvea valve that reduces the pressure of a fluid immediately downstreamof its position in a pipeline to a preselected value or by apredetermined ratio.
Pressure Relief ValveA self-acting valve that automatically opens to prevent apredetermined safe pressure being exceeded.
Temperature ReliefValveA self-acting valve that automatically opens to prevent apredetermined safe temperature being exceeded.
Why There is a Need For Pipe Supporting?The Piping Profile in general can be considered as a complex and rigid piping network consisting of various piping components, which have different diameters and weights. At the same time the above network is also subjected to temperature change while switching from installed to operating condition (and visa versa) resulting into its thermal growth in various directions in proportion to the length of pipes. The structural integrity of the above network must therefore take into account the overall weight effect of the profile besides its thermal growth.
A satisfactory design of the Piping System should therefore give a careful consideration to achieve the above requirement. This is generally accomplished by providing external attachments (known as pipe supports) at various locations of the piping profile.
This article deals with the basic purpose of the pipe supports, classification based on construction / functions and a few typical types of pipe supports. In general it deals with metallic piping systems only.To Support weight of Pipe during Operation & TestingSupports are required to support the line during all conditions i.e. during operation as well as during testing.
In case of vapor line this difference will be very large due to hydro testing. Supports should be designed for this load (unless otherwise decided in the project).Some times line is capable of having longer span but load coming on the support may be very large (especially with large diameter pipe lines). Then to distribute the load uniformly, more number of supports should be provided with smaller span.
Note : 1. It may be noted that during testing condition there is no thermal load.
2.All spring supports are locked during testing.To take Expansion LoadWhenever thermal expansion is restricted by support, it introduces additional load on the support. Support must be designed to take this load in addition to all other loads.To take Wind LoadWind introduces lateral load on the line. This load is considerable especially on large diameter pipe. This tends to sway the line from its normal position and line must be supported guided against it. In case of large diameter overhead lines, supported by tall support extended from floor, wind load introduces large bending moment and should be considered critically.To take Earth Quake LoadThe earthquake is normally associated with horizontal acceleration of the order of 1 to 3 m/sec2. This is around 10% to 30% of the gravitational acceleration and introduces horizontal force of about 10 to 30% of the vertical load (or supported mass). While designing support this should be taken care.To absorb Vibration of Piping systemWhen the pipe is subjected to moving machinery or pulsating flow or very high velocity flow, pipe may start vibrating vigorously and ultimately may fail, particularly if span is large. To avoid this it may be required to introduce additional supports at smaller span apart from other requirements. It may not take axial load, but must control lateral movements.To have Noise ControlIn most of the plants, noise is resulting from vibration and if such vibrations are controlled, noise is reduced to great extent. In such lines, between clamp (i.e. support) and pipe, asbestos cloth is put to absorb vibration and avoid noise.
Noise due to pulsating flow can be reduced by using a silencer in the line. Still if it is not below acceptable level acoustic enclosure may be used. insulation over line also helps in reducing the noise.To take Hydraulic Thrust in PipingThe hydraulic thrust in the pipeline is present at certain point such as pressure reducing valve, relief valve, bellows etc.
If the control valve has large pressure differential and line size is more, then this force can be very high.
The support should be provided and designed to take this load, otherwise this will load the piping system and may cause failure.To support the system during Transient Period of Plant & Standby ConditionTransient condition refers to the start-up or shutdown condition in which one equipment may get heated up faster and other one get heated slower. Due to this the expansion of one equipment which in normal operation will get nullified, may not get nullified and exert thermal load on supports.Standby condition is also similar. If there are two pumps, one being standby and both connected in parallel (as shown), design and operating temp. of both the connections will be same. But the expansion of two parallel legs will not be nullified because at a time only one leg will be hot and another being cold.To support the system during Maintenance ConditionsWhen for maintenance certain equipment or component like valve is taken out, remaining system should not be left out unsupported.To support the system during Shutdown ConditionsIn shutdown condition all equipment may not be in the same condition as in operating condition. The springs are, designed based on weights considering the weight of fluid as well as pipeline and thermal movements. But during shutdown condition the fluid may be drained and the pipe becomes lighter. Hence the spring will give upward reaction and shall load the nozzle beyond permissible limit.
In this case a limit stop is used which will not allow the Point C to move up above horizontal level.(However it will allow downward movement during operating condition).To support the system for Erection ConditionsErection condition can be different than the operating condition which should be considered while designing supports.
Loads due to such conditions must be considered while designing the supports.
[PPT] Yard and Rack Area PipingYard area piping: Piping out side power block is known as yard area Piping.
Yard area piping can be divided in two parts Above Ground Under Ground
In above ground piping following topic will be covered Rack Piping Sleeper Piping Clearance Human factor guide line
Rack PipingDefinition: Pipe racks are structures designed and built specifically to support multiple pipes where adequate structure is notavailable.
In rack piping following topics will be covered.Rack width Number of tier Minimum vertical clearance Clear height between tiers Arrangement of pipes on rack
Rack width : Following factors will decide the rack width. Number of Pipes laid on rackSize of PipesSpace between pipesElectrical /instrument cable traySpace reserved for future lines
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Basics of Piping Calculations The piping system of this tannery waste water treatment plant used stainless steel, austhenitic 18Cr, 8Ni type of tube as its material of construction. This type of material has a maximum allowable stress of 75,000 psi. The pressure inside the tube of waste water experiences 100psi. The assumed pressure is 100 psi. To get the schedule number of the said tube,
Since the calculated value of schedule number is less than forty, then schedule 40 type of tube will be used.
Since the Di calculated is 0.627967922 ft, the from Appendix C-6 of Foust the NPS is 0.75 in.
Schedule Number40
Do, in1.05
t, in0.113
Di, in0.824
NPS, in0.75
In the piping system design calculation, the equation below is used because the equation is for incompressible fluid like tannery waste water.
Refer to the tables of this appendix to compute for the pump power requirement between two or more equipment.
The velocity of the tannery waste water entering the next equipment can be solved as shown below,
The kinetic energy exhibited by the tannery waste water is calculated as shown. The compressibility factor, alpha is determined using the Reynolds number.
Given the calculated Reynolds number, from Fig. 20-2 page 543 of Foust, locate the value of alpha. The alpha is equal to 0.87.
The potential energy of the tannery waste water is calculated as well as shown.
The pressure involved in the specified location in different equipment can be calculated using the hydrostatic pressure formula since the waste water is mostly composed of water.
f is a function of Reynolds number and E/D. From Appendix C-1 page 540 of Foust, at Di=0.824in E/D=0.00056. From Appendix C-3 page 544 of Foust with Nre=253119.9664 and E/D=0.00056, f=0.02.
The length of the pipe used involves the straight pipes, fittings and valves.
For the Lstraight pipe,
For Lfittings, one fitting between the two equipment is needed. The fitting chosen is the 90 standard elbow.
For Lvalve, one fitting between the two equipment is needed. The valve used is the globe valve conventional with wings or pin guided disk fully open. Refer to Appendix C-2a page 542 for the literature value.
Now, the friction factor can be calculated as shown.
Power requirement of the pump that will be used to deliver the waste water from one equipment to another can now be calculated as shown below.
Pump and Pump Piping PresentationPump - Introduction to Pumps- Classification of Pump- Industry Codes & Standards- Selection Criteria for Pumps- NPSH & Cavitation- Definitions Pump PipingSuction piping for horizontal pumpsDischarge piping for horizontal pumpsArrangements of piping for pump handling hot suctions.Side suction & side discharge pumpVertical In line pumpsVertical pump (Wet Well pump)Vertical Barrel type or Cane pumpMulti Service pumpReciprocating pump PipingMetering PumpPumps in the Tankage AreaAuxiliary pump piping arrangementPipe vent & drain SystemPump Location & ArrangementPump Surrounding Support
Industry Codes and StandardsAmerican Petroleum Institute (API)
1. 610, Centrifugal Pumps for Petroleum, Heavy Duty Chemical, and Gas Industry Services.
