By now you have oil contamination in your probes (inserts, coils dewars,
tuning circuits, VT heater-dewar), upper stack (spinner turbine, sample
eject lines, probe/shim cooling lines), all the air lines in the instrument
plus valves, ant the air lines between the instrument and the compressor!
If your system uses Tygon/beverage-tubing, I'd just replace it with new
tubing. At about 10 cents/foot, it isn't worth cleaning. You have to be
careful cleaning any valves and fittings if they have Nitrile/Buna-N
o-rings or seals (don't use acetone here). The probes, heaters, and spinner
assembly will need to be disassembled and cleaned (again, be careful with
the solvents) and flushed. The compressor to system air lines should be
cleaned or replaced, as well to prevent repeat contamination.
New industrial grade oil-lubed piston compressors are often rated to put
out less than 3ppm of oil (by weight) in the air. There are many filters
available that trap sub-micron particles and droplets and can be followed
by activated carbon filters to clean up the vapors and micro droplets.
Of course, if your compressor is worn out and pumping lots of oil (if the
air lines are "wet" with oil you need to rebuild of replace your compressor.
If your compressor is in good shape, synthetic oil may also help. Synthetic
oils often have better high temp. performance and may reduce oil vapors.
It won't fix a worn compressor!
If your thoughts are leaning toward an oil-free compressor, I have a few
suggestions. The NOT recomended list starts out with oil-free compressors
from Sears (mfgd. by De Vilbiss). They are NOISY, unreliable, and wear out
very fast (less than 1000 hours operation, probably <500 hours). So unless
you want to be a part-time compressor repairman, I would avoid these ones.
In general, avoid "direct drive" types in favor of geared-down, low rpm types
for longer lifespans. Oil-free scroll type compressors also look good.
Most oil-free rotary screw types aren't made in <10 HP sizes. While most
industrial grade compressors will cost more than the hardware-store
compressors, they have longer lifetimes (and don't forget to think about
where you will get parts and service- not at Home Depot/Sears, etc.)
Roy Van Vliet
Engineer
Acorn NMR
510-683-8595
roy@acornnmr.com