Performance prediction and fault diagnosis of an axial piston pump under different leakage conditions

Abstract

In axial piston pumps (APP), the leakage fault can degrade the pump's per formance and limit its predictability and reliability. As a result, APP condi tion monitoring can be used for preventative maintenance and for selecting the most effective methods to reduce operating costs and improve perfor mance. The Leakage is modelled as laminar flow past the uniform annular gap between the piston and cylinder. With a single faulty cylinder, as the wear (annular gap) increases, the pump's time-mean outlet flow and pres sure remain constant until a critical threshold and then reduce rapidly, lead ing to deterioration in the pump's volumetric efficiency. With the increase in faulty cylinders, this critical threshold shifts to lower magnitudes, and in the limit of more than four faulty cylinders, this threshold saturates to a constant magnitude. In this research, the dynamic signal data show that the increasing severity of leakage and an increasing number of faulty cylinders modulate both the time signature and the amplitude fluctuations of the outlet pressure waveform due to the reduced flow in the discharge cycle. Further, FFT analysis of these dynamic signals and the time-mean value of pressure and flow rate leakage fault diagnosis is presented to classify the pump's condition as either healthy, moderately faulty, or severely faulty. Further, a simulation and mathematical model-based approach are pre sented to simulate the effect of increasing severity of leakage fault (increas ing annular gap) in single and multiple cylinders simultaneously on the pump performance. Moreover, when using an APP, there is a possibility of wear (internal leakage) occurring in multiple pistons-cylinders simultane ously. In the event of multiple pistons failing, inline arrangements are the ideal but not best configuration layout of defective pistons for mitigating peak-to-peak fluctuations during pump discharge. In such faulty pump con ditions, the pressure and flow variation create vibrations, which can cause premature failure of pump components.