Joss Research: Vacuum: Diffusion Pumps

A Joss Research Institute
Informal Report:

Three Diffusion Pumps
and a Small Surprise

(13 September, 2008)

The Balzers Diff 650

This is the oldest of the three diffusion pumps that we seem to have here; it was recently given to us.


As you can see, it is designed to pull 700 Watts at 110 V; I have no idea how much fluid it takes, or even what the proper fluid is.

The Big Varian in the Vacuum-UV Spectrometer

This pump actually seems to have a gatevalve on it, but I don’t think there’s a roughing pump in the box with it. It appears to have about a 6″ throat.


The Leak Detector

We seem to have a partly-disassembled leak detector. Here are some views of the guts:


The label is scratched up, and a bit difficult to read; the pump is a [rather old] Edwards SpeediVac 403A. It is water-cooled, has a 4″ throat, takes 100 cc of fluid, and pulls 500 W at 240 V. (I can make 240 V with a step-up transformer, and the heater shouldn’t care about the frequency.) I have checked the heater; it has reasonable resistance, and is not shorted to the case. So far, so good.

The surprise about this unit is that there is actually a roughing pump in there as well:


It’s a bit strange, and we will have to replace the motor if we can; it wants 240 VAC at 50 Hz. I checked, and the shaft turns freely, so there is at least some chance that the pump itself is more or less intact. (There is also a chance that I can get away with running the motor on 60 Hz power, if I get the voltage close enough and if there isn’t too much work for it to do.)

This work is supported by
the Joss Research Institute
19 Main St.
Laurel  MD  20707-4303   USA

Contact Information:

Email:, where you can replace b with joss (as in Joss Research Institute), and a with my first name (no “h”, only 3 letters).

Phone: +1 240 604 4495.

Last modified: Wed Sep 17 01:46:55 EDT 2008

Share this:

  • Facebook
  • Twitter
  • Delicious
  • LinkedIn
  • StumbleUpon
  • Add to favorites
  • Email
  • RSS

I am a Researcher of the Joss Research Institute. I work primarily on lasers and ceramics, with occasional excursions into other areas.

2 responses to “Joss Research: Vacuum: Diffusion Pumps”

  1. John Pilkington

    Please can you tell me how much oil is needed in a Metrovac pump like yours.
    What is the knurlled thumb screw for ?
    I ask because I have been given a similar pump
    Kind Regards
    John Pilkington

Leave a Reply

WP Socializer Aakash Web