2. 674, Positive Displacement Pumps - Reciprocating.
675, Positive Displacement Pumps - Controlled Volume.
676,Positive Displacement Pumps (Rotary)
5. 677. General Purpose Gear Units for Refinery Service.
6. 681, Liquid Ring Vacuum Pumps
7. 682, Shaft Sealing Systems for Centrifugal and Rotary Pumps.
American Society of Mechanical Engineers (ASME)
1. B73.1M, Horizontal End Suction Centrifugal Pumps for Chemical Process.
2. B73.2M, Vertical In-Line Centrifugal Pumps for Chemical Process
3. Process Industry Practices (PIP)
1. RESP73H-97, Specification for Horizontal End Suction Centrifugal Pumps.
2. RESP73V-97, Specification for Vertical Centrifugal Pumps.
How to do Pump Piping with Layout Explained
Tubular products are termed tube or pipe. Tube is customarily specified by its outside diameter and wall thickness, expressed either BWG (Birmingham wire guage) or in inches or in thousands. Pipe is customarily identified by nominal pipe size with wall thickness defined by schedule number.
Piping materials Carbon steel pipe is strong ,ductile, weldable, machineable, reasonably durable and is nearly always cheaper than pipe made from other materials. If carbon steel pipe can meet the requirements of pressure, temperature, corrosion resistance and hygiene, it is the natural choice.
Other metals & alloys :- pipe or tube made from copper, lead, nickel, brass, aluminium and various stainless steels can be readily obtained. These materials are relatively expensive and are selected usually either because of their particular corrosion resistance to the process chemicals, their good heat transfer or for their tensile strength at high temperatures. Copper and copper alloys are traditional for instrument lines, food processing and heat transfer equipment, but stainless steels are increasingly being used for these purposes.Methods for joining pipeButt weldedSocket weldedScrewedBolted flangeBolted quick couplingPiping componentsElbows, Tees, Flanges, Gaskets, Nipples, Unions, Valves, Reducers, Steam traps, BellowsElbows or ells :-Types of elbowsLong radius elbows:- normally used elbows are long radius with centerline radius of curvature equal to 1 times the nominal pipe size for inch and large sizes.
Short radius elbows:- SR elbows with centerline radius of curvature equal to the nominal pipe size Reducing
Elbows :- this elbows have centerline radius of curvature 1 times the nominal size of the pipe to be attached to the larger end.
Bends :- Are made from straight pipe. Common bending radii are 3 and 5 times the pipe size. 3R bends are available from stock. Larger radius can be custom made.
Returns :- It changes direction of flow through 180 degrees, and is used to construct heating coils, vents and tanks etc.
Piping DesignPiping arrangements:-Use standard available items wherever possible.Do not use miters unless directed to do so.Do not run piping under foundation.Do not run steam lines under oil lines, fire hazards may occur.Piping may have to go through concrete floors or walls. Establish these points of penetration as early as possible and inform the group connected (civil) to avoid cutting existing reinforcing bars.Include removable flanged spools to aid maintenance, especially at pumps, turbines, and other equipment that will have to be removed for overhaul.Steam lines, which are below grade in trenches provided with covers or (for short runs) sleeves.Take gas and vapor branch lines from tops of headers when it is necessary to reduce the chance of drawing off condensate or sediment, which may damage rotating equipment.Maintain vent lines at higher and drain lines at lower elevations.
Clearing and Access:-Route piping to obtain adequate clearness for maintaining and removing equipment.
Locate within reach or make accessible, all equipment subjected to periodic operation or inspection, with special reference to check valves, pressure relief valves, traps, strainers and instruments.
Take care to not obstruct access ways i.e. doorways, truck-ways, walkways, lifting wells etc.
Elevations of lines are usually changed when changing horizontal directions where lines are grouped together or are in a congested area, so as not block spaces where future lines may have to be routed.
Keep field welds and other joints at least 3 inches from supporting steel, building siding or other obstruction. Allow room for the joint to be made
Allow room for loops and other pipe arrangements to cope with expansion by early consultation with staff concerned with pipe stressing. Notify the structural group of any additional steel required to support such loops.Stresses On PipingThermal Stresses:- change in temperature of piping due either to changes in temperature of the environment or of the conveyed fluid, cause changes in temperature in length of the piping. This expansion or contraction in turn causes strain in piping, supports and attached equipment.
Settlement Strains:- foundation of large tanks and heavy equipment may settle or tilt slightly in the course of time. Connected piping and equipment not on a common foundation will be stressed by the displacement.Flexibility in piping To reduce strains in piping caused by substantial thermal movement, flexible and expansion joints may be used. However, the use of these joints may be minimised by arranging piping in a flexible manner. Pipe can flex in a direction perpendicular to its length: thus, the longer an offset, or the deeper a loop, the more flexibility is gained.
Pipe RacksA pipeway is the space allocated for routing several parallel adjacent lines. A piperack is a structure in the pipeway for carrying pipes and is usually fabricated from steel, or concrete and steel. Piperacks for only two or three pipes are made from T-shaped member, termed Tee-head supports.
Piperacks are expensive, but are necessary for arranging the main process and service lines around the plant site. They are made use of in secondary ways, principally to provide location for ancillary equipment.
Pumps, utility stations, manifolds, fire-fighting and first-aid stations can be located under the piperack. Lighting and other fixtures can be fitted to stanchions. Air-cooled heat exchanger can be supported above the piperack.The smallest size of pipe run on a piperack without additional support is usually 2inch. It may be more economic to change proposed small lines to 2inch pipe, or to suspend them from 4inch or larger lines, instead of providing additional support.
Valves in piping design Valves are used for these purposes:-Process control during operation.Controlling services and utilities steam, water, air, gas and oil.Isolating equipment or instruments, for maintenance.Discharging gas, vapor or liquid.Draining piping and equipment on shutdown.Emergency shutdown in the event of plant mishap or fire.Which size valve to use:-Nearly all valves will be line size- one exception is control valves, which are usually one or two sizes smaller than line size, never larger.
At control stations and pumps it has been almost traditional to use line-size isolating valves. However, some companies are now using isolating valves at control stations the same size as the control valve, and at pumps are using pump size isolating valves at suction and discharge. The choice is usually an economic one made by a project engineer.
