CLASS 2 - COMPRESSED GASES

1. CLASS 2 - COMPRESSED GASES NDGTC • The gas industry has a wide variety of customers from chemical industries to food packaging, from heating and cooking to refrigeration, from cutting and welding to medical uses • Gases are now an essential part of everyday life • Due to the wide variety of applications and customer sites, the industry provides gases in many ways, from tanker loads down to small aerosols

2. Toxic Gas NDGTC • Class 2 has three sub-divisions: • 2.1 - Flammable gases 2.2 - Non flammable, non toxic gases 2.3 - Toxic (and corrosive) gases and many gases have multiple hazards, e.g. flammable and toxic

3. NDGTC • PHYSICAL STATES OF MATTER • Matter can exist in three states: • SOLID, LIQUID or GAS • e.g. ICE - WATER - WATER VAPOUR • But in the gas state a substance will always have a much greater volume than as a solid or liquid • e.g. 1 kg. of water as a liquid occupies 1 litre • 1 kg. of water as a vapour - about 1600 litres • So it would be pointless to try carry or store gases in their natural state - too much space is required • The volume is therefore reduced by pressure and/or liquefication • e.g. 270 litres of propane gas = 1 litre of liquid • Some gases can be carried in the gas or in the liquid form (e.g. oxygen and nitrogen)

4. NDGTC STATES FOR CARRIAGE • COMPRESSED GASES • Usually under high pressure and entirely in the gaseous state • e.g. Compressed air for diving is carried in cylinders at 207 bar (3000 psi) • LIQUEFIED GASES • Gases carried at sufficient pressure to keep them in the liquid state at room temperature • e.g. Butane liquefies at only 1.72 bar (25 psi) • DEEPLY REFRIGERATED LIQUEFIED GASES • Gases which have been liquefied by drastically reducing their temperature • e.g. Liquid nitrogen at minus 196 deg.C. • GASES IN SOLUTION • e.g. Acetylene dissolved in acetone • AEROSOLS • Single use (non-refillable) pressure receptacles

5. NDGTC SOURCES OF INFORMATION FOR DRIVERS • Tremcards (single substance and mixed load) • Safety data sheets • Package (i.e. gas cylinder) labels • Cylinder colour coding (N.B. British manufacturers’ convention only) • Hazard warning panels (or ADR plates) on tankers and tank containers

6. THE IMPORTANCE OF SECURE CONTAINMENT NDGTC • Any uncontrolled leak or escape of gas from its containment is potentially hazardous • This can range from a small leak from a cylinder valve to the sudden and catastrophic explosion of a gas tank • Even small leaks can be hazardous if the gas is toxic or flammable, or if the escape occurs in a confined space • Typical causes in transport:- • Damage to cylinder valve by dropping during handling, or in road accident • Fire engulfment of receptacle leading to operation of relief valve, or bursting • Collision or roll over of tank, shearing of valves/pipework, loss of insulation for refrigerated liquid gases, puncturing of tank

7. NDGTC PHYSICAL EFFECTS OF LOSS OF CONTAINMENT • These arise from: • The normally high pressure of gases • Displacement of air - asphyxiation • Very low temperatures of liquefied gases & gas clouds • The effect of heat on pressurised containers Violent release can make the container a projectile Fire on containment can lead to bursting, even with relief valve operation Asphyxiating atmospheres may form, particularly in low areas, colourless and odourless but fatal! Low temperatures of liquefied gases and of gas clouds cause injuries to skin, eyes and lungs Low temperatures may also cause metals to shatter and tyres to freeze and burst

8. NDGTC CHEMICAL EFFECTS OF LOSS OF CONTAINMENT Flammable gases • Such as propane, butane, hydrogen, methane, acetylene • Can burn, or even form explosive mixture, in air • The flammability range is the range of mixtures of gas to air that can be ignited by an ignition source: e.g. • propane 2.2% to 9.5% • hydrogen 4% to 75% • acetylene 2.3% to 82%

