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Vacuum Pump problem

Posted: Sat Oct 08, 2011 2:53 am
by Carl Smith
I have a problem with my robinair 15300. I can turn on the pump and it will run for about two minutes before shutting off. After five minutes I can hear a click then I can reset the pumps switch and turn it on. What do you think is the pumps problem?

Re: Vacuum Pump problem

Posted: Sat Oct 08, 2011 7:41 am
by Jerry Biehler
Too much of a load and its tripping the thermal overload. First thing to try is separating the motor from the pump section. Hopefully it has some sort of coupling that will allow you to do this. Try the motor like this and see if it overheats. If it does than it could be a bad capacitor if it is a capacitor start, capacitor run motor. If the motor runs fine and cool then there is something wrong with the pump section itself. It may need to be taken apart and cleaned. A rebuild kit, if available, could be installed at this time.

Re: Vacuum Pump problem

Posted: Sat Oct 08, 2011 6:30 pm
by Jeroen Vriesman
I don't know the robinair 15300, but I had the same thing with my pfeiffer duo 008b.

It is probably a thermal shut-down, first try to determine if it is overheating.

1) put a thermometer in the oil and look at the temperature, shut-down should happen somewhere at 70 or 80 deg. C

If it's still cold, it can be the thermal circuit itself (that was the case with my duo 008b: ... -dead.html ), or the sensor.

2) check the oil level and locate the thermistor (usually ptc)
Sometimes too much oil will drown the thermistor in oil, and if the thermistor is in the oil it will be warmer, the reason for this is that the system should shut-down if there is way too much oil in it (thermal expansion of the oil, pressure etc..)

3) if the system does get too hot, check your bearings, or the motor itself, see where the system is getting hot.

Re: Vacuum Pump problem

Posted: Sun Oct 09, 2011 4:07 pm
by Carl Smith
Thanks I overfilled the oil reservoir which was tripping the sensor. I had to refill it with new and less oil. It was able to run constantly for 25 minutes.

Re: Vacuum Pump problem

Posted: Sun Nov 06, 2011 5:09 pm
by Carl Smith
Now a common problem seems to be that my pump is getting so hot that the oil is evaporating into mist. The pump soon is left oil less as the container of oil evaporates. Is this normal for a vacuum pump?

Re: Vacuum Pump problem

Posted: Sun Nov 06, 2011 6:02 pm
by Chris Bradley
Not if you have the right oil. It'll happen if you don't, though.

Re: Vacuum Pump problem

Posted: Mon Nov 07, 2011 4:48 am
by Chris Trent
You will also mist your oil away pretty quickly if you are constantly pumping at atmospheric pressure.

Make sure to blank off the inlet of the pump or have it connected to a sealed system before running it for long periods of time.

Re: Vacuum Pump problem

Posted: Mon Nov 07, 2011 3:03 pm
by Richard Hull
You will get mist all the time, but it will be heavy when gas ballasting and pumping against air, as mentioned. If you can't run the mechanical pump's exhaust outside with a separate line, like I do, you need a very beefy exhaust oil mist filter for your pump. See if you dealer offers one.

Richard Hull

Re: Vacuum Pump problem

Posted: Mon Sep 16, 2013 6:50 pm
by Ross Moffett
I'm digging this thread from the grave because I'm having the same problem with misting.

I blanked off the suction of an Edwards speedivac ED50 model and after about 45-60 minutes it gets hot (~110 deg F) and starts misting oil out the oil catch. What is the correct oil for this pump? It looks as if Edwards doesn't post old manuals on their site and I can't find it elsewhere to trace the correct oil.

This is the oil that I used: ... UTF8&psc=1

If this is too thin, can someone recommend to me a better one from LDS? I'm about to make an order from there anyway. Amazon would also be nice.

This pump was advertised on eBay as being tested at 20 microns vacuum pressure, with a photo of their test rig. Doesn't really mean it's not faulty though, I guess.

Edit: I saw in another post in further searches that burping the gas ballast might fix it by venting water, and it seems to have. I've run it for another hour now and it's hot, but not venting clouds of oil.