MIL-STD-2193C(SH)
5.3.1.1 Adverse tolerance conditions. The component shall function when assembled with adverse tolerance parts without degradation in component performance or life. Unless otherwise specified in the applicable
component specification, compliance to this requirement shall be made by either mathematical analysis or by testing of minimum and maximum clearance samples.
5.3.1.2 Minimum clearance specimen. 0ne specimen shall be assembled from parts which have been selected to ensure that the clearance with regard to linear and diametrical tolerances between moving and nonmoving members, conducive to malfunctioning at extreme temperatures, will not exceed 110 percent of the minimum clearance. For sliding parts where packing friction will influence the performance of the component, such as pistons operated by spring, the maximum packing friction shall be induced in the test specimen. 0-ring packing glands
shall provide maximum 0-ring squeeze, including the effect of adverse 0-ring cross section tolerance. This specimen shall be marked "MIN".
5.3.1.3 Maximum clearance specimen. The second specimen shall be assembled from parts which have been selected to ensure that the clearance with regard to linear and diametrical tolerances between moving members, conducive to malfunctioning as a result of wear associated with prolonged operation, will be not less than 90 percent of the maximum clearance. This specimen shall be marked "MAX".
5.3.1.4 Tolerance considerations. In machining these specimens, surface finishes shall be no finer than the surface finishes produced on production units. Where friction is not a factor, packing glands may be fabricated to nominal dimensions. Lapped or selectively fitted parts need not be made to adverse limits. In order to fabricate specimens with adverse tolerance, it is permissible to produce one of the mating parts required with the critical clearance outside of drawing tolerances, provided that the clearance, as fabricated, falls within the established design range.
5.3.1.5 Temperature. Unless otherwise specified herein or in the applicable component specification, the tests shall be conducted at a room temperature of 15 to 30 °C (59 to 89 °F).
5.3.1.6 Test fluid and fluid temperature. Unless otherwise specified herein or in the applicable component specification, the fluid used for pressure drop tests shall be in accordance with MIL-PRF-17331 or MIL-PRF-17672,
2135-T-H. Pressure drop and leakage tests shall be conducted with the fluid at 40 °C (104 °F).
5.3.1.7 Immersion. This test shall be conducted on all nonmetallic materials not specifically identified in this standard which may be in contact with the fluid or fluid leakage for which shrinkage or swelling could affect performance. Each material shall be subject to an immersion test in each of the following fluids:
a. Water
b. MIL-PRF-17331 or MIL-PRF-17672, 2135-T-H
c. MIL-H-22072 d. MIL-H-19457
5.3.1.8 Additional testing requirements for material shrinkage. Critical dimensions shall be measured before immersion and after immersion for 7 days at 70±2 °C (158±35.6 °F). Material subject to shrinkage or swelling shall not be used unless additional testing establishes that the shrinkage or swelling does not affect performance or operability. As a minimum, the additional testing shall include subjecting the material in the assembled component to the fluid causing the most adverse effect for a period of 7 days at 70±2 °C (158±35.6 °F) prior to conducting first article or qualification tests. After the immersion at elevated temperature, the equipment shall remain in the fluid at room temperature until just prior to testing. Flushing of the immersion fluid just prior to an operational test will be permitted. The internal parts shall not be exposed to air for any appreciable length of time until operability and performance is verified.
5.3.1.9 Parameters measurement. The measurement of average steady-state pressure for first article/qualification testing shall be in accordance with NFPA T2.12.2. Unless otherwise specified herein or in applicable component specification, the level of accuracy in test parameters measurements for first article/qualification testing shall be in accordance with Class B of NFPA T2.12.10.
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