A-VAC Info Center

Q&A

Q1: My pump was expensive. What is the most important thing I can do to maintain it?
Change your oil. This can be done more often than necessary, but like we say, change your oil too much and you waste some oil – don’t do it enough and you waste a whole pump.
Q2: Can I use my pump to evacuate oxygen tanks
No. Never pump high concentrations of oxygen with a hydrocarbon oil-filled pump. BOOM. A vacuum pump MUST be built for oxygen using hydrocarbon-free oil.
Q3: Is it OK to turn my pump off while the line is under vacuum? I heard this could cause a problem.
Do not leave a pump under vacuum when you shut it off, if possible. If you are not using the pump, vent the intake line prior to or right after cutting the power.
Q4: Is there anything special I need to do when changing pump oil?
When changing your oil, run the pump for 20 minutes or so to warm it up, then drain and change the oil. This helps heat up the oil and gets it to flow more easily from the oil case.
Q5: I see some smaller exhaust filters are a lot cheaper than larger ones. Can I use these instead?
Never use an exhaust filter smaller than is recommended. This can cause a restriction in the system, with air coming in the pump faster than it can exit. Not good.
Q6: I was installing a new pump the other day. When I first plugged it in, a lot of smoke came out the exhaust. Will this stop once I connect up the intake and exhaust lines?
Never run a vacuum pump without it pulling a vacuum on something. A wide open intake causes a huge load of air to continue blowing through the pump. Hence the oil smoke.
Q7: When is it best to check oil level?
Oil levels should be checked and adjusted while the pump is running. The oil level, when the pump is not running may appear low, but who cares? The pump is not running!
Q8: We are installing a 3-phase pump. I know rotation is important but how best to check it?
On a pump driven by a 3-phase motor, check rotation upon installation. ‘Bump’ the starter briefly while observing motor fan. Should pump be spinning backward, reverse any 2 of the 3 power wires (with power off) then recheck.
Q9: What causes smoke to come out of my pump? It doesn’t do it all the time, but should I be worried?
Smoke (oil vapor) coming from a pump exhaust means you probably have an air leak. Remember, smoke out = air in.
Q10: Whats the deal with vacuum readings? Some guys talk about 0-30” and other guys talk in microns. Which is correct?
0-30”mm is the normal range for a vacuum pump. 30” is all there is, so beware of someone selling a pump that can go over 30”. Not possible. When using a high vacuum gauge, essentially, the 30th inch of vacuum is split into tiny pieces, called ‘microns’ or ‘millitorr’. On this type of gauge, unlike the 0-30” gauge, the smaller the numbers, the better the vacuum. i.e. 5 microns is better than 10 microns.
Q11: How can I tell if I have a bad pump vs. a leaky system? They are all tied together.
Test your vacuum pump by itself, before trying to vacuum test the complete system. This is most easily done by temporarily mounting a gauge directly on to the intake of the pump. This gives you best / most accurate idea of pump performance.
Q12: When should I be changing my pump oil?
Check your pump oil for color, clarity, and level before starting your process and regularly during use. If you can, drain a ½ cup of the oil and look at it periodically. When it starts getting discolored or has an odor, it is past time to change it.
Q13: Is there a temperature range on a pump? Ours run in a closed room, which gets pretty hot.
While each pump is different, about 158F (70c) is as hot as you want to get. Always try to keep it cool. Any pump’s natural enemy is heat. Your pump should have a supply of fresh air. If it is enclosed, use a fan for cooling. If you can, install the pump in an area with open air. The heat will lower the viscosity of your oil, hindering its ability to pull a good vacuum. If your vacuum pump doesn’t pull a good vacuum, things can deteriorate rapidly.
Q14: Some people swear the Edwards E2M30/28 is the best pump ever, while other say the same thing about The Alcatel 2021-series. What is the real story?
Answer is that both are excellent pumps. Both have comparable ultimate vacuum. The difference is the Edwards displaces 8 CFM more air, meaning it will obtain its ultimate vacuum sooner. However, that is only if the intake line is not restricted, which it is on most vacuum ovens. Because the intake track on the vacuum oven usually cannot flow the same amount of air as the Edwards pump, the real useable CFM of the pump is restricted down to close to that of the Alcatel pump. This means both pumps will do a comparable job. So, the Edwards owners think their pumps work great, which they do, while the Alcatel owner has a pump doing a comparable job. One last thing to consider, because the Alcatel is a smaller pump it does cost less, meaning the Alcatel is a better value.
Q15: ‘Oil Backstreaming’. I have heard the term but don’t quite understand it. Can you explain?
When air is traveling toward your pump, as it is when you are evacuating a chamber or an oven, it is darn near impossible for anything to go the opposite direction. However, after the chamber ( or oven ) is evacuated, your system is in what is called the ‘molecular flow’ range. This just means that there is so little air flow left in the system that the remaining molecules could conceivably flow either direction. The reason this is a potential problem is that oil molecules could float ‘upstream’ from your pump all the way up into your chamber / oven, contaminating whatever is inside.