An Investigation of a Mass Flow Rate Method for Evaluating the Filterability of Hydraulic Fluids

The ability of the fluid to retain its filterability properties is critical for efficient, reliable machine performance. This is particularly true for biodegradable fluids used in environmentally sensitive areas. In this research, hydraulic fluids and lubricants of various base oil and additive composition were evaluated using a modified version of ISO 13357 that utilizes mass flow rate measurements to assess fluid filterability. A comparison of volumetric and mass flow rate filtration ratios reveals that the use of mass flow rate to determine filterability yields comparable results while improving test repeatability. These findings are the basis of a new ASTM standard to be proposed for the measurement of fluid filterability and compatibility.