Scale Formation and Deposits

Common impurities in water may lead to scale or sludge deposits in boilers and cooling towers.

Scale and sludge deposits in boilers and cooling towers impede heat transfer, which leads to higher energy costs and can cause a loss of equipment operation and premature failure. Water is treated for scale and sludge to extract all of the beneficial characteristics of water, while neutralizing the negative effects of impurities in the water. Four examples of easily identifiable impurities are Hardness, Alkalinity, Silica, and Iron.
  • Hardness: Calcium and Magnesium minerals in the water.
  • Alkalinity: Can be combined with hardness to form scale.
  • Silica: Can form tenacious deposits on heat transfer equipment and power generation equipment.
  • Iron: Can form very dense deposits on heat transfer equipment.

The Extreme Costs of Scale

Boiler Example
A 200-horsepower boiler, operating at 100 psig, 24 hours a day, 365 days a year, with clean boiler tubes, burning natural gas costing $7.00/1,000 cubic feet, will have an annual fuel budget of $581,744 for operation.

An eggshell scale deposit (generally defined as 1/32-inch) on the boiler tubes, will cost an additional $23,271 to $69,813 per year to operate, depending on the impurities in the deposit.

Chiller Example
A 500-ton chiller, operating 12 hours a day, 240 days a year, with clean condenser tubes, with an electric cost of $0.08/kilowatt hour, will have an annual energy budget of $86,400.

A 1/64-inch scale deposit on the condenser tubes, will cost an additional $12,960 to $21,600 per year to operate.

Microbiological films can easily double the cost of these figures.

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