Across many UK factories, air compressors are operational but failing to achieve the necessary pressure. This deficiency is directly impacting production lines and reducing overall efficiency.
Diagnosing pressure issues can be complex and often requires a professional eye. If you need immediate assistance to get back up and running, our team for Air Compressor Servicing Birmingham is on hand to troubleshoot and resolve the fault quickly.
The cause typically falls into one of two categories: a mechanical issue within the compressor itself or a demand issue, where air is leaving the system faster than it can be generated. Effective air compressor troubleshooting starts with identifying which of these two scenarios applies to your facility.
Is It Supply or Demand?
Before looking at the internal parts, it’s important to check the demand side of your air compression system. If your compressor is working fine, but the plant needs more air than the machine can make, the system pressure will drop on its own and not reach the cut-out setpoint.
What Is Artificial Demand?
Artificial demand is a frequent cause of pressure issues, and it occurs when a system is operated at a pressure higher than is strictly necessary for the tools or equipment being used. To make up for drops in pressure, operators sometimes raise the pressure setting, but this doesn’t really help. Just raising the system pressure by 1 bar makes it use about 7% more energy and forces more air out of existing leaks, making the problem worse instead of better.
How Do Air Leaks Impact Pressure?
Air leaks are often the hidden culprit behind pressure failure, and among UK facilities, leaks account for 20% to 30% of total air generation on average. Your compressor may be mechanically sound, but if there are leaks, it cannot pressurise a system that acts like a sieve. Leaks commonly develop at couplings, hoses, and thread connections.
Annual Cost of Air Leaks (at 7 bar)
| Leak Diameter | Air Loss (l/s) | Estimated Annual Cost |
| 1.6 mm | 2.1 | £500 – £700 |
| 3.0 mm | 7.5 | £1,800 – £2,200 |
| 6.4 mm | 29.8 | £7,000 – £9,000 |
| 9.5 mm | 67.0 | £15,000 – £18,000 |
How Do I Perform an Isolation Test?
A simple isolation test will help determine if the fault is internal or external. By closing the valve between the compressor and the factory air network, you can isolate the supply side.
- Close the isolation valve.
- Start the compressor.
- Observe the pressure gauge.
If the pressure rises rapidly and the compressor unloads, the machine is likely generating air correctly, which points to an issue downstream, such as a major leak or excessive demand. If it still fails to build pressure, the issue is likely within the compressor package.
For a deeper look at system resistance, read our guide on Common Causes of Pressure Drop in Compressed Air Systems.
What Causes Pressure Failure in Rotary Screw Compressors?
The Atlas Copco GA and GX series of rotary screw models, for example, make pressure by using a sealed system that includes the intake, oil circuit, and separator.
How Does the Inlet Valve Affect Intake?
The inlet valve is what controls the compressor’s speed. This valve needs to open to let air from the outside world into the compression element in order to build up pressure. It may get stuck in the closed position sometimes because of varnish inside or a problem with the controls, in which case the rotors will turn, but air won’t get into the system. The compressor is running, but it’s basically idling.
Why Is the Minimum Pressure Valve Critical?
Rotary screw compressors use pressure inside the machine to move oil around, and the Minimum Pressure Valve (MPV) makes sure that the compressor builds up pressure before it is sent to the factory. If this valve gets stuck open, air will escape too quickly, which keeps the oil pressure from rising. This can cause things to get too hot. On the other hand, if it stays closed, the pressure inside rises safely, but no air gets to the plant network.
How Do Oil Separators Affect Flow?
Before compressed air leaves the machine, the oil separator takes out the oil mist. The separator element can become full or blocked over time, which will stop the flow of air and cause a substantial difference in pressure. The blockage effectively stops the compressed air from getting to the outlet, even though it might be at the right pressure.
How Do Thermal Conditions Impact Performance?
Temperature has a big effect on how well compressors work. The oil in compressors gets thinner when it gets too hot, and because thin oil doesn’t seal the gaps between the rotors as well, less compressed air gets made. When it’s colder during UK winters, safety sensors might stop your compressor from loading so that the motor doesn’t have to deal with the drag of thick, cold oil.
