WorkSafe has investigated incidents involving high pressure pipes where:
- a worker was killed and another injured when struck by a 70kg temporary metal cap that blew off a 300mm diameter pipe during leak testing with high pressure air, and
- a plumber was seriously injured when struck by the temporary end-cap of a fire service pipe during system leak testing with high pressure air.
Air is compressible, unlike water, so when used for high pressure leak testing, the compressed volume of air stored in the pipe system is significant.
In a pipe or joint failure, the volume of stored air will rapidly expand and release energy in an explosion. This puts employees and others close by at risk of serious injury or death.
Recommended control measures
Use hydrostatic pressure testing
Employers can eliminate the risk of explosion by hydrostatic pressure testing pipe systems using water or another suitable fluid.
Hydrostatic pressure testing only requires a relatively small amount of liquid to develop a high pressure. It is therefore only able to release a small amount of energy in a pipe or joint failure.
Use hand-operated testers
When testing pipes for system integrity and locating leaks, hand-operated testers should be used. This is because hand-operated testers have a lower compression rate, which results in a less severe explosion should a joint fail during testing.
Adopt additional control measures if using compressed air pressure testing
Where it is not reasonably practicable to undertake hydrostatic pressure testing, compressed air pressure testing should be conducted to a maximum pressure (including pressure spikes) of 50 kPa.
If there are exceptional circumstances that necessitate the use of compressed air to a pressure greater than 50 kPa, additional protective risk control measures should be implemented.
These measures should be inspected and certified by a competent person, such as a qualified engineer.
Protective measures should include:
- appropriate procedures, equipment, materials and pipe end supports
- using a designated test zone where possible, or
- establishing an exclusion zone around pipes that cannot be moved.
Check end-cap installation
Ensure end-caps are installed according to the manufacturer's specifications, including tightening fasteners to the specified torque using appropriate tools (e.g. calibrated manual torque wrench and correct size sockets).
Ensure appropriate training
Employers should ensure that, before undertaking pressure testing, employees:
- are fully instructed in:
- the testing method and equipment to be used
- hazards and risks associated with the task
- relevant inspection and testing procedures
- understand the specifications and procedures of the relevant water agency and the need to comply with them at all times.
As necessary, employees should be supervised by a competent person to ensure the work is done safely.
- AS 2419.1 - Fire hydrant installations
- AS 2118.9 - Automatic fire sprinkler systems