Lifetime analysis of hydraulic directional valves in a contaminated fluid condition based on internal leakage due to wear

Abstract As an important part of the hydraulic system, hydraulic oil pollution will seriously affect the performance and the lifetime of the hydraulic component. Therefore, the pollution of hydraulic oil is crucial to the lifetime of the hydraulic component. In this study, an assessment model with internal leakage flow as a parameter is proposed. A Life assessment hydraulic test system is built. The test is conducted using hydraulic fluids containing test dust. It evaluates the effect of the contaminated fluid on the degradation of the internal leakage performance and reduction of lifetime. The results show that the internal leakage flow of the hydraulic directional valve, classified under ISO 4406 cleanliness level 21/19/17, increased from 6 ml to 68 ml following a test lasting 120 h. It verifies the lifetime based on the internal leakage flow is described by a logarithmic function. The hydraulic directional valve has a pressure loss of 0.8 MPa higher in port A than in port B at an operating pressure of 15 MPa. This paper provides a reference for further study on the effect of wear due to internal leakage failure on lifetime and improvement of service life of hydraulic directional valves.