[labnetwork] chiller water

[Stephen CS Howe]

Dear John,

In my experience, the color of the tubes can make quite a difference to
the presence of alghe growths in the lines and filters.
Rather than use an anti-alghe treatment, if you use black or other dark
colored non-transparent tubes, it eliminates a lot of problems.

Of course, that won't help you with corrosion though.

Yours sincerely,

Stephen Howe 
Company Owner
SDI Fabsurplus Group

 +1 830 388 1071 (Mobile)
+39 335 710 7756 (Italy Mobile)
Skype: Stephencshowe

WWW.FABSURPLUS.COM

Contact us now to buy and sell used equipment 
and enjoy the benefits of cost-saving. 


On Sat, 2011-10-15 at 08:57 -0700, John Shott wrote:
> Keith:
> 
> While I'm confident that others will contribute some important
> insights and recommendations to this discussion, let me take an
> initial stab at discussing some of the issues and approaches that we
> have tried.  Note: I don't consider myself an expert in this area, but
> have certainly had to deal with a lot of problems in these areas over
> the years .... both in tools with local chillers and heat exchangers
> and in tools connected to the building-wide process cooling water
> system.
> 
> We've likely had more problems over the years with the building-wide
> system and have tended to go to local chillers and/or heat exchangers
> when we either encounter a corrosion problem or have a resistivity
> requirement that cannot be met by the building-wide system.  That
> said, however, we also have periodically seen problems on our tools
> with local chillers and/or heat exchangers.
> 
> Note:  Just for reference, our building wide system is treated with
> Nalco TRAC107 at a 2000 ppm concentration, a pH of 7.5 to 8.0 but it
> ends up with a pretty low resistivity of about only 2000 ohm-cm (500
> microSiemens/cm) by a closed-loop control system.  We recently had a
> problem due to a failed pH probe that resulted in water with a pH of
> 6-6.5 .... which begins to be bad news for aluminum and mild steel.
> So, even a "professionally managed", closed-loop control system can
> have problems and is an ongoing struggle.
> 
> Back to your local chiller ....
> 
> 1.  I think that it's always good to understand the metals in the
> system .... including parts of the chiller as well as the materials in
> your machine through which the water flows .... to understand how much
> of a galvanic reaction problem you are likely to have.  While we can't
> always control these things, systems that have mixtures of aluminum,
> yellow metals, and mild steel tend to be more problematic.  A lot of
> tool manufacturers seem to include quite a range of metals in contact
> with the water.
> 
> 2. Can you measure the pH of the water in your recirculating tank?  If
> it has gradually drifted away from 7-ish .... particularly if it gets
> below 6.5 or so ... that may help to explain more recent problems.  If
> pH is either or low or high I'd try to fully exchange the distilled
> water.
> 
> 3. Do you have a resistivity requirement .... for example, if this
> chiller is cooling RF supplies, then you need pretty high resistivity
> water.
> 
> What are some other options?
> 
> 1. Analyzing the chemical content of the stuff that you are capturing
> in your filters is often useful to try to determine what is the
> primary corrosion material .... or whether you may be seeing organic
> material due to algae growth.  I believe that the little systems with
> open tanks are more prone to algae problems than truly closed loop
> systems because of ongoing oxygen entrapment in the water.
> 
> 2. Adding a little deionizing cartrigde, resistivity monitor, and
> solenoid so that water can periodically be passed through the
> deionizing cartridge.  I believe that a lot of people will tell you
> that something in the range of 0.5 - 1.0 Mohm-cm is about optimum.
> High enough resistivity to reduce galvanic corrosion, but not so high
> that the DI water corrodes everything in sight.  Note: if you go this
> route, you generally have a second solenoid controlled loop with the
> deionizing cartridge in it in parallel with the main flow loop.  That
> is because you can't typically get 2-3 GPM through a deionizing
> cartridge so you have a bypass flow channel that routes a little bit
> of the flow through the deionizer when you need to increase the
> resistivity.  Plus, you are only shooting for 0.5 - 1.0 MOhm-cm and
> don't want to be routing too much of the flow through a deionizing
> cartridge. I haven't priced this in a while, but I think that you can
> get a cartridge housing, a resistivity controller, and a resistivity
> probe for on the order of $1k.
> 
> 3. There are additives that claim to be able to be added to these
> recirculators to inhibit corrosion with minimum monitoring or precise
> control.  For example, there is some stuff called Optishield (and
> Optishield II and Optishield Plus ....) that you mix in at about a 10%
> concentration with your distilled water.  That is supposed to be good
> for a year and then you empty the lines and refill with a fresh mix.
> I have no personal experience with this stuff .... but maybe someone
> else has and cares to comment.
> 
> 4. We have used 50/50 mixes of DI water an ethylene glycol in a number
> of tools .... particularly if they are going to be cooling to
> temperatures near freezing.  This mix, by itself, doesn't really
> include much in the way of corrosion protection .... and, as I
> understand it, if it is run to too long, can break down into a variety
> of acids that will once again create problems.
> 
> Note: when we've had systems that have gotten significant build up, we
> have used a variety of radiator flush type products ... with a fair
> amount of trepidation .... to try to clear some of the "stuff" out of
> a system.  I'm not particularly proud to admit this ... but desperate
> times call for desperate measures and a machine with a plugged (or
> nearly so) cooling channel is a desperate situation if you can't
> easily disassemble and/or replace cooling channels.
> 
> I fear that my conclusion is that we've tried a lot of things over the
> years and still don't have a particularly good approach that has
> resolved these issues on a permanent basis.  Maybe some or our more
> enlightened colleagues will provide a more comprehensive approach.
> 
> Good luck,
> 
> John
> 
> 
> On 10/14/2011 6:31 PM, Keith Bradshaw wrote: 
> > We have used distilled water in our chillers recirculating tanks.
> > Recently we have suddenly seen the inline filters clogged with
> > corrosion.  We have seen more problems in the last 5 months than we
> > had in the previous 6 years.
> > 
> > Any advice on this?
> > Should we be using an additive?
> > 
> > 
> > cordially,
> > 
> > Keith Bradshaw
> > Garland, Texas
> > 
> > 
> 
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