Where to place valves Preferably, place valves in lines from headers (on piperacks) in horizontal rather than vertical runs, so that lines can drain when the valves are closed.(in cold climates, water held in lines freeze and rupture the piping such lines should be traced.To avoid spooling unnecessary lengths of pipe, mount valves directly onto flanged equipment, if the flange is correctly pressured.A relief valve that discharges into a header should be placed higher than the header in order to drain into it.Locate heavy valves near suitable support points. Flanges should be not closer than 12 inches to the nearest support, so that installation is not hampered.For appearance, if practicable, keep centerlines of valves at the same height above floor, and in-line on plan view.Operating access to valvesConsider frequency of operation when locating manually-operated valves.Locate frequency-operated valves so they are accessible to an operator from grade or platform. Above this height and up to 20feet, use chain operation or extension stem. Over 20feet, consider a platform or remote operation.Valves Operating HeightsInfrequently used valves can be reached by a ladder but consider alternatives.Do not locate valves on piperacks, unless unavoidable.Group valves which would be out of reach so that all can be operated by providing a plotform, if automatic operators are used.If a chain is used on a horizontally mounted valve, take the bottom of the loop to within 3feet of floor level for safety, and provide a hook near by to hold the chain out of the way.Do not use chain operators on screwed valves, or on any valve 1 inches and smallerWith lines handling dangerous materials it is better to place valves at a suitably low level above grade, floor, platform, etc., so that the operator does not have to reach above head height.Access to valve in hazardous valvesLocate main isolating valves where they can be reached in an emergency such as an an outbreak of fire or a plant mishap. Make sure that personnel will be able to reach valves easily by walkway or automobile.Locate manually-operated valves at the plant perimeter, or outside hazardous area.Ensure that automatic operators and their control lines will be protected from the effect of fire.Make use of brick or concrete walls as possible fire shields for valve stations.Inside a plant, place isolating valves in accessible positions to shut feed lines for equipment and processes having a fire risk.Consider the use of automatic valves in fire systems to release water, foam and other fire-fighting agents, responding to heat-fusible links, smoke detectors, etc., triggered by fire or undue rise in temperature advice may be obtained from the insurer and the local fire department. If there is no P&IDProvide valves at headers, pumps, equipment, etc., to ensure that the system will be pressure-tight for hydrostatic testing, and to allow equipment to be removed for maintenance without shutting down the system.Provide isolating valves at all small lines branching from header.Provide isolating valves at all instrument pressure points for removal of instruments under operating conditions.Provide valved drains on all tanks, vessels, etc., and other equipment which may contain or collect liquids.Protect sensitive equipment by using a fast-closing check valve to stop back flow before it can gather momentum.Consider butt-welding or ring-jointflanged valvesfor lines containing hazardous or searching fluids. Hydrogen is especially liable to leak.Provide sufficient valves to control flows.Consider providing a concrete pit (usually about 4ft x 4ft) for a valve which is to be located below grade.Consider use of temporary closures for positive shut-off.Provide a bypass if necessary for equipment which may be taken out of service.Provide a bypass around control stations if continuous flow is require. The bypass should be at least as large as the control valve, and is usually globe type, unless 6-inch or larger, when a gate valve is normally used.Provide an upstream isolating valve with a small-valved bypass to equipment, which may be subject to fracture if heat is too rapidly applied on opening the isolating valve. Typical use is in steam system to lessen the risk of fracture of such things as castings, vitreous vessels, etc.Consider providing large gate valves with a valved bypass to equalize pressure on either side of the disc to reduce effort needed to open the valve.
Piping Design - Pipe Rating Classifications Posted by Ankit Chugh on 12:51 PM 2 Comments .
It is usual industry practice to classify the pipe in accordance with the pressure-temperaturerating system used for classifying flanges. However, it is not essentialthat piping be classified as Class 150, 300, 400, 600, 900, 1500, and 2500. The pipingrating must be governed by the pressure-temperature rating of the weakest pressure containingitem in the piping. The weakest item in a piping system may be a fittingmade of weaker material or rated lower due to design and other considerations.
Piping Class Ratings Based on ASME B16.5 and Corresponding PN Designators
Above table lists the standard pipe class ratings based on ASME B16.5 along withcorresponding pression nominal (PN) rating designators. Pression nominal is theFrench equivalent of pressure nominal.In addition, the piping may be classified by class ratings covered by other ASMEstandards, such as ASME B16.1, B16.3, B16.24, and B16.42. A piping system maybe rated for a unique set of pressures and temperatures not covered by any standard.
Pression nominal (PN) is the rating designator followed by a designation number,which indicates the approximate pressure rating in bars. The bar is the unit ofpressure, and 1 bar is equal to 14.5 psi or 100 kilopascals (kPa). Above table providesa cross-reference of the ASME class ratings to PN rating designators. It is evidentthat the PN ratings do not provide a proportional relationship between differentPN numbers, whereas the class numbers do. Therefore, it is recommended thatclass numbers be used to designate the ratings. Refer to Chap. B2 for a moredetailed discussion of class rating of piping systems.
Other Industrial Piping Class Ratings ClassificationsManufacturers RatingBased upon a unique or proprietary design of a pipe, fitting, or joint, the manufacturermay assign a pressure-temperature rating that may form the design basis forthe piping system. Examples include Victaulic couplings and the Pressfit system.
In no case shall the manufacturers rating be exceeded. In addition, the manufacturermay impose limitations which must be adhered to.
NFPA RatingsThe piping systems within the jurisdiction of the National Fire Protection Association(NFPA) requirements are required to be designed and tested to certain requiredpressures. These systems are usually rated for 175 psi (1207.5 kPa), 200 psi (1380kPa), or as specified.
AWWA RatingsThe American Water Works Association (AWWA) publishes standards and specifications,which are used to design and install water pipelines and distribution systempiping. The ratings used may be in accordance with the flange ratings of AWWAC207, Steel Pipe Flanges; or the rating could be based upon the rating of the jointsused in the piping.
Specific or Unique RatingWhen the design pressure and temperature conditions of a piping system do notfall within the pressure-temperature ratings of above-described rating systems, thedesigner may assign a specific rating to the piping system. Examples of such applicationsinclude main steam or hot reheat piping of a power plant, whose designpressure and design temperature may exceed the pressure-temperature rating ofASME B16.5 Class 2500 flanges. It is normal to assign a specific rating to the piping.
This rating must be equal to or higher than the design conditions. The rating of allpressure-containing components in the piping system must meet or exceed thespecific rating assigned by the designer.
Dual RatingsSometimes a piping system may be subjected to full-vacuum conditions or submergedin water and thus experience external pressure, in addition to withstandingthe internal pressure of the flow medium. Such piping systems must be rated forboth internal and external pressures at the given temperatures. In addition, a pipingsystem may handle more than one flow medium during its different modes ofoperation. Therefore, such a piping system may be assigned a dual rating for twodifferent flow media. For example, a piping system may have condensate flowingthrough it at some lower temperature during one mode of operation while steammay flow through it at some higher temperature during another mode of operation.It may be assigned two pressure ratings at two different temperatures.Review of Piping Fundamentals Posted by Ankit Chugh on 9:08 AM 1 Comment .
