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7Image: Spectacle flangeTable 1 contIntermediate SurveyALL SHIPSTANKERSBULK & DRY CARGOThe scope of intermediate surveys is thesame as annual surveys.The annual survey requirements apply;however, depending upon the surveyor’sfindings during the general examination,he may require pipes to be dismantled,hydrostatically tested and have their wallthickness measured, or all three.The scope of intermediate surveys is thesame as annual surveys.ALL SHIPSTANKERSBULK & DRY CARGOThe survey involves extensive examinationsand checks to show that all piping systemsare in satisfactory condition to allow theship to operate and for the new period ofclass to be assigned (provided propermaintenance and required interimsurveys are carried out).All piping systems within cargo tanks,saltwater ballast tanks, double-bottomtanks, pump rooms, pipe tunnel(s) andcofferdams, including void spacesadjacent to cargo tanks, and pipesthat pass through the deck or connectto the shell, are examined and testedunder working conditions. The surveyorchecks for tightness and looks to establishif their condition is satisfactory.All piping systems within cargo holds,saltwater ballast tanks, double-bottomtanks, pipe tunnels, cofferdams and voidspaces adjacent to cargo holds, and pipesthat pass through the deck or connect tothe hull, are examined and tested underworking conditions to ensure that theyremain tight.Renewal SurveyMachinery and all piping systems used foressential services are examined and testedunder working conditions, as considerednecessary by the surveyor.Steam pipes are specially examined.Superheated steam pipes with a steamtemperature exceeding 450 C requireadditional tests.In addition to the annual and intermediatesurvey requirements, fixed fire-fightingequipment is tested under workingconditions, including relevant gas bottles,which are hydrostatically tested.Compressed air pipes are removed forinternal examination and are subjectedto a hydrostatic test.In addition to annual and intermediatesurvey requirements, all machinery usedfor liquid cargo services is examined,including ventilation pipes, pressurevacuum valves and flame screens.The inert gas systems are tested underworking conditions. The systems’ maincomponents are examined internally.On the basis of results of theseexaminations, additional checks canbe required, which may includedismantling, hydrostatic tests and/orthickness measures, or all three.Piping systems for fuel or lubricatingoil are carefully examined.This document, and more, is available online at Martin's Marine Engineering Page - www.dieselduck.net

8Image: Suction filterSHIPS’ PIPINGSYSTEMSBilge systemThe bilge system is used to remove small quantities of fluid thathave leaked or condensed into a dry space. The system serves themachinery spaces, cargo holds, cofferdams, voids, stores, tunnelsand pump rooms. Each space has its own piping but the pump islikely to be shared.The capacity of a bilge system is defined by the diameter of thebilge main and pump capacity for the volume of the enclosed space.In passenger and cargo ships where the engine room providesbilge pumping, the whole ship is the ‘enclosed space’. The diameterof the bilge main is:d 25 1.68 L(B D )where,d internal diameter of bilge main, in millimetresL length between the ship’s perpendiculars, in metresB extreme breadth, in metresD moulded depth, in metresIn a tanker with a separate cargo pumping and piping system,the ‘enclosed space’ is the engine room and the diameter of thebilge main is:d 35 3 Lo (B D )where,Lo length of the engine room, in metresCargo ships are required to have two bilge pumps with non-returnvalves fitted to prevent back-flow or cross-flow.The pumping system in a passenger ship must be able to drainwater from any dry space when one or more of the ship’s othercompartments are flooded. However, the system is not required toempty the flooded space. A flooded passenger ship is required tohave at least one bilge pump, with its own power supply, availablefor pumping. Bilge suctions must have remotely operated suctionvalves. The minimum number of pumps required is three or four,depending on the ship’s design.Mud boxes and strum boxes (line filters) are fitted at the ends andin bilge lines to stop debris being sucked into the pipe.The requirements for bilge systems on ships carrying dangerousgoods are basically the same as for cargo ships. However, systemsdrawing fluids from gas-dangerous spaces are kept segregatedwith their own pumps and pipes, where appropriate, from systemsserving gas-safe spaces.This document, and more, is available online at Martin's Marine Engineering Page - www.dieselduck.net

