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Cargo FirefightingonLiquefied Gas CarriersFilm/VideoStudy Notes

VOEOTELmMarine International Ltd I J

in association with theSociety of International G as Tanker & Term inal Operators L td


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Flr,t published In 1986by Witherby & Co. Ltd., 32-36 Aylesbury Street, London ECI R OET

Repnnted 1992

Videotel Manne International, LondonandSIGTTO, Bermuda1986

ISBN 0 948691018

While the mforrnanon given has been gathered from what IS believed to be thebest sources available and the deductions made and recommendations putforward are considered to be soundly based, this film/video and supportmarenal IS intended purely as helpful guidance and as a sumulauon to thedevelopment of more experence on the subject No responsibility IS accepted

by Videotel Manne International, The Society of lnter nauonal Gas Tanker andTer-rnnal Operators Ltd , Wit herby & Co Ltd, or by any person, firm,

corporation or orgarusauon who or which has been in any way concerned withthe compuauon, publicauon, supply or sale of trus trairung package, for theaccuracy of any information or soundness of any advice given herem or for

any omission herelrom or for any consequence whatsoever resulnng directly ormdirecrly from the adoptIon of the gurdanc e contained her ei n

Printed In England hy


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AcknowledgementsGrateful acknowledgement ISmade to the following for their contnbunon and assistance rn developing this tr ainmgpackageThe Film

ProducerDirectorTechrucal Co-ordinatorsCommentator

The Stud) NotesAuthor

ConsultantsP B MarriottF G.M EvansJ A. Carter/E. BloggP E Cooke/R J PriceP J RyanK. Itoh

R Blmch-EdwardsHOrtonA Lowson and S C BondA. Jones

F.G M. Evans

Bnnsh PetroleumCollege of Maritime Studies, WarsashMarine Safety ServicesPhIllIps PetroleumShell I nt er n a ti ona l ManneTokyo Gas

Additionally, acknowledgement IS made to the many orgarusanons Involved with the manne transport anon andterrnmalung mdusmes who have co-operated so wilh ngly In making available their personnel, facihnes ande x p e r ti se

FIlm "Cargo Frrefrghung on Liquefied Gas Carners" produced and distributed by and available from Videotelvlanne Internauonal In 16mm film and VIdeo format.

Videotel Manne lnter nanonalRamilhes House1/2 Rarnilhes StreetLONDON WIV IDF(Tel No 071-4396301)

Support Matenal. "Cargo Firef ightmg on Liquefied Gas Carrters. Study Notes" pubhshed by Witherby andCo Ltd

Witherby and Company Ltd32-35 Aylesbury StreetLONDON ECIR OET(Tel No(Fax No

071-2515341 or 071-2535413)071-251 1296)


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List of ContentsSection Title Page No.

INTRODUCTION2 PREPARATION3 . DEFINITION OF TERMS 24 NON-CARGO FIRES 55 THE NATURE OF LIQUEFIED GAS FIRES 5Pressure Fires 5Pool Fires 5Fires in Enclosed Spaces 6Radiation 6Expansion of Boiling Liquids 66 ACTION ON DISCOVERING A FIRE OR SPILLAGE 7

"F l.R.E."Emergency Shut Down (ESD) 7Restnct 8

7 CONTROL OR EXTINGUISH? 8General Considerations 8The Riser Fire 98. CONTROL AND EXTINGUISHMENT TECHNIQUES 9CONTROLIsolation of Fuel 9Preventing the Expansion of Contained Boiling Liquids 10Flame Bending 10Running Fires 10The Unignited Leak 10EXTINGUISHMENT 10Cooling 10Smothering 1 0Starvation 1 1Flame Inhibition 1 19. EMERGENCY PLANNING AND PROCEDURES 1 2Protective Clothing 1 2Breathing Apparatus 1 2Ammonia 1 2

APPENDIX 1: THE PROPERTIES OF LIQUEFIED GASESAPPENDIX 2: GAS CARRIER AND TERMINAL EQUIPMENTAPPENDIX 3: GAS CARRIER DESIGN AND LAYOUT

13192 1


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Liquefied Gas Firefighting FilmSupport Documentation

1. INTRODUCTIONThe objective of the film IS to demonstrate the correct procedures to be followedwhen a spillage or fire on board a liquefied gas earner Involves the cargo and toemphasise the need for regular exercises and adequate pre-planning It should beappreciated, however, that procedures followed in terminals are similar to those usedon board ship. The film should not, however, be shown in isolation. The audienceshould be prepared for the showing, motivated to want to watch It and, subsequentto the screening, be able to reinforce the learning objectives by reviewing the film'scontent and by studying the support matenal.The purpose of the support documentation IS to enlarge upon some of the tOPICSIn the film and revise tOPICS which have been assumed knowledge for watching thefilm It will enable those watching, without the benefit of an instructor, to answerthe Inevitable questions raised by the film. Similarly, the documentation IS intendedto provide the necessary background information to an Instructor showing the film,be It ship's officer, shore based lecturer, term mal safety adviser or the likeWith the complete traming package It is hoped that the lessons to be learnt Will beof benefit to the personnel of gas earners and terminals, port authonues, and thefire and emergency servicesIn this wayan incident involving liquefied gases should, with the expertise of thepersonnel and resources available, be contained and controlled efficiently.

2. PREPARATIONThe key to an interesung and effective training session IS thorough preparation. AnInstructor should read the support documentation and watch the film before presen-tation to an audience. The subject is important and the Ideas and principles whichthe film con tams should be thoroughly understood by the Instructor m order thataudience questions can be answered positively and correctly.The equipment should be prepared and checked=-artenuon is soon lost if the roomIS too light, the film is broken, etc.Because of the stress made on the need for sound operational procedures and theimpressive gas carrier safety record, the student may say "Why bother?" It is imper-ative to dispel this complacency and to stress that he should expect the unexpected.The film shows that. if the correct procedures are taught, planned and exercised Inadvance, an incident can be controlled using ship resources and prevented from escal-ating It also shows how this control can be enhanced by planned and proper useof terminal resources when such resources are available.While film IS effective since It IS a Visual training medium, it IS, however, a passivelearning situanon. Subsequent to the screening, active audience participation suchas question and answer sessions, discussions on scenanos on board ships with whichthey are Iarmhar, the techmques of cargo firefightmg, etc should be encouraged.Ideally, Within a short time of showing the film, audiences should practise lessonslearned, working out the best approach for various situations Indrffering conditionsappropnate to their own working environment, be it ship or terminal.

KEYWORDS, ETC.OBJECTIVE

MOT/VAT/ON

ARE YOUSITTINGCOMFORTABLY?THEN WE WILLBEGIN ...

PREPARA TION

EXPECT THEUNEXPECTED

PASSIVELEARNING

ACTIVEPARTICIPATION


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3. DEFINITION OF TERMSAcoustic VelocityThe speed at which a pressure wave is propagated up and down a pipeline: it is the speed of sound in the liquidbeing transferred and is typically 850/1600 metres per second for hydrocarbon/ammonia liquid.Air LockA separation area used to maintain adjacent areas at a pressure differential, e.g. a motor room air-lock on agas carrier is used to maintain pressure segregation between a gas-dangerous zone on the open weather deckand the pressurised gas-safe space within the motor room.Auto-Ignition TemperatureThe lowest temperature to which a solid, liquid or gas requires to be raised to cause self-sustained combustionwithout iniuation by a spark, flame or other source of igrution.BarA unit of pressure equal to 14.5 lbf'/inch- or 1.020 kgf /cm-.Boiling-PointThe temperature at which the vapour pressure of a liquid equals that of the atmosphere above Its surface; thistemperature vanes with pressure.Cargo AreaThat part of the ship which contains the cargo containment system, cargo pump and compressor rooms, andIncludes the full beam deck area over the length of the ship above the cargo containment. Where fitted, cofferdams,ballast or vord spaces at the after end of the afterrnost hold space or the forward end of the forwardmost holdspace are excluded from the cargo area.Cargo Containment SystemThe arrangement for containment of cargo mcluding, where fitted, a pnrnary and secondary barrier, associatedinsulation, interbarrier spaces and structure required for the support of these elements.Certificate of FitnessA certificate issued by the Administration of a country confirming that the structure, equipment, fittings,arrangements and materials used III the construction of a gas carrier are in compliance with the relevant IMOGas Codes. Such certification may be issued on behalf of the Administration by approved Classification SOCieties.Certified Gas FreeA tank, compartment or container IS deemed to be certified gas free when it has been tested using approvedtesting instruments and proved to be, at the time of the test, sufficiently free of tOXICor flammable or mertgas for a specified purpose and a certificate to this effect has been issued.Combustible Gas DetectorAn instrument used to detect combustible hydrocarbon gases, generally using a heated filament of a special metalto oxidise the gas catalyucally and measure the gas concentration as a percentage of its Lower Flammable Limit.No single instrument IS suitable for all combustible vapours. Requires frequent calibration usmg correct cah-bration gas mixture.Critical PressureThe pressure of a saturated vapour at the cntical temperature, i.e. the pressure required to cause Iiquefacnonat that temperature.Critical TemperatureThe temperature above which a gas cannot be liquefied by pressure alone.


