Compressed air pipework: Best practice
24 July 2017
The correct installation and commissioning of compressed air piping is vital for an ongoing safe and efficient compressed air system. Here Marion Beaver, technical officer for BCAS outlines best practice
In the same way that air receivers are a source of stored energy, so is compressed air piping.
For a compressed air system to be safe and energy efficient, it must be designed and installed correctly with proper procedures followed during commissioning to ensure the integrity of all of its connections.
Under Regulation 6, The Pressure Systems Safety Regulations 2000 Approved Code of Practice, the owner/user of the system must ensure that those doing the installation have the required training, skills and experience.
It is important that the user selects a supplier that can demonstrate competence through experience and evidenced training in pipe installation and jointing. The user should also check that the supplier:
• Is conversant with the safety issues surrounding compressed air
• Will carry out the work in a safe manner
• Holds the appropriate insurance
The Pressure Systems Safety Regulations 2000 do not specify piping types or specific installation procedures. Like other health and safety legislation such detailed recommendations are beyond its scope.
To demonstrate compliance with the law, users (and their contractors) should follow 'good industry practice' during the installation process. Examples of 'good industry practice' are trade bodies’ codes of practice, for example; the 'BCAS installation Guide' and the 'BCAS Pressure & Leak Testing Best Practice Guide (BPG 103)'. These two publications cover the selection of equipment, correct installation and commissioning prior to use.
The air mains can be sited at any level from under-floor ducting to overhead. For ease of servicing and draining and for access when connecting to service points, the overhead main is often used. Below are some general installation guidelines:
• Pipes must not be allowed to sag or hog, especially at threaded or flanged joints, since the bending stress could result in leakage and possible pipe fracture. Follow manufacturer’s instructions for support spacing.
• The air main should be supported throughout its length, so that the correct fall to the drain points is maintained and condensate cannot collect in the pipe itself.
• Allowance must be made for thermal expansion and contraction. This allowance will vary with the material used.
• Compressed air piping should not be attached to (i.e. hung from) other utilities such as gas mains.
• In jointing, it is important to read the instructions – many new modular piping systems may be similar in appearance, but the jointing procedure can be quite different. If not correctly carried out this presents a real risk of failure and consequent injury to personnel. Over-tightening can be as dangerous as fittings that are too loose and will subsequently fail.
Safety in commissioning
The testing of compressed air pipe systems before use is essential to establish the system leak rate for energy efficiency and reliability, and to verify the integrity of the pipe/fittings joints to ensure personnel safety.
It means two distinct tests must be completed, the leakage test and the pressure (integrity) test.
But before doing these tests, you or your supplier must carry out a risk assessment procedure and draw up a risk assessment method statement to establish which areas would be dangerous to personnel should there be a major leak or system failure.
You must then ensure that appropriate precautions are taken to include, where appropriate, the evacuation of those identified areas during the test. Where it is not possible to implement some or all of the safety procedures as identified by the risk assessment, then the testing should be undertaken outside of working hours.
Where there is an extension to an existing system, then only the new part of the system should be tested. The existing system should not be pressure tested and should be isolated before pressure testing commences. Subjecting an old system to a pressure test of up to 1.5 times operating pressure could over-stress it and lead to its premature failure.
Installing, extending or modifying a compressed air system to ensure it is safe and efficient must be completed by suitably qualified personnel. Compressed air is a vital commodity, but if a system is not installed or tested correctly it could become a serious hazard. In conclusion, make sure you are compliant and safe.