Design and Assessment of a Test Rig for Hydrodynamic Tests on Hydraulic Fluids

Abstract

The adoption of a new hydraulic fluid or lubricant in a productive process depends on performing tuning tests that require complex systems and often last as long as the normal lifetime of the oil itself. This is an important issue, since there is an intense activity of development of bio-based lubricants, with high biodegradability, intended to replace the conventional mineral ones. Based on this trend, CREA, Italy, developed an Oil Test Rig (OTR) for hydraulic fluids performing heavy work cycles with small oil volumes, with the aim of accelerating the fluid’s aging with respect to what usually occurs, e.g., in agricultural applications. The possibility to control the hydraulic workload and to repeat the work cycles allows the comparative evaluation of fluids by observing their performances and the variations in chemical–physical properties. The OTR acceptance test was carried out using a widespread and reliable mineral fluid (assumed as a reference for future tests) in a 230 h work cycle at two operating temperatures: 50 °C (150 h) and 60 °C (80 h). The applied pressure was 40 MPa and determined a thermal leap of about 20 °C. The OTR maintained constant all functional parameters during the work cycle. It seems to be suitable for comparative tests between bio-based and conventional fluids.