Why Are We Using So Much Acid?

I was asked this question by the plant engineer at a plant that manufactured mufflers and tailpipes in 1984.

This plant had a number of welding machines that used cooling tower water which was used to cool the welding tips. The plant had been running for many years with the same water treatment company using a non-acid treatment program but for some mysterious reason, they were operating the system at 1.5 cycles of concentration. I mistakenly assumed that the reason for the low cycles was because of the high LSI caused by the high alkalinity (250 ppm) in the makeup water. I sold the account on water and chemical savings by operating the system at 4 cycles of concentration using sulfuric acid for pH control.

About a month after we started up the new program, I noticed the acid usage was considerably higher than the theoretical amount needed. The problem was that cycles were only 2.0 and I told the engineer that the system was losing water somewhere which caused higher inhibitor and acid usage.

The engineer checked the blowdown line to make sure there was no bleed through when the blowdown valve was closed, checked the cooling tower on the roof to make sure there was no excessive drift or tower overflow. He also went around to check the some of the individual welding machines for leaks. His inspection proved there were no losses at any of these locations.

He called me and was naturally irate and tired (this was a large plant) because he had spent nearly 4 hours trying to find the leak(s). He told me that he wanted me to come in Saturday and walk the plant to inspect the machines that he missed during his inspection. I arrived early Saturday morning and was given a layout drawing of the machine locations and set about checking the machines omitted during his inspection. I found no leaks at any of the other machines. He was not pleased when I told him I could find no other leaks.

I asked him if he would mind if I could check the machines he previously inspected. He said. “Be my guest since you do not believe me.” I knew then I had lost credibility with him and had better come up with the answer to the system water loss. To my dismay, I found no leaks.

He escorted me to the front of the plant. As we neared the plant entrance, I saw two machines that were not on the layout drawing. I asked him why they were not on the drawing and was told that these were machines used by the New Product Development Department to determine the manufacturing method required prior to a full production run. He said these machines were rarely used and the cooling water was supposed to be shutoff when the machines were idle. I asked permission to inspect them and sure enough, both machines had water flowing through them however the discharge hose from the welder tips was going to a floor drain! I pulled the hoses out of the drain and timed the flow into a 5 gallon bucket. The water losses were equivalent to the amount of water that was preventing the tower from achieving 4 cycles of concentration.

Moral of the story. Be completely familiar with the pieces of equipment and location in the plant. Layout drawings should be requested during a plant survey however they should not be accepted as 100% accurate. As we found out, 2 new machines were installed after the original layout drawing was made and was not updated to show the additional equipment.

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