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CryogenicsThe study of the behaviour of matter at very low temperaturesDensityThe mass per unit volume of a substance at specified conditions of temperature and pressure. (See also relativevapour density).DewpointThe temperature at which the water vapour present Ina gas saturates the gas and begins to condense.FlammableCapable of being ignited and burning.Flammable RangeThe range of combustible gas concentrations in air over which the mixture is flammable. That IS the range ofconcentrations between the LFL (Lower Flammable Limit) and the UFL (Upper Flammable LImit).Flash PointThe lowest temperature at which a combustible liquid gives off sufficient vapour to form a flammable mixtureWIth ar r near the surface of the liquid. Flash POint is determined by laboratory testing in a prescribed apparatus.Gauge PressureThe pressure above that of the surrounding atmosphere.Hard ArmAn articulated pipewor k arm used in terminals to connect shore pipework to ship manifold.Heat of FusionQuantity of heat required to effect a change of state of a substance from solid to liquid without change oftemperature. (Latent heat of fusion).Heat of VaporisationQuantity of heat required to effect a change of state of a substance from liquid to vapour WIthout change oftemperature. (Latent heat of vaponsation).IMOInternational Mantime Organization. The United Nations specialised agency deahng WIth mantime affairs.Formerly the Intergovernmental Maritime Consultative Orgamzation ([MCO).Latent HeatThe heat required to cause a change Inphase of a substance from solid to liquid (latent heat of fusion) or fromliquid to vapour (latent heat of vaporisation). These phase changes for Single component systems occur WIthoutchange of temperature at the melting poim and boiling point respectively.Liquefied GasA liquid which has a saturated vapour pressure exceeding 2.8 bar absolute at 37.8C (as defined III the IMOgas codes).LNGLIquefied Natural Gas, the principal constituent of which IS methane.Lower Flammable Limit (LFL)The concentration of a hydrocarbon gas in air below which there IS insufficient hydrocarbon to support combustion.

3


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LPGLiquefied Petroleum Gas Propane and butanes and can be mixtures of the two.NGLNatural Gas Liquids. Hydrocarbons found In aSSOCIartOnwith natural gas. Ethane, propane, butanes, pentanesand pentanes plus are constituents of NGLRelative Vapour DensityThe mass of a vapour compared with the mass of an equal volume of air, both at standard condiuons oftemperature and pressure.Saturated Vapour Pressure (SVP)The pressure at which a vapour is In equ.l.bnurn with its liquid at a specified temperature. The SVP increaseswhen liquid temperature IncreasesShort Term Exposure Limit (STEL)

The maximum concentration of tOXICcontammated atmospheres at which It is generally considered that workerswill not be affected If working four penods of IS minutes each per day with at least 60 minutes between each penod.Spontaneous CombustionThe igruuon of material brought about by a heat producing (exothermic) chemical reaction WIthin the matenalItself Without exposure to an external. source of ignition.Surge PressureA phenomenon generated in a pipeline syt ern when there ISany change In the rate of flow of liquid In the lineSurge pressures can be dangerously high if the change of flow rate is too rapid and the resultant shock wavescan damage pumping equipment and cause rupture of pipelines and associated equipment.Threshold Limit Value (TLV)Concentration of gases III air to which It is believed personnel may be exposed eight hours per day or 40 hoursper week throughout their working life Without adverse effects. The baSIC TL V IS a Time Weighted Average(TWA) and may be supplemented by a TLV-STEL (Short Term Exposure limit) or TL V-C (Ceiling exposurehrmt , which should not be exceeded even instantaneously).Upper Flammable Limit (UFL)The concentration of a hydrocarbon gas In air above which there IS insufficient air to support and propagatecombust.on.Vapour DensityThe mass per unit volume of a gas or vapour under specified conditions of temperature ami pressureVapour PressureSee Saturated Vapour Pressure.


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~4. NON-CARGO FIRESRecogrnsmg that the Intended audience w ill have undergone trairung at shore-basedestablishments and on board, the techniques involved In fighting ships' accom m o-dation . m achinery , enclosed space and electrical fires and terrnmal facility fires areassumed known. Neither the film nor the accompanying docum entation thereforeexam ine In any derail the fire m anagement, contro l and exunguishmg techniques of"convennonal", non-cargo firefrghnng.In addition to the gas earner's carg o h azard s Inthe com pressor room It is necessaryto emphasise that It IS also a machinery space in which. for example. o il m ight accum -ulate in the bilges; that motor room s have comprehensive electncal contro l and powercircuits and that flammable, non-cargo, m aterials are ever present in store rooms,and that It IS Inthese areas that previous know ledge and experience w ill need to be used.

5. THE NATURE OF LIQUEFIED GAS FIRESThe properties of liquefied gases IS a ssum ed know ledge for those watching the filjn.A brief summary of these properties are, how ever, contained m Appendix I.Cargo and stored product fires m ay be broadly categonsed as follows:

pressure fires from liquid or vapour leaks. at pump glands. pipe flanges. reliefvalves or vent headers,fires from confined liqu id p oo ls,fires fron unconfined spillages, andfires in confined spaces.

Pressure FiresL eaks from pump glands, pipe flanges, relief valves, m ast head vent headers, etc.w .l! initially produce vapour and/or possib ly liquid which w ill rapidly vaporise. ThisW ill not igrnte spontaneously . Should a gas cloud occur, initial effort should bedirected, using w ater sprays, to deflecting the cloud away from potential ignitionsources an d to protect the equipment with water spray against hear damage shouldignition occur. If ignition does occur It W ill probably flash back to the source ofleakage, giving a Jet or torch fire.I f the liq uefred gas IS b eing carried refngerated and the emergency sh utdown systemand Isolating valves are closed, a high pressure m ay be caused by heat radiated upona pipeline until the trapped liquid has been expelled through the leak, either as liquidO r v apo ur.W hether the cargo is liquefied under pressure or refrigeration the end result IS thesame-a fire m which the fuel IS being fed under pressure w ith possibly a pool ora running fire on the deck beneath It.Pool FiresPrompt im tiauon of the ESD W ill do much to lim it the amount of Iiqurd sp illed andbecause the ship's deck, w ith its camber and open scuppers, w ill quickly pass liquidspillage over the ship 's Side, the size and duration of pool fires would be lim ited.A liquid spillage on shore from tank or pipeline ruptures m ay however be ID largerquantrties and w ill generally be contained W ithin bundsShould the vapours from either type of spillage reach an ignition source a resultantpool fire w ill burn , like petrol, W ith tall flam es and some black smoke. Evaporationw ill m aintain the liquid temperature at, or slightly below , Its boilmg PO int. It ISIm portant to rem em ber that the addition of water W ill increase the rate of vaporisationand intensify the fire.

NON-CARGOFIRE HAZARDS

PRESSUREFlRES,SOMETIMESCALLED JET ORTORCH FIRES

POOL FIRES

ISOLATE!

