[labnetwork] MAU Steam Coil

[Collins, Deon]

The conditions of the steam coils are directly affected by sequencing for cold weather and the condition of the steam. Carbonic Acid builds up In many steam systems and corrodes the steam coils from the inside out. While working for large industrial complexes, we saw this in boilers with little or no steam conditioning. If you have good steam quality coming in look at the sequencing of the AHU to ensure the unit properly protects itself when the free stats trip on cold days. We just happen to lose a coil last week with the cold snap. The unit tripped with the outside air dampers stuck open and froze, the steam coil failed to go to 100% heat and the coils froze. We have since looked at the sequencing for the unit. The outside dampers should close, the return air dampers should fully open, steam should go to 100% to protect the chiller coil(is so equipped) and dependent on design the chiller coil may or may not circulate a little water to help keep the unit from freezing up solid.


I will say this, if you have repaired leaks on an individual steam coil multiple times its probably time to replace/recore it.

From: labnetwork <labnetwork-bounces at mtl.mit.edu> On Behalf Of Brian K. Olmsted
Sent: Wednesday, January 4, 2023 2:54 PM
To: Mark Weiler <mweiler at andrew.cmu.edu>
Cc: labnetwork at mtl.mit.edu
Subject: Re: [labnetwork] MAU Steam Coil

We've had to back-flush several of ours because of poor water quality causing blockage issues, but never had to do repairs because of leaks. However, we do have a periodic leak in a steam coil for our main AHU. Facilities management staff repair it by soldering or torch brazing to repair the leak.

Thanks,

Brian
Brian K. Olmsted
Associate Director of Laboratory Operations
University of Minnesota | MNC
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612.626.3287
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On Wed, Jan 4, 2023 at 2:50 PM Mark Weiler <mweiler at andrew.cmu.edu<mailto:mweiler at andrew.cmu.edu>> wrote:
Hello Everyone…

I am writing to ask whether any of you have ever had to replace a steam coil of the Make-up Air Units (MAU’s) of your cleanrooms, and what you, your facilities team, or the product vendor did to solve the problem.  Are there any cost-effective solutions with minimal downtime?  We have completed three repairs of our coil since starting here in 2016…(replacing likely requires a Cleanroom shutdown and the construction of a bypass), and currently have another leak.

I’m really interested to know if this has happened anywhere else… are we an outlier?

Best regards,

Mark



Mark Weiler
Manager, Equipment & Facilities
Bertucci Nanotechnology Laboratory
Eden Hall Nanofabrication Cleanroom
Carnegie Mellon University
P:      412-268-2471
F:      412-268-3497
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