|Conductivity controller for boiler applications|
Controlling the feedwater quality can be accomplished with the addition of controlled amounts of the right chemicals to regulate various aspects of water quality. Another method is to purge, or blowdown, the boiler in a measured fashion that allows fresh feedwater to replace overly contaminated water. Filtration, which I generally deem to include ion exchange, reverse osmosis, and mechanical filtration, is a third method. All deal specifically with a limited scope of contaminates that have an impact on boiler operation and longevity.
Boiler blowdown can be used to limit the amount of total dissolved solids in the boiler drum water. As water boils, the dissolved solids in the water concentrate in the remaining liquid water. Blowdown purges a portion (or all) of this water, allowing the addition of water, presumably treated, with substantially lower total dissolved solids.
Boiler blowdown has an energy cost, since the replacement water must be heated to the design condition. It follows that executing this procedure should be undertaken when necessary, but not more frequently. A conductivity monitor and controller can accomplish properly timed blowdown cycles. The system consists of a conductivity sensor and a control unit that provides all the necessary functionality in a single integrated package. A data sheet is included below for one such unit from Lakewood Instruments.
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