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by Dom Ruggeri


As you may know by now, in the early nineties I was working for a medium sized formulating house. I was sent on a routine plant trial. This time, as in the past, I was hoping the trial would be interesting and praying that I wouldn’t be bored stiff. I was meeting a salesman whom I had never worked with. Adding to the anxiety, it was Super Bowl Sunday. Three stress risers on the same day.

I arrived at the hotel just in time to see the fourth quarter of the game. The salesman called about fifteen minutes later. We went out to dinner and he briefed me about the plant and the political situation and questioned me about the coolant we were going to test. The plant was located in the deep south and I must admit that I have always enjoyed my visits to this part of the country. Further, every time I visit, I always learn something new. This trip would be no exception.

The assistant product manager briefed me regarding the laboratory manager at this account. She felt he was an uncooperative southern boy who was out to obstruct the trial, and protect the incumbent supplier. I questioned the salesman at length regarding this point and he had a very different view of the situation. He felt the product manager mishandled the whole situation and delayed the trial. The only thing that I now knew for sure was that was why I was there rather then her. Oh well, par for the course.

The next day we were into the trial. This account had the ability to redirect the coolant flow so that an entire bank of machines could be isolated for a trial. Further, they had a mini system set up to feed coolant to the isolated bank, thus quite accurately simulating what the coolant would see in full operation. So far so good, and now it was time to meet the laboratory manager. We found the lab well lit and to my surprise it was very clean. In the past I had been in some real slop holes. The lab manager sat at his desk surrounded by plant managers and workers. I was introduced and found that all parties present were part of the trial. We discussed the coolant the requirements for success vs. failure, coolant control and microbiological control. The laboratory manager listened to my answers to his questions and the answers to the questions of the other people present. At the end of the meeting everyone left and set about the business of making the coolant work. When I was left alone with the lab manager he explained that they had two fifty thousand gallon systems he controlled, and had never lost one of them to bacteria or fungi (I will explain his procedure later in this article). I listened trying to learn all I could. We toured the systems and I helped him take his daily samples. Finally, after all the samples were taken and both he and I were questioned out, he looked at me and said, "you don’t buy my dumb southern boy act at all do you?" I answered, "Nope." He smiled and said, "you and me are going to get along just fine."

The trial was a complete success and about a year later this gentleman helped me with another project.

The control of bacteria and fungi is by far the most critical parameter in any water extendable metalworking fluid. Microbiological contamination will play havoc with a fluid and eventually cause fluid failure. My friends I speak from many years of experience when we say "the only good bacteria in a metalworking fluid is a dead one." To date I have seen no objectively reviewed scientific data to prove otherwise I would welcome the opportunity to review said data.

The lab manager I mentioned in the above story had an interesting technique for controlling his systems. He developed it using empirical data from his two systems. He controlled the systems using DO (Dissolved Oxygen). This is a relatively inexpensive method since most pH meters today are multimeters and can easily accept a DO probe. Here’s the procedure:

1. Take three 500mL samples from the central system:
One from the clean side
One from the dirty side of the filter
One from a machine sump

2. Measure the dissolved oxygen in each sample. Record the DO
reading for each sample. The DO readings will vary depending on
the agitation of the fluid where the samples were taken.

3. Cover the samples and let them stand for four hours

4. After four hours take another DO reading for each sample. If the
readings in each sample differs from the initial readings by 50% or
more, treat the system with biocide and fungicide. For example:

Sample 1 taken from clean side
Initial DO = 10ppm

Sample 2 taken from machine number X
Initial DO = 15ppm

Sample 3 taken from the dirty side of the filter
Initial DO = 18ppm

After 4 hours standing in a closed container

Sample 1 DO = 4: 60% change

Sample 2 DO = 7: 53% change

Sample 3 DO = 7: 61% change

We better treat this system with a kill dose of biocide and fungicide.

I present this method as one way but hardly the only way to control microbes. I am sure today there is equipment that can give you a count in minutes instead of hours. Whatever test for microbiological contamination you use it is vital for your system’s useful life.

Until next month thanks for reading and if you have any questions please feel free to e-mail me at the magazine.

Good Luck