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by Dom Ruggeri


As always, just when you think things are going well something always comes along and bites you on the bottom.  We had recently charged a 50,000-gallon central system at a major automotive manufacturer and for about 5 months we had not heard a single word from them.  Quite a feat, especially since every time the system leaked the wrong way they’re usually on the phone to us wanting answers.

As expected, the call finally came.  It seemed the coolant stopped emulsifying.  We asked all the normal questions concerning the water hardness; the concentration; the lot number; has anything changed in their mixing procedures, etc.  At the end of this question and answer session we were no closer to understanding the problem then when the customer first called.  I opted to contact the salesman and the regional manager.  This was a major account and I wanted all my ducks in a row.  I gave the regional manager a list of questions and instructed him that without these answers I could not help the customer.

I got the answers and a fifty-minute homily on how important this customer is and how we better get some answers fast, compliments of the regional manager.  We formulated a strategy that consisted of the following steps:

  1. Request a sample from the customer’s bulk holding tank.
  2. Check the manufacturing specifications of the last 3 batches of coolant sent to that customer.
  3. Check the emulsification properties of the retain samples of coolant in a sample of the customer’s water kept on site for just this purpose.
  4. Pray

When you have been in this business long enough you begin to develop a feel for things.  My hunch was we would find nothing.  I was not disappointed.  Everything checked: retains, bulk samples, even the customer’s blended sample checked out fine.  This was a puzzle to be sure.  I had only one option left go on site and see for myself.

Since it was tough economic times I had to seek approvals from 3 levels of management, a root canal would have been more pleasant.  The trip was approved and I was off.  When I arrived at the customer’s site I was given the plant tour, a rundown on how they maintain the coolant, control concentration, and how often they add make up coolant.  I remembered this customer charged their systems at a concentration of five percent, and added make up at a three percent concentration.  So far all was well.

Experience taught me that no matter how baffled you may be, always be confident and positive with the customer.  Rule two, never let on to the salesman that your baffled because he will tell the customer.  I did another walk through the shop on my own just to clear my head and to see if I missed anything. I  noticed one of the bulletin boards had an article giving kudos to the head maintenance mechanic for bringing in a device to recycle the spent coolant, thus saving the company big money by reducing coolant disposal costs.  The date of the posting was about 2 months ago and now they were having problems.

My investigation uncovered the following:

  1. My customer was centrifuging the coolant and selling the tramp oil for BTU value.  A very good idea.
  2. They were measuring the concentration of the centrifuge effluent with a refractometer.
  3. They were basing a concentrate addition on the refractometer reading.

The water-soluble portion of the coolant was the unknown and as always it came back to haunt them.

To read the above you would think I was against recycling.  Quite the contrary, however, when you recycle a coolant you need to completely understand exactly what you are doing, and how you are doing it.  Many people believe that a coolant can be recycled indefinitely- there is nothing could be further from the truth.  Even the most expensive coolant can only be recycled three times at most, and that depends on the water.  Very hard water on average will hamper any efforts to recycle coolant to the point that the cost savings will never be realized. 

As you recycle and add make up coolant to bring the fluid back to operating conditions, the hardness and the water-soluble portion of the coolant remains in the fluid.  Now if the hardness of the water is 100 ppm or lower, this may not be an immediate problem, but as the hardness and the emulsifier package builds up, and it will, the problems will increase and become more dramatic.  It stands to reason that the harder the make-up water, the quicker these problems will manifest themselves.

A popular method of reclaiming coolant is centrifuging.  This technique will spin out the tramp oil leaving you with clean coolant.  This method works only if the centrifuge is set correctly.  Different types of coolant require different settings and perhaps different equipment.  Your centrifuge supplier or reclaim company can be of critical service here.

A third method and perhaps the most tricky requires splitting the oil phase out of the coolant, selling it for BTU value, and reusing the water.  Once again I urge caution, as the water-soluble portion will remain behind when the oil phase is skimmed off. The emulsifiers and the water hardness will build up until the concentrate cannot emulsify.  Once again, the softer your water the longer this process will take.

Recycling, reclaiming, and reusing all will save you money.  However, for a project of this type to be truly effective you must know the reclaim limits for each coolant.  Until next month, thanks for reading and if you have any questions please feel free to e-mail me at the magazine.

Good Luck