Service Delivery 4

1. Service Delivery 4 Compressed Gases

2. Aim To 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 gases • List the hazards and appropriate operational procedures for incidents involving compressed gases.

4. Introduction Compressed gases are stored, transported and used in a variety of ways A particular gas may be flammable, explosive, toxic or possess a combination of these features Operations 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 Extent of threat depends on; • Nature of the gas • Quantity of the gas • Nature of premises concerned and surrounding exposures.

6. Storage Cylinders • Industrial gases colour code BS 349 • Medical gases colour code BS1319 Threat from fire • Flying fragments up to 100 metres • Rapid spread of fire between adjacent cylinders.

7. Safety devices • Bulk; • Pressure relief valve • Emergency control valve.

8. Safety devices Cylinders; • Pressure relief valve • Bursting discs • Fusible plugs.

9. Storage. Bulk storage; • Spheres

10. Storage. Bulk storage; • Tanks

11. B.L.E.V.E.Boiling Liquid Expanding Vapour Explosion • Hydrocarbon flame burns up to 2,000 °C • Steel weakens as temperatures exceed 350/400 °C • Dry wall attains temperature of 300+ °C • Severe 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” strategy • Where 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 space • Personnel should be fully briefed and made aware of the hazards.

14. LPGLiquified petroleum gas • Colourless • Liquid (under pressure or low temperature) • Flammable • Explosive • Odourless (has stenching agent added) • Heavier than air • High co-efficient of expansion.

15. LPG ButanePropane • Flash point -60 °C • Boiling point -6 °C • Explosive limits 1.5% - 9.0% • Flash point -104 °C • Boiling point -42 °C • Explosive limits 2.4% - 9.5%.

16. Gas release An unignited gas release can present a number of problems; • Large gas cloud • Possible ignition sources • Environmental hazards.

17. Shut off leak at source Prevent ignition Safe dispersal of gas/vapour cloud. Leakage of LPG without ignition

18. Dealing with vapour clouds • Use of fog branches / monitors • Ground sprays projecting a flat fan spray • Ground monitors set at 45 degrees spray pointing straight up • Gas detectors to monitor effectiveness.

19. Gas dispersal • Using hand held branches, under sufficient pressure, flames and/or gas may be channeled away • Using 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 dispersal • Several monitors can be positioned around a leak forcing gas upwards • Water curtain spray branches can be used to protect areas from gas and perhaps provide a safe escape.

21. Access and location Isolation 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 sources • Attempt a controlled isolation • Render the area safe.

23. Access and location If ignited; • Evacuate the area • Provide personal and structural protection • Controlled isolation.

24. Leakage with ignition Do not extinguish flames until outflow has been stopped Reduce areas of burning liquid by applying foam blanket Monitor pressure relief valves. Secure additional cooling Keep cooling water away from valves to prevent freezing Cool supporting structure

25. Acetylene • Colourless • Non-toxic • Highly flammable • Ethereal (anaesthetic ) odour • Industrial - garlic smell / lighter than air • Decomposes in absence of oxygen or air • Ignited from static charge.

26. Acetylene • Spontaneous ignition temp 335° C • Critical temperature 35.2° C • Flammability limits 2.5% - 80% • Flame temperature 2325° C.

27. Acetylene cylinders • Seamless steel cylinders • Welded steel cylinders • Colour coding • Storage (porous mass, acetone ) • General.

28. Acetylene cylinder incidents • Leaks from the cylinder safety device (if fitted ) or valve associated equipment, whether the gas has been ignited or not • Flashback from a torch into cylinder • Cylinders in vicinity of fire and subjected to heat • Shock.

29. Unignited leaks Urgent assessment of volume released - Time and rate of discharge in relation to capacity of cylinder Prevailing winds 150 metre ‘hazard zone.’ Total areas involved Ignition hazards Attempts to close leak without igniting gas Ventilate building

30. Summary of LPG • Full firefighting kit to be worn • Be aware of and use other P.P.E • Liquefiable gas • Very low flash point • Heavier than air • Stored under pressure.

31. Summary of LPG Also be aware of explosion risk due to; • Flame impingement • Container over-heating • B.L.E.V.E.

32. Summary of LPG Consider; • Sources of ignition • Wind direction • Vapour collecting (low points) • Vapour dispersal.

33. Summary of acetylene • Full firefighting kit to be worn • Be aware of and use other P.P.E • Minimum number of personnel inside the 150 metre hazard zone • Do not lift any cylinders where decomposition is suspected • Do not drop cylinders.

34. Confirmation Assessments will be based on this lesson and the corresponding study note Learning Outcomes • State the properties of compressed gases • List the hazards and appropriate operational procedures for incidents involving compressed gases.

35. THE END