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Practical Energy Savings and New Process Control Options for Parts Washing and Cleaning Processes
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Substantial potential energy savings exist for many parts washing and cleaning processes in use today. Energy usage is frequently the largest single variable cost involved in parts washing and cleaning operations. Several control parameters such as Dynamic Surface Tension, pH, Conductivity, Temperature, Turbidity and Water Softener Pretreatment can be combined using currently available sensors, data acquisition systems and process control technology to maximize production efficiency while minimizing operating process temperatures, product rejects and related operating costs. Most parts washing systems are operated at elevated temperatures to ensure that used cleaning solutions continue to clean parts as long as possible between cleaning solution bath dumps. This is based on the theory that higher temperatures will reduce the viscosity or liquefy greases to speed the removal process. This strategy can be counter productive. Operating at elevated temperatures increases water evaporation and results in substantial energy losses. Increased make up water required to replace water lost to evaporation also results in increased magnesium and calcium salts building up in the cleaning bath. Surfactants that are tied up with calcium and magnesium salts are not available to help clean processed parts. This shortens the cleaning bath life unless soft water or DI water is used for make up water additions. Excess calcium and magnesium salts precipitate to form calcium and magnesium carbonate and sulfate heater tube scaling and substantially reduces heat transfer efficiency. These costs can all be substantially reduced by lowering cleaning bath operating temperatures. Good process control data collection combined with new online process control system capabilities now allow operators to lower operating bath temperatures and replace high temperature QA/QC (Quality Assurance/ Quality Control) cleaning safety factors with real process control of cleaning bath chemistry. Process control using parameters such as Dynamic Surface Tension, Turbidity, and pH when combined with Temperature Control, make up water and cleaning additive Feed Controls make it possible to reduce overall energy, chemical and maintenance costs.
McGinness, M. (2002). Practical Energy Savings and New Process Control Options for Parts Washing and Cleaning Processes. Energy Systems Laboratory (http://esl.tamu.edu). Available electronically from