9Image: Deck pipingSHIPS’ PIPING SYSTEMSBallast systemBallast is taken on to increase a ship’s draught, particularly thestern draught, when sailing without cargo. On a dry-cargo orpassenger ship, the ballast system is operated from the engineroom. On a tanker, the entire ballast system is located within thecargo area and is operated from a pump room. Usually small-bore piping, which is dry when not in use.A water spray system is operated manually and looks similarto a sprinkler system. Ships’ firefighting systems Sprinkler systemsSmall-bore pipes kept permanently charged with freshwater atabout 10 bar pressure. A sprinkler system is arranged to releaseautomatically at temperatures of about 70 C, so the system canboth detect and extinguish a fire. The system uses saltwaterafter the fresh. After use, it is flushed with freshwater tominimise corrosion. Some systems operate at higher pressures.CO2 pipingRelatively small bore hot galvanised mild steel piping designedto withstand the surge loads that occur with the release of CO2.Main CO2 lines are designed to withstand the same pressure asthat of CO2 bottles, while distribution lines off the main valveare designed for a lower pressure. Typically, the main line ispressure tested to 200 bar, the design pressure being at least160 bar.Fire mainMild steel piping fitted with hydrants for hoses where saltwateris used for manual firefighting. The fire main is designed for atypical working pressure of about 10 bar. Pipes in the fire mainare affected by corrosion both externally and internally. Pipesare joined with flanged connections.Inert gas (IG) pipingFitted on all tankers over 20,000 dwt and on all tankers fittedwith crude oil washing (COW) systems. IG piping is usuallylarge diameter low-pressure mild steel, with smaller diameterbranch lines. The internal surface of inert gas piping does notusually corrode. The external surface is painted but will corrodeif the paint coating deteriorates.Ballast piping is usually made of ordinary mild steel. A ship’s sizedetermines the capacity of its ballast system.Piping is used extensively throughout a ship for fire control purposes.The specific features of ships’ fire-fighting equipment are governedby the Safety of Life at Sea Convention (SOLAS). Many SOLASrequirements have been put into classification society rules.They include:Water spray systems High-expansion foamUses foam with an expansion ratio of 900 to 1 in mild steellow-pressure piping. Pressure in the lines ranges from 4 to 5bar. Foam compound in storage tanks is pumped to a foamgenerator. The system is required to deliver foam at a rate ofone metre of compartment depth per minute.This document, and more, is available online at Martin's Marine Engineering Page - www.dieselduck.net

10Image: Low expansion foam monitorSHIPS’ PIPING SYSTEMS Low expansion foamUses foam with an expansion ratio of 12 to 1 in mild steellow-pressure piping. Typical pressure in low expansion foampiping is 12 bar. Dry powderUsed mainly for the fixed fire-extinguishing system on the deckof gas carriers and on older chemical tankers. Dry powder isheld in tanks and is propelled by nitrogen gas stored inpressure bottles. Dry powder delivery pipes are pressurisedto 18 bar.Pipes carrying fuel oil andflammable liquidsThere are two principal types of pipes that carry fuel and they arecategorised by the pressure the pipe is designed to withstand.Low-pressure pipes are used to move fuel from a storage tank toa service tank to an injection pump; high-pressure pipes are usedto deliver fuel from an injection pump to an engine combustionchamber. Ships’ fuel is usually stored in double-bottom tanks,deep tanks, side bunker tanks, settling tanks or service tanks.Piping between a service tank and a fuel transfer or boosterpump is rated as low pressure. However, between each pumpingstage, pressure increases.It is a mistake to assume that even if a pipe’s pressure is relativelylow, fuel will not spray from a crack or small hole.Pipes from fuel tanks can pass through ballast tanks and pipesserving ballast tanks can pass through fuel tanks. Because ofpollution risks, classification societies have stringent rulesrestricting the length of any oil pipe passing through a ballast tank(and vice versa); it must be short, have increased wall thicknessand stronger flanges.The Safety of Life at Sea Convention (SOLAS) includesrequirements for fire safety in engine rooms. In particular, specialdouble-skinned pipes must be used to deliver fuel to enginecombustion chambers. These are made of low carbon steel alloysand operate at high pressure, between 600 and 900 bar. Doubleskins are necessary because pipe fracture will cause fuel to sprayin a fine aerosol. Fuel will ignite on contact with a hot surface,such as a turbocharger casing or exhaust pipe. The second skin isto guard against direct spraying. The pipe is designed so that fuelwill be contained in the space between the outer skin and themain pipe, and will drain into a collecting tank fitted with ahigh-level alarm.Low-pressure lubricating and fuel oil pipes passing close to a hotsurface have to be secured against the possibility of oil sprayingfrom a flange. To prevent this, the flange is usually taped. Inaddition, and whenever possible, the pipes are routed clear of hotsurfaces. Similarly, to prevent leaking oil falling onto a hot surface,pipes should never be allowed to run above a hot surface.Regular thermographic surveys of hot surfaces will identify thoserisk areas that are sufficiently hot to ignite spraying or leaking fuel.Preventive measures to be taken include additional lagging, sprayor drip shields.Fuel oil transfer pipes are usually mild steel and may corrode.The calculation for minimum wall thickness includes a smallallowance for corrosion. As a pipe ages and corrodes, leakagecan occur. Inspection programmes should concentrate onidentifying worn or corroded pipes.This document, and more, is available online at Martin's Marine Engineering Page - www.dieselduck.net

