Tools, Sharpening and Power Machinery - Air compressor pressurising sump
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hypnodude
11-25-08, 05:22 AM
I have a small cheap air compressor purchased from Supercheap and it will not pump up to full pressure (about halfway) as it is blowing into the sump. I removed the head and found that the valves consist of flexible reeds that flex to allow the compressed air to flow into the reservoir and prevent compressed air from escaping. I replaced the head after inspecting it and it continued blowing into the sump so I removed the head again and replaced head without metal gasket but it still blows into sump. I cannot find a name on this compressor. The most prominent marking on it is HP 2.0
GregH
11-25-08, 06:51 AM
If it is a diaphragm type compressor the diaphragm could have a crack or hole, or it is somehow leaking past where the diaphragm seals to the head.
If a piston type it could have damaged piston rings and the air is leaking by.
If a piston type it could have damaged piston rings and the air is leaking by.
hypnodude
11-25-08, 06:52 PM
If it is a diaphragm type compressor the diaphragm could have a crack or hole, or it is somehow leaking past where the diaphragm seals to the head.
If a piston type it could have damaged piston rings and the air is leaking by.
Thank you for your response. It is a piston type. The rings and piston appear OK to the eye and the machine has not had a lot of use.
If a piston type it could have damaged piston rings and the air is leaking by.
Thank you for your response. It is a piston type. The rings and piston appear OK to the eye and the machine has not had a lot of use.
GregH
11-25-08, 08:13 PM
If a piston type then the most likely cause of your problem is bad rings .
How do you know the rings are good?
It is possible that they are worn but not visibly, or the cylinder was overheated and warped.
Inexpensive compressors have a very limited duty cycle, the number of minutes out of ten it can run without overheating.
It is possible that your compressor has only 5 hours on it but if it is 5 continuous hours with a duty cycle of 50% that would be enough to kill it.
A 50% duty cycle means that it can only run a maximum of five minutes and then needs to cool for five.
Could your unit be a refurbished one that could have a lot of hours?
How do you know the rings are good?
It is possible that they are worn but not visibly, or the cylinder was overheated and warped.
Inexpensive compressors have a very limited duty cycle, the number of minutes out of ten it can run without overheating.
It is possible that your compressor has only 5 hours on it but if it is 5 continuous hours with a duty cycle of 50% that would be enough to kill it.
A 50% duty cycle means that it can only run a maximum of five minutes and then needs to cool for five.
Could your unit be a refurbished one that could have a lot of hours?
markiz37
11-26-08, 07:26 AM
One sure way to tell if the rings are shot - look inside the cylinder bore on a down stroke. If there is no cross hatch pattern on the wall and it looks "glazed", the rings are gone. Another problem could be that the ring gaps were not staggered properly when installed, but this would be a little harder to see without taking the piston out. Some oil blowby will always happen, even in a perfect machine, so don't sweat the small stuff. The reverse is true too, some air will always find its way into the crankcase.