BUNDS


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When using water to disperse spilled liquid, to prevent possible brittle fracture, thewater should, wherever possible, be introduced a little at a time. Jets of water shouldnever be directed Into burning liquid gas as this will cause a violent Increase In flame.When contained in drip-trays, the cold liquid may also be spilJed on to the deck andshould therefore be avoided.Fires in Enclosed SpacesLeaking gases may form a flammable mixture within an enclosed space which maycause an explosion If a source of ignition is found. However, once a fire is burrungsuch an explosion is unlikely unless the heat can affect, and cause failure to,containment vessels or adjacent tanks. The supply of oxygen to the spaces shouldbe minimised by closing openings where possible and shutting down mechamcalventilation. Enclosed spaces containing cargo related plant such as compressors, heatexchangers, etc. will normally be provided with a fixed and remotely operated firesuppressant system=-Ctj., Halon or medium/high expansion foam.RadiationThe radiant heat from a flame is caused mostly by excited carbon particles in a flamewhich, unless they combine with oxygen soon after forming, radiate away their energyas heat and light, forming soot particles in the process. Whereas hydrogen flamesare almost invisible, high levels of radiated heat are a feature of hydrocarbon fires,the soot density being dependent upon the fuel source. Where black smoke is profusethe smoke, to a Imuted extent, will shield the firefighters from radiation. Where someliquefied gas fires are concerned, rates of vaponsation are such that high burningrates are achieved with little black smoke to absorb radiation and therefore it isessential when fighting a liquefied gas fire to wear full protective clothing and takeadvantage of water spray protection.Expansion of Contained Boiling LiquidsWhen fires involve contained liquefied gases, (,contamed' in this respect applymgnot only to pressure storage tanks but also to pipelines containing trapped liquid),the heat of the fire Increases the Internal pressure and the container's metal may beweakened by high temperature to the point of failure, particularly at the top partof the container not internally wetted by the liquid product. The sudden release ofthe container's contents to atmosphere and the Immediate Ignition of the resultantrapidly expanding vapour cloud can produce overpressures and heat radiation.A point to note ISthat If a vessel contains fully refngerated liquefied gas, which wouldbe liquid at atmospheric pressure, the chances of this phenomenon occurnng arelessened and is dependant on heat input. Some fully refrigerated gas carriers, however,have deck storage pressure tanks and as mentioned above, a section of pipe betweentwo closed valves, if heated, becomes a pressure vessel.

Means of preventing this phenomenon are discussed in Section 7.

QUESTIONYOUR SHIP IS LYING AT A TERMINAL, LOADING LPG, WITH THEWIND FROM THE OFFSHORE BOW. IF YOU WERE FORWARD OFTHE MANIFOLD WHEN A LEAK OCCURRED WOULD YOU RUNAFT TO THE ACCOMMODATION OR RUN FURTHER FORWARD?

KEEP THOSEJETS OUT OFFULL DRIPTRAYS

DON'T FORGET:ENCLOSEDSPACES MAY BEHARMFUL TOTHE UNWARY

RADIANT HEAT

H4ZARDS OFCONTAINEDLIQUEFIEDGASES


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Were You Right?Every particular circumstance will be a little different but in the event ofan emergency It is best if you have anticipated what you might do. Theformation of a large premixed cloud is a slow process and will probably onlyoccur near the source of the leak and at low wind velocities.As a general principle you should run upwind to clear the area and seek shelterfrom possible flashback. You may, however, be able to pass upwind of theleak to gain the safety of the accommodation.You should raise the alarm Immediately and take action to stop the transferof cargo.

6. ACTION ON DISCOVERING FIRE OR SPILLAGE .FIR E There IS a well known rern.nder of the actions to be taken In successf ullyfighung a FIRE'

FInd Extinguishnform ResrnctSInce this reminder was first considered, In the long and distant past, methods ofImdrng, mforrnmg , restrictmg and exunguishing have advanced Immeasurably.Nonetheless the same principles, modified where necessary, still applyThe f ir st acuon to be taken on discovering a fire must be to raise the alarm andirnrnediately alert others who may be In the VICInIty. SInce only cargo related firesare being considered In the film and support material, the discovery of a fire in the,hIP'S cargo area should be reported to the Bridge and Engine Room or the CargoControl Room as appropriate. ThIS may be by radio, talk-back system or similar.For terrnmal-related fires involving the terminal control centre and ItS cornmurucanonf'acihttes , sirmlar considerations apply.Upon receiving advice of a fire, and dependant upon the pre-planned emergencyprocedures on the ShIP, an emergency control centre WIll be established.Simultaneously, In the event of a ship's fife WIth the ship alongside, the ternimalwill be Informed of the fire and. in accordance WIth methods previously discussedat the pre-cargo transfer meeting between terminal and ShIP, the ESD system WIllbe operated.Both the ship and the terminal will have then own individual contingency plans fordealing WIth an incident but It IS a necessary part of the ship/shore Interface that suchplans are mutually and fully discussed during pre-transfer meetingsEmergency Shut Down (ESD)Consideration should be given when activatmg ESD to the prevention of pressuresurges In the transfer pipelmes, both at the terminal and on board ship. A numberof factors are relevant to this consideration:

whether the ship IS loading, In which case the terminal ESD system should operatefirst, or discharging, when the ship ESD should be operated,the liquid velocity In the pipeline,the product being transferred Surge pressures are Influenced by the acousncvelocity of the Iiquid,valve closure timmgs, andlength of transfer pipelines In use

FIND, IF YOUDISCOVER AFIRE,INFORM, RAISETHE ALARM

RESTRICT,OPERATE ESDAND ISOLATEOTHERVALVESEXTINGUISH, INA SAFE ANDCONTROLLEDMANNER


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It IS often the case that, in the ship loading situation. the term inal supplies to theshrp a cable pendant extension of their ESD to enable the ship to shut down the shoresystem . Sim ilarly m the discharge situauon, the ship may provide a pendant fromtheir ESD system to allow the shore Jetty operators to stop the transfer.Re~trictO nce the ESD system has been acnvated and transfer stopped any other valves shouldbe closed which w il! lirru t the further supply of fuel to the fire or reduce the lengthof pipeline affected by the incidentIn order to protect the term inal dunng an mcident on board, term inals are frequentlyfitted w ith water spray systems to protect their hardarrns, surge suppression tanks,and other Jetty head equipment These would normally be activated immediatelyFoam equipment IS not generally considered SU Itable for attacking liquefied gas firesbut a foam morutor can be used effectively for coohng and may assist in vapourdispersal .Gas earners are luted w ith comprehensive water spray systems for cooling in the eventof fire, The appropriate spray systems should be acuvated to restrict further theeffects of the fire.To lima [he dangers of a cargo fire spreadmg to other parts of the srnp,accornrnodanon front and control room water spray systems should be acuvated

7. CO~TROL O R E XT IN GU ISH ?Gen era l C on sid era tio nsI f a leak IS umgruted a cloud forms whIch m ight Iind a source of igm tion Becauseth e vapour cloud IS ,0cold, the air 111contact W Ith It w ill be cooled below It, dew pom tand a visible wnu e cloud IS s een There IS a temptation to trunk that th is I, the lim itof the gas cloud It must be remembered, however, that the flammable cloud mayextend beyond the VISible cloudIf a fire mvolv mg liquefied gas IS extinguished W Ithout isolation of the fuel sourcea Iapour cloud may form W hich, upon fmding a source of igrnuon, would re-igniteand flash back to the leakage This IS an Important point to remember since, havingcvnnguished the Initial fire, the f.re teams m ay be In the process of, for example,coohrig down hot areas when the flash back occursThe Iil m states that those in charge must m ake a posmve decision as to whether tocontrol or exnnguish the fire. The pnme factors on which to base such a decision are.

w ind strength and direction l s there plenty of w ind to drvperse the vapour, afterevnncnon? W Ill the w111d carry the vapour, out m t o open water?potenual rgruuon sources. A re they Isolated or removed from the downw ind area?(Potential sources of igrntion include hot surfaces; people operating machineryor elect neal equipm ent outside the safe area; prtvate housmg: pleasure boat, or~Cf\ Ice craft-a com pression igrution engine draw ing flam mable vapour'> into theair intake m ay over speed and dism t egr ate , etc),IIhat volume of gas w ill be released If the fire IS extrngurshed?

The answer more often than not m ust be to Isolate the fuel source and control thel n e rather than to extinguish It

QUESTIONA SM ALL HO LE HAS APPEARED IN A 300M M PIPE WHICH HASA TWENTY METRE RUN BETW EEN CLOSED VAL VES IF THE LEAKCATCHES FIRE, WO ULD YO U EXTINGUISH O R CONTROL?

FLASHBACK

POTENTIALIGNITIONSOURCES


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Were You Right?rt D2 L

4(3.142/4) x (0.3)2 x 20= 1.41ml or 0.84 tonnes

which would give a lot of vapour to be dispersed if you extinguish. The criteriafor deciding to extinguish or control are given in the text.

