TECHNOLOGY FOCUS

CENTRAL SYSTEMS -  PART 8

COOLANT MAINTENANCE - HOW SELECTIVE IS DEPLETION?

by Dom Ruggeri

MARCH 2003:

I have always said that the day this business of metalworking fluids stops amazing me I’ll retire, because then I have seen everything. Well I am still around so I guess there is still more for me to see. Like the time I was working for a large formulating house, a customer was using one of our fluids, and in my opinion this particular fluid was not well formulated. However, I was the new kid on the block so what did I know?

This particular customer used this fluid for about 3 years and never complained. All at once it seemed like the floodgates opened and there was a complaint with every shipment. It appeared that the coolant worked for a time, and then tool life began to fade and finishes went to pot. Whenever they added fresh make up coolant, everything went back to normal for a time, then the cycle began again. The Fluid Analysis Group and I analyzed at least a sample a day from this account to no avail. There was nothing wrong with this fluid according to our standard tests.

It was very odd that a product that ran trouble free for many years would begin to cause a ton of trouble. Certainly, a customer visit was necessary, but I was too new to go, so a more senior chemist was sent. As always, the same battery of tests was run at the customer’s site and once again the same results were obtained. When the chemist returned there were the usual battery of meetings and of course his field trip report that said nothing, but was treated like the gospel nonetheless. What could possibly be going wrong? Was it the customer’s system?

Early in my career, I learned that before you go to a customer and tell them they created their own problem, you better be 200 percent right and you better have at least 10 people that agree with you. One of those people had better be the president of the company where you are currently working. Be that as it may, I was not convinced that this was the customer’s problem. I began my own investigation.

In this type of investigation, the best place to begin is the formulation. This one was fairly simple:

Carrier, Base oil-Napthenic
Emulsifier, Sulfonate, Surfactant
Lube additives, Ester/ Amide
Corrosion Preventative, Amine/Borate
Preservative, Grotan/ Omadine

Nothing made sense until I noticed the ester; this particular ester was oil soluble. As we remember from our P-Chem. class (we all aced that one) hydrolysis of esters under basic conditions is not favored, but it can happen. I set up samples in our recirculation systems and began measuring the acidity and alkalinity of the coolant emulsion. It was impossible but the ester was hydrolyzing. The increase in acidity and decrease in alkalinity proved this initially.

On to phase two. I began to determine the rate of degradation of the ester. I accomplished this by running dried samples of emulsion in an IR spectrophotometer. I did this before the days of FTIR so I actually had to measure peak heights using absorbance paper and calculate the ester concentration based on standards I ran previously. Fortunately the results worked out to be a straight line. The IR proved beyond any doubt that the ester was degrading. Since the ester was not water-soluble, this was highly unlikely. However, there it was with supporting data. Upper management began in investigation and found that the purchasing group had switched suppliers of one raw material used in the manufacture of this ester. They did not check with the lab as the supplier in question showed that it was the same material. Therefore, the labs need not be involved. Of course, this policy was quickly changed.

Selective depletion. This phenomenon has plagued the metalworking industry for many years between everyday use of the fluid and drag out. If the system is not maintained properly, a real disaster can occur. In this article, I spoke of an investigation which eventually proved selective depletion. There is an easier way:

1. Coolant Control:
Run the coolant control tests as your supplier recommends, in the long run it will pay huge dividends.

2. Keep and Maintain Good Records:
It’s one thing to run the control as your supplier recommends, but if you do not keep good records of the results how can you identify and troubleshoot a problem should one occur. The quicker a problem is identified and resolved the shorter the downtime and fewer scrap parts are produced.

3. Analyze the Data You're Generating:
You can have excellent records but if you’re not using them to control your system they are just numbers on a piece of paper. Many times a potential problem is staring you in the face but if the records are not reviewed you will not find it until it is a large expensive problem.

4. Act; do not React:
Should your data look suspicious contact your coolant supplier quickly that is the surest way to keep small blips in your data from becoming major expensive catastrophes

Until next month thanks for reading METALWORKING FLUID MAGAZINE.  If you have any questions, please feel free to e-mail me at the magazine.

Good Luck
Dom