What I'm wondering is if there's an easy way to clean out any significant gunk if need be, or if the darkening of the fluid and the vapour after refilling is normal. Also, I now have a litre and a half of dirty pump oil and I'm wondering if anyone knows how to filter and re-distill the stuff so that it can be reused. Its the standard Fisher Scientific mechanical pump oil, paraffin I think.
Thanks!Cleaning a rotary vacuum pump.?
I've been in this situation before. Flushing w/ new oil is a good idea (and not a small amount, a full fill should be used - or at least enough to get to the lower level line / sight glass. Also let the pump run against atmospheric pressure, not vacuum. This will cause air to be pulled through the pump, heating it up and churning the oil, which will help loosen accumulated solids.) However, if you have a lot of accumulated solids, it may not remove all of them. I would recommend pulling off the pump housing and manually scraping out the gunk. This is fairly straight forward and doesn't require disassembly of the actual pump itself.
I've also had limited success w/ adding some water to the oil to dissolve salts. The problem w/ this is that you really need to be careful about removing all the water. Say you have a pump requiring 500mL pump oil. Add 100 mL water (and the oil too), run the pump for 5 minutes, then drain, add new oil and a water miscible organic solvent like IPA, run for a few minutes, then drain and fill w/ fresh oil. Run for several hrs under load to blow off any residual water / IPA.
Mineral oil based vacuum pump oil is pretty cheap. I wouldn't recommend trying to redistill and reuse.
