Fracture Research on Preheating Installation of Directly Buried Heating Return Water Pipe with Large Diameter

Abstract

Pipe fracture and compensator tear may happen when directly buried pipes with large diameter, high temperature and pressure adopt preheated installation. Combined with engineering, this paper analyzes theoretically the fracture accident on DN1200 return water pipe during the period of cold operation and analyzes various factors which cause the pipeline fracture, when adopt open ditch electric preheating. By the numerical simulation, the size of influence factors on fracture was obtained, and the conclusion that the tensile stress is greater than the compressive stress was also obtained, where the preheating temperature was defined by means of “intercycle temperature”. It is worth nothing, the buried pipeline will emerge vertical bending under the main impact of soil and transportation loads. The vertical bending is related to pipe base, and the value of curving stress will be very big if the pipe base is mishandled. The coupling effect of curving stress and the temperature tensile stress can lead the pipeline to fracture, such as the disposable compensator place, the pipeline welding place, corners, the pipe wall flaw place and so on. This paper proposed the effective preventive measure which may reduce the occurrence probability of pipeline fracture during temperature drop process.