Abstract
Mechanical seal is a kind of shaft sealing equipment. Face wear is one of the main causes of mechanical seal failure. Mechanical seal condition is also related to the reduction of energy consumption and carbon emission. Therefore, we need to detect the centrifugal pump seal condition. At present, vibration signal is a common method for fault monitoring and diagnosis of centrifugal pump. In this paper, the vibration signal under the condition of damaged centrifugal pump seal is measured by studying the characteristics of vibration signal after the end face damage of centrifugal pump. Statistical indicators such as RMS and kurtosis were taken to analyze the average energy and shock wave energy of vibration signal. The time-frequency characteristics of vibration signal are analyzed by frequency spectrum. The results show that there are a large extent variation of vibration amplitude in the direction of base and axis and a weak variation of vibration amplitude in the direction of radial and vertical. With the increasing of flow rate, the RMS of vibration signal falls at first, then keeps steady, and mounts at last when the flow rate is over the design flow rate. It can be shown from the time-frequency spectrum that there is a shock wave and pause signals caused by the shock wave, which are reflected by the higher frequency band components of the vibration signal that can provide a reference to the diagnosis of the occurrence of damaged mechanical seal. From the analysis, the energy of vibration signal is related to the running condition, we can find that the occurrence of mechanical seal wear makes the centrifugal pump to produce high-frequency vibration signal, and the axial vibration is the strongest and the instability in the fluid makes the vibration signal produce high amplitude characteristics. Analyzing the vibration signal characteristics of centrifugal pumps with damaged mechanical seal is of great significance to find the mechanical seal failure of the centrifugal pumps and adjust the operating parameters.
Highlights
Centrifugal pump is an important energy conversion and fluid transportation device [1]
Fault diagnosis of rotating machinery plays a significant role in the industrial production and engineering field [3]. e vibration characteristics of centrifugal pump during operation are related to the type, location, and cause of the fault
Damaged mechanical seal; Moving ring (b) mechanical seal selected for the test. e result from the analysis shows that the pump system leaks due to the damage of the machine seal, and the internal flow of the pump is unstable, which leads to the lift and efficiency of the centrifugal pump head decreases, but the shaft power has no obvious change
Summary
Centrifugal pump is an important energy conversion and fluid transportation device [1]. Failure of mechanical seal is one of the common faults of centrifugal pump. It is a common method to monitor and diagnose the fault of centrifugal pump by using vibration signal. Each component may have fault and produce high-frequency vibration, which could be analyzed by vibration signal [4] Unsworth et al [8] analyzed the frequency spectrum of motor current and voltage signal through Fourier transform and realized the fault diagnosis of centrifugal pump seal. Birajdar et al [13] studied the fault diagnosis of impeller damage by means of sound pressure level and vibration spectrum analysis. Is paper mainly studies the vibration characteristics of the centrifugal pump under the normal and damaged conditions of the dynamic ring and the static ring of the mechanical seal. The change in vibration character causes damage in mechanical seal of centrifugal pump, which serves as a reference for understanding the vibration signal of the pump and predicting the degree of damage on the mechanical seal
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