Vacuum Pumps - General Info / Maintenance Tips

Figured there is some good knowledge to be shared and discussion to be had on the topic of pump maintenance.

While I’m here, does anyone have a good SOP for flushing/ refilling a Welch 1400?? I have used and/or considered a couple of methods but none seem as efficient or effective as they could be.

How often do you all typically change your oil? Is it simply dependent upon application and usage as I’ve come to realize??


Good cold traps will lessen the amount of oil changes. Run pump with crap oil till hot,Fill with 50/50 kerosene/ vac pump oil. Run for an hour, keep doing this till oil comes out clean. Fill with 100% pump oil, run for another hour. Dump it again, refill once more. Done!


Hi there, new to this great community. Really look like a great place.

Anyhow, I think in the case of rotary vane vac pumps they are used and abused and people do not generally change the oil often enough. My background in is chemical process development and scale up in pharma with experience in R&D pharma chem labs and scale up. Just put that there because this is my first post.

I picked up 2 Edwards E2M5 pumps that were out of an organic lab, and I just couldn’t believe how nasty the internals were on tear down; It looks like both pumps are in need of full rebuild, with one even showing scoring on the vanes at least on the first stage. To me, it is obvious the pumps had exposure to acid vapor as evidenced by minor pitting of the metal surface. One of the pumps was even lightly seized. Furthermore, both pumps were leaking at the main case gasket seal (cork as supplied by Edwards in the rebuild kit).

I found that the E2 series has common assembly and rebuild procedures, and luckily I found an outstanding into to pump rebuilds on the eevlog forum. I credit to the eevlog OP for all of the following, whereby he thoroughly documents his rebuild of am E2Mx pump. Her you go:

Special thanks to pcmeiners on eevlog forum for all the below that I copied!

eevblog dot com/forum/review…rhaul-cleanup/

Here are some copy and paste links from the above to save time- get the exploded diagrams and order the parts kits with vanes or without the rotary vanes if yours are still in good shape…

Some parts dealers…
ajvs dot com
capvac dot com

Downloads sources…

gasflovac dot com/GASFLO_DOWNLOADS.htm

Exploded Parts diagrams

idealvac dot com/downloads/ex…oded_Views.pdf

E2m12 Manual…

ajvs dot com/technical_librar…ath=0_34&man=7

That is that, and in my next post I have some pump rebuild questions of my own. As I am new to the group here, I am not sure if I should have created a new thread for this. Furthermore, I would like to start a few new threads to introduce myself, describe my goals and current equipment and overall situation. Hope this helps when it comes to pumps; in my experience they are all generally the same, at least within the manufacturer and especially series. Some mfgs have very simple rebulid kits and few parts, and others have way more o-rings and little parts. I would say the Edwards series E2 rotary vane pumps and middle of the road with quit a few o rings; I may show some of my other pumps if there is interest.


Recently had to take apart an Edwards e8 that had been sitting in warehouse for a year. It had not been used more than once, then mothballed. I took it out and found the oil had leaked out the drain plug, and internals were corroded bad. Filled and flushed. Would not turn over. Successfully disassembled, soaked all wetted parts in mineral spirits, air dried for a week, used some fine grit sandpaper to remove build up on the vane casing parts, put back together with TLC, and working like a champ, pulls close to ultimate, as good as I need.

The root cause of failure was due to the shit plastic thread oil drain plug… Whoever put it back in had cross threaded it and the oring didn’t seal the oil drain completely… drip drip drip. Lesson learned.

Glad to see another Chemical Process Development scale-up nerd around. :grinning:


Perhaps @Future can chime in here??

Oh btw, WELCOME!! :upside_down_face:

One question I have in reference to rotary vane vacuum pumps that are dirty but need an often recommended multiple hot oil change flush. IE you get a pump, its a little contaminated, and you don’t need or feel like rebuilding the pump.
Referencing Soxlet,he recommends using 50/50 kero/PUMP OIL. I wonder what are the implications of using a synthetic automotive grade oil versus the real proper pump oil in this procedure to run till hot and take up some of the filth; dump the oil, refill with a lower viscosity automotive synthetic, run it a few hours and dump again. Now do a partial tear down, get most of the crud and automotive oil out, and finally refill with proper vacuum pump oil and do a overnight no vacuum run then check your vacuum level. Maybe one more final oil chang to the food vac oil. The question: is the automotive oil run in this case for just cleaning purposes OK to use? I know one thing that the automotive oil has for example is zinc, and other additives that vacuum oil (often a clear quality mineral oil) does not. One thing I am thinking, a detergent motor oil may actually help, but MAY hurt. I don’t know. Ultimately the real dedicated vacuum oil is necessary for multiple reasons, the least of which if the lower vapor pressure of vacuum oil.

