[labnetwork] Help ... Please !!! ... our safety guys have not clue about gas cabinets ...

[Paolini, Steve]

Leo, If you're gas cylinders are piped in such a manner that air bubbles can be introduced simply by shutting the cylinder valve, you have much more to worry about that the mandate of shutting them down.
Federal and local regulations dictate which type of valve can be installed for use on compressed gas cylinders. Almost all common cylinders whether containing inert or hazardous contents use some variation of a diaphragm valve, what this means is that you will not get leak-by at the stem (under the handle) when opening or closing. It is critical that this stem seal is durable and that is why the Compressed Gas Association regulates the type of valve and connection for all compressed gases. 
I see absolutely no problem in shutting the cylinder valves at any given time. When I first started in the semiconductor industry we had all manual gas equipment and this was a nightly ritual after pumping out the lines. The statement that you made about air bubbles concerns me; have you experienced any indication that the gas circuit could be breached? I would suggest shutting the cylinder then pumping the lines back and noting the pressure reading. If you return from your break and notice degradation by a rise in pressure, you must leak check your gas circuit (after purging thoroughly).
Stay safe and don't hesitate to contact me if a question should arise.
Regards,

Steve Paolini
Principal Equipment Engineer
Harvard University Center for Nanoscale Systems
11 Oxford St. Cambridge MA 02138
Tel. 617 496 9816
Cell. 617 851 4793
spaolini at cns.fas.harvard.edu


-----Original Message-----
From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Leonidas E Ocola
Sent: Wednesday, December 22, 2010 3:45 PM
To: 'Rob Ilic'; Daniel Christensen; Fab Network
Subject: [labnetwork] Help ... Please !!! ... our safety guys have not clue about gas cabinets ...


All,

Can anyone tell me if you shut the valves of the gas bottles in your 
cleanroom
during winter break ? Our safety guys are under the impression that it is
hazardous to leave them open. They will only listen to me that they are 
wrong
if other labs leave them as is.

(We have gas cabinets with gas alarms, shutoff valves, manifolds, etc. They
are hooked up to our RIE tool with 12 sticks for different gases)

I do not want to shut all the gas bottles for winter break because I 
believe it is
unnecessary and in some cases could introduce air bubbles into the line
which could affect my RIE recipes if I do not flush the line.

If you can reply within the next few hours I would appreciate it.

Thanks

Leo

-- 
Leonidas E. Ocola, PhD
Nanofabrication Group

Center for Nanoscale Materials
Argonne National Laboratory
9700 South Cass Ave, Bldg 440, Rm A129
Argonne, IL 60439

Email: ocola at cnm.anl.gov
Phone: 630-252-6613
Fax :  630-252-5739
Web:   nano.anl.gov
http://nano.anl.gov/docs/people/ocola.pdf



_______________________________________________
labnetwork mailing list
labnetwork at mtl.mit.edu
https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork