PROCEDURES FOR THE USE OF GAS CYLINDERS

Safe Use of Gas Cylinders
Gas Cylinders in Fires
Characteristics of Some Commonly Used Gases
References and Further Information

1. Safe Use of Gas Cylinders

1.1 Cylinder Fittings

To prevent the interchange of fittings between cylinders containing combustible gases and non-combustible gases the cylinder valve outlets have different threads. Non-combustible gases, like oxygen, nitrogen, argon and air, all have right-hand threads. Combustible gases like acetylene, hydrogen, propane and mixtures containing fuel gas all have left-hand threads.

These precautions mean that oxygen and fuel gas regulators are not interchangeable. Spindle keys, however, are interchangeable.

The cylinder valves on all gas cylinders, whether they contain combustible or non-combustible gas, are opened by turning the spindle anti-clockwise and closed by turning the spindle clockwise.

Never let oil or grease touch your cylinder or fittings. Never use jointing compounds.

Lubrication of cylinder valves and fittings is highly dangerous as well as being unnecessary. High pressure oxygen will react violently with oils and grease which may explode or ignite violently.

1.2 Cylinder Identification

All cylinders should be labelled in accordance with the Classification, Packaging and Labelling of Dangerous Substances Regulations 1984.

Cylinder labels identify the gas contents of the cylinder and provide basic safety information. The format and the various sections are shown in Figure 2 below.

Fig. 2: Cylinder Identification

Propane cylinders can be identified either by a red hazard diamond stencilled on the body of the cylinder or by a label on the shoulder of the cylinder.

1.3 Cylinder Labels

Use cylinders only if they are properly labelled.

Do not accept supply of any cylinder if its contents cannot be positively identified. Companies label cylinders clearly and in accordance with the Classification Packaging and Labelling of Dangerous Substances Regulations 1984. When you take deliver or collect cylinders, check the label against your requirements. If a cylinder is not clearly labelled, contact the supplier who will have a procedure for replacing it.

1.4 Lifting Cylinders

Be aware of hazards of manually handling large cylinders, particularly of cylinders sliding away when lifting from the horizontal to the vertical or vice versa. Do not attempt to catch a toppling cylinder - get out of the way. Never roll a cylinder. Always use a cylinder trolley.

1.5 Moving Cylinders

Always shut valve before moving a cylinder on a trolley. When using a cylinder trolley to move cylinders, make sure cylinders are properly located and secured, and the cylinder valves are shut. Never transport cylinders with the pressure regulator and hose attached unless on a purpose designed trolley or carrier. Never transport a cylinder over long distances with the pressure regulator attached.

1.6 Storage of Cylinders

Full or empty compressed gas cylinders should be stored in a well-ventilated area - preferably in the open, but with some weather protection. Cylinders should be stored securely on a well-drained surface, to prevent corrosion, in a location free from fire risk and away from sources of heat and ignition.

1.7 Protective Clothing

All persons handling gas cylinders should wear protective footwear and industrial gloves and avoid loose clothing, particularly sleeves which may catch on cylinder valves.

1.8 Segregation of Cylinders

Within the storage area, oxygen should be stored at least 3 metres from fuel gas cylinders. the use of a fire wall may provide the required separation.

In addition, full cylinders should be stored separately from the empties, and cylinders of different gases, whether full or empty, should be segregated from each other.

2. Gas Cylinders in Fires

2.1 Action to be taken when fire is discovered

Gas cylinders involved in a fire may explode. If cylinders are in a fire the key actions to be taken are:

Call the fire brigade.
Advise persons between 100 and 300 metres from the cylinder to take cover.
Evacuate the area (minimum 100 metres).
When the fire brigade arrives inform them of the location and number of gas cylinders directly involved in the fire, and the names of the gases they contain.

2.2 Acetylene cylinders - key actions to be taken only by authorised personnel and fire brigade

Do not approach or attempt to move cylinders.
Drench the entire surface of all cylinders with water for at least one hour after the fire has been extinguished, from a safe position. Do not use a jet of such strength that it would knock over a free-standing cylinder.
Check visually from a safe position. If steam is seen to be coming from the surface of the cylinder when water spray is interrupted, continue spraying with water.
Then check at half-hour intervals until it is seen that steaming has ceased.
Once steaming has stopped, observe from a safe distance whether the surface of the cylinder remains wet after half an hour (repeat this operation until all surfaces remain wetted after water spray is stopped) paying particular attention to the centre cylinders and any cylinder where some difficulty has been experienced in maintaining a good supply of cooling water.
Once all cylinder surfaces remain wetted after the water spray is discontinued, check (using bare hands) that the cylinder remains cold for 30 minutes and repeat procedure until cylinder remains cold for one hour. When you are satisfied that the entire surface has remained cold for one hour, submerge cylinder in water (carefully avoiding shocks and bumps).
Normally, after 12 hours immersion the cylinder will be blown down and recovered by the supplier.

3. Characteristics of Some Commonly Used Gases

3.1 Oxygen

Cylinder colour - black.
No smell. Generally considered non-toxic at atmospheric pressure. Will not burn, but supports and accelerates combustion. Materials not normally considered combustible may be ignited by sparks in oxygen-rich atmospheres. Advice should be sought from supplier before using any materials for oxygen service which have not been supplied for use with oxygen and marked accordingly.

3.2 Nitrogen

Cylinder colour grey with black shoulder. (Oxygen-free nitrogen has opposed white spots on shoulder).
No smell, does not burn. Inert, except at high temperatures. Non-toxic but does not support life so will cause asphyxiation if insufficient oxygen is present.
At high concentrations almost instant unconsciousness may occur followed by death. The prime danger is that there are no warning signs before unconsciousness occurs.

3.3 Argon

Cylinder colour - blue.
No smell. Heavier than air. Does not burn. Inert. Will cause asphyxiation in absence of sufficient oxygen to support life. Will readily collect in the bottom of a confined area.
At high concentrations almost instant unconsciousness may occur followed by death. The prime danger is that there will be no warning signs before unconsciousness occurs.

3.4 Acetylene

Cylinder colour - maroon.
Distinctive garlic smell. Fire and explosion hazards are similar to those of propane. However, it is lighter than air and less likely to collect in ducts and drains. Requires minimum energy to ignite in air or oxygen. Never use copper or alloys containing more than 70% copper or 43% silver with acetylene. Consult BGCA Codes of Practice 5 & 6 for full list of materials which are not allowed or recommended only under certain conditions.

3.5 Hydrogen

Cylinder colour - bright red.
No smell. Non-toxic. Much lighter than air. Will collect at the highest point in any enclosed space unless ventilated at high level. Fire and explosion hazard. Very low ignition energy.

3.6 Carbon dioxide

Cylinder colour - black, or black with two vertical white lines for liquid withdrawal.
No smell, but can cause the nose to sting. Toxic. Will cause asphyxiation. Much heavier than air. Will collect in ducts, drains and low lying areas.

4. References and Further Information

Publications

Cylinder Emergency Response Manual, published by Air Products PLC
Safe Under Pressure, published March 1991, BOC Limited

Addresses and Web Links

BOC Limited

Head Office

The Priestley Centre

10 Priestley Road

The Surrey Research Park

Guildford

Surrey GU2 5XY

Telephone number: 01483-579-587

Web: http://www.boc.com

Air Products PLC

Special Sales Department

Weston Road

Crewe

Cheshire

Telephone number: 01270-583-131

Web: http://www.airproducts.com