Jon,

Maybe my use of thermal shutdown isn't the proper term.  The vacuum gradually decreases from 30 milibar to atmosphere after about 1.5 hours.  During this time the motor is still running.  I assumed it is some issue related to things heating up.

Did the faulty coupling result in a gradual to complete loss of vacuum?

Thanks, Ben

-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Jonathan Karr
Sent: Monday, January 29, 2007 8:45 AM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] Analyzer pumps, high vacuum shutdown

Ben,
I did have a faulty magnetic coupling on one Duo 
5, and have had overheating issues but never a 
thermal shutdown. Also, I now point a blower fan 
directly onto my forevac pumps as a precaution to avoid overheating.
Jon

At 06:54 PM 1/26/2007, you wrote:
>Thanks for all the suggestions.  The problem was 
>thermal shutdown of the rotary pump.  I 
>connected a spare RV5 to the vacuum line and the 
>original DUO5 to a pressure gauge and put the side panels back on the MS.
>
>The suspect pump pulled down to <30 millibar 
>immediately but was reading zero after 
>approximately 1.5 hours.  The RV5 is still 
>running as are all the other pumps.  Mass 40 is 
><50mV and dropping while flooding the down to air valves with Argon.
>
>After turning the faulty DUO5 off for about 20 
>minutes and restarting, it starts to pull down 
>the vac again since it has cooled off.
>
>This leads me to another question regarding the 
>Pfeiffer DUO5.  When it had no vacuum the motor 
>was still running.  Could the problem be with 
>the magnetic coupling?  Has anyone had 
>experience with thermal shutdown with a DUO5?
>
>Thanks,
>
>Ben
>
>
>
>Benjamin Harlow
>Washington State University
>School of Biological Sciences
>P.O. Box 644236
>Pullman, WA  99164-4236
>
>Office:  509-335-6161
>Lab:     509-335-6154
>Fax:     509-335-3184
>
>Laboratory for Biotechnology and Bioanalysis Stable Isotope Core
>http://www.isotopes.wsu.edu
>
>-----Original Message-----
>From: Stable Isotope Geochemistry 
>[mailto:[log in to unmask]] On Behalf Of Gilles St-Jean
>Sent: Friday, January 26, 2007 5:32 AM
>To: [log in to unmask]
>Subject: Re: [ISOGEOCHEM] Analyzer pumps, high vacuum shutdown
>
>Hi Ben
>Another possibility is the down-to-air valve on 
>one of the turbos.  If the solenoid is getting 
>weak it may be slowly opening.  You can monitor 
>your background in Instrument Control over time 
>on N2 or Ar.  You can also put a plastic bag 
>around the valve and flood it with Ar.  Do this 
>about one hour after startup and monitor the Ar peak through a scan
>
>Gilles
>
>Gilles St-Jean
>Chercheur / Research Scientist
>Université d'Ottawa / University of Ottawa
>Sciences de la Terre / Earth Sciences
>140 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5
>Tel: 1-613-562-5800 xt 6830 (Bureau / Office)
>                     xt 6839 (Bureau / Office Lab)
>                     xt 6836 (IRMS lab)
>Téléc. / Fax: 1-613-562-5192
>Courriel / E-mail: [log in to unmask]
>Toile / Web: www.isotope.uottawa.ca
>
> > -----Message d'origine-----
> > De : Stable Isotope Geochemistry [mailto:[log in to unmask]] De la
> > part de Benjamin Harlow
> > Envoyé : 25 janvier 2007 18:23
> > À : [log in to unmask]
> > Objet : [ISOGEOCHEM] Analyzer pumps, high vacuum shutdown
> >
> > Listmembers,
> >
> > I am having vacuum problems on a Delta plus XP with dual inlet.  After
> > about
> > 2hrs runtime the analyzer pumps shut off.  The inlet pumps remain on.  The
> > system starts up as normal, with turbos reaching 80% and high vac Ok,
> > setpoint for the source ok in about 5 minutes.
> >
> > The problem seemed to occur after a series of about 4 power failures over
> > a
> > short time period.  I do not know if the turbos always got to fully spin
> > down or
> > vent properly during the power blinks.   I found a small amount of oil in
> > the line
> > going to the waste turbo for the dual inlet.  I cleaned that line and
> > checked all
> > others.  After about 2 weeks of pumping and normal backgrounds the
> > analyzer
> > pumps shut down one day.  Now they shut down after about 2 hours even
> > after achieving the set point for turning the source on.
> >
> > I cleaned the penning and pirani gauges and that did not resolve the
> > problem.
> >
> > I also tried unhooking the penning gauge, and the pumps still shut down
> > after
> > about 2h.  I'm planning on checking the max vac of the rotary pump and
> > looking for leaks.  Does anyone have any other suggestions or similar
> > experiences?
> >
> > thanks,
> >
> > Ben Harlow
> > Washington State University
> > Stable Isotope Core Laboratory
> > (509) 335-6161

Jonathan D. Karr, Ph.D.
Technical Director, Duke EnVironmental stable Isotope Laboratory (DEVIL)
Duke University Dept.of Biology & Nicholas School 
of the Environment and Earth Sciences
Phytotron Bldg, 71 Science Drive
Durham, NC 27708-0340

(919) 660-7418
Fax: (919) 660-7425
[log in to unmask]
laboratory website: http://www.biology.duke.edu/jackson/devil/




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