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Rick and the labnetwork community:<br>
<br>
Our facility (Stanford Nanofabrication Facility) uses DI water off
our main DI system for humidity injection/control in the lithography
portion of our cleanroom. While I'm not an authority on that
sub-system, I'll share with you what I know, what I like, and what I
don't like about that system.<br>
<br>
I believe that we have a total of 3 humidifier units that are model
STS Humidifier made by the Dri Steem Company. They use campus-wide
steam to provide the heat source and DI from our lab to be the
source of moisture. We have run two DI supply/return loops (one on
each side of the cleanroom) up into the interstitial space above the
clean room to provide a DI source up there. Those lines are run in
welded 1/2" PVDF lines and have a small valve and 1/4" teflon line
that runs from the distribution system to each humidifier.<br>
<br>
While I don't know the flow through the 1/2" distribution lines, I
suspect that it falls below the generally accepted minimum velocity
specs for high-quality DI distribution. While that is something of
a concern, our DI system is old enough that this is not the only
place where that happens so I don't lose sleep over it.<br>
<br>
What is the flow that we use for steam generation ... that is, how
much is actually extracted from those loops? I don't know, but it's
likely a piddly little amount. Well less than 1/2 GPM, I suspect
...<br>
<br>
As far as returning it to the main system, however, I think that DI
is like chewing gum: it's OK to let someone have some, but you DON'T
want it back when they are done with it. Even at 1/2 GPM, I'd
likely be inclined to dispose of that water rather than try to
re-use it. Certainly, 1/2 GPM can't be converted into steam to
humidify a room, so I'd ask if they can use less so that you don't
feel bad about dumping water down the drain. If their usage is on
the order of 100 sccm per minute or less, you probably can live with
that.<br>
<br>
Whether DI is sufficiently corrosive to cause them problems is
likely their problem (particularly if you aren't getting the
"unused" water back) ... but I'll bet that it is. However, the good
thing about DI is that you won't have problems with "stinky steam"
as long as you avoid bacteria growth. Our system used to use some
form of "treated water" ... and we would periodically be able to
smell the steam. Not a good thing in a lab where you try to train
people to be on the lookout for and sensitive to funny smells.<br>
<br>
<br>
That's at least my initial reaction and relevant experience. I'll
be interested to hear what some of the newer facilities have done in
this area.<br>
<br>
Have a good weekend,<br>
<br>
John<br>
<br>
<br>
<br>
On 9/14/2012 12:19 PM, Morrison, Richard H., Jr. wrote:
<blockquote
cite="mid:D3862732F46DEB4B93B4A7A80614D288106367@mbx2.draper.com"
type="cite">
<p class="MsoNormal">Hi All,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Facilities at my labs want to run 18megohm to
a boiler for humidity control in another lab. I think it should
be RO water as 18Megohm water is very corrosive. Any thoughts on
this?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Their suggested design would draw 0.5gmp from
my supply loop and return it to the DI tank? My belief is that
this return water would be contaminated by the boiler system.
What do you guys think?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Rick<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
</blockquote>
<br>
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