Up to 30% of a compressor's normal output can be lost through leakage, and poorly maintained equipment will generally be leaking compressed air at around 20% of its total capacity. Leaks may also cause your whole system to lose pressure, leading to less efficient functioning of pneumatic devices, and loss of production output.
Not just the compressor, but almost all your system equipment will have its lifespan reduced, as leakages force more frequent cycling and consequent wear. To estimate how much your pneumatic system may be leaking will require running the compressor for a specified time when it is not driving any devices, and measuring the average time it takes to load and unload the system. This loading and unloading occurs as leaks cause pressure drops in the system, and the compressor then cycles on and off to compensate.
Not all leakages can easily be prevented, and system design should incorporate some standard allowance for a pressure drop rate per unit time. These parameters could be anticipated in the circuit design, so that appropriate pressure rates and reservoir sizes are determined.
Sometimes, unnecessary additional compressor capacity is installed to compensate for pressure lost due to leakage. A better and more cost-effective alternative is to introduce a proactive programme of detection and repair, which can bring down your average leak rate to under 10%. The most common areas where leaks can occur include joints, couplings, seals and fittings, as well as hoses and areas which have missing welds or worn packing. Missing O-rings are a common problem, as are improperly installed FRL units and worn point-of-use tools.
Air is invisible, of course, so once you've calculated the amount of air you're losing through leakage, you'll have to find some way of detecting the specific locus of the leak(s). A modern solution to this is ultrasonic detection, by means of an acoustic device to identify the high frequency sounds made by leaking air.
Since this type of equipment is commonly portable, it makes the detection of leaks very fast, accurate and versatile. Ultrasound is directional in its transmission, emitting a louder signal the closer it is to the source, so leak sites can be very easily pinpointed by scanning the general area where the equipment is located. Tests can be carried out while equipment is in use, and the detectors are capable of finding many different types of leak. This kind of device is very simple to operate, and it takes only a few minutes to learn how to use it.
Leaks are most often found at junction points between the system and end-use pneumatic applications, especially around connectors and joints. Fixing a leak can mean a straightforward tightening-up of a connection, or more complex replacements of faulty components like hoses, fittings, couplings, joints, pipe sections, traps or drains.
Connectors are a very large family of components used to join hoses, tubes or peripheral devices. They need to be chosen carefully and precisely to ensure that a leak-proof joint is achieved, and sealed where necessary. Push-in connectors are very popular due to the simplicity of their installation, but they may be prone to suffer more leakage if a cycle involves frequent connection and disconnection.
Leakage may also ensue if the pressure load on valves or connectors exceeds their specified rating. The flow rate of air depends on the pressure differential pertaining across a leakage point, so a lower overall system pressure will help reduce the rate of leakage. If you can stabilise the header pressure of the system at the minimum range that is practical, the leakage rate should also be minimised.
However carefully you seal your connections, if they are pushed to function outside their pressure parameters, some leakage is bound to occur. Furthermore, the more connections there are in the system, the greater the likelihood of multiple leakages leading to a cumulative drop in overall pressure. Increasing the number of connections is not therefore a cost-effective way to expand your pneumatic system, as it also makes the system more complicated, and more difficult to detect leaks.
Thread types come in many varying styles and sizes, and tend to differ according to their country of origin and use. Connections typically use male and female mating parts, so it's important to make sure that the thread types match. There are also recommended torque values for most threaded joints, and connections should not be over or under-tightened in relation to these values. Threaded joints should be secured with teflon tape.Seal Degradation
Exposure of some materials to chemicals may make them degrade. Items such as rubber washers may develop cracks that allow leakage, or thread sealant might be of the wrong type, or not properly applied. All fittings, tubing, hoses, disconnects, etc, should be of high quality, and properly installed with the right thread sealant.
It's possible for a pneumatic cylinder to suffer excessive wear on the bore if it doesn't have the proper lubricant. Misalignment or improper mounting can also cause lateral forces to be applied on the bore, which could cause air to leak along the piston's periphery.
Establishing a good leakage identification and repair programme is critical to maintaining a stable, reliable, efficient and cost effective pneumatic system. Such a programme should involve employee teams in the identification and tagging of leaks, tracking performance, carrying out repairs and verification. Whenever leaks are identified and repairs instituted, the whole system should be reassessed. Scheduled predictive maintenance can help you detect and deal with leaks, so that you save on reactive maintenance and unscheduled downtime. An aggressive programme of leakage prevention and reduction should therefore form part of the overall performance improvement of pneumatic systems.
This post was originally posted on www.rowse.co.uk.