Hi Carolyn,
I am interested in the special veins (mentioned below) you fit to your
rotary pumps to avoid damage?
The roughing pump on our freeze drier (a Edwards E2M12) takes a lot of abuse
and I'm interested in any way to help it along.
Cheers,
Steve Taylor
Lab Manager
Isotope Science Laboratory
University of Calgary
Calgary, AB
Canada
> -----Original Message-----
> From: Stable Isotope Geochemistry [mailto:[log in to unmask]]On
> Behalf Of Chenery, Carolyn A
> Sent: Monday, August 14, 2000 2:57 AM
> To: [log in to unmask]
> Subject: Re: foreline traps
>
>
> Hi Natalie
> We use activated alumina with all our pumps except those on the water
> equilibration system which pumps high amounts of water vapour. And yes
> alumina is very good at absorbing oil, moisture, acids etc efficiently.
> Ours do not need changing that often ( 2x year), but that really
> depends on
> the state of your pumps and how you use them. Back streaming of
> oil should
> not be a major problem with turbo pumps. Most instances of back streaming
> occur with diff pumps when the backing pump is shut down with out closing
> isolation valve first. The mass specs. do not have electronic isolation
> valves but all of our extraction lines do.
> Water is a different problem. I had a lot of trouble with water in the
> roughing pump on our water / CO2 equilibration system. So I
> thought why not
> fit a forline trap, several days later I learned why. The pumping
> efficiency dropped and eventually I could not get an acceptable
> vacuum. The
> alumina oxide absorbed the water to saturation point and then began to
> outgas continuously. As we could not avoid pumping water vapour, we first
> had special veins fitted to the pumps that resist water damage and every
> morning while we are setting up the system we run the roughing pump on
> ballast for 1/2 hour to get rid of water in the pump oil.
> On our fluorination lines where there is a small risk of pumping
> acid vapour
> I precede the alumina trap with a soda lime trap.
> As far as I know you can heat the Alumina up to 1200 deg to burn
> off oil etc
> without adverse effects where as most zeolites do not like temperatures
> above 600 deg and cannot cope with acids (only stable over range PH 5 -11)
> As for size of pellet the smaller the pellet more surface area.
> With either
> trap avoid mounting it directly over the pump, any breakdown products
> falling in can cause damage.
> Good luck, Cheers,
> Carolyn
>
> Carolyn A. Chenery
>
> NERC Isotope Geoscience Laboratory
> British Geological Survey
> Kingsley Dunham Centre
> Keyworth, Nottingham
> U.K. NG12 5GG
>
> e-mail: [log in to unmask]
> Phone: (+44) 01159 363406 (office)
> (+44) 01159 363119 (laser laboratory)
> (+44) 01159 363302 (fax)
> (+44) 01159 363100 (switchboard)
> The NIGL Web Site is: http://www.bgs.ac.uk/nigl/index.htm
> The BGS Main Web Site is: http://www.bgs.ac.uk/
>
> Carolyn
>
> Carolyn A. Chenery
>
> NERC Isotope Geoscience Laboratory
> British Geological Survey
> Kingsley Dunham Centre
> Keyworth, Nottingham
> U.K. NG12 5GG
>
> e-mail: [log in to unmask]
> Phone: (+44) 01159 363406 (office)
> (+44) 01159 363119 (laser laboratory)
> (+44) 01159 363302 (fax)
> (+44) 01159 363100 (switchboard)
> The NIGL Web Site is: http://www.bgs.ac.uk/nigl/index.htm
> The BGS Main Web Site is: http://www.bgs.ac.uk/
>
>
>
> -----Original Message-----
> From: Shrimp, Lab [mailto:[log in to unmask]]
> Sent: 10 August 2000 18:15
> To: [log in to unmask]
> Subject: [ISOGEOCHEM] foreline traps
>
>
> Hello Isogeochemers
>
> Although no longer a part of the stable isotope community, I am still an
> Isogeochem subscriber and would like to ask a technical question
> on a topic
> that all mass spec users have in common. (I tried the listserver most
> relevant to me but got no responses.) I am about to order replacement
> molecular sieve for our foreline traps, and can't figure out what I should
> get. We are using rotary pumps to back turbo pumps in pumping out a large
> clean system and just want to prevent oil vapour backstreaming as well as
> water contamination of roughing pump oil. There seems to be two main
> choices: synthetic zeolite (generic "molecular sieve") and activated
> alumina. Activated alumina is way more expensive, and I'm not sure whether
> the higher cost is worth it, and if so, why. I've read suggestions that it
> lasts longer between regenerations, or that it removes moisture, acids and
> particulates more effectively than synthetic zeolite. If the activated
> alumina really is less trouble in terms of frequency of
> bakeout/replacement,
> then it may be worth the difference in cost. Any advice coming from
> practical experience would be appreciated.
>
> (Then of course there is the question of bead/pellet size and
> shape...beads
> vs. pellets? 1/8" pellets vs. 1/16" pellets? Does it matter?)
>
> Thanks in advance
>
> Natalie
>
>
> ************************************************************
> Natalie Morisset
> J.C. Roddick Ion Microprobe Laboratory/
> Laboratoire de microsonde ionique J.C. Roddick
> Geological Survey of Canada/
> Commission géologique du Canada
> 601 rue Booth St., #G-20
> Ottawa, ON K1A 0E8
> Tel.: (613) 992 9023
> Fax: (613) 995 7291
> e-mail: [log in to unmask]
> ************************************************************
>
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