[labnetwork] chiller water

[Stephen CS Howe]

Dear John,

I have been involved in installing cooling water systems to mass
spectrometers when I was an install and field-support engineer. The
cooling water was needed to cool diffusion pumps, power supplies and
some magnetic coils that carried high currents, so the high temperature
was between 30-100 celcius, which I guess was creating a good
environment for alghe. I had the opportunity to see a lot of different
installs, and we often got a buildup of organic gunge that blocked
cartridge filters and small-diameter (1/4 inch ID ) cooling pipes in the
worst cases. The effect of transparent pipes was really very noticeable
so I strongly recommend black pipes or pipe lagging, even though that
means you can't physically see the water flow. The only alternative is a
chemical based anti-alghe treatment, but you have to be very careful
with the pH which can have a bad effect at temperature on the insides of
copper pipes, pumps etc. if you get it wrong....


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 Sun, 2011-10-16 at 08:03 -0700, John Shott wrote:
> Stephen:
> 
> Good point ... in the past we've often used translucent Polyflo tubing
> to hook up tools because it's cheap and almost universally available.
> I agree that that creates an additional likelihood of creating algae.
> Over the long haul, it's also almost guaranteed to get brittle and
> break at some point as well.  I think that we now use Parker PushLok
> hose by default with different colors for supply and return ... but
> there are lots of opaque and better quality hose choices than
> translucent Polyflo.
> 
> Additionally, even though it adds a bit of clear material, we've
> learned the hard way that having a readily visible variable-area flow
> meter provides and easy way to monitor gradual flow degradation.  The
> initial cost of these flow meters ... and they aren't that
> expensive ... pays for itself the first time you catch a reduced flow
> condition in the early phases rather than waiting for a serious
> cooling flow problem.
> 
> Thanks,
> 
> John
> 
> 
> Stephen CS Howe wrote: 
> > 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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> > 
> >   
>