General A pipe or a tube is hollow longitudinal product. A tube is general term used for hollow product having circular, elliptical or square cross-section or for that matter cross section of any closed perimeter.A pipe is tubular product of circular cross-section that has specific sizes and thicknesses governed by particular dimensional standard. Tubes can be ordered for any OD or ID and thicknesses, pipes are ordered on basis of nominal sizes.Classification:Pipes can be classified based on methods of manufacture or end use.Methods of Manufacture:Seamless Pipes are manufactured by drawing or extrusion process. ERW Pipes (Electric Resistance Welding pipes) are formed from a strip which is longitudinally welded along its length. Welding may be by Electric resistance, high frequency or induction welding. ERW pipes can also be drawn for obtaining required dimensions and tolerances.Classification Based on End Use:Pipes are also classified as:Pressure pipes or Process pipesLine PipesStructural Pipes1. Pressure pipes are those which are subjected to motive pressure and system pressure and or temperatures. Fluid pressure in generally internal pressure due to fluid being conveyed or may be external pressure (e.g. jacked piping) and are mainly used as plant piping.2. Line pipes are mainly used for long distance conveying of the fluids and are subjected to motive pressures. These are generally not subjected to high temperatures.3. Structural pipes are not used for conveying fluids and therefore not subjected to fluid pressures or temperatures. They are used as structural components (e.g. handrails, columns, sleeves etc.) and are subjected to static loads only;Pipes Dimensional Standards:A. Diameters: Pipe are designated by. Nominal size, starting from 1/8" Nominal size and increasing in steps up to 36 inchesFor the Nominal size upto and including 12", there is one unique O.D. (different from nominal size) and 1.0. would vary depending on schedule nuniber. For Nominal sizes 14" and above, 0.0. is same as Nominal size.Thickness:Pipe thicknesses are designated by schedule number (which determine internal pressure) or weight designation like Std. (S), Extra Strong (XS) and Double Extra Strong (XXS). Pipe schedule number S is defined as:Sch. No. S = 1000 P/SWhere P = Internal Pressure (PSI) S = Allowable tensile strength of material used.Common pipe schedules are Sch 40, Sch 80, Sch 120, Sch 160, for larger pipe sizes intermediate schedule numbers (Sch 20 Sch 30 etc.) are also employed (Ref. pipe dimension Chart).For Carbon steel, Pipe wall thickness tolerance is 12 1/2% i.e. Pipe wall thickness can, vary 12 1/2% from thickness obtained from dimension chart.For stainless steels schedule numbers are designated by su~Tix S i.e; lOS, 40S, 80S etc.Length:Pipes are manufactured in random length which is 20+ -2.5 and in double random length 40 + - 5.0.Pipe Fittings:Pipe fittings are the components which tie together pipe lines, valves, and other parts of a piping system. They are used in making up a pipe line. Fittings may come in screwed, welded, soldered, or flanged varieties and are used to change the size of the line or its direction and to join together the various parts that make up a piping system.The majority of pipe fittings are specified by the nominal pipe size, type, material and the name of the fitting. Besides the end connections as above (screwed, welded, soldered, flanged) it is also possible to order bell and spigot fittings, which are usually cast iron and used for low pressure service.In general, a fitting is any component in piping system that changes its direction, alters its function, or simply makes end connections. A fitting is joined to the system by bolting, welding or screwing, depending on many variables in the system.1. Butt-Welded FittingsWelded fittings are used primarily in systems meant to be permanent. They have the same wall thickness as the mating pipe. Among the many advantages of butt welded systems are the following: They have a smooth inner surface and offer gradual direction change with minimum turbulence. They require less space for constructing and hanging the pipe system. They form leak-proof constructions. They are almost maintenance free. They have a higher temperature and pressure limit. They form a self-contained system. They are easy to insulate They offer a uniform wall thickness through-out the system.One of the major disadvantages of butt-welded systems is that are not easy to dismantle. Therefore, it is often advisable to provide the system with enough flanged joints so that it can be broken down at intervals. (One of the main uses of the butt-welded system, is for steam lines, which are usually in high temperature/ high-pressure service).2. Socket Welded Fittings Socket welded fittings have certain advantages over butt-welded fittings. They are easier to use on small-size pipelines and the ends of the pipes need not be beveled since the pipe end slips into the socket of the joint. With socket welded fittings there is no danger of the weld protruding into the pipeline and restricting flow or creating turbulence. Thus, the advantages of the socket welded system are: The pipe does not need to be beveled. No tack welding is necessary for alignment since joint and the pipe are self -aligning. Weld a material can not extend into the pipeline. It can be used in place of threaded fittings, therefore, reducing the likelihood of leaks, which usually accompany the use of threaded fittings. It is less expensive and easier to construct than other welded systems. One of the major disadvantages of this type of fitting is the possibility of a mismatch inside the fitt~ng where improperly aligned or mated parts may create a recess where corrosion could start. Socket-welded fittings have the same inside diameter as standard (Schedule 4O), extra strong (Schedule 80), and double extra strong (Schedule 160) pipe, depending. on the weight of the fitting and mating pipe. Socket-welded fittings rare covered in ASA 816.11. They are drilled to match the internal diameter of schedule 40 or schedule 80 pipe. 3. Flanged Fittings Flanged connections are found on piping systems throughout the petrochemical and power generation fields on pipelines that are a minimum of 2 in.(5.08 cm ) in diameter. The majority of flanged fittings are made of cast steel or cast iron. Flanged steel fittings are used in place of cast iron where the system is subjected to shock or high-temperature/ high-pressure situations where the danger of fire is prevalent, because cast iron has a tendency to c rack or rupture under certain stresses. A flange may be cast or forged onto the ends of the fitting or valve and bolted to a connecting flange which is screwed or welded onto the pipeline, thereby providing a tight joint. An assortment of facings, ring joint grooves, and connections are available in flange variations.One advantage of flanged systems is that, they are easily dismantled and assembled. One of the disadvantages is that they are considerably than an equally rated butt-welded system, because of the large amount of metal that go into making up joints and flanges. Moreover, flanged fittings occupy far more space than the butt-welded or screwed equivalents. Because of this higher weight load, a flanged system becomes far more expensive to support or hang from the existing structure
Piping Design - Material Specification Posted by Ankit Chugh on 2:39 AM 2 Comments .
Basis of SpecificationThe following documents shall form the basis of project piping specifications:
Basic piping specifications from process department or process licensor.
Service summary indicating service against basic material of construction (MOC) for each service. This is available either from process discipline or process licensor.
For utility piping, the project piping specifications for these services may be based on in-house experience. However, the clients project manager shall be consulted in such cases before proceeding.
Design Criteria1. Design PressureThe design pressure of each component in a piping system shall be the severe condition of the following:
a. 1.1 x maximum operating pressure as given in line list or service summary.
b. Design pressure as given in the line list or the service summary by the Process Licensor.
c. Design pressure of equipment to which it is connected.
d. Set pressure of a pressure relieving device which protects the system.
Shut-off discharge pressure of a centrifugal pump, not protected by a pressure relieving device. If the shut-off discharge pressure is unknown, it may be determined by the largest of the following:
i. 1.2 times the differential pressure at nominal flow plus the maximum pump suction pressure.
ii. 1.1 times the pumps discharge pressure at normal flow. Full vacuum for a system operating below atmospheric pressure.
2. Minimum Wall Thicknessa. The required pipe wall thickness shall be determined in accordance with the ASME B 31.3 using the design pressure and temperature mentioned above. The calculated wall thickness shall include mechanical allowance, including manufacturing minus tolerance and weld joint efficiency factor plus the corrosion allowance.
Unless otherwise specified, the minimum corrosion allowance shall be:
Carbon Steel Alloy Steel: 1.5 mm
Ferritic Steel: 1.5.mm
Austenitic Stainless Steel for general purpose: 0 mm
The pipe wall thickness determined according to the above procedure shall be checked for ambient and mechanical influences and other loadings described in the ASME B 31.3 in addition to the process pressure temperature requirements.
The following minimum pipe wall thickness shall be used for carbon and low alloy steels of process and utility piping including the items mentioned above.
NB
Welded Joint
Threaded Joint
112 and smaller
Sch 40
Sch 80
2" to 6"
Sch 40
8" to 12"
Sch 40
14" and over
Sch 40 3. Design Temperature
Design temperature as given in the line list for each pipeline. Design temperature as given for each service in the service summary by Process Discipline or Process Licensor.
When maximum operating temperature (T) is given in line list or service summary, the design temperature (T) shall be as follows :
T = T 0+ (+20) 0 C, When T0 is between 0 to 200 0 C
T = T 0+ (+10 to + 20 ) 0 C , when T0 is over 200 0 C
T = T 0+ (-5) 0C, when T 0 is 00 C and under
Where = T = Design Temperature
T 0 = Maximum Operating Temperature
The design temperature of a piping system shall be the design temperature of connected equipment.
For un-insulated piping, the design temperature may be determined in accordance with ASME B 31.3.
The reducing co-efficient for piping components not specific in the ASME B 31.3 shall be 95% for fluid temperatures over 370 C .
4. FittingsLong radius (R= 1.5 D) but welding elbows shall be used wherever possible. Unless otherwise specified, flanged elbows shall not be used.
Pipe bends may be used in place of elbows, which shall not be used. Pipe bends may be used in place of elbows, but the minimum-bending radius shall be 5 times the nominal pipe size.
Miter bends may be used within the limitations specified in the ASME B 31.3.
Generally for utility services (except steam) miter bends shall be used for pipelines 8" NB and above.
Branch connections shall be preferably made by fittings such as tees, half couplings or weldolets. If the ranch connections are made by welding the branch pipe directly to the run pipe, the required reinforcement shall be designed in accordance with the ASME B 31.3.
Fittings of 2 NB and larger shall be the butt weld type and fittings of 1 12 NB and smaller, socket weld or threaded type.
