Accidents involving gas cylinders can cause serious injury or even death. This guiding principle provides simple practical advice on eliminating or reducing the risks associated with using gas cylinders.
The main hazards are:
- impact from the blast of a gas cylinder explosion or rapid release of compressed gas;
- impact from parts of gas cylinders that fail, or any flying debris;
- contact with the released gas or fluid;
- fire resulting from the escape of flammable gases or fluids (such as liquefied petroleum gas);
- impact from falling cylinders;
- manual handling injuries.
The main causes of accidents are:
- inadequate training and supervision;
- poor installation;
- poor examination and maintenance;
- faulty equipment and / or design (eg badly fitted valves and regulators);
- poor handling;
- poor storage;
- inadequately ventilated working conditions;
- incorrect filling procedures;
- hidden damage.
Anyone who uses a gas cylinder should be suitably trained and have the necessary skills to carry out their job safely.
- new employees should receive training and be supervised closely;
- users should be able to carry out an external visual inspection of the gas cylinder, and any attachments (eg valves, flashback arresters, and regulators), to determine whether they are damaged.
HANDLING AND USE
Use gas cylinders in a vertical position, unless specifically designed to be used otherwise.
- Securely restrain cylinders to prevent them falling over.
- Always double check that the cylinder/gas is the rig the intended use.
Do not drop, roll or drag gas cylinders.
Close the cylinder valve and replace dust caps, where provided, when a gas cylinder is not in use (including each break).
Store gas cylinders in a dry, safe place on a flat surface in the open air. If this is not reasonably practicable, store in an adequately ventilated building or part of a building specifically reserved for this purpose.
- Avoid storing gas cylinders so that they stand or lie in water.
- Ensure the valve is kept shut on empty cylinders to prevent contaminants getting in.
- Store gas cylinders securely when they are not in use. They should be properly restrained, unless designed to be freestanding.
- Gas cylinders must be clearly marked to show what they contain and the hazards associated with their contents.
- Store cylinders where they are not vulnerable to hazards caused by impact, eg from vehicles such as fork-lift trucks.
- Adequate access for forklift trucks should be provided.
Consideration should be given to the detection of leaks from containers and the method for collection and disposal of such spills to reduce the possibility of cross-contamination and domino effects. Training should be provided to operators on dealing with spills and emergency procedures.
Whilst drums containing flammable liquids can be transported securely on a simple pallet, cylinders containing compressed or liquefied gases require special care and appropriate means of transport such as cylinder trolleys or purpose designed attachments for fork lift trucks should be used at all times.
Records should be kept demonstrating that personnel involved in the movement of drums and cylinders have received training in the hazards involved in handling them and in the operation of any machinery involved such as cranes and fork lift trucks.
Transport with forklift trucks
Great care must be taken when operating a forklift truck in flammable atmospheres or when they are used to handle flammable materials.
Safe work practices are also vital when fuelling forklift trucks or charging batteries.
Potential ignition sources include:
- flames or sparks from an exhaust
- heat generated by the engine or exhaust
- flashback produced by vapours being drawn into the engine
- over-revving the engine
- excess speeding
- sparks and heat generated by brake components
- sparks from tynes striking concrete
- static electricity discharged by tyres rubbing up against something
- an arc from a starter motor or electrical equipment.
Using non-flameproof forklift trucks where flammable dangerous goods are stored or handled without precautions can create an immediate and severe risk of fire or explosion.
Do not allow non-flameproof forklift trucks into an area where mixing, transferring or decanting of fuels and other flammable materials is carried out.
- Use suitable cradles, slings, clamps or other effective means when lifting cylinders with a hoist or c.
- Do not use valves, shrouds and caps for lifting cylinders unless they have been designed and manufactured for this purpose.
- Gas cylinders should not be raised or lowered on the forks of lift trucks unless adequate precautions are taken to prevent them from falling.
CONNECTION AND DISCHARGE TO PROCESS
All containers should be secured in position before connection to process plant. A procedure should be in place for making the connection and all employees should have received adequate training in the use of the procedure. An appropriate leak test should be carried out when the joint has been made.
The pipework that the container is connected to should be designed to an appropriate standard.
There are three main types of protective devices related to the flow and/or use of flammable gases or gas mixtures; the backflow preventer, the flashback preventer, and the free flow preventer. Each of these types of devices have specific models based on the type of gas being used.
The backflow preventer is a spring-loaded device that prevents gas from flowing back into a lower pressure hose, such as oxygen flowing back into the acetylene hose when the acetylene cylinder is approaching empty. This device prevents the creation of a flammable mixture of gases in the hose itself.
A flashback preventer is a device with an interior mesh screen that prevents a flame from entering back into a hose. A hose without either a backflow preventer or flashback preventer could potentially have a flammable or explosive gas mixture in the hose that is ignited by a flashback. One or both of these types of devices should be installed between the hose and welding nozzle assembly.
A free-flow preventer is a spring-loaded device that will automatically close if a free-flow situation, such as a ruptured or cut hose, occurs. This type of device should be placed between the regulator and the hose. If a single device that incorporates all of these functions is used, it should be placed between the regulator and the hose.
CONTROL OF IGNITION SOURCES
Where flammable liquids or gases are stored, the area should be subject to hazardous area classification for the control of ignition sources.
This requirement should be reflected both in the equipment installed and in the control of operational and maintenance activities in the location. The movement of drums and cylinders often involves the use of forklift trucks, which can provide a source of ignition for flammable vapours.