Hello,
I'm not familiar with the GV Isoprime, but in the case of a brief power outage, the turbo vacuum pump (it probably has one) may not have stopped spinning before power was applied to it again. If this happens, the jerk when the power comes back on with a freely-spinning turbo can do all kinds of horrible things to the bearings and/or bearing casing. We've noticed that the default HV and LV readings on the monitor (when there is no vacuum) are deceptively close to an expected value rather than a default, making it a little more difficult to pinpoint the problem. What software are you using with your GV Isoprime MS? Are the readings the default readings?
-tom

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
http://www.uark.edu/ua/isotope/
http://comp.uark.edu/~tmillic/
--note to self: "data" is plural

----- Original Message -----
From: Supriya Ghotge <[log in to unmask]>
Date: Wednesday, April 5, 2006 11:36 pm
Subject: [ISOGEOCHEM] Pirani reading showing high

> 
> Hi all,
> We have GV Isoprime MS in our lab. Last week we had a power 
> failure when the system was kept on pumping overnight. 
> Now after starting the system and getting it baked, the analyser 
> HV is showing 6e-8mbar and LV is 3e-3mbar, but the pirani reading 
> is 3.5e0. Before the powerfailure the pirani was reading 3.0e0-
> 3.2e0. 
> We checked all the valves and also the Activated Alumina sieves 
> has been changed but no improvement in pirani reading. Background 
> scans are also clean with no moisture and any other gases. 
> What could be the possible cause for this??? 
> It would be very helpful if anyone could suggest something on this.
> Regards,
> Supriya.
> 
> 
> 
> 
> Supriya G. Karapurkar
> JTA
> IRMS Lab, COD
> National Institute of Oceanography
> Dona Paula, Goa. 403004
> INDIA. 
> email: [log in to unmask]
> Tel: +91-0832-2450465
> Fax:+91-0832-2450607 
> 
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