2 AimTo familiarise students with the procedures for dealing with compressed gases.
3 Learning Outcomes At the end of the session students will be able to: State the properties of compressed gasesList the hazards and appropriate operational procedures for incidents involving compressed gases.
4 IntroductionCompressed gases are stored, transported and used in a variety of waysA particular gas may be flammable, explosive, toxic or possess a combination of these featuresOperations at incidents involving compressed gases will vary according to volume, method of containment, specific properties of gas involved and nature of surrounding exposures.
5 Storage Nature of the gas Quantity of the gas Extent of threat depends on;Nature of the gasQuantity of the gasNature of premises concerned and surrounding exposures.
6 Storage Cylinders Industrial gases colour code BS 349 Medical gases colour code BS1319Threat from fireFlying fragments up to 100 metresRapid spread of fire between adjacent cylinders.
7 Safety devicesBulk;Pressure relief valveEmergency control valve.
11 B.L.E.V.E. Boiling Liquid Expanding Vapour Explosion Hydrocarbon flame burns up to 2,000 °CSteel weakens as temperatures exceed 350/400 °CDry wall attains temperature of °CSevere hazard unless massive cooling.
12 B.L.E.V.E. Firefighting procedures If no risk to life or property, give serious consideration to a “non-attack” strategyWhere only property is at risk, it may still be necessary to consider a “non-attack” strategy.
13 B.L.E.V.E. Firefighting procedures If attacking the fire, immediate cooling must be undertaken, concentrating on the exposed vapour spacePersonnel should be fully briefed and made aware of the hazards.
14 LPG Liquified petroleum gas ColourlessLiquid (under pressure or low temperature)FlammableExplosiveOdourless (has stenching agent added)Heavier than airHigh co-efficient of expansion.
15 LPG Butane Propane Flash point -60 °C Boiling point -6 °C Explosive limits 1.5% - 9.0%Flash point °CBoiling point °CExplosive limits 2.4% - 9.5%.
16 Gas release Possible ignition sources Environmental hazards. An unignited gas release can present a number of problems;Large gas cloudPossible ignition sourcesEnvironmental hazards.
17 Leakage of LPG without ignition Shut off leak at sourcePrevent ignitionSafe dispersal of gas/vapour cloud.
18 Dealing with vapour clouds Use of fog branches / monitorsGround sprays projecting a flat fan sprayGround monitors set at 45 degrees spray pointing straight upGas detectors to monitor effectiveness.
19 Gas dispersalUsing hand held branches, under sufficient pressure, flames and/or gas may be channeled awayUsing portable monitors small leaks may be entrained into a low pressure area in the centre of the spray and directed to a safe area.
20 Gas dispersalSeveral monitors can be positioned around a leak forcing gas upwardsWater curtain spray branches can be used to protect areas from gas and perhaps provide a safe escape.
21 Access and locationIsolation is the most effect method of eliminating any danger from an uncontrolled gas release.
22 Access and location If unignited; Evacuate the area Eliminate any ignition sourcesAttempt a controlled isolationRender the area safe.
23 Access and location If ignited; Evacuate the area Provide personal and structural protectionControlled isolation.
24 Leakage with ignitionDo not extinguish flames until outflow has been stoppedReduce areas of burning liquid by applying foam blanketMonitor pressure relief valves.Secure additional coolingKeep cooling water away from valves to prevent freezingCool supporting structure
25 Acetylene Colourless Non-toxic Highly flammable Ethereal (anaesthetic ) odourIndustrial - garlic smell / lighter than airDecomposes in absence of oxygen or airIgnited from static charge.
26 Acetylene Spontaneous ignition temp 335° C Critical temperature ° CFlammability limits % - 80%Flame temperature ° C.
28 Acetylene cylinder incidents Leaks from the cylinder safety device (if fitted ) or valve associated equipment, whether the gas has been ignited or notFlashback from a torch into cylinderCylinders in vicinity of fire and subjected to heatShock.
29 Unignited leaksUrgent assessment of volume released - Time and rate of discharge in relation to capacity of cylinderPrevailing winds150 metre ‘hazard zone.’Total areas involvedIgnition hazardsAttempts to close leak without igniting gasVentilate building
30 Summary of LPG Full firefighting kit to be worn Be aware of and use other P.P.ELiquefiable gasVery low flash pointHeavier than airStored under pressure.
31 Summary of LPG Flame impingement Container over-heating B.L.E.V.E. Also be aware of explosion risk due to;Flame impingementContainer over-heatingB.L.E.V.E.
32 Summary of LPG Sources of ignition Wind direction Consider;Sources of ignitionWind directionVapour collecting (low points)Vapour dispersal.
33 Summary of acetylene Full firefighting kit to be worn Be aware of and use other P.P.EMinimum number of personnel inside the 150 metre hazard zoneDo not lift any cylinders where decomposition is suspectedDo not drop cylinders.
34 Confirmation Learning Outcomes Assessments will be based on this lesson and the corresponding study noteLearning OutcomesState the properties of compressed gasesList the hazards and appropriate operational procedures for incidents involving compressed gases.
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