As far as possible, use of threaded fittings shall be avoided, except in the case of galvanised piping for instrument air and drinking water services.5. FlangesThe number of flanges in piping systems shall be kept to a minimum and should be installed only to facilitate maintenance and inspection and where construction or process conditions dictate. For instance:Where pipelines are connected to flanged equipment and valves.Where frequent dismantling of piping is required.Where clearance for dismantling equipment such as compressors and reactor heads is required.Where steel piping is connected to non-metallic or non-ferrous piping.6. Flange Types6.1 Slip-on FlangesSlip-on flanges may be used where the following requirements are met :
i. Carbon steel piping
ii. Pipes handling non-toxic fluids
iii. Pressure - temperature conditions are within the ANSI 300 LB rating.
iv. Design temperature exceeds minus 20 0C
Slip-on flanges of austenitic stainless steel may be used within the limitations of item ii. through iv. above, if justified from the cost point of view.
6.2 Welding Neck Flanges
Welding neck flanges shall be used in all instances where slip-on flanges, socket weld flanges and screwed flanges are not permitted.
6.3 Socket Weld Flanges For 112 NB or smaller, socket weld flanges may be used within the limitations specified in paragraph 4.3.4 but S.W flanges shall not be used for piping under IBR purview.
6.4 Flanges FacingFlat face flanges shall be used for connecting flanges to flat face cast iron or bronze piping components and equipment. In this case, gaskets shall cover the whole flange face.
Raised face flanges shall in general be used:
i. For flanges of 600 LB or lower rating in process services.
ii. For flanges of 1500 LB or lower rating in utility services.
iii. Regardless of the above limitations a) and b) for design temperatures not exceeding 4500C.Ring joint type flanges shall be used for flanges of 1500 LB rating or higher, or for design temperatures exceeding 450 0C. The flanges can also be used for lower ratings, for service conditions which requires higher degree of tightness. Small and large tongue and groove faced flanges shall be used for services requiring higher degree of tightness and for all lethal services.
7. BoltingStainless steel galvanised cadmium plated nuts and bolt studs should be specified in cases where:
1. The spillage of pipeline fluids on the bolting shall corrode them.
2. The plant atmosphere may contain gases which may corrode the bolting.
The basic documents indicated above may not specify this clearly. However this needs to be verified during the preparation of piping specifications and finalised in consultation with clients and project manager.8. Gasketsa. Specific approval from the Project Manager, Client ProcessLicencor, Process Discipline (as the case may be) shall be obtained if material specifications are different from those specified in the basic documents.
b. Full-face gaskets shall be specified as far as possible, where both RF and Flat Face Flanges are used in the same piping class (e.g. cast iron valves in carbon steel piping with raised face (RF) flanges).9. ValvesThe types of valves specified shall be as per either P&I Diagrams or as per basic piping specifications from processlicencoror Jacobs H& G Process Discipline.
Types of valves may be revised as per the clients requirements. However, this shall be done only after the review of suitability of the same for the intended service and proper documentation of the change required.
Ball valves may be used in place of gate or plug valves with the following limitations.
i. Operating conditions are within the permissible pressure-temperature range of seat materials.
ii. The Fire safe type is used for flammable services.
Large diameter check valves shall be provided with anti-knock device if swing check valves are specified.Check list for valve requisitions may be referred to if required, to specify special requirements for valves in the project piping specifications.10. Branch Connection ChartThe standard branch connection chart shall be used to specify use of tees, etc. for a specific piping class.
When the details following, order or preference shall be kept in mind to facilitate procurement and reduce cost of materials (arranged in reducing order of preference i.e. (a) is most preferred).
a. Pipe to pipe branch.
b. Use of half couplings
c. Use of weldolets, sockolets. etc.
d. Seamless tees.
However requirements of basic documents shall not be diluted in this process
Things You Must Know When you do Piping Design Posted by Ankit Chugh on 12:21 PM 0 Comments .
Tubular products are termed tube or pipe. Tube is customarily specified by its outside diameter and wall thickness, expressed either BWG (Birmingham wire guage) or in inches or in thousands. Pipe is customarily identified by nominal pipe size with wall thickness defined by schedule number.
Piping materials Carbon steel pipe is strong ,ductile, weldable, machineable, reasonably durable and is nearly always cheaper than pipe made from other materials. If carbon steel pipe can meet the requirements of pressure, temperature, corrosion resistance and hygiene, it is the natural choice.
Other metals & alloys :- pipe or tube made from copper, lead, nickel, brass, aluminium and various stainless steels can be readily obtained. These materials are relatively expensive and are selected usually either because of their particular corrosion resistance to the process chemicals, their good heat transfer or for their tensile strength at high temperatures. Copper and copper alloys are traditional for instrument lines, food processing and heat transfer equipment, but stainless steels are increasingly being used for these purposes.Methods for joining pipeButt weldedSocket weldedScrewedBolted flangeBolted quick couplingPiping componentsElbows, Tees, Flanges, Gaskets, Nipples, Unions, Valves, Reducers, Steam traps, BellowsElbows or ells :-Types of elbowsLong radius elbows:- normally used elbows are long radius with centerline radius of curvature equal to 1 times the nominal pipe size for inch and large sizes.
Short radius elbows:- SR elbows with centerline radius of curvature equal to the nominal pipe size Reducing
Elbows :- this elbows have centerline radius of curvature 1 times the nominal size of the pipe to be attached to the larger end.
Bends :- Are made from straight pipe. Common bending radii are 3 and 5 times the pipe size. 3R bends are available from stock. Larger radius can be custom made.
Returns :- It changes direction of flow through 180 degrees, and is used to construct heating coils, vents and tanks etc.
Piping DesignPiping arrangements:-Use standard available items wherever possible.Do not use miters unless directed to do so.Do not run piping under foundation.Do not run steam lines under oil lines, fire hazards may occur.Piping may have to go through concrete floors or walls. Establish these points of penetration as early as possible and inform the group connected (civil) to avoid cutting existing reinforcing bars.Include removable flanged spools to aid maintenance, especially at pumps, turbines, and other equipment that will have to be removed for overhaul.Steam lines, which are below grade in trenches provided with covers or (for short runs) sleeves.Take gas and vapor branch lines from tops of headers when it is necessary to reduce the chance of drawing off condensate or sediment, which may damage rotating equipment.Maintain vent lines at higher and drain lines at lower elevations.
Clearing and Access:-Route piping to obtain adequate clearness for maintaining and removing equipment.
Locate within reach or make accessible, all equipment subjected to periodic operation or inspection, with special reference to check valves, pressure relief valves, traps, strainers and instruments.
Take care to not obstruct access ways i.e. doorways, truck-ways, walkways, lifting wells etc.
Elevations of lines are usually changed when changing horizontal directions where lines are grouped together or are in a congested area, so as not block spaces where future lines may have to be routed.
Keep field welds and other joints at least 3 inches from supporting steel, building siding or other obstruction. Allow room for the joint to be made
Allow room for loops and other pipe arrangements to cope with expansion by early consultation with staff concerned with pipe stressing. Notify the structural group of any additional steel required to support such loops.Stresses On PipingThermal Stresses:- change in temperature of piping due either to changes in temperature of the environment or of the conveyed fluid, cause changes in temperature in length of the piping. This expansion or contraction in turn causes strain in piping, supports and attached equipment.
Settlement Strains:- foundation of large tanks and heavy equipment may settle or tilt slightly in the course of time. Connected piping and equipment not on a common foundation will be stressed by the displacement.Flexibility in piping To reduce strains in piping caused by substantial thermal movement, flexible and expansion joints may be used. However, the use of these joints may be minimised by arranging piping in a flexible manner. Pipe can flex in a direction perpendicular to its length: thus, the longer an offset, or the deeper a loop, the more flexibility is gained.
Pipe RacksA pipeway is the space allocated for routing several parallel adjacent lines. A piperack is a structure in the pipeway for carrying pipes and is usually fabricated from steel, or concrete and steel. Piperacks for only two or three pipes are made from T-shaped member, termed Tee-head supports.