The Riser FireTo Illustrate the statement that the fire should be controlled rather than extinguishedlet U'; take the example of a fire on top of the ship's masthead vent nser Gas wouldnormally only be released from the riser If a pressure relief valve were to lift or Ifa relief valve was opened. If dunng venting the release was ignited, the decision mustbe made as to whether to control or extinguish the fire.

I f the fire IS exunguished , and venting continues, a gas cloud would form which,being normally heavier than air, may roll down on to and along the ship's deck seekinga source of igrution If ignition occurs then the cloud will burn and flash back tothe sourceSome ships are able to inject a smothering gas at the base of the riser which can snuffout the fire This will not stop the emission of gas and If either the top of the riserIS hot enough or If burrung liquid IS flowing down externally, Immediate re-igmtioncan occur The masthead should therefore be cooled by water sprays.If, however, the decision IS made to control, rather than extmguish the fire, thenthe source of fuel should be cut off or diverted by SUitable means and the fire allowedto burn itself out preventing the formation and potential hazards of a gas cloud.

8. CONTROL AND EXTINGUISHMENT TECHNIQUESCONTROLIsolation of FuelAs already stated, one of the fast actions to be taken when a fire occurs is to activatethe ESD system Whilst this effectively stops the transfer of product, the nature andposition of the fire may be such that It IS being continuously fed by liquefied gasentrained in pipelines. To lirmt the supply of fuel or the effects of further pipe rupture,It may be necessary to close other valves in the VICInity of the fifeIn order to do this It may be necessary to use water sprays to allow access to thevalves The technique IS Illustrated in the film.Note that the person controlling the operation, and who IS going to operate the valve,IS the man between the two hoses. He does not reach forward until he IS certain thatthe two hoses are correctly positioned, the hose teams are concentraung on their Joband not looking at the man, and the valve is adequately cooled. In reaching forward,care should be taken not to penetrate the protective water spray curtain.If the type of nozzle that produces a flat water-wall IS being used, this should beclosed slightly to help push the flame away from the firefighters, but the resultanthollow flame may produce a vortex which draws flame into the centre of the coneThis IS acceptable, albeit disconcerting, provided the men stand firm.

ISOLATE

PRACTISEGETTINGPROTECTEDACCESS TOTHOSE VAL VESIN AWKWARDPLACES


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Prevennng the Expansion of Contained Boiling LiquidsTI1lS phenomenon (see Section 5) IS obviously something to be avoided and this ISbest done by cooling of the containm ent vessels by the Immediate actrvatron o f fix edwater spray system s supplem ented where necessary by hand-held spray lines. Watersprays should be used rapidly or their effectiveness IS dirmmshed SInce above 200Cthe water droplet, tend to skate off on a layer of steam W ithout cooling the metal.Flame BendingIf a pressure flam e IS impmging on other pipcwork , surrounding steelwork or pressurevessels, It may be ,100\ly "bent away" using a spray Jet Care must be taken not toe v ung uish th e flam e un in tention ally If the spray Jet IS applied too close to the leakthe \\ a rer m ay be carried into the flame, which I, ext mguishcd The technique I,illustrated 111 the film ,lee form ation may also exunguisf a fire, If the pr cv.ure I, 11'11 1ted, but be alert toth l.,-the Ice may subsequently blow off gIV ing an urugnitcd le ah si tu ati onRunning Fire-,The me of \\ ater sprays 011 a running III e \\ h ich may ha ve start cd beneath a pressurenrc should flash off the liquid belo-, Thus the I.re w ill be reduced to a p ressu rel ir e , chnunaung the ef t ect-, on pipework 01 the radiated heat 110m the r unrung IncThe urugrnted LeakThere IS one Important point that should be made and emphasisedFrom what has been said about not e xungurshmg a fire, never convider lighnng anumgnued leak The hazards involved III s o doing far outw eigh any possible advantagesEXTI"I,Gt:ISHME"ITCoolingIn fires m volving liquid, cvnngurshment I, usually effected by cooling the hquid below1[, t lash point This I ., not povvib le In tnc case ot nque ncu ga,c, 011 till' c o nr r ur y\\ ater incrcase-, the burning rate by the addiuon of heat thereby pI ornoung evaporauonot the spilled hquidSmotheringSmothcr mg of liquefied gas lire, I' difficult and may only be effective under certaincondiuons

m enclosed spaces such as ships' compressor room s where fire suppression maybe achieved by CO, or H alonv,In mast nser sIn high Sided drip trays or \\ i thm storage tank bunds M edium and, in particular ,h igh expansion foam s applied m COPIOU'i quantities rna} be successful in reducingburrung rate, and controlling the fire by suppressing the radiauon from the nameto the hquid below , thereby reducing the vaponsation rate Foam , however, I,unh k e l y to ext mguis h a liquefied gas In e

QUESTIONIF A SPRAY JET IS UNINTENTIONALLY APPLIED TOO CLOSE TOTHE BASE OF A PRESSURE FIRE IT MAY EXTINGUISH IT. HOWDO YOU THINK THIS IS ACHIEVED. SELECT A, B, C, D, OR E

A) BY STARVATIONB) BY COOLINGC) BY SMOTHERINGD) BY FLAME INHIBITIONE) BY NONE OF THE ABOVE

IMMEDIATEACTIVA TlOS OfDECK WATERSPRAYS

FLAMEBENDING


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Were You Right?D is the most correct answer as the water spray is atomised into a fine fogand carried into the flame The term cooling in firefighting usually refersto cooling a fuel below the temperature at which vapour is given off andthis IS not possible in liquefied gas fires. The fog Will of course also coolhot surfaces which could otherwise cause reignition. When a narrow Jet ISused, however, it probably achieves exnnction by deflecung the gas awayand starving the flame of fuel.

StarvationBy shutting off the fuel source the fire will consume the gas until It IS extinguished.After the valves have been closed the contents of the pipe will continue to feed thefir e unt il the prpeline IS free of pressure.Flame InhibitionInhibiting a flame IS the most effective way to extinguish a free bur rung liquefiedgas fire. Dry powder does not starve, smother or cool to any extent. What It doesIS to absorb the energy in the flame. A fuller explanation of this can be found inAppendix 1 Dry powder also shields the fuel and the firefighter from the heat ofthe flame The practical aspects of the use of dry powder are as follows:

When dry powder settles a mixture of flammable vapour and air remains whichwill be reignited If any flame or hot surface exists.It should be remembered that dry powder has a rmrurnum apphcation rate fora given fire for efficient exnnguishing of the fire, provided the correct techniqueIS used.The technique With a pool fire is to sweep Side to Side and from the front to theback For larger fires thought must be given to delaymg the attack until a combinedatt ack can be made using addiuonal resources.

2. Care should be taken not to agitate the surface of a pool of liquid by directapphcation of a dry powder Jet at close range.3 The presence of objects such as steel supports may cause problems by shielding

parts of the fife from the chemical and, because powders have a negligible coolingeffect, may also leave 'hot spots' able to produce re-ignition after the mrtialextinguishment. For this latter reason special attention should be given toehrnmaung hot spots by cooling with water sprays when using dry chemicalpowders, making sure that the source of spillage has been Isolated. ExperimentsIndicate that, Inthe shielded areas under and around ships' cargo rnamf'old pipmg,the apphcation of fixed water sprays and dry powder together may providesuffic.ent turbulence for the powders to be carried into the shielded areas

4 The specialist technique of extinguishing a pressure fire must be learned. If thepowder IS directed at a pressure fire from the from or Side the powder will bepushed away Without extmguishrnent. The powder must be directed into the baseof the gas Jet so that It will be entrained and exunguish the fireTo prevent a flash back, secondary fires and burning liquid below a pressure fire


