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944 CHAPTER 42 1954 Guide cordingly, it is necessary the designers of electric heating installations obtain specific information from the local electric utility company on both existing and anticipated future conditions at the location, before specifying the capacity and voltage for equipment, wiring and controls. BIBLIOGRAPHY Electric House Heating--Load Characteristics and Economics, by W. F. Friend (Proceedings of Midwest Power Conference, April 1951). Electric House Heating, by E. E. Parks (Electrical Engineering, August 1951). Electric House Heating, issued by Rural - Electrification Administration (REA Bulletin 142*1, November 1952). Complete Electric House Heating, by F. A. Compton (Edison Electric Institute Bulletin, May 1950). Experience with Electric Space Heating, by R. H. Giedd (AIEE Conference Paper, January 1953). House Heating Experience, by C. E. Simpson (Electrical World, October 9, 1948). Heating by Electricity in Tennessee Valley Area, by B. H. Martin and T. W. Newberry (Heating and Ventilating, May 1948). Longview House Heating Data, by H. G. Kelsey (Electrical West, September 1945). .Electric Storage Heating Serves New Oregon School, by W. Bruce Morrison, (Heating, Piping and Air Conditioning, June 1949). Electric Space Heating and Resulting System Load Factors, by T. H. Alien and C. D. Anderson, Jr. (AIEE Conference Paper, January 1953.) Electric House Heating Load Characteristics, by R. E. Sinclair (Electrical West, September 1950). House Heating Load Characteristics as They Affect Wiring Costs, by J. B. Cochran (Electrical World, April 12, 1947). Heat Factor Formula to Calculate Electric House Heating, by H. C. Bender (Electrical World, May 12, 1945). Modulating and Load-Limiting Controls for Electric House Heating, by W. F. Friend (Proceedings of American Power Conference, March 1953, also Heating and Ventilating August 1953, p. 82). Progress Report on the Heat Pump, by W. F. Friend (Refrigerating Engineering, January 1951). Methods Developed for Built-In Radiant Heat (Electrical West, December 1948). Performance of Electrical System of Panel Heating with Four Stages of Insulation, by R. J. Lorenzi and J. F. Schreiber (Heating, Piping and Air Conditioning, January 1949). Radiant Heating by Electricity, by L. N. Roberson (Heating and Ventilating, September 1946, p. 89). Low-Voltage High-Current Radiant Heat, by R. S. Tice (Electrical West, December 1947). Applications of Radiant Energy (Lighting Handbook, Illuminating Engineering Society, 1952, Section 18). Radiant Glass Heating Panels (Technical News Bulletin, National Bureau of Standards, May 1953). Radiant Glass Heating Panels by P. R. Achenbach (Heating and Ventilating, January 1953, p. 83). American Standard--Household Automatic Electric Storage-Type Water Heaters, ASA C72.1-1949 (Na tional Electrical Manufacturers Association Publication No. WHj-1949). Federal Specification for Domestic Electric Storage Water Heaters, W-H-196, amended May 1949. Application of Electric Water Heaters to Domestic Service, by C. G. Hillier (Heating, Piping and Air Conditioning, November 1946). Industrial Electric Resistance Heating, by Lee P. Hynes (American Institute of Electrical Engineers, Paper No. 48-247). , Induction and Dielectric Heating, by Rennard Pinder (Electrical Engineering, February .1947). EEI'NEMA Preferred Voltage Ratings for A-C Systems and Equipment (Edison Electric Institute Publica tion No. R-6, May 1949, also National Electrical Manufacturers AssociationPublication No. 11, May 1949). Standard Handbook for Electrical Engineers (McGraw-Hill Book Co., 1952). CHAPTER 43 CORROSION AND WATER FORMED DEPOSITS, CAUSES AND PREVENTION Definitions, Classification and Characteristics of Water, Causes and Prevention of Scales and Sludges, Causes and Prevention of Slimes, Under-Water Corrosion, Atmospheric Corrosion, Buried.Pipe Lines, Handling Water Treating Chemicals, Legal Regulations THE surfaces of heating and ventilating equipment that are in in timate contact with water sometimes are affected by the chemical characteristics of contacting waters to such an extent that prohibitive amounts of insoluble materials are formed or corrosion ensues at an in sufferable rate. To avoid or to correct such troubles, it is desirable that heating and ventilating engineers have a general appreciation of industrial water chemistry. The'principal purpose of this chapter is to provide those criteria by which the average engineer may judge whether a problem is one that will yield to rather simple remedies, or will require the skill of an experienced water technologist. DEFINITIONS The following definitions for water-formed deposits, corrosion, and closely allied terms have been proposed : Water-Formed Deposits. A water-formed deposit1 is any accumulation of insoluble material derived from water or formed by the reaction of water upon surfaces in contact with water. Deposits formed from or by water in all of its phases may be further classified as scale, sludge, corrosion products, or biological deposits. Scale. Scale1 is a deposit formed from solution directly in place upon a confining surface. It is a deposit which will retain its physical shape when mechanical means are used to remove it from the surface on which it is deposited. Scale, which may or may not adhere to the underlying surface, is usually crystalline and dense, fre quently laminated, and occasionally columnar in structure. . Sludge. Sludge1 is a water-formed sedimentary deposit. It usually does not cohere sufficiently to retain its physical shape when mechanical means are used to remove it from the surface upon which it deposits. Sludge is not always found at the place where it is formed. It may be hard and adherent, and baked to the surface on which it has been deposited. Biological Deposits. Biological deposits1 are water-formed deposits of biological organisms or the products of their life processes. Biological deposits may be mi croscopic in nature, such as slimes, or macroscopic, such, as barnacles or mussels, olimes are usually composed of deposits of a gelatinous or filamentous nature. Corrosion. Corrosion* is destruction of a metal by chemical or electrochemical reaction with its environment. In the corrosion process, the reaction products formed may be soluble or insoluble in the contacting environment. Insoluble cor rosion products may deposit at or near the attacked area, or be carried along and deposited at a considerable distance from the attacked area. Corrosivity. Corrosivity* is the capacity of an environment to bring about de struction of a metal by the process of corrosion. Corrosivity is a property of the environment, but it has no significance until the metal in question is specified. 945