Piperacks are expensive, but are necessary for arranging the main process and service lines around the plant site. They are made use of in secondary ways, principally to provide location for ancillary equipment.
Pumps, utility stations, manifolds, fire-fighting and first-aid stations can be located under the piperack. Lighting and other fixtures can be fitted to stanchions. Air-cooled heat exchanger can be supported above the piperack.The smallest size of pipe run on a piperack without additional support is usually 2inch. It may be more economic to change proposed small lines to 2inch pipe, or to suspend them from 4inch or larger lines, instead of providing additional support.
Valves in piping design Valves are used for these purposes:-Process control during operation.Controlling services and utilities steam, water, air, gas and oil.Isolating equipment or instruments, for maintenance.Discharging gas, vapor or liquid.Draining piping and equipment on shutdown.Emergency shutdown in the event of plant mishap or fire.Which size valve to use:-Nearly all valves will be line size- one exception is control valves, which are usually one or two sizes smaller than line size, never larger.
At control stations and pumps it has been almost traditional to use line-size isolating valves. However, some companies are now using isolating valves at control stations the same size as the control valve, and at pumps are using pump size isolating valves at suction and discharge. The choice is usually an economic one made by a project engineer.
Where to place valves Preferably, place valves in lines from headers (on piperacks) in horizontal rather than vertical runs, so that lines can drain when the valves are closed.(in cold climates, water held in lines freeze and rupture the piping such lines should be traced.To avoid spooling unnecessary lengths of pipe, mount valves directly onto flanged equipment, if the flange is correctly pressured.A relief valve that discharges into a header should be placed higher than the header in order to drain into it.Locate heavy valves near suitable support points. Flanges should be not closer than 12 inches to the nearest support, so that installation is not hampered.For appearance, if practicable, keep centerlines of valves at the same height above floor, and in-line on plan view.Operating access to valvesConsider frequency of operation when locating manually-operated valves.Locate frequency-operated valves so they are accessible to an operator from grade or platform. Above this height and up to 20feet, use chain operation or extension stem. Over 20feet, consider a platform or remote operation.Valves Operating HeightsInfrequently used valves can be reached by a ladder but consider alternatives.Do not locate valves on piperacks, unless unavoidable.Group valves which would be out of reach so that all can be operated by providing a plotform, if automatic operators are used.If a chain is used on a horizontally mounted valve, take the bottom of the loop to within 3feet of floor level for safety, and provide a hook near by to hold the chain out of the way.Do not use chain operators on screwed valves, or on any valve 1 inches and smallerWith lines handling dangerous materials it is better to place valves at a suitably low level above grade, floor, platform, etc., so that the operator does not have to reach above head height.Access to valve in hazardous valvesLocate main isolating valves where they can be reached in an emergency such as an an outbreak of fire or a plant mishap. Make sure that personnel will be able to reach valves easily by walkway or automobile.Locate manually-operated valves at the plant perimeter, or outside hazardous area.Ensure that automatic operators and their control lines will be protected from the effect of fire.Make use of brick or concrete walls as possible fire shields for valve stations.Inside a plant, place isolating valves in accessible positions to shut feed lines for equipment and processes having a fire risk.Consider the use of automatic valves in fire systems to release water, foam and other fire-fighting agents, responding to heat-fusible links, smoke detectors, etc., triggered by fire or undue rise in temperature advice may be obtained from the insurer and the local fire department. If there is no P&IDProvide valves at headers, pumps, equipment, etc., to ensure that the system will be pressure-tight for hydrostatic testing, and to allow equipment to be removed for maintenance without shutting down the system.Provide isolating valves at all small lines branching from header.Provide isolating valves at all instrument pressure points for removal of instruments under operating conditions.Provide valved drains on all tanks, vessels, etc., and other equipment which may contain or collect liquids.Protect sensitive equipment by using a fast-closing check valve to stop back flow before it can gather momentum.Consider butt-welding or ring-jointflanged valvesfor lines containing hazardous or searching fluids. Hydrogen is especially liable to leak.Provide sufficient valves to control flows.Consider providing a concrete pit (usually about 4ft x 4ft) for a valve which is to be located below grade.Consider use of temporary closures for positive shut-off.Provide a bypass if necessary for equipment which may be taken out of service.Provide a bypass around control stations if continuous flow is require. The bypass should be at least as large as the control valve, and is usually globe type, unless 6-inch or larger, when a gate valve is normally used.Provide an upstream isolating valve with a small-valved bypass to equipment, which may be subject to fracture if heat is too rapidly applied on opening the isolating valve. Typical use is in steam system to lessen the risk of fracture of such things as castings, vitreous vessels, etc.Consider providing large gate valves with a valved bypass to equalize pressure on either side of the disc to reduce effort needed to open the valve.
How to do Pump Piping with Layout Explained Posted by Ankit Chugh on 1:04 PM 6 Comments .
1.0 PURPOSETo provide the layout designer guidelines for developing pump piping designs that fully consider safety, operation, maintenance and economics.2.0 EXCLUSIONSAll or part of this guide may be superseded by client mandatory standards or by the codes and regulations imposed by governmental jurisdictions covering the location where the piping is installed.
3.0 DISCUSSION3.1 SAFETYProper consideration for personnel safety around pumps requires piping and valve arrangements that do not obstruct access for operation, maintenance or egress. Care must be exercised not to create tripping hazards with auxiliary piping.3.2 OPERATIONPumps normally require minimal attention during operation. Valves however, must be located for easy access; this is particularly true for paired or spared pumps. Where manual valves cannot be operated from grade, chain operators shall be used. If chain operators are not allowed per client specifications, platform access to valves shall be considered.
3.3 MAINTENANCEPiping shall be arranged in a manner to allow adequate access to the pump without requiring excessive dismantling of the piping system. The coupling between the pump and its driver must be easily accessed in order to align the pump and driver. Pump seal access must also be considered. Piping must be kept clear from above the pump for horizontally split pump casings to allow maintenance. For vertically split casings, access must be provided in front of the pumps.
Clearance for forklifts or mobile cranes should be provided for maintenance. In cases where pumps are located in a building or other areas where overhead access is limited, monorails or rigging beams should be considered for removal of the pump and/or motor.4.0 TYPES OF PUMPSPumps are available in many different types. The most common are centrifugal, reciprocating and rotary. Reciprocating and rotary pumps are positive displacement pumps. Centrifugal pumps will usually be one of three types; horizontal, vertical in-line or vertical can type. They may have electric motor or steam turbine drivers. (See Figure 1 for examples of horizontal, vertical in-line and vertical can type centrifugal pumps) Reciprocating pumps may have a direct steam piston driver.
Types of Common Centrifugal Pumps
Rotary pumps usually have an electric motor driver but may be steam turbine driven. In many cases, the fluid pumped by rotary pumps is so viscous that block valves are not necessary. In that case, the relief valve may not be necessary. If turbine driven, there will be a gearbox between the pump and turbine.5.0 PUMP LOCATIONPump location will affect the piping layout and how the piping can be supported. Pumps in flammable service shall be located outboard of overhead pipe-racks or structures. Those in non-flammable service may be located beneath the pipe-rack (subject to allowance in client specifications). Pumps shall be located as close as possible to the source of suction in order to minimize pressure drop in the system while satisfying piping flexibility requirements and nozzle load allowable. Line size and temperature should be determining factors in routing the piping.6.0 GENERAL PUMP PIPINGPump suction piping shall be arranged such that the flow is as smooth and uniform as practicable at the pump suction nozzle. To accomplish this, the use of tees, crosses, valves, strainers, near run-size branch connections, and short radius elbows shall be avoided near the suction nozzle. Suction piping shall be designed without high points to prevent collection of vapors. Suction piping shall not be pocketed. When pump flanges are flat faced, mating flanges must also be flat faced and the joint made up using full-faced gaskets.
