Mysterious Slime Goos Up Coolant Mixing

Complexities of Mixing Coolant

Don Thomas of Abrasives and Tools of New Hampshire called because he was using one of our machinist's mixers, and it was getting a 1/2 inch of concentrate slime all over it. The slime would build up and choke it off so it wouldn't work. They could scrape it all off, but it would appear again.

I told him as much as I could about it - galvanized steel stand pipe, stainless steel check valve, machined bronze casting head, etc. One of the clues was that this unit had been hard-plumbed into their system. Normally this is a good thing, because it means that the mixer won't move, and will get a good supply of high pressure water, necessary to drive the venturi mixing process.

I asked him to check for stray electrical currents transmitted through that pipe. I asked because it is well known that in many plating processes an electrical current passed through a solution will cause the solution to separate. This is normally a desirable thing, such as when we plate steel with nickel or zinc. By dissolving zinc into water, then putting a metal part inside the tank and passing a current through that part, the zinc leaves the water and ends up coating the part. Perhaps the same thing was happening to Don. He said he would check.

Two weeks later, Don leaves a message for me saying that sure enough, when the electricians checked the pipe, they found stray currents! Seems that when they had wired another machine a while ago in the factory, they had accidentally also connected up some plumbing. This subsequently charged the pipes in the factory! Needless to say, they corrected this problem so that the pipes are now properly grounded and protected from the electricity. The mixer and the coolant concentrates are now working without incident, and we have another satisfied customer. This is also another example of how the complexities of coolant maintenance often act as indicators of other problems within the factory.

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