Identification Technology Of High Risk Parts Of Micro Leakage Of Pressure Equipment And Pipeline

Pressure piping is widely used in chemical production process.Under the complex pipeline load,once the pressure pipeline conveying hazardous media leaks or breaks,it may cause major accidents such as explosion,poisoning and so on.Usually,micro leakage occurs in the process of structure from reliable bearing to unreliable bearing.Therefore,it is necessary to identify and monitor the high-risk parts of micro-leakage in pressure equipment and pipelines.High-risk parts of micro-leakage include the part of local wall-thinning defect caused by erosion and wear of the fluid containing particles and the part of micro-cracks at the root of cylinder nozzle.At present,the research on the identification and prediction of high-risk parts of micro-leakage is not in-depth,and the risk of micro-leakage cannot be accurately evaluated.In this paper,the finite element method is used to study the risk of micro leakage in the pipe with local wall-thinning defects and the root of cylinder nozzle with micro-cracks.For straight and bent pipes with local wall-thinning defect caused by particle-containing fluid erosion,the finite element analysis method is used to calculate the limit load of the pipe with local wall-thinning defect under internal pressure,bending moment,torque moment,axial force and their combinations.The limit load empirical equations of the pipe with local wall-thinning defect under single load and complex loads are fitted.According to the default pipeline load on equipment nozzles,the influences of torque and axial force on the load bearing capacity of the pipe with local wall-thinning defects are quantitatively analyzed.Based on the limit load analysis,the risk assessment system of micro leakage part of pipeline with local wall-thinning defect is established.Based on the water sand system,the variation law of erosion wear area and depth of pipeline is analyzed by CFD and dynamic grid method and the equivalent local wall-thinning range and depth corresponding to the limit load of the actual thinning morphology are determined.The results show that the maximum erosion wear depth is the maximum erosion wear depth and the area of the maximum erosion wear depth of 24%is the local wall-thinning area.On this basis,the variation of erosion thinning range and maximum erosion depth with time are obtained to evaluate the risk of pipeline micro-leakage.For the root of cylinder nozzle with micro-cracks,the stress intensity factors of mode I,mode II and mode III at four positions(inner crack at 0°position,inner crack at 90°position,outer crack at 0°position and outer crack at 90°)under internal pressure,bending moment,torque and axial force are calculated by finite element analysis.The empirical equations between stress intensity factor with internal pressure,pipe load,crack defect size,cylinder size and nozzle size are fitted.Considering the material properties and pipe system load,the Risk assessment system of micro-leakage at the root of cylinder nozzle with crack defects is constructed according to the ratio of equivalent stress intensity factor and material fracture toughness K_r is close to 1.0.