The protection of sub‐sea pipelines operating at elevated temperatures Available to Purchase

An extensive investigation simulating the behaviour of coal tar protective systems on steel pipelines under concrete weight coatings has been carried out. In particular the study has been made of the behaviour of synthetic primer/high temperature coal tar enamel with glass reinforcement under the stresses caused by expansion of the steel pipe within its concrete weight coating. The possibility of shearing of the sacrificial anodes has been given special consideration. At high oil temperatures there tends to be an initial creep of the pipe which gradually ceases within 1/2 weeks, but the total movement amounts merely to a few millimeters. This has been found to apply up to temperatures in excess of 100°C. In order to establish this conclusion, laboratory studies were carried out by three different techniques and the effects evaluated. At elevated temperatures some coal tar oils pass from the enamel to the concrete, resulting in an increase in softening point of the coal tar enamel of up to 20°C. The resistance to creep of the enamel is thus greatly increased while the integrity of the corrosion protective coating is maintained. The conclusion that the coal tar enamel system provides a fully reliable protection at the highest submarine oil temperatures is borne out in experience. A North Sea line has been operating satisfactorily at 113°C, for the last four years.