[labnetwork] Toxic Gases tubing

[Kamal Yadav]

Thanks Steve,

I think John mentioned about you strongly recommending using
sub-atmospheric regulators. We will take that into consideration.

Thanks for your valuable advice.
Kamal

On Wed, Sep 16, 2020 at 2:26 PM Paolini, Steven <
spaolini at cns.fas.harvard.edu> wrote:

> 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> 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
>
>
>


-- 
Thanks,
Kamal
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