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Hi all
Thanks for the excellent descriptions on the art of rebuilding MOVPT valves and assemblies.  While I think I have finally got this 'right' (after several very painfull - mentally and physically - attempts) I always thought this 'rights of passage experience' could have been avoided by either a methodical video or a series of illustrative photos.  These could explain blow by blow what is what and what goes where.
 
I have photographed the assembled valve in my last attempt.  I was wondering if anyone else has done this or could at some stage in the future.
 
Best
Brett
 
________________________________

From: Stable Isotope Geochemistry on behalf of Nick Collins
Sent: Sat 7/05/2011 1:37 AM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] Problem with a MOVPT valve



Hi Karine,
The most likely fault is the 25um silica was not retained in the 004 end of
the 004-003 ferrule. This can be tricky especially for a first time. Even
now I bring a few spares when doing this on site just in case.... If you
look into the male end of the Tee that seats on the pointed end of the
ferrule it should be drilled out to a cone shape. If not you can do an OK
job with a little care and a regular drill. It is possible to seal it w/o
this modification, just not as easy as the amount of torque to seal is not
much less than that to crush the end of the ferrule.

To check I would start by turning the CO2 pressure right down. If the He
gauge still rises when the valve is opened then you have a compressed air
leak, if not then it is CO2.
Cheers

Nick..


Nick Collins
President

Elemental MS
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College Station
TX 77845

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-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Karine Charlier
Sent: Friday, May 06, 2011 4:20 AM
To: [log in to unmask]
Subject: [ISOGEOCHEM] Problem with a MOVPT valve

Dear Isotopists,

I work with a Carlo Erba EA linked to an Isoprime IRMS.

I thought one of the MOVPT valves of the reference gas injector (the CO2
valve) was leaking, so I re-built and tested it for atmosphere and
internal leaks.
There is no atmosphere leak, but when I open the CO2 valve, Helium
pressure in the reference gas injector increases considerably (several
psi). When I open the N2 valve which works prefectly, Helium pressure
doesn't increase...

When I rebuilt the valve, I changed all the ferrules according to both
the manufacturer (SGE) and Isoprime schematics. But these schematics are
either different of the configuration I have, or not complete, so I'm
not sure if I used the correct ferrules.

Has anybody ever encountered this problem, or can explain what's
happening in the valve ?

Thanks for your help,
Best regards,
Karine

--
*********************************************************

Karine CHARLIER
Environnements et Paleoenvironnements OCeaniques
UMR CNRS 5805 EPOC
Universite Bordeaux I
Avenue des Facultes
33405 TALENCE Cedex
FRANCE

Tel : 0 (33) 5 40 00 83 62
Fax : 0 (33) 5 56 84 08 48
E-mail :[log in to unmask]
Web :http://www.epoc.u-bordeaux.fr/

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