16/29

9. EMERGENCY PLANNING AND PROCEDURESCornprehensrve contingency planning, thorough t ianung, ct tecuve exercrsing and theLhe of w ell maintamed equipment can vcr y ~lglllflL antly contr.bute towards the sue-cevsf ul management of an emergency situauon and prevent escalation of thatemergency A lthough It IS n ot the purpose of the documentation to en ter into greatdc t.ul on any of these aspects, th e f ilrn an d accompanying support material servea~ \ e r y useful rerrunders of the need to review and amend the procedure, on boar da gas carr re r an d m term in als w herever nccessar yProtective ClothingProtective clothing should alw ays be worn by p er so nne l attending an incident mvolvmgliquefied gases Speed of response IS a ll important therefore protective clothing should110t be stow ed a \\ a y in a holdall or box bu t left W it h the n ouser-, t lim ed down overd p.u: 01 bootv, the coat on a hook , ih e glove-, and hat ready The n ouvei s muvte lil\a)~ b e \\0 11 1 over th e boot, a '> I t would be undesu able to h a v e I IC j ll ld gas runningIn [O the boot ,II a per-en w earing protective clo th ing fee" overheated he should leave the sceneof t hc fire and hale his SUit opened up Never cool W ith water until thiS I~ do ne--calding may result Tlns problem may be alleviated If C O PIO U , water pr otect ron I,u-cd n orn the our sct , dui mg tile approach, am i III clove PIO \ll11lt) to the t n c(_ lo t lung I, 01 tw o type" en he : insul.ucd clot hing made 01 l irc-rcvivtant c lo th or allatumuuscd cloth designed to reflect radiated heat, the latter I'> probably the rnor e.ipproprratc for gas flre~ clue to the high radiant heal', involved Both types ale,how cv c r, effective, even more so If plenty of clot lung I, w orn under them\ w o id of w.u nmg some man-made material, such as nylo n -, a re hazar dous III th e\ IL ll 1I t> 01 III e-thc) can melt onto [he sk m (Woo" and cortous are preferable)Brcathmg Apparatus

T n r cspo nd r aprdly to an emergency situanon, personnel must be thoroughly farruhar\\ uh the fuung , w eanng and me of cornpi evscd ai r breatnmg apparatus (CABA)To iigidly defme when, and when not, to use CABA IS d ifficult depending as It doeson the actual situation at the tim e, but generally breathing apparatus IS n ot normally.eq Lured for a hq uefied gas fire but would be needed for an urugrutcd leak and w herethe car goes or the products of combustion may be tOXIC'lom e C ,lIg oc , may be to vic b) , " 1 1 1 abvor puo n m wluch ,-.1'>~ CABA Will be mvu l l u . i cn tpr otcc non rile t yp c 01 clothing dcscnbcd af loi ds pi orecuon (111) Irom radiant heat.uid not 110111t o v ic or harmful \ apoui ~The ha/aids 01 pai ncular cargoe- must be under stood Data m t or m ano n shect , 101liquefied ga, cargoes arc available III tile lCS pubhcation "Tauk er Safety GUide(I iquet ied Gd~)"Ammonia'\ mrnoma IS oft en considered to be non- flammable This, however, IS incorrectalthough ammonia has a high rrurumum Ignition energy and a high lower flammable1II111tm aking a flamm able m ixture III the open air unlikelyBeing voluble 111water, arnmoma VclPOUI, c an be conn oiled by water 'PI ay"

W J - I ES TJ - I ER I:' ISA LARGE RELF4SFOR FIRE OiYDECK THEA CCOMMODA TfO,\MA Y PROVIDE 4PROTECTIVE'ClT4DI:L'

PROTECT/VECI 0 THINGIT SHOLLl) BLPOSSIBLE TODOl'/ FULLPROTECT/VI:'CLOTHING ir:UVDER THRFF/'v I1 \ C T/:'.~T H I.S T4K I: ', )PRACTICE!


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APPENDIX 1THE PROPERTIES OF LIQUEFIED GASES

Com bustion I') a chem ical process but m any of the featu res of the ay liquefied gases behave during sprllageand fire , and the techniques and hazards of firefrghung, are due to the physrcal properties of the gas and thephysical changes which take p lace1. Phv s ic al P ro p er tie sIn general term , a liquefied gas 15 the liqu id sla te of a substance which at am bien t tem perature and at at m osphericpres sur e IS a gasFor economic purposes, gases are liquefied fo r transportation. For exam ple, a sh ip would have to be som e 250nmes larger to carry propane as a gas rather than as liquid at atrnosphenc pressure2. S tate ') o f M atterM ost substances can exist m either the so lid, hquid or vapour sta te In chang ing-from solid to hquid (m elting)or from hquid to vapour (vaponsauo n), heat m ust be supplied to the substance In changing from vapour toliqurd (condensanori/L quefymg) or from liquid to so lid (sohdifrcanon/freezm g), the substance releases heat Theheat supplied to or released by the substance in changing sta te IS called laten t heat Solidifrcauon occur') a t aspccif rc tem peratu re for the substanceVaporrsauon or condensation occurs at a tem peratu re which increases If the pressure exerted on the substanceIS increased . The gas IS therefore liquefied under pressure or refrrger ation, or a com bm ation of bo th A list o fhquefied gases together W Ith their Im portan t cn teria IS given in Table I.It IS c onven ient here, against the background of the preceding paragraphs, to consider what happens when alrquef red gas IS spilled Firstly, consider the escape from ItS containment of a fully refrrgerated I Iq l1 Id . T h e IiqurdI' already at or neal atm ospheric pressure bu t, on escape, It I, m evit ab ly brought rmmediat el y rnto contact wit hobjects such as structu res, the ground or the sea which are at am bien t tem peratu re The tem perature differencebetw een the co ld liqu id and the objects it con tacts prov ides an im m ediate transfer of heat to the hquid, resu lnngIn rap id evo lu tion of vapour. A s the tem perature difference i'i reduced the rate of evaporation slow s down butcon tinues un til the hquid IS com pletely evaporated. In the case of a spill co rnmg in to contact W Ith w ater, th ew ater gives to the liquefied gas no t on ly its heat as It cools, but also ItS latent heat as It tu rns to Ice. T his e xp la in s\1 h) a w ater je t d irected Into a drip tray f.re 'W ould greatly Increase the rate o f b urru ngThere IS enough energy 111 a given volum e of w ater to evaporate abou t 3 tim es that volum e of liquefied gas

This sta tem ent m ay be checked by m eans of a sim ple, albeit no t precise calculation, applicable to p ro pan econtained 111 a dnp tray.Assum ing that there IS enough propane to absorb the heat from the w ater which IS at 15C.Specific heat of w ater S~L aten t heat o f so lid ification of w ater L r"L aten t heat o f vaporisation o f pro pan eDensity of propane, sayDensity of fresh w ater

4.2 kJ kg- 1333 kJ kg- 1303 kJ kg- I600 kg m-'1.000 kg m-1

Am ount of heat given as one cubic m etre of w ater coo ls from TI to T2= S" (T1 - T2) = 4.2 x (15 - (-42)) X 10' = 42 x 57 x 103 2.39 X 105 kJ (A)

L aten t heat o f so lid ification of one cubic m etre of w ater 3 33 x 10' kJ (B )Available la tent heat fo r vaponsation of propane A + B = 5.72 x 10' kJ

1.84 x 10J kgas') o f propane vaponsedVolume = mass/density

5.72 x 105/3031.84 x 10'/600 3.1111'

The energy 111 I m ' of w ater therefore can evaporate 3 m ' of liquefied propane in to gas

13


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-S-,rn-p-le- -T -\-'-apo-u-r-pr-e-s-sur-e--A.-trnosPheriC --;elatl'l -----",,' I,, m " , , ; ; ; ; " ; : ' ' " ' ' ' ' ' l - - [ rEL ~ ~-T-[-l2 - - [focrnui:o I .u 37 s-c boiling vapour -=Lo,nt range iempcr a ture Shr TWA l Onun 1 W 1\(Bars absolute) point densuv ("C) (010 by vol ("C) value value

-------t tt~'---~)--Al = I) In air) '_'P _m_ -t-__ ppmI Methane Methane --t-_C_H " - [61 5 -+ 0 554 175 5_2= I~ _ 595 --t---l~hane Ethane __SI_ as' - 8H6 Itt08 125 3 1-1.:2_ .L. 51~ _100_ --+ _l-:0panl 1 Propane CIU__ 13 I - 423 I 55 - 105 + - 2 1- ~ 468 + =~Hutane----1 BlHane C41~---+ 3 6 ~ - 05 --2 ~ - 60 + - ~ 85 J_ -~ 6_00 tL'l_u_ta_n_c____ ~-r~;~~~1 C.H_'O_ -t 5_' -__ "_7_ 2 07 1 - - - " ' - 1 ' 8-",- L SOO s o oI Ethylene Erhene C2H4 Gas' - 10' 9 0975 150 3 -~ 4'>3 I -1__~opylene Propene C,H6 157 - 477 148 180 ~

