How Not to Clean a Closed Loop

When I first began my career in 1976, I was given an account in Evansville, Indiana to service. The customer file I received from my manager had previous service call reports but no information about the system volumes, recirculation rates, metallurgy, temperatures, etc.

This account was a plastics extrusion plant that had a Niagara fluid cooler with a closed loop that cooled small hydraulic oil coolers for the extrusion machines. We were using a patented all organic corrosion inhibitor blend called Drewgard 100 and the feedrate was controlled by a titration test.

One day I visited the plant and was shocked to see the closed loop water looked like tomato soup. Normally it was clear or slightly cloudy white. Hard water makeup was used for the system and there was no meter on the makeup water line. The water sample was obtained from a large concrete sump and was so turbid that it took several minutes to filter it through Whatman #5 filter paper. What bothered me was the total iron in the system was over 50 ppm. When I showed the process engineer the rusty water sample he said, “Oh yeah. I forgot to tell you that we cleaned the system over the weekend and the water is usually very rusty for a few days and then it usually clears up after about a week.” Since I was a rookie and really knew nothing about the system and the treatment history, I accepted the engineer’s response without questioning further and left the plant. On my drive home, I had a very uneasy feeling about what I saw.

I received a phone call from our Regional Industry Manager who lived in Lorain, Ohio asking if he could work with me in two weeks and wanted me to schedule calls on any accounts that were having tough technical problems. This guy had been with the company for 18 years and he really knew how to solve technical problems. Naturally, I scheduled a visit to the Evansville plant. Just before our visit, I received a phone call from the Purchasing Agent who I had never met before. He had recently purchased $ 49,000 worth of new heat exchangers for the closed loop system to replace the old ones that were only 2 years old! He wanted to know what happened. I was shocked and did not know how to respond. I told him that I was bringing in a technical manager and we were going to investigate the problem. Keep in mind that this customer was spending only $ 8,100 per year with my company and the heat exchanger replacement cost would have paid for 6 years of water treatment chemicals.

Before we arrived, I told John (our Regional Industry Manager) about the problem and had no idea about the previous plant history and that the P. A. had requested we meet with him after we talked to the Process Engineer.

Our meeting with the Process Engineer was eye opening. He first told us that they normally acid cleaned the closed loop system once per month and used uninhibited hydrochloric acid. We found out that he dropped the pH down to 2.0 and let the cleaning solution circulate for 24 hours. He then neutralized the acid cleaning solution with lime! Yes, I said lime! He then flushed the system until the water was clear and the rusty water was usually noticed the Monday after production resumed. You should have seen the look on John’s face. He just shook his head and said, “Gene, these guys really need our help.”

We politely told the Process Engineer that his cleaning procedure was actually causing more harm than good. He did not receive this well however John offered to send him a detailed cleaning procedure which would specify the correct cleaning chemicals and amounts. The Process Engineer was OK with this as long as the procedure did not require more time than his current procedure.

We then met with the P.A. and told him we thought the heat exchanger failures may be a result of aggressive cleaning procedures and the Process Engineer was going to follow our new cleaning procedure recommendations. We also explained that we were going to begin monitoring corrosion rates (this should have been done long ago) in the closed loop and fluid cooler systems.

There was a happy ending to this story. We kept the account. Heat exchanger failures were eliminated and cleaning procedures were reduced from monthly to annually.

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