Gas safety and pressure systems
What are pressure systems?
Pressurised systems are:
- systems comprising one or more pressure vessels of rigid construction, any associated pipework and protective devices
- the pipework with its protective devices to which a transportable pressure receptacle is, or is intended to be, connected
- a pipeline and its protective devices
- systems containing gases or fluids pressurised to 0.5 bar or more above atmosphere, or a gas dissolved under pressure in a solvent (acetylene)
Risk assessments
- Any process that uses gas or a pressure system must be risk assessed.
- Use of compressed gases must be covered by a risk assessment.
- New users must be trained, and must read and sign the relevant risk assessment.
- To handle, maintain and modify pressurised systems, such as moving and connecting compressed gas cylinders, you must have completed the required training and completed a separate risk assessments.
If you hear an alarm
if an oxygen-depletion or toxic gas alarm sounds:
- Evacuate and secure the area
- Find a member of staff and tell them there is an alarm sounding
- Wait for the all-clear before re-entering the area
Identifying the risks
Pressurised gases present various hazards including:
Chemical
Gases have a variety of chemical properties.
Gases may be inert (nitrogen, helium or argon), flammable (hydrogen), rapid oxidisers (oxygen), acidic (carbon dioxide) or toxic (carbon monoxide).
Materials, operating procedures, chemical compatibilities, PPE and monitoring (eg, alarms) must take this into account, alongside the risk assessment.
Always check the Safety Data Sheet (SDS) for information on their chemical properties before use.
Asphyxiant
Pressurised gas and compressed gases may cause asphyxiation by displacing O2 from the air.
Gas cylinders should therefore be stored in well-ventilated areas and, if the expanded volume is sufficient to reduce breathable oxygen below safe limits, an O2 depletion monitor should be in use.
All gas cylinders must be fitted with the appropriate regulator, which must be checked before use.
Never ignore an oxygen alarm if it is sounding and always report it if you believe the oxygen alarm is not functioning properly.
Explosive
Pressurised gas is a store of potential energy that can be explosively released on equipment failure.
All parts of a pressurised gas system must be fit for purpose (designed to withstand the pressures intended to be delivered), checked before use and regularly examined by an appropriate person.
Regulators and cylinders should be replaced every five years, unless on a corrosive gas, in which case it is every six months.
Propulsive
The jet of compressed gas released from a tool or nozzle can fire material over significant distances or disperse dusts effectively into the atmosphere.
PPE must be used where advised to safeguard against eye and skin damage.
Any dusts that might be formed during a process should be covered in the risk assessment.
Manual handling
Compressed gas cylinders represent a significant manual handling and crush risk.
All cylinders must be secured to a wall, column or fixed/heavy item with cylinder safety brackets or held in a safety stand.
Cylinders should be transported with their cap in place and on a cylinder trolley. You should not ride in any lift with a cylinder.
Accidental dropping of a cylinder can cause serious injury and can result in the failure of the cylinder.
Personal protective equipment
Always wear eye protection when working with compressed gases.
When moving compressed gases cylinders, wear a sturdy pair of shoes, ideally with a reinforced toe.
Storage and incompatibilities
The safe management of hazardous chemicals includes storing and using gases in an appropriate manner to reduce the risk of injury or physical damage resulting from reaction through incompatibility.
For instance, cylinders containing oxidising gases (eg, oxygen) and flammable gases (eg, hydrogen or propane) must not be stored in the same lab.
Some gases will have specific handling and storage requirements that should be detailed in your risk assessment. If in doubt, seek further information from your supervisor.