Ski Builders Forum

Hi guys,

Im using a vacuum pump now for some time for sublimation, it is one with the oil, I think it might be diaphragm vacuum pump. The issue is that it collects water from the vacuuming, thru the hose, so I have to change the oil every few times.

1) Any solution, like a filter or similar for the water coming and mixing with the oil?

2) I was thinking to replace it with a Membrane pump. Would this one work well for this application, will it be able to create same vacuum as the oil one?

Thanks!

I've mainly only worked with large industrial rotary vane pumps and these all have an exhaust valve which needs to be opened periodically while running or on newer units they have a an exhaust that can be left partially opened all the time while running and this helps remove the water.

You are only sucking down a small volume so I'm surprised you are having so much trouble, sounds like your setup has a decent leak and your pump is continuously working fairly hard.

You are correct. There is an oppening on top, and this lets some mist out. However, since I have a large surface and not perfectly flat one, there is a leak, it never gets total vacuum, so I can imagine this is what you are talking about. Also I work indoor so the air is humid, I can see a lot of water forming in the press/tubes. The oil gets white-ish color after few short runs.

Couldn't you just add an air/water separater in line filter. There are like $8.
http://www.tooldiscounter.com/ItemDispl ... oCzCbw_wcB

I don't think that separator will work in a vacuum circuit. They are for compressed air.

Water boils below ambient temperature at vacuum pressures.
So even if you did install a filter it wouldn't condense the water out of the gas.
More likely the mist from your pump is oil vapor.
This vapor is very bad in your workshop as everything in there will be getting a very fine coating of oil.

I work with vacuum pumps everyday and have never seen anything come from the exhaust except oil vapor. And that is only really noticeable when the pump seals are worn out.

The pump is designed to catch the moisture in the oil and the oil should be replaced every time you use to pump. Most vacuum pump oil is hygroscopic.

For vacuum bagging you can use a highly refined mineral oil, it will have a higher vapor pressure so won't pull as low a vacuum, but we don't need to measure our vacuum in microns so it won't be a noticeable difference. Should be a bit cheaper than proper top tier vacuum pump oil.

If you want your rotary vane vacuum pump to last, you have to change the oil every time you use it.

Oil-less diaphragm pump will work great for your application. Once again you can get better vacuum with a rotary vane pump but you're only looking for in/hg not microns.

sam