[labnetwork] Question regarding SF6 intermediate gas delivery line pressures

[Tom Britton]

Hello Bob,



A good rule of thumb to go by is that the cylinder regulator needs to be able to supply enough flow at the correct pressure so that when the maximum flow needed is called for, the system can deliver it without starving the line. So, at each tool you need, worse case, 1.5 SLPM and 22 psi. If multiple, say 5, lines are flowing, you'll need a max of 7.5 SLPM at 23 psi.



Attached is a flow curve for an AP1010 regulator, the standard line regulator from APTech for 1/4" service, and what is in many VMBs. This curve shows that with a 50 psi inlet to the regulator, and an outlet pressure set at 30 psi, the regulator will deliver 7 SLPM with around a 3 psi drop. Figure line losses from the regulator to the MFC taking a psi or two and feasibly you would deliver 5 slpm at approximately 24 to 25 psi. The more comfort factor you want, the higher the inlet pressure to the regulator, and the more available flow you have at that pressure.



In your situation, based on what  we know here, I would set up the line regulator with 60 to 70 psi coming in from the cylinder regulator, and dial the output to 40 psi - 45 psi. This way you have ample safety factor in the system so you don't starve a regulator at max flow.



If you have any questions, please let me know. I hope this helps.



Best regards,

Tom Britton
Sales Manager
Critical Systems, Inc.
7000 W. Victory Road
Boise, ID 83709
Direct: 208-890-1417
Shop:   877-572-5515
www.criticalsystemsinc.com<http://www.criticalsystemsinc.com/>

"World Leader in UHP Reconditioned Gas
   Delivery & Abatement Technologies"






-----Original Message-----
From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Robert M. Hamilton
Sent: Thursday, March 7, 2013 10:50 AM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Question regarding SF6 intermediate gas delivery line pressures



Colleagues,



What is the preferred line pressure for delivering SF6 from a gas vault to a valve-manifold box?



The SF6 cylinder pressure in our indoor cylinder vault is

~320 psi. The final delivery pressure is ~18-22 psi. There is a cylinder regulator at the cylinders as well as line pressure regulators in the VMB. Our delivery volume varies from ~100 sccm to 1.5 slpm.



Thanks for any enlightenment,

Bob Hamilton





--

Bob Hamilton

Marvel NanoLab

University of CA at Berkeley

Rm 520 Sutardja Dai Hall

Berkeley, CA 94720-1754

bob at eecs.berkeley.edu<mailto:bob at eecs.berkeley.edu>

(e-mail preferred)

510-809-8600

510-325-7557 (mobile - emergencies)





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