~Butylc-n-e--- +-_B_u_t-_I-_e_n_e -t--_c_4~ 4_4 -(,~HutYlene But-2-ene C4Hg 4.. - 6_9__ +-- __ 1_9_4_+2 tI Butadiene +--B_u_ta_d_l_en_e +_C_4Hb _~ _I_ -__ 5 _ 0 _ _ -1-- I 88 - 60

I~oprenc 3 or 2 rnethyl-I, 34 23 50. 3 butadiene CjHg

Table 1: PROPERTIES OF LIQUEFIED GASES

name

I 942 -111 453_--- f--- -

I16- 93 44018- 88 4652 -126 418 --

I I -~ 220II 4 -33 472 7! 3 -100 429 5II 28-17 465 100I 16 -25 615 25F)n-flaIllmahl-;:-

------_ -- -----I--

80

Chior oethene

37

~(_-:-'_l _~ I hyIenc oxJd_e_-+_E_p_o_,Y_e_l_h__n_e_ r---_C_2 _ H _ 4 _ 0_ -- +

~ro_pYlene oXide Epo xypr opane C1H60---- ------ ---- t----

I Allmor_"_a___ Ammon-a, Nil] 147 - 31 4 () 597 '7I-::: anhydrous I 1- -Chlorine Cil IOf!ne__ = = = J - _ _C = _ 1 _ 2 .L_-_-~~~1~0-7~~~=~~+-___ __ - = = 3 _ 4 = = ~ - _ - + J _ - _ = = ~ 2 - _ = 4 = 9 = _ -~~~i ~~~-

C2HjC-+-----S 7 - 13 8 2 15 7827 107 I52 - 18

342 200

*'7 8( ISabove the cruical t emperature for these gases

---- --Methane --

125 EthanePropane----- --

750 I n Butane-- --750 i-Buranc -

EthylenePropylene--

I oButylcne-- ---y-Buty1ene---- -Butadiene---- l o p r e n e --

3 VOl .-- Ethylene OXIde--1';0 Propylene OXIde35 Ammonia-- -- --

3 Chlorine

Long Term Expo-ure l rrmt2 Short Term Exposure [ nm :


19/29

Spillage from a pressunsed container IS,initially, different In that the liquid before escape ISat ambient temperature.At atmospheric pressure rapid vaporisation takes place. The necessary latent heat is taken pnrnanly from theliquid Itself which rapidly cools to Its temperature of vaponsation at atmosphenc pressure. This IScalled flashevaporation and, depending upon the change In temperature as the liquid escapes from Its containment, aproportion of the liquid flashes off In this way. The considerable volume of vapour produced within the escapingliquid causes the hquid to fragment into small droplets and again, depending upon the change in pressure, asthe liquid escapes, these droplets will be ejected with a considerable velocity. These droplets take heat from thesurrounding an and vaponse. Water vapour In the air condenses to form a white visible cloud. Thereafter anyliquid which remains will evaporate in the same way as for spilled fully refrigerated liquid until the spillage ISwholly vaporised. Apart from the hazards Introduced by the generation of vapour becoming flammable as ItISdiluted with the surrounding air, the rapid cooling Imposed upon contacted objects will cause cold burns onhuman tissue.3. Flammability and Explosiona) CombustionCombustion ISa chemical reaction, irunated by a source of rgninon or by heating to Its auto-igmtion temperature,m which a flammable vapour combines With oxygen In suitable proportions to produce carbon dioxide, water\ apour and heat Under ideal conditions the reaction for propane can be wntten as follows

+ + 4Hp + Heatpropane oxygen combustionenergy carbondioxide watervapour energy available forfurther combustionUnder certain circumstances when, for example, the oxygen supply to the source of fuel IS restricted, carbonmonoxide or carbon can also be producedThe three requirements for combustion to take place are fuel, oxygen and igrution energy.A bunsen burner with the air-hole open gives a clear blue flame The an and fuel have been mixed togetherbefore they get into the flame, this IS called a premixed flame. (See Figure 1a)With the air-hole closed the gas has to find air to mix With by ordinary diffusion of gases. The result IS a lazyyellow flame EXCited molecules which fail to find oxygen to react With Immediately, radiate their energy awayAs the nch gases can only burn as they mix With air by diffusion this IScalled a diffusion flame. (See Figure lb)

Air holeopen Air haleclosed

Fig. la Fig. Ib

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The gases produced by combustion are heated by the combustion reaction. In open. unconfined spaces theconsequent expansion of these gases IS u nrestricted and the combustion reaction may proceed smoothly w ithoutundue overpressures developing. If the free expansion of the hot gases IS restricted In any way, pressure') W illrise and the speed of flame travel w Ill Increase, depending upon the degree of confinement encountered lncr easedflame speed in turn gives rise to more rapid increase In pressure W Ith the result that damaging overprevsure-,may be produced and, even In the open, If there 1 < ; sorne confinement from surrounding pipewor k , plant andbu.ldmgs, escalation of the combustion w ill O CCUI In severely confined condrnons, a, W ithin a buildmg iOI c'd l1lpl,'where the expanding gases cannot be adequately relieved, the Internal pressure and It, rate of incrcavc rna , besuch as to disrupt the containment Here, the resultant explosion IS n ot so much directly due to high combuvtronrates and flame speed as to the violent expulsion of the contained high pressure upon conramment r u pt u reb) R an ge of F lam mabilityThe term range of flarnmabihty gives a measure of the proportions of flammable vapour to all n ec cs -.a r , tO Icombustion to be possible. The flammable range I, the range between the m inimum and maximum conccntranun-,of vapour (per cent by volume) In air which form a flammable m ixture Below the lower flammable hrm t (l l l)the m ixture IS said to be "too lean" to burn and above the upper flammable hrrut (UFL ) the nuvt ur e I , vardto be "too nch" to burn ThIS concept IS Illustrated for propane in Figure 2

D .---------.100%

RichPropane vapour

in air(% by volume)

Flammable rangeI(In air) c F l a m m a b J e 9.5%PropaneFig. 2

A ll thc liquefied gases transported In g as c ar rie rs , w ith the exception of chlorine, are flammable but t lu , x aluc ,ot the flammable range are var iable and depend on the particular vapour The flammable range 01 a parnculaiv apour IS broadened In the presence of oxygen In excess of that normally If1 air; the 100\el tlarnmablc lnnu I'not much affected whereas tile upper ftamrnabte hnut I, considerably raised All flammable \,IPU lIl, c x lubu [111,pr opcr iy and as a result oxygen should not llolJ llally be mn oduccd IllIO a space \\helc f lam muhlc v anoiu-, C\hlThe ovygen c ylu id er s a ss oc ia te d w tt h ovy-acctylene b ui ner-, and oxygen r evuvcn atoi s should onl} be m t ioduccd11110 hazardous areas under str rctly co ntro lled co nduio ns

----1QUESTIONIF AN INCENDIVE SPARK IS INTRODUCED INTO A SPACE CONTAINING 6070 BY VOLU:\IEOF PROPANE VAPOUR, THERE WILL BE AN IGNITION.TRUE OR FALSE?


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\\ ere you Right?True , If the propane IS m ixed w ith air conta irung 21070 oxygen If the atmosphere contained only 10070oxygen, however, no igrution would occur.

c) Flavh PointI he t lavh pouu 01 a liquid I, the lowest temperature at w luch that liqurd 1\ il l evolve sufficien t vapour to 1'01111d t l .muuable nu vt ur c w it h .nr Hrg h vapour pr ev sur c liqu id, vu c h a, liquefied gases have extr cm e l y 101\ t l.rvhpmnt s Hov ev cr , although liquefied gases are never car ned at temperatures below their flash pornt , the vapourspace, above such cargoes are non-flammable since they are virtua lly, under most operational conditions. 100pel ecru r.ch \\ .t h cargo vapour and are rhus far above (h e upper flamm rnable lim nd) Auto-Igruuon Tempera tureThe auto-rg n rnon rernperann e of a substance I') the tem perature to w hich It, va-pour in air must be heated forIt to ignue spontaneously. The auto-igruuon tempera ture IS not related to the vapour pressure or to the flashpoin t of the substance and, since most igru tion sources In pracnce are external flam es or vpar k s, 1 1 I, the flashpoint rather than the auto-rgrutro n charactenstrcs of a substance which IS generally u,ed for the flammabilu ,clasvrficauon of hazardous matenals Nevertheless. in term s of the igrnuon of cv.apmg vapour by steam nine ,01 other hot SUI face'> , the auto-igrutrori tempera ture of vapour, of liquefied gaves are worth) of note.t. Flam e Inh ibrtionl nlubu mg a flame I, th e lTIO'i( eff'ecuve way (0 cxurigursh a free burn ing liquefied ga s fire In order mar t lu ,m ax < ucc ev vf'u lly be achieved It I, f irvt necessary to understand the relevant theoryvlci hanc ma , be released from rhe hydrocarbon m ixture and m ixed w itn oxygen but tne two do not react togetheruntil either a . rnauvo t these reactions produce more than one radical producrng branched cham reactions which can proceed v er ,Iapidl, Thus-

