[labnetwork] Toxic Gases tubing

[Paolini, Steven]

Kamal,
  I have been a little busy to chime my opinion on your questions. I would, however, like to briefly express my experience with heat tracing gas lines. In a nutshell, don’t do it! If your gas is stored in a reasonably climate controlled area where the temperatures are not much less that the area where the tool is, you would be better off delivering your gas at sub-atmospheric or near sub-atmospheric pressures. Simply put, one law of physics states that if you lower the pressure of a gas or liquid, you lower its boiling point. This only effective in vacuum systems where there is a pressure differential. Heat tracing gas lines might, and I emphasize might, work for some folks if the insulation is impeccable but sooner or later, those gases will liquify in the first cool surface that they touch…usually in an MFC. Over the years, I became frustrated with these setups and the downtime it causes and looked into simple physics for a solution. I have been running sub-atmospheric for over 25 years in two different facilities without issue. You need special regulators that will allow and control at 5”Hg-5 PSI. Regular tied diaphragm regulators are too “jumpy” for this task.
I hope this helps.
   Steve Paolini Equipment Dood

Steve Paolini
Principal Equipment Engineer
Harvard University Center for Nanoscale Systems
11 Oxford St.
Cambridge, MA 02138
617- 496- 9816
spaolini at cns.fas.harvard.edu
www.cns.fas.harvard.edu

From: labnetwork-bounces at mtl.mit.edu <labnetwork-bounces at mtl.mit.edu> On Behalf Of Kamal Yadav
Sent: Wednesday, September 16, 2020 12:55 PM
To: labnetwork at mtl.mit.edu
Subject: Re: [labnetwork] Toxic Gases tubing

Dear All,

Thank you everyone for all your responses on toxic gas tubing for Cl2/BCl3/HBr.
I received many responses and may write directly write to them for subsequent queries.

To summarize: Overall recommendation and also mostly required by code as well to have co-axial for these gases, along with heat tracing for BCl3, and scrubbing, with VCR fittings.

Thanks,
Kamal

On Mon, Sep 14, 2020 at 9:43 AM Kamal Yadav <kamal.yadav at gmail.com<mailto:kamal.yadav at gmail.com>> wrote:
Dear All,

We will be installing SS gas tubing for Cl2, BCl3, HBr, SiH4.

I have some experience in how industry does it, but wanted to know how different universities do this. From some prior posts, I got to know University of Michigan has co-axial tubing for all these gases and every connector location for these gases is exhausted as well at their facility

My queries are:
1. Is this how most of the Universities do it or there are places where these gases are in single tubing [non co-axial or double contained].
2. Also if you do orbital welding or just bending of the tubes?

I have been informed it is based on the fire code of the city or county, but it's not apparent from those documents.

Thanks for your help.

--
Thanks,
Kamal



--
Thanks,
Kamal

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