Research And Application Of Vibration State Monitoring Of Pipeline In Pumping Station

Facing the uneven distribution and huge demand of water resources in China,in order to make rational use of water resources,transregional water transfer has become the main method to solve this problem.Therefore,many long-distance water transfer projects have been built in many areas of China.As a key part of water diversion project,the safety and stability of pressure pipeline is particularly important.However,in normal operation,the pipeline structure is inevitably affected by external environment,human factors,hydraulic conditions and other factors,so that it can withstand varying degrees of interference and vibration.At the same time,the coupling vibration between foundation,water flow and pipeline is also an important reason for the vibration of pressure pipeline.Therefore,under the influence of many factors,the vibration characteristics of pipeline have diversity and complexity.The real-time monitoring of pipeline has become an important way to protect the safe operation of the system.The condition monitoring of pipeline structure is based on the pipeline transportation of the Seventh Pumping Station in the second phase of Jingtaichuan Project.The pipeline prototype test data are used to classify and extract the signal characteristics according to the signal characteristics under the three conditions of instantaneous start-up,stable operation and shutdown.The vibration state of pressure piping is analyzed.The research contents are roughly divided into the following:(1)Extraction of vibration characteristic information of pipeline in cascade pumping station.Taking the pressure pipeline of the seventh pumping station of Jingtaichuan Phase II as the research object,the environmental excitation is obtained by switching on and off.The operation of the pipeline is divided into three working conditions: start-up instant,stable operation instant and shutdown instant.Aiming at the complex coupled vibration characteristics of pipeline,the CEEMDAN-SVD combined filtering method is used to pre-process the vibration information of pipeline,eliminate the high frequency white noise and low frequency flow noise,so as to highlight the structural vibration characteristics,effectively avoid the false information interference in the later stage of modal parameter identification,and improve the accuracy and accuracy of identification.(2)Multi point data information fusion.In view of the high similarity in the local location of the structure,the common and real components of the high signal-to-noise ratio vibration signals support each other,and the mean square deviation of the vibration displacement reflects the fluctuation degree of the structure in the balanced position,that is,the variance of the vibration displacement reflects the intensity of the structure vibration.A data-level fusion method based on the variance contribution rate is introduced in order to obtain a set of anti-vibration signals.New data on the overall vibration characteristics of the structure should be obtained.In order to acquire the vibration characteristics of pipeline structures,sensors with different orientations are installed on the surface of the structures.Therefore,the local data information of multi-orientation is synthesized by data fusion of variance contribution rate,and a group of new data reflecting the overall vibration characteristics of the structure is obtained.The data fusion method based on variance contribution rate can dynamically adjust the proportion of all measured data on the basis of traditional data fusion,so that the fusion coefficients of the measured data change with time.It can automatically pick out the prominent information in the signal,and effectively simplify the monitoring process of structural vibration state.(3)Selection of parameters for phase space reconstruction.Phase space reconstruction is an important process in Permutation Entropy(PE)and Recurrence Theory.Its parameters determine the accuracy of the analysis results.In this paper,pseudo-nearest neighbor method and mutual information method are used to select phase space reconstruction parameters,respectively.Pseudo-nearest neighbor method is the most common method in the selection of embedding dimension.When the percentage of pseudo-nearest neighbors suddenly drops to zero,the corresponding dimension is the best embedding dimension Mutual information method determines that the delay time is the optimal delay time when mutual information reaches the minimum for the first time.(4)The vibration state of pipeline is analyzed and monitored.According to the theory of pipeline vibration,combined with the severity of pipeline vibration under various working conditions,based on the theory of permutation entropy method and recursion theory,combined with digital information processing technology to extract signal characteristics,the vibration state of pressure pipeline is analyzed according to signal characteristics.Taking the pressure pipeline of the seventh pumping station of Jingtaichuan Phase II as the research object,the environmental excitation is obtained by switching on and off the machine.The oscillation status of the pipeline structure under each working condition is calculated from three states: the instantaneous start-up,the stable operation and the instantaneous shutdown.The entropy value,recursive graph and recursive quantification index of pipeline vibration signals under different working conditions are compared,which shows the effectiveness of the above methods in pipeline condition monitoring.