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- Posts: 481
- Joined: Fri Jun 02, 2017 11:10 pm
- Location: Western Colorado
I've switched my 5971 over to hydrogen as the carrier. with the minimum flow I can achieve (0.83 mL/min) I get a vacuum of 7.2E-5. The built in vacuum gage at the diffusion pump (accessible in MS software) exit says 44 mTorr.
I put in new PFTB fluid and seals. When the tune valve opens the vacuum goes up to 1E-4 Torr. Can't seem to get the seal any better and it does not pump down any lower when tune valve is open. Is this normal or do I perhaps have a leak in the solenoid or the vial seal?
Is this a source pressure problem somehow made worse by hydrogen? Hydrogen flows so easily that the lowest flow achievable with DB624 column 20m x 200um x 1.2 um; is 0.83 mL/min. If there is a frit I can change in the flow controller please suggest.
Finally, could this be a diffusion pump problem. I've not checked but diffusion oil might be low. I am seeing 25 mTorr at the Edwards E2M2 pump via a DV6 gage.