Design And Repair Test Of Outsourcing Pipe Fittings In Water Supply Pipeline Based On Finite Analysis

With the rapid development of China's economy,the total length of urban water supply pipe network is also growing rapidly.However,the water leakage rate is still high,which not only causes a great waste of water resources and energy,but also has a negative impact on the surrounding environment.Pipeline leakage is mainly due to the low strength of the pipeline in some weak position,and when the pressure is large enough,the weak position is damaged.Therefore,it is necessary to understand the stress and strain distribution characteristics of the weak position,and study the reinforcement method.Firstly,flange interface and localized corrosion zone is selected as typical weak position of the water supply pipe,and then used finite element software ANSYS to simulate these two position.For corrosion defects,the columnar groove defects is used as the simulation object.The stress and strain distributions of different axial length,different circumferential width and different corrosion depth were simulated respectively,The results show that axial length of the defect is the main factor that restrains the remaining strength of the corrosion area,and there is a large difference in the equivalent stress distribution between the defects at different axial lengths.The second significant factor is the corrosion depth,and as for the ring width of the defect,the change in size has little effect on the residual strength around the defect.For flange interface,a simplified flattened steel flange is used as a mock object,the stress distribution of the flange and the bolt,and the deformation characteristics of the gasket were simulated under bolt preload and different water pressures.Simulation results showed that,with the increase of water pressure,bolts and the flange were always at low stress levels,while the deformation of the gasket at different positions was quite different.The minimum deformation was at the bottom of the screw hole,and was close to the inside of the gasket.The maximum deformation was between two screw holes,and at the outer edge of the gasket.Leakage is likely to occur near the screw hole.Based on simulation results,an outsourcing pipe fitting for reinforcement of partial weak position was designed,the concept of "active repair" was put forward,and waterabsorbent rubber was firstly used in the field of water supply pipeline repair.Combined with the relevant test,the study of intelligent tube was carried out.By filling the pipe fitting with absorbent rubber and strain gauge,the two functions that self-repair and loss monitoring were achieved.In order to verify the practical effect of outsourcing pipe fittings,the "static pressurization" and "dynamic water" tests were carried out by using plexiglass pipe and carbon steel pipes.In the "static pressurization" test,the material of outer tube is plexiglass,and the strain sensor was affixed to the inside of the tube ear plate.Leakage signal is detected within a few hours of loss,and the outsourcing pipe fitting could reduce the loss for more than 90% after 72 hours of loss.In the dynamic test,carbon steel was chose as the material of outsourcing tube,and strain sensors were attached to the surface of vulcanized expansion rubber,significant loss signal could be monitored within half an hour,and loss rate declined more than 90% after 72 hours of the leakage.Most of the loss in urban water supply pipe network occurred in the pipeline interface and local weak position,The pipeline leakage warning and pipeline self repair could be repaired by using outsourcing pipe fittings.The loss rate of pipeline can be significantly declined and a large number of water resource can be saved in low cost.