Multiple pump arrangements that connect to a common discharge header shall have the discharges connected to the header such that the discharges from pumps operating simultaneously do not oppose one another.
The suction line for all systems designed to API recommendations that connect to API pumps with end, top or side suction nozzles, or API in-line pumps, shall have a straight run of five pipe diameters (nozzle size) between the suction flange and the first elbow, tee, valve, reducer or permanent strainer (Figure 4). The suction line for pumps other than API, shall have a minimum straight run length of three pipe diameters. This straight run length should be maximized, but in any case the pump manufacturers recommendations should be followed (Figure 5).6.1 REDUCER TYPE AND LOCATIONEccentric reducers in horizontal pump suction lines shall be flat on top in order to prevent any entrained vapors in the liquid from accumulating in the high point and possibly causing cavitation in the pump. Pumps in boiler feed water service operating at close to the vapor pressure of the liquid are particularly susceptible to this problem.
The reducer shall be concentric for overhead piping into a top suction pump. (See Figure 2) Reducers in pump discharge lines shall be concentric and located as close as possible to the pump discharge nozzle. In cases where a combination of nozzle size, nozzle location, pipe size and insulation thickness create flange to pipe/insulation interference, eccentric reducers may be used to gain the required clearance.
Reducers locations at pumps
Care should be exercised when using a top flat reducer next to a pump suction nozzle where the change in diameters exceeds 4in / 100mm, as this could result in a disturbed flow pattern into the impeller and cause vibration and rapid wear.6.2 VALVE LOCATION AND ORIENTATIONValve handwheels shall be oriented in a manner resulting in good access to the valve and pump. The suction line valve shall be installed with the stem in the horizontal. (i.e. install valve in the vertical run of pipe). Gate valves installed in the horizontal can accumulate vapor in the bonnet cavity and cause cavitation in the pump when the trapped vapor breaks loose.6.3 HORIZONTAL DISCHARGE OFFSETIf existing steel is not available for support of the discharge piping, or if the check valve must be installed in a horizontal run, then Alternate 1 in Figure 3 shall be used.
Typical Pump Discharge Piping
When discharge piping is horizontally offset, care must be exercised not to block access to the pump coupling, seals or bearings (See figures 3 & 12) .6.4 TEMPORARY AND PERMANENT SUCTION STRAINER INSTALLATIONSpecial attention must be given to the location of temporary suction strainers to allow for removal. Figures 4 & 5 show examples of suction strainer installation.
TYPICAL PIPING FOR END SUCTION - TOP DISCHARGE PUMPS (API PUMPS ONLY)
TYPICAL PIPING FOR END SUCTION - TOP DISCHARGE PUMPS (NON API PUMPS ONLY)
For permanent T-type and Y-type strainers installed in a horizontal suction line, the preferred position of the clean-out connection is 30 to 40 degrees from the vertical making sure that there is enough clearance for strainer removal at grade.
Consideration shall be given to the handling of large T type strainer covers, and a permanent handling device (e.g. a davit) supplied if access by mobile equipment is not possible.6.5 COMMON SPAREOccasionally, one pump is installed as a common spare between two other pumps in different services. The pump must be manifolded in such a way that accomplishes this. Figure 6 illustrates an arrangement commonly used.
Piping for Pumps with a common Spare
7.0 CENTRIFUGAL PUMP PIPING LAYOUT7.1 HORIZONTAL CENTRIFUGAL PUMPSHorizontal centrifugal pumps usually fit into three categories:
(1) End Suction -Top Discharge(2) Top Suction -Top Discharge(3) Side Suction -Side Discharge
The most common are end suction or top suction. Suction piping shall be supported at grade below the elbow for end suction pumps. The discharge line (top discharge) shall be supported from overhead steel whenever possible to allow as much free area as possible around the pump for operation/maintenance. Figure 7 illustrates how piping may be designed for these pumps.
Typical arrangement for End/Top Suction Centrifugal Pumps
7.1.1 Typical End Suction Top Discharge arrangementFigures 4 & 5 show common piping arrangements for end suction - top discharge centrifugal pumps. The suction line shall have a straight run between the suction nozzle and the first elbow, tee, valve, reducer or permanent strainer as dictated by the type of pump and/or manufacturers recommendation.7.1.2 Side Suction / Side Discharge Pump PipingPumps may be single stage or multi-stage. Multi-stage pumps are usually side suction - side discharge. These pumps require significantly more space, and present special layout considerations. The pump suction line for side suction pumps shall have a minimum straight run of three pipe diameters (for non-API pumps) or five pipe diameters (for API pumps) between the suction flange and the first elbow, tee, valve, reducer and permanent strainer. If a horizontal suction line cannot be avoided, then the straight run length should be fivediameters minimum for all pumps (Figure 8).
Piping Arrangement for Side Suction - Side Discharge Pumps
7.2 VERTICAL CENTRIFUGAL PUMP PIPINGVertical centrifugal pumps may be in-line, can (self contained) or sump pumps. In-line pumps are mounted in the line and supported by the piping as the name implies. A pedestal is often required for larger in-line pumps or where the load is too high for the nozzles to handle. The designer must consider access for maintenance and operation in the same way as for horizontal pumps.
Vertical can type pumps are installed in a concrete cylinder but the process fluid is completely contained in the pump "can." They are used when there is a high NPSH requirement or at surface condensers. This allows the surface condenser to be mounted at a lower elevation. The same is true for a vessel connected to a vertical can pump. The primary concern for the designer is to provide adequate overhead clearance to remove the pump for maintenance.
Vertical sump pumps are usually used to pump waste products or water from a collection sump. Here again a primary concern is to provide adequate overhead clearance to remove the pump for maintenance. The clearance requirements, between the sump walls or bottom and the pumps inlet nozzle as well as the pumps length must be given careful consideration during the layout phase of the project. The sump design at the pump intake shall be based on Hydraulic Institute Standards.8.0 RECIPROCATING PUMP PIPINGReciprocating pumps are used when high head is required. These pumps require a pressure relief valve (PRV) to be installed between the pump and the discharge block valve. The PRV can be external, in the piping, or integral with the pump casing.
Due to the pulsating action of reciprocating pumps, the designer must consider space requirements for pulsation dampeners. These are usually furnished with the pump but take up additional space.
Pump access is even more important for reciprocating pumps since they require more maintenance than other pumps. Do not install any bend (i.e. 90 degree elbow) directly adjacent to the pump discharge. For typical egress and clearance requirements, refer to Design Guide for Compressor Piping Layout (Reciprocating Compressors) 3DG-P22-00008.
The discharge pulsation dampener must be installed as close to the discharge as possible. Pipe supports must be given special consideration due to the pulsations.9.0 ROTARY PUMP PIPINGRotary pumps are used for very heavy or viscous fluids. They deliver a constant pulsation-free flow. Piping for these pumps is very similar to that of centrifugal pumps but is usually characterized by the absence of block valves in the suction and discharge piping. If block valves are used, a pressure relief valve must be installed between the pump discharge and the block valve. The PRV discharge is usually routed back to the pump suction.10.0 PUMPS OPERATING BELOW ATMOSPHERIC PRESSUREPumps operating below atmospheric pressure (e.g. Vacuum Tower Bottoms Pumps) present special problems. Since the system operates at a negative pressure and very high temperature, the pumps must be located very close to the suction source. This is often directly below the tower or immediately outside the tower support columns. Pumps located directly beneath the tower can be mounted on a special spring base as shown in Figure 9.
Typical Pump Suction Piping at Vacuum Tower
11.0 AUXILIARY PIPINGConsideration must be given to lube oil and seal oil systems and any cooling water requirements. Care must be exercised not to block access to the pump seals, bearings, seal pots, starter button stations and motor conduit connection when routing these lines. (Figure 10) The pump data sheet shall always be reviewed to make sure these requirements are not missed. For very large pumps these may be on separate skids.