What Do Controller Alerts Indicate?
Modern units with digital controllers, such as the Elektronikon, monitor various sensors. If a sensor drifts and reports an incorrectly high pressure, the controller will stop the machine from loading. Similarly, safety features like pressure switches and motor overload protection will halt operation to prevent damage. Monitoring these alerts will often provide the first clue to the root cause of your problem.
Why Won’t My Piston Compressor Build Pressure?
Reciprocating (piston) compressors are usually strong, but they use mechanical valves and rings that wear out over time.
What Causes Valve Issues in Piston Models?
Valves on piston compressors control the flow of air in and out, but air will come out of the filter instead of going into the tank if the inlet valve doesn’t fit right. You can often hear this as a clear hissing or “chuffing” sound. If the discharge valve breaks, air from the tank can get back into the cylinder, meaning that the piston is only moving the same air back and forth, which doesn’t increase the pressure.
How Do Worn Piston Rings Affect Output?
Piston rings seal the combustion chamber. As these rings wear, gaps appear which let compressed air get past the piston and into the crankcase, which is called “blow-by.” If the rings on a compressor are worn, it might be able to build up pressure to a certain level, like 3 bar, but it might have trouble getting higher than that because the air leaks past the seals.
How Does the Check Valve Function?
Tank check valves make sure that air only flows into the receiver, but if this valve gets stuck open, the tank’s back pressure will push against the piston head. When the motor tries to start again, it will have to fight this pressure, which will often cause it to stall or trip a breaker.
If you think your current machine is too small for your needs, read our guide ”What Size Air Compressor Do I Need?”
How Do System Defects Reduce Pressure?
Sometimes the compressor is working, but system components are restricting the flow or venting the pressure.
How Do Filters and Dryers Cause Restrictions?
Air must flow through various treatment stages. If the intake filter is clogged with dust, the compressor gets starved of air. Similarly, inline filters and dryers can become blocked over time. A blocked refrigerant dryer, for example, can act as a bottleneck, restricting flow to the point where downstream pressure drops significantly.
Why Does Pipework Layout Matter?
The condition of the distribution piping affects pressure delivery. Older galvanised pipes often suffer from internal corrosion which creates a rough surface that slows down airflow and causes pressure drops. Modern systems using AIRnet aluminium piping avoid this issue, as their smooth internal surface allows for efficient, low-friction airflow.
Is Air Coming Out of the Drains?
A simple but common cause of pressure loss is an open drain valve. Manual drains left slightly open, or automatic drains that have jammed, can vent a significant volume of compressed air continuously. This constant loss makes it difficult for the compressor to maintain the target system pressure.
What Are the Compliance Considerations?
According to the Pressure Systems Safety Regulations 2000 (PSSR), it is against the law to keep an unsafe pressure system.
How Does PSSR 2000 Apply?
For most industrial systems a Written Scheme of Examination (WSE), a document that outlines safe operating limits, is required. If a safety valve is lifting too soon, it needs to be replaced with a part that meets WSE standards. It is not safe or compliant to change a safety valve to “fix” a pressure problem.
What Inspections Are Required?
Regular checks make sure that things are safe and work well, and most of the time, air receivers need to be checked every 12 months. An ultrasonic leak detection survey is also a useful maintenance tool that can help find and fix leaks that cause pressure failure.
Conclusion
If a compressor doesn’t build pressure, it’s usually because of a mechanical problem on the supply side (like a stuck valve) or a problem on the demand side (like leaks or blockages). A structured inspection method that goes from the distribution system back to the compressor will help you find the problem quickly.
J Ll Leach supports businesses across the Midlands and North West of England with comprehensive compressed air services. From identifying leaks to supplying PSSR-compliant parts, our team will ensure your system operates safely and efficiently.
Need support with a pressure issue?
Contact J Ll Leach for expert troubleshooting and repair in Stoke-on-Trent, Birmingham, and Shrewsbury.