[labnetwork] Question: use of gas alarm logic to prevent building evacuations on silane bottle changes...

[Schweiger, Dennis]

Ian,

Is your current gas cabinet located within your lab proper?

You could set your system up so that it looked at multiple criteria;


1)     Is it in an exhausted enclosure?

2)     Is the exhaust level at specification?

And have it create an alarm event based on that event criteria.  Another thing you might want to consider, is creating a "dust cap removal station" outside of your facility.  This would simply need to be a location where you can secure a cylinder for the time it takes to perform that operation.  You could then reseat the dust cap, and move the cylinder into your gas cabinet.

Here at the UofM, our toxics and pyrophorics are stored in bunkers outside of the building proper.  Our gas detection system treats this area as a separate "zone", so if we detect a leak in a gas cabinet, within this "zone", we only evacuate the lab proper, not the building.

Dennis Schweiger
Facilities Manager

Lurie Nanofabrication Facility
University of Michigan
1301 Beal Ave.
Ann Arbor, MI 48109-2122

734.647.2055 Ofc
877.471.6208 Fax
734.320.4474 Cell

"People can be divided into 3 groups - those that make things happen, those that watch things happen, and those that wonder what happened."


From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Ian Harvey
Sent: Thursday, May 05, 2011 8:45 PM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Question: use of gas alarm logic to prevent building evacuations on silane bottle changes...

Dear Labnetwork,

Question:
How to prevent spurious gas/silane alarms (e.g., from cylinder change burps) from unnecessarily evacuating an entire building?

Background:
We recently had a very brief burst/decay of silane associated with the removal of the dust cap in preparation for installing a new silane cylinder. The burst was captured by our gas alarm as a single "spike" that exceeded the level-2 alarm threshold (10 PPM) for 3 seconds and decayed back to below level 1 (5 PPM) after 12 seconds (peak was 19 PPM).  However, the fire alarm was triggered, the entire engineering building was evacuated for 20 minutes, and six fire trucks showed up.

This cylinder was 13 months old, 1 month past its expiration date.  The cylinder was chained and strapped into position inside the gas cabinet when the dust cap was removed.  At present, we feel it is best to evacuate the building, since our old lab is in a B-class occupancy area.  However, in our new facility, our silane will be behind a 2 hr firewall in a special gas room, attached to the single-story fab wing and 50 yards from (but still attached to) the multi-story research tower.  We are looking for more robust system-level solutions limiting unnecessary evacuation of the research tower in our new facility.

Approaches: Aside from procedural approaches like "Don't use expired cylinders", and "Open dust caps very slowly", has anyone attempted to use alarm logic in their HPM system, such as: "<<If>> the alarm originates in the gas box <<and>> room air sensor is below threshold...  or variations on timing between sense and decay to stage the triggering of different alarm levels??

How do others handle this situation in your respective labs?

Thank you in advance for your inputs!

--Ian

********************************************
Ian R. Harvey, Ph.D.
Associate Director, Utah nanofab
College of Engineering / University of Utah

Research Associate Professor
Department of Mechanical Engineering
Adjunct Associate Professor
Department of Electrical & Computer Engineering
2232 MEB

mail to suite 2110 MEB, 50 S. Central Campus Drive
Salt Lake City, Utah   84112-9011
801/585-6162 (voicemail)
801/581-5676 (lab main number)
www.nanofab.utah.edu<http://www.nanofab.utah.edu>

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