Pressure Surge Analysis of a Test Bench for Biodegradable Hydraulic Oils

A test bench for biodegradable hydraulic oils generates pressure surges by cyclic pressure loading. The parameters of these pressure surges (maximum pressure, amplitude, frequency etc.) are defined by the characteristics of the pressure valve and pipe line system. The response of the hydraulic system was recorded and studied in the case of four test bench modifications by comparing the maximum pressure, maximum pressure increase and the opening time of the pressure valve. The test bench with steel pipe between the hydraulic pump and pressure valve shows the highest maximum pressure increase (4.28 MPa). The opening times of pressure valve were measured for the evaluation of dynamic stability of the test bench. In case of all test bench modifications the opening time of pressure valve did not exceed the calculated limit value. The experiments were also aimed at the response of hydraulic system to three different frequencies (1.5 Hz, 2.5 Hz and 5 Hz) of cyclic pressure loading. Increasing the frequency only minimally increases the maximum pressure during the pressure surge. On the other hand, it increases maximum amplitude after the maximum pressure depending up to frequency of cyclic pressure loading. Fast Fourier Transform (FFT) confirms the facts mention above.