I am looking at getting a powermax 30 plasma cutter. I dont think i can run the cutter and the compressor in my garage at the same time. Hence the petrol compressor.
I have heard that the air would have to be dry and free of contamenents hene the filters....
Yes, it needs to be clan and dry especially on Tramfet-style torches (push down to start type.) My torch was screwed up twice by a previous owner, torch jammed up, probably with corrosion.
As I said, most plasma's come with their own reg/filter/water trap. A long hose will make sure the air is cool and any water can easily be filtered out by the trap.
Water is a real pain, my old 3.5hp compressor spewed lots of water as it was too small and you ended up using warm air. You may look at a water trap for everything and use the one on the plasma as a second-level filter.