| Source Newsletter 2007 issue 1 |
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Lou-Rich Cuts Water
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| Karl DeWahl, MnTAP chemical engineer, reviewed
project status with MnTAP intern Kyle Page. |
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When the city of Albert Lea increased water and sewer rates by 20 percent, Lou-Rich Inc. was motivated to reduce water use. Lacking the time to take measurements and evaluate opportunities, the contract metal manufacturer requested a MnTAP intern to investigate its four highest water uses.
Phosphatizing
Lou-Rich has a five-stage metal pretreatment system that prepares part surfaces prior to painting. It had been modified to cascade the phosphatizing rinse (stage 4) into the cleaning rinse (stage 2) to reduce water use. The design did not provide enough pressure to return the rinse to the earlier tank. The intern modified the tank to create sufficient pressure; the company was able to shut off the 15 gallon per minute (gpm) fresh water feed to stage 2. The intern found that operators were gauging the flow rate at stage 4 by the position of the ball valve’s handle. Ball valves are on/off and do not indicate flow rate. The intern installed a rotameter which gives visual feedback on how much water is being used. Using guidance from the chemical supplier, the intern experimented to reduce flow in stage 4 from 15 gpm to 2.5 gpm. Conductivity rose but remained well within guidelines.
Non-contact cooling water
The intern observed that the temperature of the cooling water exiting the heat exchangers for the hydraulic presses was not perceptibly higher than when it entered, indicating that excess cooling water was being used. By replacing a solenoid and ball valve with a rotameter to control flow and reducing flow to the hydraulic presses from 24 gpm to 3 gpm, the company cut water use by 2.57 million gallons per year (gpy).
Previously the spot welders had a constant flow of water for cooling the welding tips and power supply. Flow was reduced from 10 to 1 gpm; timers and solenoids were installed to synchronize water flow with use. These changes reduced water use by 1.1 million gpy, saving $2,800.
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