[labnetwork] H2 Generators

[Weaver, John R]

I know that some people consider me far too conservative, but I guess the number of incidents (fires, etc.) that I have seen over the past 40 years has led me down that path. I prefer doubly contained piping for hydrogen, with LEL sensors in the generator, VMBs, and tools. I run N2:He in the interstitial at half the delivery pressure of the H2. This is static, and I monitor the interstitial pressure real time. If the pressure goes up, I have a leak in my H2 line. If the pressure goes down, I have a leak in my outer containment. If my pressure goes to zero, someone drove a fork truck through my line and I evacuate the facility.

I'm also a believer in excess-flow sensors and fixed orifices. It seems obvious (but I have seen this mistake), but the excess-flow sensor must be set above the flow rate allowed by the orifice :).

We have had a Proton Hogen since we opened the BNC and have been very happy with it. We have had the usual maintenance issues, but nothing serious. John Coy (jcoy at purdue.edu<mailto:jcoy at purdue.edu>) and Kenny Schwartz (kfschwar at purdue.edu<mailto:kfschwar at purdue.edu>) have more solid information that I do. They are the engineers who keep the system running.

John

John R. Weaver
Facility Manager
Birck Nanotechnology Center
Purdue University
(765) 494-5494
jrweaver at purdue.edu

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Abbie Gregg
Sent: Thursday, July 19, 2012 10:50 PM
To: Rizik; 'Grimard, Dennis'; labnetwork at mtl.mit.edu; Mark Winter
Subject: Re: [labnetwork] H2 Generators

Yes, the flow restricting orifice is key, as well as an excess flow sensor in the hydrogen lines, regardless of the source.

Abbie Gregg
President
Abbie Gregg, Inc.
1130 East University Drive, Suite 105
Tempe, Arizona 85281
Phone 480 446-8000 x 107
Cell 480-577-5083
FAX 480-446-8001
email agregg at abbiegregg.com<mailto:agregg at abbiegregg.com>
website www.abbiegregg.com<http://www.abbiegregg.com>

CONFIDENTIALITY NOTICE:   All information contained in or attached to this email constitutes confidential information belonging to Abbie Gregg, Inc., its affiliates and subsidiaries and/or its clients.  This email and any attachments are proprietary and/or confidential and are intended for business use of the addressee(s) only.   All other uses or disclosures are strictly prohibited.  If the reader is not the intended recipient you are hereby notified that the perusal, copying or dissemination of this email is strictly prohibited. If you have received this communication in error, please notify the sender, and delete all copies of this message and its attachments immediately.


From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Rizik
Sent: Wednesday, July 18, 2012 6:11 PM
To: 'Grimard, Dennis'; labnetwork at mtl.mit.edu
Subject: Re: [labnetwork] H2 Generators

The average cost runs about $6,500 per gas sensor including hardware, programming, sensor, wiring, conduit, functional testing, commissioning, etc. Pull Stations and horn/strobes each runs about $1,500 installed.

You really got a point there. And yes, you will need to place gas sensors to overlap in the area of work so that they will not miss a gas leak. Although this is quite difficult to achieve, you try to install welded tubing from the generator to the point of use then provide as sensor at each point. Again, cost will be an issue. In a previous email, I mentioned that the gas monitoring system shall be interlocked with the generator to ensure that it shuts down upon gas detection, manual activation and fire alarm signal initiation.

One more item to consider, is installing an orifice in the tubing leaving the generator to ensure that we do not allow more than 150% of the process gas demand to be supplied to the tools. On past projects, we installed excess flow mechanical valves that would trip if H2 flow rate exceeds a preset limit. This will allow us to limit H2 leakage to a level that would not exceed 25% of the LEL concentration in the lab space. All these parameters MUST be taken in consideration by the engineer of record. Occasionally, these parameters are overlooked and are only discovered during the plan review cycle by the AHJ.

Regards

Rizik Michael, PE
Principal
Integrated Engineering Services
Office: +408 261 3500, Ext. 201
Cell:      +408 718 0927


From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Grimard, Dennis
Sent: Wednesday, July 18, 2012 1:37 PM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] H2 Generators

All:

I have been watching the discussion regarding H2 generators.  Although I agree with most of what has been said I worry about being able to shut off the generator in case of a leak.  The generator does not know that it is delivering into a leak and unless the leak is detected then the generator will continue pumping to that leak.  Adding detectors is not the solution.  H2 detectors are difficult to place such that they will pick up a leak.  Do you add detectors at every possible leak point?  Add in the high velocities of the cleanroom and I hesitate to change from bottles to generators.

When considering the costs, you also have to consider the cost of the added detectors ... which are not cheap ...

Dennis Grimard, Ph.D.
Managing Director
Lurie Nanofabrication Facility
1246D EECS Blding
1301 Beal Avenue
Ann Arbor, MI 48109-2122
(734) 368-7172 Cell
http://www.lnf.umich.edu

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mtl.mit.edu/pipermail/labnetwork/attachments/20120720/b630da67/attachment.html>