Security Research on Preheating Installation of Directly Buried Pipes

Local buckling may happen when directly buried pipes with large diameter, high temperature and pressure adopt cold installation. When preheated installation is operated in cold water or during the cooling process, it will lead to serious accidents such as pipeline rupture, compensator fracture and so on. Based upon the analyzing of conditions such as pipeline pressure resistance, radial stability, local buckling and pipeline tensile fracture, the study worked out minimum wall thickness and the function formula of lowest and highest temperature limitation for preheating under idealized conditions. The correction coefficient of calculation results is proposed with reference to the influence of the possible stress effect generated in construction, pipe characteristics and its defects. An important conclusion is drawn: the preheating temperature is not only related to the heating medium temperature variation, but also related to heating medium pressure, pipeline wall thickness, pipe bedding properties, construction quality, and pipe characteristics, etc. The minimum wall thickness and preheating temperature range corresponding to the wall thickness can be calculated when system temperature and pressure are defined. When preheating temperature is controlled in the temperature range, the heating-supply pipeline is in safe condition; in the meanwhile, a great deal of steel can be saved and preheating consumption can be reduced notably.