Pentti Häkkinen Piping chapter 9.2 Wärtsilä New Propfessorionals 3.-7.11.2008 Outfitting in pipe systems Fitting (armature) is a passive member in pipe.

Pentti Häkkinen Piping chapter 9.2Wärtsilä New Propfessorionals 3.-7.11.2008

Outfitting in pipe systems

Fitting (armature) is a passive member in pipe system: support, penetration, filter, mud box, vapour separator, cock. Valve is active system components, but often considered as active member. According of application duty the valve is:

Close or separation valve Control valveNon-return valveSafety valve Pressure reduction valve Change-over valve Instant shut valve

Material is often same as the pipe itself, generally steel. For sea water rubber lining in cast iron casing, bronze internal parts. Fuel valves are typically of nodular cast iron or cast steel.


Denotions and symbols

Close valve (general) Slide valve

Hand operated close valve

Non-return valve

Safety valve

3 way valve

Termostate valve with electric actuator

Cock (no tightness requirement) Buttefly valve

Throttel

Screw down non-return valve

Suction filter (mud box)

Steam trap / Condense trap

Steam condenser M

Valve chest), 2 outlets with non-return valves

Pump (general

Centrifugal pump.

Hand operated pump

Screw pump

Ejector pump

Heat exchanger (generally cooler)

Filter (general / hand operated)

Air filter with condense trap


Valves

Valve type is chosen according to application:

Glove valve high flow resistance and length. Closing causes pressure pulse. Easy maintenance, seal exchange when pressure is on. Gate valve gate/slide is round wedge type disc that seals against bronze ring. Suitable for control, small resistance. Ball valve general separation valve for small diameters. Also available in large sizes. Suitable for control purposes.Butterfly valve is short and low cost unit. Small flow resistance. Common as isolation and also control valve.


Valves

Non return valve is generally a glove valve. Instant closure, small resistance in open condition. Often manually closed model, NRSD Change over valve often sector valve. Not fully tight, but suitable for flow distribution control. Temperature control is often made with two mechanically connected butterfly valves. Valve chest 3 - 5 globe valves connected in one casing, common inlet and outlet chambers.

Actuator pneumac, electric, hydraulic. Small temperature control valve is often self-actuated with was cartridge (right AMOT). Always position display and manual operation.


Heat exchangers

Cooler or heaters. Flow media is gas, steam or liquid. Small temperature differences lead into large heat transfer surface. Heat transfer also depends on:

Logarithmic temperature difference

tlog=(tmax - tmin) / ln(tmax / tmin)

•Properties of media (specific heat and convection) •Media flow velocities•Wall material•Wall thickness•Wall surface, possible coating•Parallel or opposite flow direction (also cross flow) n)

General problem is the improvement of heat transfer.

Here tmax is highest temperature difference and tmin smallest in the heat exchanger

T1

T1

T2T2

t1

t2t2

t1

tlog tlog

Parallel Opposite

Hot medium Cold medium


Heat exchangers

shell & tube heat exchanger

One fluid inside the tubes connecting inlet and outlet chambers, the other around tubes inside the shell.

Frequently guide plates which support the tubes and create turbulence.

Gas or steam outside the tubes, liquid inside tubes. Low pressure loss on both sides.

Cleaning and repair require withdrawal of the tubes, which may create space problems.

Typical shell and tube heat exchanger


Heat exchangers

plate heat exchanger

Metal plates tightened between thick end plates. Surface pattern promotes turbulence. Flow channels created by holes in each plate corner. Rubber gaskets between plates.

Suitable for all fluids and steam. For sea water 0.7 mm titanium plates.

Rather high flow resistance, 0.5 – 1 bar. Several advantages:

Compact, small space demand for cleaning and plate exchange. Accurate dimensioning, capacity can be afterwards increased.


Pipe material and corrosion

Material selection basis: corrosion resistanceregulations Material and labour costsStrength and deformationsOperation temperatureReparabilityRequirements on cargo

Materials Aluminium bonze and brassCopper nickel alloys (Cunifer 10, 30)Stell (plain and galvanized)Acis resistant steelCast ironPlastic and fibre reinforced plastic Titanium

Corrosion two metals with different potential level, conductive electrolyte nad free oxygen. If any of these is missing, no corrosion occurs.

