[Sneap] De-Ionized water

[Nicholas Pastore]

Allen,

 At LAC we use a mixture of 50% distilled water and 50% ethylene glycol
without having noticed any ill affect.  Our accelerator has just under 8000
hrs. of operation on it, so that might not be enough run time to draw a
reasonable conclusion compared to other machines.  On the other hand it has
been in service since 1991 with this mixture being in the system the entire
time except for a few weeks 6 to 8 years ago when we had to drain it in
order to replace a bad pump.  During the period of repair we used municipal
water.  I would appreciate any comments on our mixture.

 Fermi National Lab used to use de-ionized water to chill the old 500 GeV
accelerator.  I don't ever recall a problem with the water itself, but I do
remember an instance when a microbe was discovered in the system and it was
attacking the copper piping.  Fortunately it was found before it could cause
any major damage.  Imagine if we would have had to replace 1000 magnets
weighing thirteen tons each.

Nick Pastore

______________________
Nicholas Pastore
Operations Manager
Louisiana Accelerator Center
UL Lafayette
______________________



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Message: 1
Date: Thu, 10 Jan 2008 16:32:55 -0500
From: kerna <allan.kern at wmich.edu>
Subject: [Sneap] De-ionized water
To: sneap at tunl.duke.edu
Message-ID: <00b201c853d0$5ce25960$7f3cda8d at rod0861>
Content-Type: text/plain; charset="us-ascii"

Dear SNEAPer's,

 

A few years ago, after being in service for almost 30 years, a heat
exchanger in our closed loop chilled water system sprung a leak.  Because
the system was woefully energy inefficient, the entire system was replaced
(It was calculated that the energy savings over 5 years would pay for the
system replacement costs which was $125,000).  We were instructed by the
project engineer to add a water treatment solution to the system.

 

Last year a problem developed in our magnet power supplies.  Some of the
brass fittings (where the rubber hoses are attached that route the water
from heat sink to heat sink) began leaking.  After some investigation, we
discovered that the water treatment solution, which contained Sodium
nitrate, was making the water very conductive.  This conductivity was
causing oxidation and reduction to take place between heat sinks in the
power supply where there was a voltage difference.  The fittings were being
etched away wherever current flowed through the water.  After this
discovery, we flushed out all of the water in the system, replacing it with
water from our municipal water source.  Fortunately the damage to the power
supplies could be repaired before this etching phenomena ruined them.  

 

At the last SNEAP Symposium I was talking to Nathan Jones about chilled
water in the equipment that he works with.  He told me that they used
de-ionized water in their equipment.  I found an article on the internet
that talked about advantages and disadvantages regarding using de-ionized
water.  Here is an excerpt from that article that addresses disadvantages:

 

"The disadvantage of de-ionized water is that it is very corrosive to metal.
Since it has no dissolved solids in it, water will seek equilibrium with
whatever it contacts.  So water with a pH of 7.0 can dissolve metal pipe.
Especially yellow metals like copper and brass.  It is also very aggressive
to mild steel or "black" iron, and forget about galvanized pipe.  Piping is
best as PVC or glass."

 

I ask Nathan Jones to review and comment about the article.  His comments
were:

 

"We have a simple go-nogo cell in our system that lights a neon glow lamp as
long as the conductivity is less than 1micro mho / cm. Our system also
contains a sacrificial anode of zinc rod to prevent galvanic corrosion due
to dissimilar metals (the zinc corrodes instead). The only time that I have
heard of one of the sacrificial anodes being attacked was when a customer
let their deionizer run for three years without replacement (supposed to be
replaced annually) and then over-temped the system resulting in the
deionizer dumping all that it had collected back into the system at once.
They had a zero ohm short on everything and gray slime circulating in the
system. The anode was 50% consumed in just a few hours. Luckily for them
they were able to flush the system, install a new deionizer, and return to
operation in just a few days with no damage. I would have volunteered to go
help them recover - it was at Queen's Hospital in Honolulu!"

 

Additionally, I talked to several local companies that are in the water
treatment business.  They hold the same view with regard to the
corrosiveness nature of de-ionized water

 

My question to the SNEAP community is:  What do you do regarding maintenance
of the water in your closed loop chilled water systems.

 

Thank you taking the time to read this very lengthy email.

 

 

Allan Kern

Western Michigan University, Kalamazoo, MI

269-387-4958

 

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