11SHIPS’ PIPING SYSTEMSEngine cooling systemWater carried in pipes is used to cool machinery. The main engineis cooled by two separate but linked systems: an open system(sea-to-sea) in which water is taken from and returned to thesea (seawater cooling), and a closed system where freshwateris circulated around an engine casing (freshwater cooling).Freshwater is used to cool machinery directly, whereas seawateris used to cool freshwater passing through a heat exchanger.The particular feature of an engine cooling system is continuousfluid flow. Fluid in motion causes abrasive corrosion and erosion.To reduce the effects of turbulent flows, seawater systemsincorporate large diameter mild steel pipes, the ends of whichopen to the sea through sea chests where gate valves are fitted.If a seawater cooling pipe bursts, both suction and dischargevalves will have to be closed to prevent engine room flooding.In order to make sure the valves operate correctly when you needthem to, open and close them at regular, say monthly, intervals.Seawater pipes are usually mild steel, but galvanised steel,copper or copper alloy are also used. Freshwater cooling pipesare generally made of mild steel.Air and sounding pipesAir pipes allow an enclosed space to ‘breathe’. They preventover-or under-pressure by letting air in or out of the space whenliquid is pumped in or out, or when temperature changes cause airor fluids to expand or contract. Cargo holds are ventilated by airpipes passing through the weather deck and these are fitted withself-closing watertight covers (headers). This is a Load Linerequirement.Sounding pipes are small-bore mild steel pipes used to measurethe quantity of fluid in a tank or a hold bilge. The pipe allows atape or sounding rod to pass through to the bottom of a tank orhold. Deck sounding pipes pass through the weather deck andare fitted with screw-down caps. Sounding pipes for engineroom double-bottom tanks are fitted with self-closing cocks.It is imperative that sounding pipe caps or cocks be kept shut.Sounding pipes are a potentially dangerous source of progressiveflooding. An engine room can be flooded through an open soundingpipe if a ship’s bottom is holed. A cargo hold can be floodedthrough an open deck sounding pipe when water is washed ondeck in heavy weather. Holes in weather deck air pipes also causehold flooding during heavy weather.Air and sounding pipes are normally constructed of mild steel.Most of the time, these pipes do not come into contact with liquid,either inside or outside. The size of an air pipe serving a tank isdetermined by comparison of the pipe’s cross-section area withthat of the pipe that will fill or empty the tank. This determination,by the designer, is to avoid the risk of over- or under-pressure.Air and sounding pipes that pass through other compartmentsare a potential source of progressive flooding. It is difficult toinspect air and sounding pipes located inside cargo spaces orballast tanks. However, the integrity of air pipes for ballast tankscan be checked by overfilling the tanks. Pipes passing through adry cargo space must be inspected for damage caused by contactwith grabs, bulldozers, etc. It is advisable to open and to inspectair pipe headers on the exposed weather deck once every fiveyears following the first special survey. This is necessary becausecorrosion on the inside of an air pipe header will not be noticeableexternally. Screw-down caps are fitted on the top of soundingThis document, and more, is available online at Martin's Marine Engineering Page - www.dieselduck.net

