Structural Failure Analysis And Structural Optimization Of Centrifugal Pump In Large Refineries

Centrifugal pump is the most important oil and water conveyance equipment in oil refinery,and its safety guarantee is particularly important.A large number of corrosive components in oil have a great impact on the structure and transportation of centrifugal pumps,leading to changes in the structural stress of some centrifugal pumps,the rise of vibration value,leakage of seals,breaking the safety critical point,causing accidents.Based on the above problems,for the vibration rectification project of on-site centrifugal pump starting,this paper explored the main causes of excessive vibration of centrifugal pump from the aspects of pipeline layout,overall structure of centrifugal pump,cavitation influence and structure optimization from the perspective of field practice and theoretical analysis,and put forward the improvement scheme and structure optimization.Taking the centrifugal pump of a chemical enterprise in this project as the research object,the operation state of the centrifugal pump under different working conditions is studied and analyzed to find out the reasons and optimize them.The main contents of the study are as follows:(1)The causes of pump body vibration caused by external factors of centrifugal pump are studied,mainly from the aspect of pump body vibration driven by pipeline vibration.The influence of pipeline pressure pulsation is analyzed to find out the factors causing vibration and calculate the pressure pipeline loss,so as to compensate for the selection of pipeline.The vibration caused by the fluid unstable movement in the pipeline to the pump body is analyzed through the arrangement and stress of the pipeline.In this paper,the influence of the vibration is eliminated by increasing the diameter of the pipeline to stabilize the fluid flow,changing the diameter of the pipeline and increasing the support of the pipeline.(2)Disassemble and inspect the structure of each part of the centrifugal pump system on site to find out the damaged parts,mainly including the motor,shaft,bearing,impeller,pump body itself,etc.Found that motor bearing joint wear,impeller mouth ring is wrong,the leakage of mechanical seal,such as unit operation will cause instability,this paper mainly through to the impeller mouth ring replacement,improve clearance and renewed,to add lubrication motor mouth,tighten the anchor bolts,strengthen the maintenance of motor,increase the auxiliary sealing system to prevent leakage of centrifugal pump,to a certain extent reduce the vibration amplitude of the pump.(3)According to the operating characteristic parameters of the centrifugal pump(mainly cavitation),the static pressure distribution at the outlet is simulated by ANSYS and its dynamic characteristics are analyzed.It is found that under different working conditions,the centrifugal pump speed and operating frequency are in a different position,and its velocity distribution is related to working conditions.When the flow rate in working condition is small,its displacement,velocity and acceleration are inversely proportional to the change in working condition.The smaller the flow rate is,the more obvious the change amplitude is.Combined with field monitoring and simulation,it is concluded that excessively small flow rate(thedesign flow rate is 90m3/h,while the actual flow rate is 20m3/h)and the thickness at the blade edge is 5mm thinner than the design value,which are the main reasons for cavitation.(4)The anti-cavitation performance of the pump body can be improved by changing the blade shape and blade thickening,changing the placement Angle and cutting the outer diameter of the impeller.Combined with the simulation,on the premise of ensure constant impeller assembly size,adopted the grinding blade edge into elliptical,leaf thickening,Angle of attack increases,leaf entrance not face chamfer impeller structure optimization,and the optimization results are run and test on site,found that average effective power and pump efficiency has improved,its vibration data all decreased significantly;After the operation time of the new impeller reaches 72 h,it can be observed that the blade is in good condition and there is no cavitation trace.The pump is in normal operation.