Presentation on theme: "Service Delivery 4 Compressed Gases Aim To familiarise students with the procedures for dealing with compressed gases."— Presentation transcript:
Service Delivery 4 Compressed Gases
Aim To familiarise students with the procedures for dealing with compressed gases.
Learning Outcomes State the properties of compressed gases List the hazards and appropriate operational procedures for incidents involving compressed gases. At the end of the session students will be able to:
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.
Storage Extent of threat depends on; Nature of the gas Quantity of the gas Nature of premises concerned and surrounding exposures.
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.
Safety devices Bulk; Pressure relief valve Emergency control valve.
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.
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.
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.
LPG Liquified petroleum gas Colourless Liquid (under pressure or low temperature) Flammable Explosive Odourless (has stenching agent added) Heavier than air High co-efficient of expansion.
LPG Butane Propane 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%.
Gas release An unignited gas release can present a number of problems; Large gas cloud Possible ignition sources Environmental hazards.
Leakage of LPG without ignition Shut off leak at source Prevent ignition Safe dispersal of gas/vapour cloud.
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.
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.
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.
Access and location Isolation is the most effect method of eliminating any danger from an uncontrolled gas release.
Access and location Evacuate the area Eliminate any ignition sources Attempt a controlled isolation Render the area safe. If unignited;
Access and location Evacuate the area Provide personal and structural protection Controlled isolation. If ignited;
Leakage with ignition Do not extinguish flames until outflow has been stopped Reduce areas of burning liquid by applying foam blanket Secure additional cooling Cool supporting structure Keep cooling water away from valves to prevent freezing Monitor pressure relief valves.
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.
Acetylene Spontaneous ignition temp 335° C Critical temperature 35.2° C Flammability limits 2.5% - 80% Flame temperature 2325° C.
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.
Unignited leaks Urgent assessment of volume released - Time and rate of discharge in relation to capacity of cylinder Prevailing winds Total areas involved Ignition hazards Attempts to close leak without igniting gas Ventilate building 150 metre hazard zone.
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.
Summary of LPG Flame impingement Container over-heating B.L.E.V.E. Also be aware of explosion risk due to;
Summary of LPG Sources of ignition Wind direction Vapour collecting (low points) Vapour dispersal. Consider;
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.
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.