Corrosion means disposal of the less noble metal. Potential difference can be also created between areas of piping with uniform material.


Corrosion forms

General evenly advancing corrosion

pit corrosion

crevity corrosion

stress corrosion

Crystal border corrosion

Erosion and caviation corrosion

Galvanic corrosion

Selective dissolving


Pipe materials and corrosion

The organic growth on pipe surface in still water can create corrosion.

Many metals have a passivation layer, that prevents further corrosion. In unfavourable conditions this layer is broken or not even created.

Corrosion control methodssuitable material selectiongalvanic protection use of chemicalscombination of several corrosion methods

Selection depends on Sea water salinity, temperature and contamination. Baltic Seabrackish water is not good! Discontinuation of water flowResidual installation time stress levelPossibilities to uniform materials in system.


Pipe materials and corrosion

Black steel cannot be used without protection. Rubber lining or epoxy coating are good. Additionally cathodic protection is required in case of local coating damage.

Galvanized steel reistant for still sea water. Continuous flow above 0.5 m/s causes erosion. Suitable for ballast water, not for cooling pipes.

Aluminium bronze is low cost among special materials. Resistant in clean sea water. In contaminated water erosion and stress corrosion can create problems.

Copper nickel alloys are common in cooling water systems. Resistant in clean sea water, copper prevents organic growth.

Titanium is expensive. Small mass, no corrosion. Growth control need at least sacrifying copper anode. Permits high flow velocities, good in high speed craft,

Acid proof steel is common name for many grades. The cheap materials suffer pitting corrosion in sea water. Mo-Ni alloy 254SMO is suitable for many purposes.

Galvanized steel or GRP for ballast water pipes, also cast iron. For cooling water piper Cunifer. 254SMO is possible depending on sailing area. Electric protection and chemical growth control also required.


Dimensioning of piping

Too small pipe diameter increases flow resistance and pumping power demand rises. Lifetime may be shortened and flow distribution be wrong.During ship commissioning the correct flow distribution is confirmed by measurement using throttle plates.

Flow resistance is created of single component resistance and pipe resistance. Component share of losses is dominating. Turbulent flow, Re 104 – 105.

FluidSea water

Fresh waterFuel oil

Lube oil

Cargo oilHydr. oilSatur. steamSuperheat.s.Compress. air

MaterialGalv.steel

Cast ironAl-bronze

Rubber liningAcid proof st.TitaniumGalv.steelCast ironSteelSteel

Steel

SteelSteelSteelSteelSteel

ApplicationCooling.Cool. suctionCooling.Cooling.Cool, suctionCoolingCooling.Cooling.Ballast wtrBallast wtrCooling.TransferTrans, suctionTransferTrans, suctionTransferPwr transmiss

V m/s0.50.51.0

2.5.2.03.03.55.01.51.02.01.00.52.00.81.52.0253545


Pipe system planning and manufacturing

Computer aided design helped also automation of the manufacture. Cutting, bending, branching and flange fitting were mechanized.

Main part of engine room pipe systems are prefabricates. Pipes are assembled into packages before hoisting and fastening in ship.

Fitted pipes arranged between packages according to true dimensions. Installation is critical in GRP pipes and sea water pipes where the stress corrosion risk is high. Service operations must be foreseen in engine room pipe systems. Too tight pipe packages must be avoided. Distance between flanges max 3 –4 m. Generally welded flanges. For bronze piping loose flanges are soldered or tightened around collar. Certain positions in fuel piping demand thread or welded connection.

Several special type flanges used in sanitary water systems. Plastic pipes joined with cement.


Basic forms of prefabricated pipes

Proposal for the types. In addition to pipe diameter and length the position of branch or bend is indicated, also to angle in degrees.

Pentti Häkkinen Piping chapter 9.2 Wärtsilä New Propfessorionals 3.-7.11.2008 Outfitting in pipe systems Fitting (armature) is a passive member in pipe.

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Pentti Häkkinen Piping chapter 9.2 Wärtsilä New Propfessorionals 3.-7.11.2008 Outfitting in pipe systems Fitting (armature) is a passive member in pipe.