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WATER REVISITED

by Dom Ruggeri

July 2005:

Back in the mid 1990’s, I was working for a small formulating house servicing the silicon wafer market.  We sold a cheap soluble oil used for lapping around the world.  As luck would have it, one day we get a customer complaint from overseas.  As we all know, customers will complain about almost anything.  However, this particular complaint required attention - it seemed the soluble oil was not emulsifying.  Since the complaint originated in India, it was in our best interests to resolve it without bringing the material back to the plant.

My policy back then as now is to request a sample of the suspect material and a sample of the customer’s water.  While waiting for the samples to arrive, just to be safe, I would recheck the retain sample of the suspect batch.  This approach really annoyed the CEO.  In his mind (warped as it was) I was blaming manufacturing before I had all the facts.  As we all know, that was hardly the case, especially since even under ideal storage conditions any emulsifiable product can change upon standing.

The samples arrived on a Friday.  We jumped right on them.  Once again we checked the specs the make sure nothing happened during transit.  From there we began an analysis of the problem.  We checked the customer’s water; nothing was amiss.  We began to check the emulsion using both the retain sample and the customer’s sample in various types of water.  In distilled water the emulsion was fine.  Soft water (<10 ppm) everything checked out.  In 100 ppm water there were still no problems.  Even up to 500 ppm water, the emulsion was fine.  However when we used the customer-supplied water both samples failed to emulsify.  The answer was obvious.  We checked the customer’s water sample and found the hardness was around 850 ppm.  Our records indicated the customer’s water to be at about 250 ppm.  A significant difference.  Further we were told the water came from city services.  Not so.  It came from a well.  The technical staff all agreed; the problem was the customer’s water.  The CEO refused to believe that we had performed the tests three times.  He ran the tests himself just once (lazy SOB) and then grudgingly agreed we might be right.  Oh well.

Water in many cases is 95% of the coolant emulsion.  Whether it is in a central system or a series of single sump machines, the water quality is critical.  However, many times it is ignored and the coolant supplier pays a dear price. 

First and foremost, before any product recommendation is made, analyze a sample of the customer’s water.  This will give you an idea of what type of product to recommend.  So what should you analyze?

1.  Water Hardness:

 Whether you use grains or parts per million this is a critical specification and should not be taken lightly.  Hardness is measured as Calcium Carbonate but remember there is Magnesium Carbonate reported as Calcium.  In natural water the Calcium to Magnesium ratio is 2:1.  Check this ratio - if it is 1:1 the water will not emulsify the same as it would if the ratio were 2:1. 

2.  Chlorides:

The chloride level in the water should be less then 10 ppm.  Any higher and you will get corrosion.  No matter how much corrosion preventive you have in your product you will not be able to effectively stop the chlorides.

3. Water Origin:

What is the source of the water?  This question is almost never asked and yet it is the most important.  City water will be more consistent than well water, which is different from river or lake water.  All of the above must be known before a trial is arranged.  Of course, soft water and RO water are the most consistent sources of water but even they can cause problems.  These potential problems need to be addressed before they become uncontrollable.

As you can see water quality is very important, and the more you know about the customer’s water the easier the first trial will go.  And who knows, we may just get that boring field trial... and that would be good.

As always should you have any questions please feel free to e-mail me in care of the magazine.  Till next month,

Dom