Study On The Hydraulic Transition And Protective Measuures Of The Water Conveyance System Of The Third Stage Pumping Station Of Gao Jiata

When the pump unit is started or shut down,or the power is cut off in an accident,the whole pump station system,including the unit and pipeline,will have a hydraulic transition process,which may cause water hammer seriously.According to statistics,most water hammer accidents are caused by power failure.The harm caused by water hammer accident is inestimable.Therefore,it is necessary to study the transient of unit flow,pressure,rotation speed and torque,as well as the flow and pressure transients of pipeline nodes in the process of pump accident power-off transition,and take reasonable protective measures to ensure the safety of the whole project.In this paper,the possible water hammer hazards caused by the long-distance diversion pipeline pumping station system are studied,and the application of different protective equipment in such projects is analyzed.Based on the characteristic method,with the help of hammer software,taking the three-stage pump station of GAOJIATA in YuLin Yellow River diversion as an example,the hydraulic transition process of emergency power failure of the long-distance diversion pipeline pumping station system is studied.The research conditions include not taking any protective measures and taking different protective measures.This paper focuses on the comparison of hydraulic transition process and protection results of setting surge tank in front of pump station,and studies the necessity of setting surge tank.The main research results are as follows:(1)There is no pressure regulating tower in front of the station:one DN300 micro vent valve with a diameter of 5mm is arranged at the stake No.1+166m of two pipelines respectively By adjusting the closing law of the slow closing valve behind the pump,it can play a role of water hammer protection,and the results meet the requirements.As the system is relatively stable,the maximum positive and negative pressure difference of each valve closing scheme is very small.It is recommended to close 85%in 9s and complete in 60s.After protection,when the water hammer is cut off in case of an accident,the overall pressure rise of the system is not large,and the pressure rise before the station is larger than that after the station(2)Pressure regulating tower is set in front of the station:one bidirectional pressure regulating tower is set in front of the pump station,the other boundary conditions remain unchanged,and the protection results meet the requirements.The results show that the larger the inner diameter of the surge tank is,the more gentle the pressure fluctuation at the pump inlet is(3)Comparison of setting surge tank or not:after setting surge tank,the overall pressure rise of the system is smaller than that without the surge tank,and the difference between the upstream booster lines of the pump station is larger,and the difference between the two lines is small.Whether the surge tank is set or not,the protection results meet the requirements.In general,the pressure fluctuation is relatively gentle and the maximum pressure is reduced after the pressure regulating tower is set.Compared with no surge tank,the fluctuation period of the pump inlet pressure is longer,the amplitude is reduced and the fluctuation becomes slowe,The analysis shows that although the water diversion pipeline is long,as long as the slow closing valve behind the pump is properly closed,it is not necessary to set pressure regulating facilities in front of the station.The research results of this paper can provide reference for the protection of water hammer in this kind of engineering.