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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>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. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>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. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>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. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><p class=MsoNormal><span style='color:#1F497D'>Rizik Michael, PE<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Principal<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Integrated Engineering Services<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Office: +408 261 3500, Ext. 201<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Cell: +408 718 0927<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p></div><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> labnetwork-bounces@mtl.mit.edu [mailto:labnetwork-bounces@mtl.mit.edu] <b>On Behalf Of </b>Grimard, Dennis<br><b>Sent:</b> Wednesday, July 18, 2012 1:37 PM<br><b>To:</b> labnetwork@mtl.mit.edu<br><b>Subject:</b> [labnetwork] H2 Generators<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>All:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>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.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>When considering the costs, you also have to consider the cost of the added detectors … which are not cheap …<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Dennis Grimard, Ph.D.<o:p></o:p></p><p class=MsoNormal>Managing Director<o:p></o:p></p><p class=MsoNormal>Lurie Nanofabrication Facility<o:p></o:p></p><p class=MsoNormal>1246D EECS Blding<o:p></o:p></p><p class=MsoNormal>1301 Beal Avenue<o:p></o:p></p><p class=MsoNormal>Ann Arbor, MI 48109-2122<o:p></o:p></p><p class=MsoNormal>(734) 368-7172 Cell<o:p></o:p></p><p class=MsoNormal><a href="http://www.lnf.umich.edu">http://www.lnf.umich.edu</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>