Some Aspects of-Water Treatment for Central Heating Systems

Abstract

Problems considered are hardness and scale formation and the occurrence of noise in central heating systems, and methods of corrosion inhibition. CaCO³ formation is usually not on a large enough scale to cause trouble, although small amounts may be deposited at specific points and lead to failure. The use of sequestrants as scale controllers may produce unwanted sludge, and suitable threshold treatment reagents are not yet commercially available.

Mechanical noise problems are usually solved by venting air from the system, and the use of additives such as Calgon may prevent scale formation and reduce noise.

Criteria for corrosion control are listed, and the merits of phosphate, silicate, borate and benzoate inhibitors are compared, and it is concluded that benzoate/nitrite systems are the most suitable.