Preferred Auxiliary Piping Arrangement and Access Zones
Fire-water deluge piping shall be routed so that it does not interfere with pump operating or maintenance access. If the deluge piping design is sub-contracted, the vendors design should be checked to ensure that safety egress, operating and maintenance access-ways are maintained.12.0 FIELD WELDSConsideration should be given to the placement of field fit-up welds in shop fabricated piping 2 and larger. Early in the project, Plant Design should review the options with Construction and the decision documented. Options include:
(i) Tack weld the flange adjacent to the pump suction and discharge nozzles to permit piping installation in accordance with the machinery flange fit-up requirements.
(ii) Provide field welds that allow fit-up in three directions.
(iii) No field welds other than those required by spool transportation size limitations.13.0 STEAM TURBINE PIPINGPiping at steam turbines present somewhat different considerations from that of pumps. The piping must be designed to prevent the possibility of introducing a slug of condensate into the turbine, which could destroy the turbine vanes.
The inlet piping must have the block valve or control valve installed in the horizontal run with a drip leg and steam trap upstream of the valves whether the turbine is set-up for manual or automatic operation. In cases where the throttling valve is furnished with the turbine and located on the inlet nozzle, the drip leg and steam trap shall be located immediately upstream. (See figure 11).
Typical Steam Turbine Piping
Reducers installed in the inlet piping to steam turbines shall be eccentric with the flat side on the bottom to prevent the accumulation of any liquid.14.0 SUPPORT OF PUMP PIPINGIt is preferred that pump discharge piping be supported from overhead steel whenever possible. This allows piping at the pump to be removed for maintenance. (See figure 12).
Pump Discharge Piping Support Options
The piping layout must permit both suction and discharge pipes to be supported independent of the pump(s), such that very little load is transmitted to the pump casing.15.0 DIFFERENTIAL SETTLEMENTWhen differential settlement is a problem, it is preferred that the pump suction piping be supported from the pump foundation. This can be accomplished by extending the foundation as shown in Figure 13.
Pump Suction Support for Differential Settlement Problem
16.0 REFERENCESHydraulic Institute StandardsPump Handbook (ISBN 0-07-033301-7)Typical Questions For Piping Engineers Knowledge Testing (With Answers)Note: Each answer will appear to be wrong to some readers and right to others. Some questions will have what seems to be an absolute right answer. Others will not. So if you have got any good answer for below questions, leave us a comment. Find more details see at the end of article.
1. Can you explain in detail three or more major differences between code ANSI B31.1 and code ANSI B31.3?
Answer: There is only one major difference between the two, B31.1 is for Power Piping and B31.3 is for Refinery/Chemical Plant Piping.
2. There is a power plant inside a Process refinery. Where exactly the ANSI B31.1 & ANSI B31.3 scope break occurs?
Answer: Based on my experience there were two cases. Case #1, B31.1 stopped at the Power Plant Unit block valves. Thus all piping inside the Power Plant was B31.1. Case #2, B31.1 stopped at the equipment (Boiler) isolation block valves and then all other piping was B31.3. This is normally the choice of the owner/operator/client.
3. Which of the following piping system is more health hazardous. A) Fuel oil piping b) Process piping with Caustic c) process piping with HF acid d) Sulphuric acid piping.
Answer: c) process piping with HF acid
4. There is a steam piping with low pocket but without steam trap. What will be worst consequence of this layout?
Answer: There will be a build up of condensate to the point that a slug will be pushed by the steam flow. This slug of condensate will cause water hammer and could rip the piping apart.
5. In what circumstance, the reducer of a pump suction piping will be in bottom flat position. Explain why the reducer should be so.
Answer:When reducers are placed in pipe Rack they are generally bottom side flat to maintain BOP to facilitate supporting. (Answer Credit: Samir Kumar)
6. A P&ID shows a spec break (at Flange) between carbon steel & stainless steel specification. What additional arrangements you have to make for that dissimilar material flange joint?
Answer: Use the Gasket and bolts from the SS spec.
7. A stainless steel piping specification mentions Galvanized carbons steel bolts. What is your first reaction ti this and how do you rectify it?
Answer: If that is what the Spec call for then that is what I am supposed to use. But, I would ask the Piping Material Engineer (PME) why he/she specified galvanized bolts.
8. How many types of piping specialty items do you know? Why it is called a piping special? Why not we include them in standard piping specification.
Answer: I could possibly count 50 or more depending on the PME and how the piping material specs were developed. They are called them SP items because they are NOT written into the normal Piping Material (Line Class) Specifications. They are not included because they are normally of limited use, purchased from a limited product line vendor and are often after thoughts.
9. Draw a typical steam trap station layout and explain why the existence of a by-pass line around the trap is not a good idea, when the condensate is returning to a condensate header?
Answer: (No drawing) It is not advisable to have a bypass around a steam trap because the block valve could be left open and defeat the purpose of the trap.
10. Explain what is a Double block & Bleed valve? Why we need a bleed valve? When do we use this?
Answer: The primary purpose of a Double Block & Bleed is Safety. However it is not fail safe. The next better Safety set-up would be Double Block Valve with a Spec Blind between the valves. The higher level of safety would be double block valves with a removable spool for absolute isolation.
11. In a typical tie-in where should the spectacle blind be inserted? a) after block valve and towards existing plant b) before block valve and towards new plant. Explain why.
Answer: The Spec Blind shall be placed on the Unit side of the Unit Block valves. This placement allows for the closing of the Unit isolation block valve, the unit side is depressured and drained. Then the spec blind can be installed for isolation of the unit.
12. Stress intensification factor (SIF) Where do we use this? Explain this term. How many types of these SIFs exist?
Answer: Stress Intensification Factor (SIF) is a multiplier on nominal stress for typically bend and intersection components so that the effect of geometry and welding can be considered in a beam analysis. Stress Intensification Factors form the basis of most stress analysis of piping systems. As for the quantity, ask a Stress Engineer.
13. When all design parameters are same, whose thermal expansion is higher among the following? A) Carbon steel b) Stainless steel c) Duplex steel d) Cast Iron e) Galvanized Carbon steel.
Answer: b) Stainless steel
14. In a hose station the hose couplings used for water, air & steam should be different type. Do you agree? Explain your view.
Answer: I agree. If they are all the same then the hoses can be connected to the wrong services and could result in the injury of an operator (i.e.: thinking the hose is connected to water when it is connected to steam).
15. What is your view on the usage of Metallic expansion joints? When they become necessary and when they could be avoided?
Answer: I do everything I can as a piping designer to avoid the use of all types of expansion joints. Expansion joints are always the weakest point in any system where they are used.
16. A water cooler heat exchanger, located on a 20 m high structural platform. Water header is located u/g. What precaution do you take, in case of Pressure loss in cooling water header?
Answer: I do not understand this question it does not appear to be a piping issue. I would assume that the cooling water system has a (loss of) pressure sensor and the plant shut-down alarms and sequence would be activated.
17. In what order do you arrange the pipes in the Pipe rack and why? How much % of area should be reserved for Future expansion? Specify a range.
Answer: The largest hottest lines on the outside edge of the pipe rack working in with cooler lines in towards the middle of the rack. This allows the longer loop legs as you lay the loops back over the other lines to the other side of the rack and back. The lower temperature loops would be nested inside the larger, hotter loops.
Future rack space is normally at the direction of the Client. It may be anything from 0% to as much as 25%.
18. When a utility line (like condensate or water etc) is connected permanently to a process piping what precaution we have to take to avoid cross contamination?
Answer: Option #1, double block valve with a drop-out spool.Option #2, Double block valve with a spec blind.Option #3, double block valves with a bleed valve.
19. A air fin cooler (2 air coolers with each having 2 inlet nozzles) needs a Typical piping arrangement. How many types of piping arrangement is possible.
Answer: There are a number of ways to pipe a Fin-Fan cooler depending on what the P&ID call for?
Thanks to (for the answers)