9. NDGTC Flammable gases • The ignition temperature is the lowest temperature at which the gas-air mixture will ignite e.g. • propane 470 deg. C. • Possible ignition sources: • naked flames, in some cases even lit cigarettes • electrical and mechanical sparks • again, in some cases even hot surfaces • Acetylene cylinders that have been dropped, knocked or exposed to excessive heat may explode without warning

10. Toxic Gas NDGTC CHEMICAL EFFECTS OF LOSS OF CONTAINMENT Toxic & corrosive gases • Only minute amounts of a toxic gas can be enough to kill - measured in parts per million • Thus, there is great danger even outdoors • Although primary hazard is toxicity, secondary hazards may be important: • Chlorine • Sulphur dioxide • Ammonia • Carbon monoxide • Hydrogen sulphide Toxic and corrosive Toxic and highly flammable

11. NDGTC CHEMICAL EFFECTS OF LOSS OF CONTAINMENT • Oxidising gases • Such as oxygen itself, (either gaseous or liquid,) nitrous oxide and refrigerated liquid air • Oxygen itself does not burn, but is a key component of the fire triangle • Thus materials that are flammable in air can become explosive in oxygen enriched atmospheres • Materials only just combustible in air can become highly flammable • Materials that do not burn in air may burn in oxygen • So in oxygen enriched atmospheres: • smoking is dangerous • oxygen may become trapped in clothing • prolonged breathing is harmful to health

12. SAFE HANDLING/STOWAGE NDGTC 1 Wear protective footwear and gloves in good condition. Avoid loose clothing, particularly sleeves which may catch on cylinder valves 2 Vertical cylinders must be secured or under your direct control. Never turn your back on a free standing cylinder

13. NDGTC 3 When standing or churning cylinders, be aware of the hazards of uneven, sloping, slippery and vibrating surfaces, as well as debris 4Check that cylinders in pallets are stable before releasing strap or chain

14. NDGTC 5 Park vehicle on level surface when making delivery/collection. If this is not possible,try to work only on cylinders leaning away from you 6 Wherever possible, lift cylinders by approved hoists using approved slings or hooks 7 Be aware of the hazards of manually handling cylinders, particularly of cylinders sliding away when lifting. Use kinetic handling methods

15. NDGTC 8 Never load cylinders into a pallet which has defective restraining straps or chains or severely distorted bases. Ensure base is clear of debris 9 Never hide round-bottomed or unsuitable cylinders in the middle of a pallet 10 Do not attempt to catch a falling cylinder. Get out of the way With acknowledgements to B.O.C.

16. NDGTC SAFE HANDLING & STOWAGE • Open vehicles, or closed vehicles with good ventilation • Liquid gases should be handled and transported upright, otherwise any leaks will be of liquid gas • Toxic gas cylinders should never be carried in closed vehicles without separate compartments for load and driver • Gases may need segregation: • oxygen from flammable gases • gas cylinders from corrosives • Prevent fire/explosion by not smoking or using naked flames in the vicinity • Flames from leaking valves on flammable gas cylinders should be left to the fire brigade • Continually be on the alert for leaks: hissing sound and sometimes a smell

17. NDGTC PERSONAL PROTECTIVE EQUIPMENT • The main hazards of gases suggest certain PPE: • High pressure gas venting - ear defenders • Low temperatures - non absorbent leather gloves, suitable overalls, goggles/face visor. Overalls resistant to absorption, no pockets or turn-ups. Trousers outside boots • Asphyxiation & toxicity - breathing apparatus for suitably trained drivers during handling of toxic gases and in potentially asphyxiating atmospheres • Flammability & oxygen enrichment - anti-static and flame retardant overalls afford some protection. Clothing must be free of oil and grease in oxygen enriched atmospheres • Mechanical impact - leather gloves, safety helmet, goggles and full protective footwear when handling cylinders

18. Toxic Gas NDGTC SUMMARY Three divisions and their danger signs Main physical states for transport Sources of information available to the driver Physical & chemical effects of loss of containment Safe loading, stowage and unloading Personal protective equipment required