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