17


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1o

Figure 4-Molecular Chain Reaction of CombustionIn a pool fire, radiant heat from the flame provides energy to vaporrse the fuel and the cham reactions proceedthrough the vapour cloud wherever u IS sufficiently mixed wah air.Dry powders, Haloris and water fog first shield the fuel and the firefighter from the heat of the flames and secondlyabsorbs the free radicals to break the cham reacnon of combustion.5. Vaporisation of Spilled LiquidWhen a gas IS stored as a liquid, whether under pressure or refrigerar ion, It will vaporise when released to theatmosphere, taking heat from its surroundings In so doing. Depending upon the liquid spilled, the spill size andwhether on land or water, the rate of vapor isauon and the temperature and density of the ensuing vapour ",JlIvary Almost certainly the cloud w.ll be Initially cold and will be low lying and will dnft downwind: ItS occurrencewill, Ingeneral, be visible as a white 'cloud' which IS condensed atmosphenc water vapour. Methane when warmerthan - 100 C and ethylene are lighter than air but at transportation temperatures and immediately after a spillheavier than air Ammonia, while lighter than air, will react In a very similar manner In the event of a spill


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APPENDIX 2GAS CARRIER AND TERMINAL SAFETY EQUIPMENT

1. THE GAS CARRIERThe requirements of safety equipment for liquefied gas carriers are contained In the relevant Codes and Conventionsof the International Maritime Or garusatron and the appropriate rules of the vanous National ManneAdministrations and Classification Societies. It I') not the purpose of this document to list all the equipmentto be found on board Rather, to famihanse non-carrier personnel with the emergency and firef'ighung resourcesthat are typically provided and which, Inthe event of a fire on board whilst alongside a termmal, may usefullycontribute towards a successful combined attack on a fire involving cargoWater\\ mer IS a prime contr ibutor to liquefied gas frrefrghung, and IS available In copious quantities. It IS an excellentcooling agent for surfaces exposed to radiation or direct flame Impingement and In spray form may be usedeffectively for flame bendmg, as a radiatron screen or to deflect an urugruted vapour cloud away from igrutionsources In some CIrcumstances, water can be used [0ext mguish a jet or column of burning gas.In addrnon to conventional fire hoses fitted With dual purpose nozzles, gas earners are provided WIth fixed waterdeluge systems for surfaces such as shrps ' accornmodatron fronts, control rooms, compressor rooms, deck tank'),tank domes, manifold valves, etc. Such fixed water spray systems are designed to provide a layer of water overall the exposed surfaces to be protected and by this means the cooling water's sensible and latent heat IS harnessed.\\ ater sprays from fixed morutors or from handheld hose nozzles can provide adequate radiation protectionfor personnel In their approach to shut-off valves or to pressure or vent fires()r~ Chemical PowderDry chemical powders can be very rapidly effective In extinguishing small LNG or LPG fires. Gas carriers arefirted wuh comprehensive fixed dry powder Installations capable of dehvering considerable quantities of powderto any part of the cargo area by means of fixed monrtors and/or handheld hoses. Many ships also have wheeleddry powder Units In addition to conventional hand-held extinguishersFoamSince foam will not extinguish a liquefied gas fire and IS effective only when applied to a substantial depth ItI, only suitable Inbunded areas and IS not normally provided on gas carriers for cargo firefightmg except forenclosed spacesInert GasGas carners are frequently fitted WIth fixed inert gas or mtrogen generators for oper auonal, as opposed toemergency, reasons. However, because of the compar atively low rate at which such gas can be delivered, It ISnot normally used for the mertmg of an enclosed space InWhICh a fire already exists.FOl this purpose high pressure bottled CO2 or halogenated hydrocarbons (halons) IS Injected Into the enclosedspace through the fixed multiple nozzle mstallanon. the mechanical venulation system to the space having frrstbeen shut-off2. THE TERMINALFire protection facihnes Installed at the terminal and on the Jetty Will depend on such factors as local and/ornanonal regulations, location of the terminal, availability of local fire services, type and size of storage, typeof ships and types of product handledMany of the fac.hties here discussed are Similar to those applicable to the gas carner\\ aterFivcd deluge system" designed to provide a layer of water over all exposed surface'), are customary for storagetanks and plant In potential fire areas and apphcation rates can vary from two to ten or more lures per squaremetre per minute Addiuonally, many terminals have fixed deluge systems Fitted at the jetty head to protect thehard arms and associated cargo transfer equipment from mordents mvolving liquefied gases on board a gas carrierSuch systems are often able to provide protection to the ShIP from on mcident at the terminal.Handheld hose lines and powered fire engines are also normally available

19


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Dry Chemical PowderDry powder IS also normally available from fixed, m obile or portable equ ipment Required application Iate,to! successfu l exungurshrnent are very dependent on w ind speed and directionFoamM edium and high expansion foam applied In generous quanut ies to the surface at a bur rung , coru m ed , hquidgas pool w ill largely suppress the radiation from the fire to the liqu id below , reduce vaporrsauon and thus them tcnsuy of the fire. The rate of apphcauon should be suffrcien t to m aintam a foam depth of one to two m etresCO2 and Halogenated Hydrocarbons (Halons)A lthough substantia l quannues of CO, m ay be rcqu ir ed , It can act rapidly and cf'Iecuvelv In d ea lin g w n henclosed space files CO, exungurvher s - thele1ore are of little value on open jctues but they rna: be pr ov rclcdtal the local exnnguishm cnt of etect ncal flre~ and trie likeSmularly halons, although m uch lower concentrations are required to mhibrt combustion cornpar ed to CO" ell Ceffecnveiy only of value when used In enclosed space') In very hunted W Ind condinonv, however, they m ay besuccessful on small pool fires and halon exungurshers are therefore occasionally p laced w lth Ill the rerrrunal andon jetties in the VICInity of dnp trays, e tc3. GE~ERALSections I and 2 of this Appendix deal W Ith the major frrel rghnng resource, that are available Oil tile ga-, c a: I ic:or at the t errrunal and are specifrc to the liquet led gas inc.dentA ll m stallauons, be they ship or shore terrnm al, w ill of cour se be pr ovided W ith m obile and portable cvt mgur-hc,and other racumes for dealing w ith non-cargo fire,


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APPENDIX 3TYPICAL GAS CARRIER LAYOUT

