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Troubleshooting of Diffusion Pump System
d. Check the fluid level and condition of the foreline pump, if it’s time for
maintenance, change the oil.
e. If a foreline trap is used, replace the pellets.
f. Check all the vacuum seals: diffusion pump, elbow, foreline pump, etc.
The diffusion pump seals may leak if the clamp is not tight or because
the seals are worn or damage. Worn or damaged seals must be
replaced.
g. Contact your Varian Customer Support Representative.
2. CI Gas Settings (must be checked in Diagnostics)
a. Pressure Readings should not exceed 350 mTorr. Confirm CI reagent
gas head pressure at gas cylinder is set at 5 psi.
3. Diffusion Pump Overheated
a. Overheating causes the diffusion pump to turn OFF. Switch the power
OFF for 15 minutes. then, switch it ON to reset the diffusion pump.
b. Check the ambient temperature of the laboratory does not exceed 35 °C.
c. Check fluid in the diffusion pump.
d. Ensure all baffling is in place.
e. Check the fan.
f. Check to make sure left side cover is in place.
g. Contact Varian Customer Support Representative.
4. High background levels (low ionization time) in the mass spectra may be the
result of contamination in the ion trap, GC and/or the diffusion pump. If
numerous samples have been analyzed, the high background maybe the
result of trap contamination, and the trap components must be cleaned. If the
ion trap components have been cleaned and the system has been baked out,
the high background levels in the mass spectra maybe the result of
contamination in the GC and/or the diffusion pump. Comparison of mass
spectra at high and low GC column and injector temperatures may help to
identify source.
a. Reduce GC column and injector temperature to 100 °C or lower and
acquire a 2-minute mass spectral data file.
b. Increase GC column and injector temperature (~250 °C) and acquire 2-
minute mass spectral data file.
c. Identify the most intense mass peaks for both runs, and/or subtract
spectra.
d. Use the following table to identify the most likely source(s) of
contamination.
e. Call your Varian Customer Support Representative.
