Risk analysis and control measures of hydrostatic testing in winter for long-distance pipeline

During hydrostatic testing of long-distance pipelines in winter, pipes are often subject to blockage due to freezing or rupture after expansion at low temperature. In order to avoid these high risks and ensure the operation progress in winter and subsequently the safety after commissioning, the freezing time is predicted by modeling calculation as per the thermotechnical principles and based on ambient temperature, geological conditions, pipe parameters, insulation structure and other factors, and the risk possibility is analyzed, so as to provide a theoretical basis for scientifically selecting insulation, protection and control measures. Taking the long-distance pipeline project in Beijing as an example, its possible freezing time in hydrostatic testing is calculated accurately using the thermo-technical model. The results show that, according to the predicted freezing time, such technical measures as ground temperature monitoring, aboveground insulation and bare pipe heating are successfully adopted in different sections (e.g. buried pipelines and overhead bare pipelines) to guarantee the safety and quality.