1、m 3535789 0025535 T m DEPARTMENT OF THE ARMY Office of the Chief of Engineers DAEN-FEU Washington, DC 20314 Technical Note 7 June 1977 NO. 77-12 Maintenance and Repair Control of Mineral Deposit (Scale) Buildup in Water Pipes 1. the control of mineral deposits in water pipes. Purpose. This technical
2、 note provides general guidance to assist in 2. Applicability. This technical note applies to all facilities engineering elements responsible for real property maintenance activities at installa- tions within the purview of AR 420-10. 3. Discussion. Crystal clear water, excellent for domestic use, m
3、ay contain enough scale-forming minerals to render it harmful, even dangerous, in boilers, heat exchangers, and hot water lines. is most likely to be a continuing problem in geographically inland installa- tions. When any new water source is to be used, suitable precautions should be taken. Scale pr
4、obably will occur at heat transfer surfaces in boiler tubes, heat exchangers, and slow-flow areas, such as cooling tower open decks, hot water heating lines, steam condensate lines, and over-sized pipes. This _I_ mineral buildup It can occur at any installation, however. a. Scale deposits are usuall
5、y composed of calcium, magnesium, iron They consist of hard, crusted material, tightly Advanced scale or aluminum compounds. bonded to the pipe surface. deposits is greatly increased when the water is heated. deposits may completely block the passage of water or heat transfer. has caused dangerous c
6、onditions, such as boiler tube failures. in heat transfer rates is also very costly in terms of energy losses. Rate of precipitation of scale forming mineral This The reduction - . b. Mineral deposits are normally caused by the use of “hard“ water, where it is subjected to heat, evaporation, chlorin
7、ation, and corrosion inhibiting products. They may also result from the natural or the man- made changes to the chemical makeup of even “soft“ water. c. Scale may be detected by several means, including routine visual inspection of water pipes, chemical analyses of makeup water, reduction in heat tr
8、ansfer, gradual decrease in liquid flow or increase in pressure, and observation of mineral flakes or chips deposited on filters or at boiler blowdown drains. - 3683 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3515789 0025536 925 i?. Where scale
9、is a problem, it is important that preventive measures be instituted at an early date. include consideration of the interrelated effects and coordination with the treatments for corrosion and fouling, the other two elements of proper water conditioning. Additionally, any scale treatment should e. Pr
10、evention of scale, where water with high mineral content must be used, is often very difficult or costly. However, scale may be reduced to manageable amounts by one or more of the following means: (1) Chemical treatment of makeup water for closed systems. (2) Ion exchange water softener installation
11、s, (3) Routine, continuous, or automatic blowdown of boilers. (4) Reduction of makeup water by elimination of leaks. (This is the most economical and effective procedure to stop scale buildup in heating systems). f. Factors affecting scale formation are temperature, heat transfer rate, calcium sulfa
12、te, magnesium, silica, alkalinity, and pH. The attached nomograph provides a rapid means for determining the tendency of calcium carbonate to either dissolve in or precipitate from the water. g. Scale prevention should not be attempted on an uncontrolled basis. Each system should be analyzed to dete
13、rmine the optimum approach. chemical analysis of the water used, under normal use conditions, should be performed prior to initiating any control methods. TM5-660, and TM5-650 provide key guidance in this area. A AR 420-46, AR 420-49, FOR THE CHIEF OF ENGINEERS: 1 Incl as DAVID M. CRABTREE Chief, Ut
14、i1 Engr & Ops Division Facilities Engineering 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-= 3535789 0025517 861 W .- 8 c 2 3 c d II II II II II II v o M HARD COPY Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