Another trick I got from the eevlog op was to take a high strength hard drive magnet and stick that in the bottom of the oil reservoir, just for good measure to grab any metallic contaminants. Certainly couldn’t hurt.


I have inherited an edwards e28 rotary vane that seems to be giving me a little more difficulty even after a fresh rebuild by in Anaheim. In the application of pulling vacuum for a 20l rotary evaporator for ethanol recovery with an appropriate cold trap setup, how often should I anticipate having to change the oil and what is my best indicator of the time to do so? In regards to pump oil, are there different high performance vacuum oils? What is the correct type in this application and where is the most cost-effective source for purchase?

API Vacuum Pump Fluid
A highly distilled, hydrocarbon based fluid. Great for rough vacuum pumps and harsh environments where corrosion resistance and lower base pressures are a must.

Our NEW Pro-Torr White Gold pump fluid is a highly-refined hydrocarbon mineral oil. Works great in both rotary vane and rotary piston pumps. Provides good sealing, lubricity and ultimate vacuum (current selection)

Direct-Drive Vacuum Pump Fluid
A highly distilled, water-white hydrocarbon based fluid. Great for direct-drive pumps and harsh environments where corrosion resistance and lower base pressures are a must.

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You should probably change oil out every day depend upon upon usage levels. also you dont need that good of that of vacuum when distilling ethanol


To clarify, are you suggesting that I do not use a rotary vane for this 20l rotary application for the reasons that I do not need to pull an ultimate vacuum and to save the maintenance of having to change the oil daily?

Anyone else concur?

Pump suggestion off top?


Yeah, get a chemical duty scroll, piston, or diaphragm pump.Rotety vane oil pumps are easy to contaminate, hard to protect, and not suited to the application. In addition they acheive a level of vaccum deeper than required for the rotovap.

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I’ve had good luck running diaphragm pumps on rotary evaporators


Just so I’m clear, is this what you would recommend for flushing my vacuum pump?

-Turn on pump (filled with bad oil) - run for 30 min until oil hot.
-Drain oil.
-Refill with 50/50 kerosene/vacuum pump oil.
-Run for 1 hour.
-Drain oil.
-Repeat with 50/50 until oil comes out clean.
-Fill with 100% good vacuum pump oil?

Is this better than wasting my time/money on flushing fluid? At $30+/gallon, seems pricey. Any recommendations on type of kerosene? I assume just stop by my local hardware store? Or should I be sourcing something a bit more pure?

My freeze dryer vacuum pumps are getting icky, want to give them some TLC.

Thank you!


Just good old kerosene, I use marvel mystery oil too.Rotary Vane Vacuum Pump Blues - Fusor Forums


has anyone tried welch’s crv pro8 i have a guy thats telling me its better than the edwards 30

I have it. It was working good. I then tested the vac directly at the pump before the first oilchange, it pulled 15 micron which is as low as it can go according to the specs. After that ive done two more oil changes every 2-3runs but the ultimate vac is getting higher now. After first change it was 25 micron. After this last one it is 36. I don’t know why i can’t get it back down to 15. I haven’t done a acetone flush, cause i don’t know how much to use and how to properly do it.

No acetone. Kerosene +pump oil 50/50.

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Does the SOP apply to any vacuum pump…
I have one those no name orange cheap pumps for purging

And CPS 2 stage that’s for purging too


Not all, but most.


The ones I showed you? Or do I just drain and change… Im sure that they could use the best treatment…

I bought mastercool brand that was called for the CPS…I hope it’s the same stuff to use in my cheap orange

You can do that to your pumps, try marvel mystery oil too. I said not all because there are different styles out there, piston, rotery, diaphragm,scroll ext. This trick only works for a few types.