If you have a pneumatic cylinder that is leaking, you may see reduced performance and speed. If you have a piston that is leaking you may have bypass going. You try and activate it on the cap side and air’s just flowing right across the piston to the rod side.
In some cases, you may even see cylinders move backwards because of this pressure differential issue. You may see it move slowly. You may see them unable to hold a load or will have a weaker load holding capacity. If you try to position a pneumatic cylinder, it may drift. That’s the way to tell if it’s a piston problem.
If it’s anything other than internal leakage, which is piston leakage, the only way you can have a leak internally, you’re going to hear it. Anybody has any experience in pneumatics has a soapy spray bottle. They can just walk around and you just start spraying places and you see some bubbles coming from that soapy water you know you have an air leak.
One is performance and the other one is literally you can listen for the leaks. That’s one of the advantages actually to pneumatics.