12Image: Ventilation pipesSHIPS’ PIPING SYSTEMSpipes. These caps should never be mislaid or replaced withwooden plugs. To extend the life of air pipe headers, they shouldbe galvanised. The self-closing cocks on engine room soundingpipes should never be tied open.Cargo piping – tankersCargo piping in tankers is usually mild steel and is protected fromrusting by external painting. Most large oil tankers have a ringmain system that allows increased operational flexibility but withthe penalty of reduced segregation. Tankers fitted with deep-wellpumps in cargo tanks have dedicated piping. Each tank will haveits own pump, pipe and cargo manifold. Stainless steel piping isinvariably used with stainless steel tanks. On chemical tankers,cargo pipes must be joined by welding. Flanged connections areallowed on oil tankers, as well as on chemical tankers at valveconnections and for fitting portable spool pieces, which areremovable short lengths of pipe used for segregation of piping.Regular pressure testing of cargo pipes is essential to detectweak points before they fail.Hydraulic piping systemsHydraulic pipes are high-pressure pipes. Hydraulics are used for: Manoeuvring the steering gear Actuating controllable pitch propellers and thrusters Control of watertight doors and valves Lifting appliances and deck equipment Opening stern, bow or side doors Moving mobile ramps for hatch covers Driving cargo and ballast pumps and for many other minorshipboard utilities.It is a requirement that hydraulic systems for steering, pitch controland watertight doors have dedicated piping and pumps.Some hydraulic fluids are highly flammable. As a result, hydraulicequipment and pipework must be kept clear of hot surfaces.Alternatively, hot surfaces must be protected by spray shields.It is important to prevent the external corrosion of hydraulic pipinglocated on deck. Hydraulic pipes operate at very high pressure andcorrosion-induced weakness frequently causes hydraulic pipes toburst. A high standard of cleanliness is necessary when workingwith, or replacing, hydraulic piping. Check the systems regularlyfor leaks, corrosion or mechanical damage.Use only good-quality and clean hydraulic fluid.This document, and more, is available online at Martin's Marine Engineering Page - www.dieselduck.net

13PIPE DESIGNClassification societies publish rules for design and fabricationof ships’ piping. The rules consider how the pipe will be used,the fluid conveyed, materials for construction, and welding andtest procedures. Ships’ piping is grouped into three categories,each of which has different technical requirements.Class I pipes have to comply with the most stringent rules. Theyinclude fuel oil pipes operating above 16 bar pressure or above150ºC, and steam pipes where the temperature exceeds 300ºC.Class II pipes fall between the two rule requirements.Class III pipes have the lowest requirements. They includefuel pipes that operate at or below 7 bar pressure and 60ºC.During design of piping systems, fluid temperature, pressureand the type of fluid conveyed have to be considered.MaterialsMost pipes are made of mild steel. But pipes that carry dangerouschemicals or particularly corrosive fluids are manufactured fromstainless steel. Some chemicals can be carried only in stainlesssteel cargo tanks and pipes. Some seawater pipes are copper, butplastic is often used for ballast, brine and sanitary pipes. The useof plastic pipes elsewhere in a system is restricted because of therequirement for them to pass a standard test for fire-resistance.It is not usual for plastic pipes to be constructed in a way that willenable them to pass the most stringent, level 1, fire test.minutes with a dry pipe at level 2 and 30 minutes with a wetpipe at level 3. Passing the level 1 fire test is the highest standard.If plastic pipes are to be used, the fire-resistance rating andclassification society rule requirements must be checked first.Pipe dimensionsA pipe is sized by its internal diameter. The required diameter ofa pipe depends on the minimum cross-section area necessaryto permit passage of a fluid of given

2 Introduction 3 Pipes and P&I claims 4 Basic information 5 Pipes and ship classification societies 8 Ships’ piping systems 13 Pipe design 16 Causes of pipe failure 20 Dealing with pipe failure 21 Pipe maintenance 23 Pipe repair 24 Do’s and Don’ts 25 Appendix I - Mechanical joints in common use 27 Appendix II - Pressure t