Research On Monitoring And Locating The Leakage Of Buried Heating Pipelines Based On EMS System

In recent years,with the continuous expansion of China’s central heating system scale,simple and quick direct-buried heating pipelines have been widely used,but the problems of fault warning and detection of direct-buried heating pipes have become more and more prominent.Currently,the commonly used leak detect methods are mostly based on the temperature field,sound and flow rate changes generated when hot water in the heating pipelines has penetrated into the soil layer.When a fault is detected,it will inevitably bring problems such as heat shutdown and high temperature hazards,so it cannot minimize the loss caused by pipelines leakage.EMS(European Monitoring System)systems are gaining traction in the heating sector.Through the alarm lines embedded in the insulation layer of heating pipes,EMS system can monitor the operation of heating networks in real time.EMS system can also be used to monitor the construction quality of pipes patch and the Leak-proofness of outer protective layer.The system uses the working principle of time-domain reflection to obtain the impedance fluctuation between the alarm lines and steel pipes by transmitting pulses to locate the leakage point.Therefore,EMS system is an efficient,accurate and intelligent fault monitoring system,in line with the "intelligent heat supply" industrial development concept.In order to solve the problems existing in practical application of EMS system,this paper starts from the working principle of EMS system,through simulation and experiment,this thesis also studies and analyzes the operation regularity of current engineering application of EMS system,and obtains some characteristic data to guide its practical application.Firstly,this paper analyzes the reasons for the fault of direct-buried heating pipelines,compares the common fault detection methods,analyzes the problems existing in the current detection methods,and summarizes the possible fault conditions in actual application of EMS system.Secondly,based on the properties of polyurethane insulation material,this paper establishes the equations of mass conservation,momentum conservation and energy conservation for the leakage fluid,and uses the methods of continuous medium and finite difference to simulate the leakage of direct-buried heating pipelines.Through two dimensions and three dimensions simulation by using CFD software,obtain the seepage rules in the insulation layer under different leakage conditions.This thesis derives the formula for calculating the resistivity of three-component mixture.Through theoretical calculation and COMSOL simulation,the thesis obtains the relationship between the resistivity of heat pipes insulation layer and the amount of water leak(or immersion)into the insulation layer.To understand the influence rule of the leakage of heating steel pipes on the resistance of insulation layer material can be used as the basis of subsequent experimental research on the subject and give full play to the early warning function of EMS system.This thesis builds the EMS system test bed to artificially create different degrees of leakage conditions.According to the leak fault positioning principle of EMS system,the paper obtains the law and characteristics of reflected waveform in different fault conditions by using time-domain reflectometer,and corrects the factors affecting the accuracy of leakage orientation.