ASTM D5621 - Sonic Shear Stability of Hydraulic Fluids
Significance and Use
4.1 This test method was developed using Test Method D2603–91.
4.2 This test method permits the evaluation of shear stability with minimum interference from thermal and oxidative factors that may be present in some applications. It has been found applicable to fluids containing both readily sheared and shear-resistant polymers. Correlation with performance in the case of hydraulic applications has been established.
1.1 This test method covers the evaluation of the shear stability of hydraulic fluids in terms of the final viscosity that results from irradiating a sample of the hydraulic fluid in a sonic oscillator.
1.2 Evidence has been presented that a good correlation exists between the shear degradation that results from sonic oscillation and that obtained in a vane pump test procedure.2
1.3 This test method uses millimetres squared per second (mm2/s), an SI unit, as the unit of viscosity. For information, the equivalent unit, cSt, is shown in parentheses.Extracted, with permission, from ASTM D5621-20 - Sonic Shear Stability of Hydraulic Fluids, copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be purchased from ASTM International, astm.org