Robert,

      Years ago, I had the unenviable chore of cleaning out a Nuclide
3-60-RMS after the thermal run-away of an oil diffusion pump. It was a
lengthy and
laborious procedure.
      Generally, the rotary pump oil is easier to remove than the diffusion
pump oil, but you have baked the oil on to the internal metal surfaces
and maybe into the pores of the metal. Clean up will be more difficult due
to the premature bakeout.
      I did most of the parts cleanup in a fumehood. The larger parts were
cleaned with hot degreasing solvents in a large stainless steel pot with a
tight
lid to reduce solvent evaporative loss. These large parts were air dried in
the fume hood, then oven dried. The small metal parts were cleaned with
polishing compound, then cleaned with degreasing solvents with sonication.
These parts were dried in a 100 C oven. Some of the ceramics simply had to
be replaced. The glass insulators were cleaned with hot degreasing
solvents, then heated to about 600 degrees C in a furnace.
      With your more modern source, you may have to perform a more thorough
cleanup. That may mean replacing the ceramic insulators, the filament,
and other source parts. And don't forget to dismantle and clean the
detector parts.
      Viel gluck!

Glen Martin




                      "Geldern, Robert"
                      <R.Geldern@GGA-HA        To:       [log in to unmask]
                      NNOVER.DE>               cc:
                      Sent by: Stable          Subject:  Failure of fore vacuum pump and opening of the source  (Delta S)
                      Isotope
                      Geochemistry
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                      UVM.EDU>


                      04/06/04 05:07 AM
                      Please respond to
                      Stable Isotope
                      Geochemistry






Greetings,
one of our rotary vane fore vacuum pumps (Pfeiffer Duo 5) on our Finnigan
Delta S failed and it seems that oil vapor entered the vacuum tube
connection from the fore vacuum to the turbo pump (the large one under the
source). The backround scan showed lots of peaks. The complete vacuum tube
system (from all three fore vacuum pumps) was disconnected and cleaned
carefully. The large turbo pump under the source was dismounted and after
putting it on the side, some oil seeped out of the pump. We cleaned the
pump as good as possible, but I am not sure if this was enough. The fore
vacuum pump was replaced. By the same time the source was opened since a
leak was detected on the tube connecting the change over with the source.
The gaskets were replaced.

After re-connecting everything and the reintegration of the source we
pumped over the weekend an reached good vacuum (HV and FV, the FV took a
while...). We checked for leaks with Argon but did not find something. We
heated the source and the flight tube to 130 to 150 °C overnight (baking
and a kind of heating wire wrapped around the source and flight tube).

The backround scan (slow magnet scan) this morning still showed lots of
peaks which should not be there. We will check for a leak again, but I am
concerned that the contamination with oil vapour (maybe into the
source/tube itself?) is causing this.

Any suggestions on what we can do are highly appreciated.

Robert



--
Robert van Geldern
GGA-Institut (Leibniz Institute for Applied Geosciences)
Stilleweg 2, D-30655 Hannover (Germany)
fon: +49 (0)511 643-2716 (fax: -3665)
mailto:[log in to unmask]