Viscosity Stability and its Importance in Hydraulic Oils
Posted by Hamid Shakouri on 3rd Sep 2024
Viscosity Stability and its Importance in Hydraulic Oils.
Maintaining viscosity stability is a crucial factor for any lubricant, particularly hydraulic oils. Equipment manufacturers (OEMs) suggest specific ISO-grade hydraulic oils, and the hydraulic oil needs to retain its recommended ISO grade throughout its operational lifespan.
The degree of viscosity stability is assessed through shear stability tests, employing three distinct methods:
CEC L45-A-99
ASTM D5621
DIN 51382
CEC L45-A-99 evaluates the shear stability of hydraulic oils by assessing the viscosity loss under a designated load on the fitted tap roller bearing after 20 hours. Many equipment manufacturers favor this test for evaluating the shear stability of hydraulic oils. The viscosity of the oil is measured both before and after the test, allowing for the calculation of the percentage of viscosity loss.
ASTM D5621: An emerging method for assessing shear stability and measuring viscosity loss involves employing a sonic oscillator. In this technique, the hydraulic oil sample undergoes a shearing process lasting 40 minutes, and the percentage change in viscosity is subsequently evaluated after the test.
