Steel Pipe Cleaning and Coating Plant of the Bureau of Water Works and Supply of Los Angeles

Abstract

In 1930 the Bureau of Water Works and Supply of the City of Los Angeles installed 45,000 feet of steel pipe that had been dipped in asphalt coating. Part of this was handled in a horizontal dipping kettle, with the result that the coating was ribbed and lumpy from draining. Then dipping, after pre-heating, in a vertical kettle was specified, and this produced a very fine appearing finish, smooth and of uniform thickness. During this time observations in the field were indicating that the materials suitable for dipping in a kettle were not as durable as reputed to be, and, especially in wet soil, left much to be desired in protecting the steel from corrosion. Some of our steel tanks were coated on the inside with hard coal tar enamel brushed on hot, the first being done in April, 1929, and many small sections of pipe were coated by hand with such enamel. Tests conducted in our corrosion laboratory confirmed the evidence of our short time observations in the field concerning the relative merits of asphalt and coal tar. We were so convinced of the superiority of coal tar enamel that the 3f mile long 80to 94-inch Bouquet Canyon Reservoir pipe was enameled by brushing by hand, on the inside. (See Water Works Engineering, June 26, 1935.) The hand application of enamel with a dauber is expensive, leaves a rough surface, and is extremely hard on the workmen, especially in application to the interior of a pipe. Of course, a man cannot enter a pipe smaller than about 24 inches diameter with a bucket of hot enamel and a dauber. Figure 1 shows a hand enameled job, the checkered effect being produced by the quick brushing of each spot. For two or three years the problem of improving the method of applying enamel to large pipes as well as getting it applied to the interior surface of small pipes was studied and experimented with.