Joe,

In my former position we had a switchover system from Matheson that worked beautifully.  A shut-off valve was installed before the regulator and a purge valve was installed upstream of the shut-off valve so that the "air" could be purged from the line before the tank was brought on-line.  You could probably install a similar system with the 3-way valve.

Regards,

Mark

Mark Monk
Laboratory Manager
Urban Environmental Biogeochemistry Laboratory
Fisher College of Science and Mathematics
Towson University
P: 410-704-2566
F: 410-704-3511
E: [log in to unmask]


-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Joe Lambert
Sent: Monday, April 09, 2007 10:52 AM
To: [log in to unmask]
Subject: [ISOGEOCHEM] He Carrier Gas

Hi everyone,

      I wanted to ask how other labs are handling using two He cylinders to supply their peripherals. We will soon have a Gasbench, TC-EA, EA, and Conflo III so we will be going through a lot of He.  I know they make "switchover" systems/regulators ($1000+) that automatically switches the flow from the full cylinder as the other becomes empty.  I assume we could simply use a 3-way valve ($70) and switch the flow manually.  However, for both methods I wonder if there is an impact of having a volume of air being pushed through the lines as you switch from one tank to the other.  This "air"
would be a result of removing the empty tank with a fresh one which would allow air to fill the tubing between the cylinder and the 3-way valve or switchover system.  Any ideas?

Thanks,

Joe



W. Joe Lambert
Research Scientist
Alabama Stable Isotope Laboratory
University of Alabama
Geological Sciences
202 Bevill Building
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P.O. Box 870338
Tuscaloosa, AL 35487-0338
Phone: (205) 348-4404
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Visit our web-site: http:www.geo.ua.edu/asil