[labnetwork] Anhydrous HCl after it escapes ...

[John Shott]

Tom, Craig, and Dennis:

Thanks for each of your comments.  I should have thought to mention more 
about the details of our gases:

We are using electronic grade HCl specified to be 99.995% pure. While I 
think that there is one grade higher, at $1200 a cylinder it should be 
pretty good ...
Note: this is also set up with a DISS fitting (CGA 634 for HCl).

For our purge gas we use 10% He in a balance of nitrogen, again with a 
DISS fitting.  Each of the component gases is of UH grade that, I 
believe translates in to:

Nitrogen:

02 < 1ppm
H20       < 3ppm
THC      < 0.5ppm

Helium:

02 < 1ppm
H20       < 2ppm
THC      < 0.5ppm

After a cylinder change, we do a He leak check of the purge gas 
following each cylinder change.  I think that we are currently using 30 
purge cycles both pre- and post-purge ... it sounds as if that should be 
bumped up.  While I believe that we have hastelloy running between 
cabinet and tool, I believe that the components in the panel are all SS 
... but I believe are electopolished to

We have a manifolded two-cylinder (plus purge) cabinet that supplies an 
epi reactor.  It is not uncommon to use a 60 pound cylinder of HCl in a 
period of 1-2 weeks ... so, we unfortunately, have a number of chances 
for problems each year.

Thanks again for all of your input,

John


On 6/6/2014 1:07 PM, Tom Britton wrote:
>
> Hi John,
>
> Sorry to hear about your HCl issue. As we all know, HCl is very 
> difficult to manage once it escapes. Neutralizing is seldom effective 
> in a clean room environment, and replacement of metal components that 
> have come in contact with the HCL is the proper way to keep it from 
> spreading.  If the proper leak test procedures are in place, one thing 
> that could be causing the leaks is residual moisture that may be 
> present due to either  low quality purge gas or inadequate purging.
>
> To solve the problem of how to prevent leaks with HCl and other 
> corrosives these are the questions I would start with.
>
> ·What is the quality of the purge gas?
>
> ·Are you using a purifier on the purge gas?
>
> ·Is H2O or O2  analysis done on the gas system prior to gas introduction?
>
> ·How many purge cycles on gas line prior to gas introduction?
>
> ·How many purge cycles post cylinder change are being done?
>
> If you want, I can set up a conference call with Troy Reese, who was 
> the gas systems manager at ON Semi before he came to us, and we can go 
> over these questions. Troy is very knowledgeable in these situations 
> and we would be happy to help wherever possible. He is also presenting 
> with you at the Bootie Camp coming up at the UGIM conference, so we 
> can talk about it there as well if necessary.
>
> See you at Harvard.
>
> Thank you!
>
> Tom Britton
>
> Director of Sales
>
> /Critical Systems, Inc./
>
> Direct: 208-890-1417
>
> Office: 877-572-5515
>
> /www.CriticalSystemsInc.com/ <http://www.criticalsystemsinc.com/>/__/
>
> /__/
>
> logo for email signature png
>
> -----Original Message-----
> From: labnetwork-bounces at mtl.mit.edu 
> [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of John Shott
> Sent: Thursday, June 05, 2014 1:09 PM
> To: labnetwork at mtl.mit.edu
> Subject: [labnetwork] Anhydrous HCl after it escapes ...
>
> Labnetwork Community:
>
> Sooner or later, it seems, anhydrous hydrogen chloride (or a number of 
> equally corrosive materials) is going to escape.  At least that is our 
> experience at the Stanford Nanofabrication Facility.  Despite our best 
> efforts to use quality components, do proper leak checking, etc., it 
> seems as if we end up with a leak either in a gas cabinet or in a tool 
> near a mass flow controller.  At that point, anything near the site of 
> the original leak has been covered with now moisture-laden hydrogen 
> chloride ... which, I believe, is far more corrosive than the original 
> anhydrous material.
>
> For those of you who have encountered similar situations, how do you 
> recover or what to you replace?  Do you have effective means of 
> neutralizing those metal surfaces?  Do your replace VCR gaskets with 
> thicker-than-normal or grooved "super gaskets"?  Do you replace the 
> entire assembly?  Do you leak check, put back in service, and pray?
>
> Thanks for sharing your experience and insights,
>
> John
>
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