Protect your compressor, with the right air compressor oil filter, and save money on expensive repairs.
Oil filters are normally only found on bigger compressors, like oil-injected screw compressors.
Obviously, they filter the oil to remove any dirt. In other words: they protect your compressor from damages by dirt, sand, pieces of rust, etc.
Dust and dirt will damage the filter element, wear the bearings and clog the oil-separator.
Typically, an air compressor oil filter looks like a can with openings on one side. Inside the filter is a paper filter element which is folded like a harmonica to create the biggest possible surface area (so that maximum oil can flow through).
But be aware: not all air compressor oil filters are the same!
Oil filters on rotary screw compressor
The number one job of the oil is too cool the compressor element and air during compression.
If for some reason the oil flow stops, the compressor element will become very hot very quickly; this will destroy your compressor element.
Did you know that (proper) oil filters for air compressors contain a bypass-valve?
When the pressure difference becomes too large, the bypass-valve will open and will allow the oil to flow, without going through the oil-filter.
This happens when the filter is very dirty, or when the oil is still very cold.
Why? It's better to supply dirty oil to the compressor than no oil at all! Some cheap air compressor oil filters clog up very quickly and/or don't have this bypass valve. Or the bypass valve works at the wrong pressure.
So be careful when buying a new oil filter for your air compressor - make sure they have such a bypass valve.
Also, automotive oil filters might look the same; they often can't withstand the high temperatures of the synthetic compressor oil.
Oil-free compressors with oil filter (?)
Oil filters can also be found on oil-free rotary screw compressors...
Although the air compression is done without oil, the gearbox (on which the compressor elements and motor are installed) contains special gearbox oil which needs to be filtered.
Small reciprocating compressors normally don't have any oil filter. Lubrication is done by the splashing of the crankshaft in the oil bath.
So there is no oil pump or filters. You just need to replace the dirty oil with clean oil once in a while.