基于平均应力的直埋供热管道预热温度

针对大直径、高温、高压预热安装供热直埋管道,在冷水试运行、降温等过程中被拉断、补偿器被撕裂等问题,提出基于"平均应力温度"的预热温度.从升温压应力等于降温拉应力出发,建立起预热温度函数式,绘出"平均应力温度"随压力和管径的变化曲线,并用于事故管道分析.结果表明:大管径的预热安装温度高,是降温断裂的主要原因.预热温度不仅要考虑循环最高温、循环最低温,还应考虑管道内压力、管径大小及其壁厚等因素."平均应力温度"随内压力和管径的增大而显著降低,而"循环中间温度"与这些因素无关.用"平均应力温度"取代"循环中间温度"来计算各项预热参数,能使预热安装直埋管道的降温拉应力显著减小.

A study of the preheating temperature of directly buried heat-supply pipelines based on average stress

When directly buried pipes with large diameter,high temperature and pressure are installed by preheating,serious accidents such as pipeline rupture,compensator fracture will happen in cold water running or during the cooling process.Based on "Average Stress Temperature",preheating temperature is proposed and its function formula is set up on the condition that the heating compressive stress is equivalent to the cooling tensile stress.The curve of "Average Stress Temperature" changed with pressure and diameter is drawn,which can be used to analyze pipeline accidents.Results show that high preheating temperature of large diameter pipes is the main reason for fracture during cooling.When calculating preheating temperature,not only the minimum and maximum cycle temperature,but also the pressure,the diameter and the wall thickness and so on should be considered.The increase of pipeline pressure and diameter plays an important role in reducing "Average Stress Temperature",but has nothing to do with"Intercycle temperature".When all preheating parameters are calculated by using "Average Stress Temperature" instead of "Intercycle temperature",cooling tensile stress for preheated directly buried pipes can be reduced evidently.