REMEDIAL MEASURES OF SCALING IN INDUSTRIAL PIPE-NETWORK SYSTEMS

Abstract

Water is an essential commodity for carrying out various operations in an industry. In the event, the water being used does not satisfy the relevant standards in respect of pH, alkalinity, hardness, total dissolved solids and temperature, some of the scale forming substances present in the water may tend to deposit in the industrial pipe network. Deposition of scale is undesirable since it is asso-ciated with decrease in pressure and discharge in the pipelines. Also since the scale would provide a thermal barrier to the heat transfer, the use of this water may be objectionable for cooling and/or boiler purpose in the industry. In this dissertation, a case study of B.H.E.L., Hardwar was made wherein a total length of 3.5 km of pipeline was reported to have been affected. The magnitude of scaling can be judged from the fact that the diameter of a pipe, carrying hot process water, was reduced from 60 mm to 20 mm in a matter of six months. Experimental work involved analysis of water samples and deposited scale material. The water samples were highly alkaline and were found to be in the scaling range on Langelier's Index. The scale material predomin ntly contained carbonates and hydroxides of calcium and magnesium. Dissolution of scale was tried using hydrochloric acid and chlorine. iii It was noted that as a remedial measure HC1 with an inhibitor could be effectively used whereas treatment of the source water with chlorine will serve as a preventive measure for further scaling. A chemical feed schedule has been suggested for the -industry to overcome the problem. Cost analysis is also presented.