<div dir="ltr"><div><div class="gmail_default" style="font-family:arial,sans-serif">Travis,</div><div class="gmail_default" style="font-family:arial,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,sans-serif">Good morning. Here at the LNF, we have a single exhaust plenum that provides exhaust across roughly 18,000 square feet of cleanroom, and ancillary lab spaces. This exhaust plenum is just a large box that has six +25,000CFM strobic exhaust fans sitting on the top surface. This facility needs five of those six to remain operational, so once a month we stop one, and ramp the standby unit up. That way all of them see some run time. On this plenum module there are several large bleed-in dampers that allow for the regulation of static pressure inside of the plenum (currently 7.5" of static). In addition to the bleed-in dampers, there are isolation dampers under each strobic fan that keep the air from returning through the fan that is currently off. Upstream of the exhaust plenum we have two distinct exhaust systems in the fab. One is for scrubbed exhaust (supporting seven wet scrubbers) and is fabricated from PSP (Poly Shield Pipe - internally teflon coated stainless steel), and the other is for general/heat exhaust, and is fabricated from galvanized ductwork This system has been running since 2007 with only minor hiccups in operational integrity. The intent when we installed this system was to share the redundancy of a single fan across multiple points of need , and to keep all of our "contaminated exhaust air" system negative till it is outside of the building.</div><div class="gmail_default" style="font-family:arial,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,sans-serif">Now with all that background, I must tell you that currently we're running all six fans 24/7. It seems that over time the pneumatic actuators that modulate/isolate the various functions on the plenum have failed, as have some of the damper mechanical assemblies due to their lack of protection from the elements. Later this spring, we will shut down the exhaust system for a couple of days and do our first major overhaul in 18 years, replacing all of the dampers (both bleed-n and isolation) and replacing the pneumatic actuators with a mechanical screw type actuator. I haven't seen the final drawing submittal yet, so I'm not sure if the design has addressed all of the shortcomings the current technology has in regard to isolation from the elements. We're currently modulating the pressure in the plenum manually by blanking off some of the bleed-in openings. It's not a difficult task, just a bit windy up there.</div><div class="gmail_default" style="font-family:arial,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,sans-serif"> I've attached a picture of our rooftop plenum to give you some idea of arrangement, and location.</div><div class="gmail_default" style="font-family:arial,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,sans-serif">If you'd like to take a look at what we have, please feel free to give me a call or stop by. I'd be happy to share what we've learned.</div><br clear="all"></div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div>Dennis<span class="gmail_default" style="font-family:arial,sans-serif"> Schweiger</span></div><div><span class="gmail_default" style="font-family:arial,sans-serif">University of Michigan</span></div><div><span class="gmail_default" style="font-family:arial,sans-serif">Lurie Nanofabrication Facility (LNF)</span></div><div><span class="gmail_default" style="font-family:arial,sans-serif">Ann Arbor, MI</span></div><div> </div><div>734.647.2055 Ofc<br></div></div></div><br></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Tue, Feb 25, 2025 at 9:17 AM Massey, Travis <<a href="mailto:massey21@llnl.gov">massey21@llnl.gov</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg-8740626652466401719">
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<p class="MsoNormal"><span style="font-family:Calibri,sans-serif">Hi all,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:Calibri,sans-serif"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-family:Calibri,sans-serif">LLNL is planning a significant cleanroom expansion, and the question arose whether we
<i>need</i> separate exhaust for hoods and tools/gases, or if they can be combined into a single shared exhaust. Or do you have a single exhaust with 2+ exhaust fans pulling simultaneously, so there’s always
<i>some </i>exhaust air moving if one fan is down? The conventional wisdom around here has its share of holes, so I’m out to learn from the broader nanofab cleanroom community. How are your cleanrooms’ exhaust systems are configured, especially if you’ve
had to go down this cleanroom design rabbit hole?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:Calibri,sans-serif"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-family:Calibri,sans-serif">I’m also broadly open
<i>any</i> other lessons learned regarding provisioning exhaust or other utilities – whatever you feel like sharing. Too much information during the design phase is far better than too little.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:Calibri,sans-serif"><br>
Thanks,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:Calibri,sans-serif">Travis Massey<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:Calibri,sans-serif">Center for Micro and Nano Technology (CMNT)<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:Calibri,sans-serif">Lawrence Livermore National Laboratory (LLNL)<u></u><u></u></span></p>
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