This test method differentiates the relative stability of hydraulic fluids in the presence of water under the conditions of the test. Hydrolytically unstable hydraulic fluids form acidic and insoluble contaminants which can cause hydraulic system malfunctions due to corrosion, valve sticking, or change in viscosity of the fluid. The degree of correlation between this test method and service performance has not been fully determined.

1.1 This test method covers the determination of the hydrolytic stability of petroleum or synthetic-based hydraulic fluids.

Note 1—Water-based or water-emulsion fluids can be evaluated by this test method, but they are run “as is.” Additional water is not added to the 100-g sample. In these cases, the person requesting the test needs to let the test operator know that water is present.

1.2 The values stated in SI units are to be regarded as the standard. The English units given in parentheses are provided for information only.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific warning statements are given in 3.1, 6.1, 6.3, 6.9 and Annex A1.