Research On The Application Of Operating Deflection Shapes In Centrifugal Pump Fault Diagnosis

Centrifugal pump is widely used in petrochemical industry as the core equipment of fluid transportation.Its working environment is complex.Once a fault occurs,if it is not diagnosed in time,the maintenance time will be prolonged and economic losses will be caused.At present,the single fault diagnosis method such as spectrum analysis is mainly used in the field,which is easy to cause misdiagnosis.The fault diagnosis technology based on modern signal processing technology and artificial intelligence technology is difficult to be understood and used by field technicians because of its complex methods,and many are in the laboratory research stage,and the field application effect is not good.Therefore,it is urgent to study the fault diagnosis method of centrifugal pump which is convenient for practical application.The Operating Deflection Shapes is simple and easy to understand,and has strong applicability.It can achieve accurate positioning of fault sources,but there are few applications in centrifugal pump fault diagnosis.In this paper,by means of Operating Deflection Shapes,the cantilever centrifugal pump is taken as the research object,and its application in centrifugal pump fault diagnosis is studied by combining theoretical research,simulation analysis and experimental verification.The main research contents and conclusions are as follows :Firstly,the research status and trend of Operating Deflection Shapes and centrifugal pump fault diagnosis at home and abroad are expounded.The problems of fault diagnosis method based on modern signal processing technology and artificial intelligence technology are pointed out.Secondly,the analysis method of Operating Deflection Shapes is studied,which shows that it is suitable for the analysis of rotating machinery.Through the study of time / frequency domain test method and ODS calculation method,the advantages and disadvantages of time /frequency domain test method are summarized,the principle of each ODS calculation method is analyzed,and the conclusion that ODS FRF has the strongest anti-noise performance and the best calculation effect is obtained.Thirdly,the fault mechanism of unbalance and misalignment of cantilever centrifugal pump is studied,and 1 frequency doubling and 2 frequency doubling are determined as two fault characteristic frequencies.The cantilever centrifugal pump is abstracted as a cantilever rotor-rolling bearing system model.The finite element model is established by COMSOL software and the dynamic simulation analysis of normal and unbalanced fault conditions is carried out.The accuracy of the model is verified by the above characteristic frequency,which provides a reference model for subsequent analysis.Then,Combined with the structural characteristics of the cantilever rotor-rolling bearing system,a fault diagnosis method based on the combination of time domain ODS test and operating deflection shape frequency response function(ODS FRF)calculation method based on two-point method is proposed.On the basis of the benchmark model,two kinds of rotor unbalance,coupling horizontal misalignment,drive end bearing horizontal misalignment and non-drive end bearing horizontal misalignment faults with different fault degrees are set respectively.COMSOL software is used for simulation analysis.According to the two-point method time domain ODS test method,the vibration acceleration response signals at the two bearings are obtained,and the ODS FRF is calculated and the frequency domain ODS analysis is carried out.The results show that the operating deflection morphological characteristics of the same fault are consistent under different degrees,and the operating deflection morphological characteristics of each fault and the phase difference characteristics of the unbalanced fault are summarized.The phase difference in the horizontal direction of the bearings at both ends is about 180 °,and the phase difference in the vertical direction is about 140 °.Taking the experimental device of cantilever rotor-rolling bearing as the research object,the fault diagnosis of horizontal misalignment and compound unbalance fault of non-drive end bearing based on ODS FRF is studied respectively.Through the operating deflection shape method,the above two kinds of faults are accurately diagnosed,and the effectiveness of this method is verified.Finally,The ODS FRF based Operating Deflection Shapes was used to diagnose the abnormal vibration of a cantilever centrifugal pump in a petrochemical company.According to the operating deformation characteristics of 1 and 2 times frequency,the centrifugal pump and its basic faults were excluded.Finally,it was determined that the filter blockage fault was caused by the crystallization of the conveying fluid medium.