Pressure testing a compressed air system requires careful preparation before forging ahead with the test itself. Before a pressure test you must carry out a risk assessment, which is often submitted to the client along with a method statement. Hazards involved in over-pressurising the system need to be brought forward. The pipework system itself must be mapped out and components specified.

The next stage is the actual pressure test. The system or particular part of the system will be isolated and a stab in point identified. Pressure relief valves should be changed for higher pressure models and a high pressure mobile compressor and regulator will be installed at the stab in point.

Next, increase the system pressure by 0.5 bar increments. Once the pressure is at 1.5 times standard operating pressure, valve off the compressor and take readings from our testing gauge system. Readings will be taken at 10 minutes intervals. Once the test is complete we will exhaust excess pressure in the system through a safe diffuser, replace safety valves and recommission system. Results will be analysed and a test certificate issued.

This may seem like a bit of stupid question. The obvious answer is, of course, that a smaller air compressor is suited to jobs require compressed air at lower pressures; for example, pumping up an inflatable mattress or a bicycle tire. The largest air compressors are designed to fulfil industrial requirements, such as manufacturing processes.

However, there is more to this question than meets the eye. The lesser know answer is to do with the capacity of an air compressor. Capacity is to do with the air compressor being able to deliver compressed air at a particular CFM and particular air pressure at that specific CFM of flow.

Confused? To explain, lower capacity air compressors are unable to cope with applications which require a high capacity level and would eventually destroy itself trying to succeed. This is due to the fact it would be running to its full capacity but has a restricted duty cycle.

When choosing a suitable air compressor it is vital that you take capacity into account so that it delivers the correct pressure and flow of compressed air at the required pressure.