GAS CARRIER TYPES, AND TYPICAL LAYOUTSAn Introductory outhne of the varIOUS types of gas carrier currently In service IS considered relevant IO thisdocumentation for the benefit of personnel from fife services, terminals, port and emergency services, etc1. DESIGN AND CONSTRUCTIONFull) Pressurised CarriersCargo IS car ned at ambient temperature in uninsulated pressure vessels of spherrcal or cylindrical shape andIndependent of the hull structure except for their supporting cradles. Design working pressure IS usually around19 bar absolute, enabling propane to be carried at temperatures up to 45C. Cargo capacity of these ships rangefrom a few hundred cubic metres to 5,000 cubic metres. This was the earliest type of carrier built for dedicatedliquefied gas service (late 1940s) and still remains the most numerous (about 300 ships out of a world fleet In1983 of some 750 gas carriers of all types). The number of fully pressunsed carriers in the world fleet IS, however,declmmg as refrigerated carnage of LPG becomes more widespread both for regional distribuuon and for oceantransport.Refrigerated, Semi-Pressurised LPG CarriersThis type also carries Its cargoes In pressure vessel tanks Independent of the hull structure but, by permittingthe cargo to boil and by rehquefymg the boil-off vapour, IS able to maintain cargo pressures within the tankdesign limits which range, generally, from 4 to 7 bar The tank steel is SUitable for the minimum cargo temperatureenvisaged and the tanks are Insulated to minimise heat input from the surroundings The first ships of this type(early 1960s) were limited to minimum cargo temperatures which enabled LPG to be earned within the designpressure limitation of the cargo tanks More recently built ships, however. are provided with tank matenals andrehquef acuon plants allowing fully refrigerated carriage of LPGs and the chemical gases ( + 45C to - 50C).Some few specially constructed ships in this category extend this range down to the fully refngerated carriageof ethylene (- 104q. The combination of facihties for low temperature and a degree of pressunsarion providessuch ships with trading flexibility enabling them to load LPG from pressunsed storage, cool the cargo dunngthe voyage and deliver it to fully refrigerated storage at near atmospheric pressure. The lower design pressureof the cargo tanks permits a greater size range than for fully pressunsed carriage and modern serm-pressurisedships may be up to 30,000 rn ' capacity.Fully Refrigerated LPG CarriersThese ships carry LPG and the chemical liquefied gases only under fully refrigerated conditions at near atmosphencpressure. The cargo tanks generally are self-supporting, are independent of the ship's hull structure and are ofpnsrnauc shape, so utilising the available ship hull contours more completely than is achievable with sphericalor cylindrical pressure vessel tanks. While tank design pressures up to 0.7 bar gauge are permitted they are usuallyaround 0.25 to 0.35 bar gauge. Tank construction matenals, msulation and liquefaction plant permit cargotemperatures down to - 55C and the cargo systems may be equipped to carry ammonia or vinyl chlonde monomeras well as the full range of LPG. Ship sizes range from 5,000 to over 100.000 rn'LNG CarriersLNG IS'invariably carried fully refngerated at around - 162C in prismatic or spherical tanks of aluminium,nickel steel or stainless steel. Prismatic tanks may be of the self-supporting type, Independent of the ship's structureand fabricated in aluminium or nickel steel but are also of the type where the cargo is contained by a membraneof stainless steel or Invar mounted on load beanng Insulation which IS supported by the inner hull structure ofthe ship. Alternatively, cargo may be contained in spherical tanks of aluminium or 9070 nickel steel designedand constructed on pressure vessel prmciples and supported around their horizontal circumference. The tanks,however, are not classified as pressure vessels.Cargo containment for LNG is well Insulated to control boil-off IO a designed level. The boil-off vapours arenot rehquefied as in refrigerated LPG carriers but are used as fuel for the ship's steam propulsion plant.

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Fig. 5: Typical sections through liquefied gas carriers

No secondarybarrier required

Cargo tankStiffened support

Spray sh,eld

Type C tanks as utilised on semi-pressurisedfully refrigerated gas carriers Insulat IonSelf-supporting spherical Type B tank

Water ballast

Water ballast

Primary barrier

InSulation---_+

BulkheadHOld space ----;-;--

Secondary barrier

Prismatic self-supporting Type A tankfor a fully refrigerated LPG carrier

Inner t..JI ------IInsulation -====::j~,

I invar membraneseconoary Darner

A membrane type containment systemas utilised on larger-sized LNG carriers

Protect rve steel dome

lns ulat ron Withsplasn barrier

Insulationpart waydown skirt


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In quest of greater economy, however, design proposals for future LNG carriers usually Incorporate dieselpropulsion, Increased cargo tanks Insulation and a plant for reliquef'acnon of boil-off Consideration has alsobeen given, alternatively, to the development of a dual fuel main propulsion diesel for boil-off consumption.LNG earners presently In service range from cargo capacities of 2S ,000 m 1 to 133,000 m 1 However, presentconstruction and future designs are mvarrably for cargo capacines at the top end of this range and beyondEthylene CarriersThe cargo IS usually fully refrigerated at -104C; the cargo tanks are made from alurrumum , ruckel steel orstainless (austenitic) steel. Insulation and rehquef'action plant is fitted The cargo tanks used are independentIf a secondary barrier IS fitted this IS not part of the hull A full Inner hull IS provided WIth double bottom andwing ballast tanks fitted The ships tend to be specialised, mostly from 1,000 to 12,000 m ' capacny and WIthone to four tanks They are often equipped so that higher boilmg point cargoes such as LPG can be carriedTYPIcal sectional arrangements are shown in FIgure S .2. LAYOUTFIgure 6 IS a diagr amrnatrc representation of a typical gas earner It IS not Intended to portray any particulartype of ship and specific ships may have some or all of the Items fitted which would be located In alternativeposiuons.The purpose of this Appendix IS 10 Identify to non-gas carrier personnel the type of situauons which may beencountered on board. the nature of the hazard that each presents and the problems that may be encounteredAccornmodanonThe accommodation and machinery spaces are areas where non-cargo associated fires may occur and hence haverelevant extinguishment systems for this purpose. In the event of cargo fifes WIll be the area where the emergencycommand centre IS established. May be the location of the cargo control room. Accommodation front IS protectedby a fixed water spray systemMotor/Compressor RoomEnclosed space WhICh, In addition to cargo machinery, may contain oils/greases etc. Fitted WIth either CO, orHalon fixed extmgu.shing system which requires ventilation to be stopped and personnel to be evacuated pr.orto release. The SIdes of the structure are protected by a fixed water spray systemShip/Shore Cargo Transfer ConnectionArea on deck where, In the alongside situanon, the ship piping meets that of the terminal via hardarms or hoses.POSSIble areas of Iiquefied gas spillage and where limited pools contained in drip trays may occur Consrderedas potentially hazardous area and should contain no ignition sources. Protected by frxed water spray systemMast RiserPOSSIble source of flammable vapours from lifting relief valves or cargo vennlation. Sometimes fitted With mertrngarrangement.Pipeline Systems and ValvesEncountered along length of cargo deck some of which protected by fixed water spray system but others mayrequire use of mobile water spraysTank DomeContains cargo piping and mstrumentation and may contain electric motors, pump seals, etc WIll contain cargoIsolating valves. Protected by fixed water spray systemlnterbarrier and/or Hold SpacesDepending on type of sh.p, may be continuously merted and Incapable of supporting life WIthout external arrsupply. Also may contain msulation which gives off highly toXIC fumes in the event of fife Entry should bestrictly controlled In the event of major incident, WIth outer and inner hulls damaged, may also contain flammablevapours and/or hquid cargo

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MOTOR/COMPRESSOR ROOMEnclosed space Fire suppressant gasf it ted Venti la tion to bestopped Inf iresituation May also containC AR GO C ON TR OL R OO MUsed by personnel supervising cargotransfer operationsHouse protected bywater sprays

SHIP/SHORE CONNECTIONProtected by water sprays,vulnerable area whenalongside

M AS T R IS ERFrequenlly fitted with Inertgas smothering at baseCooling required Infiresituation

T AN K D OM EContains pipework,instrumentation pumpseals, valves, etcProtected bywater sprayPIPELINE SYSTEM AND VALVESPart protected byf ixed water sprays I fnot. cooling by mobile sprays requiredInf ire s ituation May run whole length ofdeck

ACCOMMODATIONFront protected bywater sprays

D EC K S TO RA GE P RE SS UR E T AN KProtected by water spray Pressurevessel

DRY POWDER MONITOR,Fitted and often remotelyoperated to protect manifoldarea

Usually Inert atmosphere Entry to be strictlycontrolled Infire situation insulation maygive off tOXICumes

INTERBARRIER AND/OR HOLD SPACES

Fig. 6: La~out of typical ga~ carrier


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Dr} Powder InstallationsCapable of dehverrng dry powder at high application rates either by fixed monitors or by handheld hose lines,may be remotely operatedDeck Storage Pressure TanksDepending upon arrangement, mayor may not be fitted. If fitted may contain liquefied gas cargoes or liquefiednitrogen, spillage from which could crack the ship's steel deck and could cause cold (or "frost") burns Requirescooling, particularly above Internal liquid level, In the event of fire Protected by fixed water spray system.Deck Fire Water MainMay be continuously pressunsed. Capable of supplying handheld fire hoses along length of deck and shouldhave Isolating valves to minimise pressure loss should sections of pipe be disrupted.International Ship/Shore Fire ConnectionAn internationally agreed size of flat bolting face to which an external supply of firefjghtmg water can be connectedinto the ship's firernam via accessible firernam hydrant, flange or hoseEngine RoamContains major supply services such as electncity, firemam water pumps, water spray system pumps, etcEmergency back-up supplies are also normally available externally.

x s29 cargo fire figthing on lgc

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