This SAE Recommended Practice defines a procedure, which will aid in assessing the contaminant sensitivity of hydraulic valves. The approach taken defines a test procedure with flexibility for testing valves in a wide range of contamination levels. The user of this procedure must establish the contamination levels for testing. Three levels are suggested which should cover the range for most valve applications. This procedure does not establish the contaminant sensitivity requirements for any valve. The user of this procedure needs to be aware of the system contamination level that the valve will operate in and select test contamination levels significantly higher than the operating level to assess the suitability of the valve. The test procedure permits a valve to be tested without disassembly and therefore permits protection of proprietary design information. This procedure assesses the contamination sensitivity of valves by contaminant lock. The procedure indicates the sensitivity of valves by contaminant lock due to various sizes of contaminants. The test is designed to assess the contaminant sensitivity of valves in tests of relatively short duration. See Appendix A for guidance as to how the tests and their results may be used. The tests are purposely designed to be severe in order to be applicable to a wide range of contaminated environments. The use of valves in many applications and for various purposes results in differing levels of acceptable performance. That is, the same valve may be unacceptable - in relation to operation in a contaminated environment - in one application and be acceptable in another. The user must make that decision based on a review of the expected level of the specific application and the test results obtained.