Hi everyone,

One of the Pfeiffer DUO 005M rotary vane pumps in one of the four mass
spectometers in this lab seems to be behaving differently than the others.
I have tried to ask the manufacturer, Pfeiffer, about it to ask if this
symptom is normal but they will not allow me to communicate with anyone in
their service department who actually does the repairs and who is
knowledgeable about this. So, I am unsure of what to do about it, and I am
unsure if it is okay to continue to use it in the condition that it is now
in. Here are details:

When I replace the oil in three of the four pumps in this lab, the oil
level as seen in the transparent window in the back of the pump will rise
and stabilize quite rapidly, and this is good. I fill them to 3/4 of the
way between the upper and lower marks. When I then place these pumps back
in operation, the oil level either stays exactly at the same level or
decreases slightly.

But pump #4 behaves differently. When I stop pump #4 and refill it with oil
to 3/4 of the way between the marks, the oil level (as seen in the
transparent window in the back of the pump) rises very, very slowly (by
comparison to how the oil level rises when I fill the other pumps). This
seems strange, but at least the oil level will eventually stabilize at 3/4
of the way between the marks. When I then connect this pump #4 to the mass
spec and switch it on, strangely, the oil level rises rapidly until it
reaches the full mark and then the oil level stays at the full mark. So in
this way it behaves oppositely to all other pumps in this lab. I have sent
this pump once to Pfeiffer and they replaced the seals and replaced one
internal item that according to them was "cracked". But when pump #4
returned from the Pfeiffer service department, the oil level would rise in
exactly the same way as before when it was sent for service. One more thing
I can add is that the vacuum that pump #4 attains with SGE valve closed is
2.2e-3 millibars, but the same model of pump on an identical instrument
achieves a somewhat better vacuum: 1.6e-3 millibars with SGE valve closed.
(The Pfeiffer specification is <5e-3 millibars.)

Have anyone of you seen these same symptoms happen in a rotary vane pump in
your lab? In your opinion is this normal?

Thanks for considering this,

Myles Stocki
University of Saskatchewan
Canada