Edwards E2Mxx pumps

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
Post Reply
Rex Allers
Posts: 262
Joined: Sun Dec 30, 2012 8:39 am
Real name:
Location: San Jose CA

Edwards E2Mxx pumps

Post by Rex Allers » Sun Jan 14, 2018 3:52 am

This is in response to Jackson Oswalt's thread...
"A Bunch of Failures"

That thread was getting kind of long so I thought I'd reply in this one, just focusing on his Edwards E2M5 pump.

In that original thread, I was going to suggest that a picture might help the discussion but then he did post one. The one picture is a bit jumbled and hard to make out important details. It is also posted as full size from the camera with a whole bunch more blurry pixels than necessary. It would be nice if people learned how to shrink their picture size down to just what is necessary to convey in reasonable quality.

Here's a cropped and reduced version of that original image.
E2M5 close.jpg
At first I was confused by the corregated tubes and the KF-25 cross, but looking closer it appears this is not connected to the pump in the picture. It does block some details of the pump, though. From the little I can see of the Ballast valve, it may not look like what I would expect. I'll provide more details later.

First, my experience buying vacuum pumps on eBay is not good. I know others here have done OK but I have two instances of crapped out pumps. One was an Edwards E2M12, a bigger version of what you have.

I bought my E2M12 on eBay, but fortunately from a local seller. It looked clean and was described as working fine: "Like new vacuum pump in good working order. Pumps down with no issues. Great for vacuum molding, automotive use, and laboratory use as well."

I picked it up myself and on getting is home I was seeing crap vacuums -- about 20 T. After a day or two of testing more it seized up. I talked with the seller and I kept the pump but he gave me an almost complete refund which I gambled on a complete rebuild kit. After rebuilding, it seems to be working pretty good pulling down to about 15 millitorr.

I think it was used for vacuum on fiberglass moulding and had sucked lots of bad stuff through its guts. I think that type of abuse is pretty common on eBay pumps unless from a knowledgable seller -- then pricey.

Now on comparing mine to yours...
My exhaust port looks like this.
KF-25 Exhaust.jpg
So mine has a plastic KF-25 built in, making it easier to connect to a filter or plumbing. Your looks like it might take some kind of tube. Not critical, it's just a hole straight into the case.

My input port looks like this.
KF-25 Intake.jpg
So it has a KF-25 built onto it. Between the big circular base and the case, there is a gasket to seal it. The case has a circular depression to hold this gasket.

The brass fitting on yours looks very different. Did that come with your pump or is it something you added? -- I just looked at the eBay listing and it seems both the inlet and exhaust had some kind of hose nipples. Changing the input shouldn't be a problem as long as it is sealed well.

Here's the Ballast valve on mine.
Gas Ballast valve.jpg
From the little I can see in your picture, it doesn't look like this to me. In the ebay picture it does look like mine, though. If this ballast hole was wide open for some reason it could make the vacuum poor and cause a lot of oil to come out the exhaust.

Your picture of oil level drop from full looks extreme. When you first turn on the pump, it could drop a bit as the pump internals fill, but I wouldn't expect as much as your picture showed. Is the room covered in an oil film now?

Here's a picture of the ballast knob screwed all the way out so you can see the parts.
Gas Ballast out.jpg
The spring keeps tension on the knob as it is opened. Between the screw part and the knob part, if you look closly, there is a foam filter ring to keep dirt out when the ballast is open and sucking air. Closing the ballast, screw the knob all the way in until you just feel the o-ring compress to seal (finger tight). On mine the ballast valve starts to suck air at only about 1/2 turn unscrewed.

On that picture, if you look into the inlet, you can see the edge of a metal mesh filter that should be in there too.

On the close up of your picture that I made it looks like one set of screw threads may not be sealed. (The top end of the top KF connector.) If true that's probably not enough to make the vacuum so bad. You do have a centering and o-ring between the KF-25 fittings, I hope.

If nothing big wrong with the input fittings or the ballast valve, it's possible the internals of the pump have major problems like mine did.

In case you haven't seen it in a manual, here an exploded parts view for an E2M5.
E2M5 explode.png
That all looks about the same as my E2M12.

As one more diagnostic for you, I made three mp3 recordings of my pump running. With the pump pulling a good vacuum into a closed input it makes very little noise other than the motor humming. I'm not sure if the forum allows mp3 files, so I zipped them and put the zip on my server. You can download it here.
Rex Allers

Rex Allers
Posts: 262
Joined: Sun Dec 30, 2012 8:39 am
Real name:
Location: San Jose CA

Re: Edwards E2Mxx pumps

Post by Rex Allers » Sun Jan 14, 2018 3:54 am

After copying the image that Jackson posted of his pump, I noticed something that I don't think I have seen mentioned here before. A possible security concern for those who might care.

* Aside about posting images.
Many digital cameras have GPS available these days. If the camera is enabled to save that data, it will be recorded in the EXIF metadata that is saved as part of the jpg file. Maybe most of us don't care, but there is probably a way to turn this off in the camera. There are also tools to strip the EXIF data from the jpg. (Stripping EXIF can also resolve the sideways or upside down pictures we sometimes see.)

Question for Jackson: Does this neighborhood look familiar?
Also seems that you took the pump picture with an iPad Pro.
-- end of aside --
Rex Allers

Post Reply