MIL-DTL-19068B
4.4.2 Minimum and maximum clearance analysis. The analysis shall be conducted on
two different designs, one to the minimum clearances and the other to the maximum clearances.
o
Conduct the analysis with temperature excursions from room temperature to -65 F and from the
room temperature to the highest temperature. The analysis shall show forces on all internal
components due to thermal expansion and contraction, material property changes and any other
factors caused by temperature changes. The analysis report shall include details of any friction
or possible binding which might inhibit the valve from functioning over the extremes of
temperature. The analysis shall clearly show detail of the design and manufacturing tolerances
that are being analyzed.
4.4.3 Test fluid. Unless specified by the acquiring activity (see 6.2), test fluid shall be
hydraulic oil in accordance with MIL-PRF-5606, MIL-PRF-83282, or MIL-PRF-87257.
4.5 Conformance inspection. Conformance inspection shall include the acceptance tests
as specified in 4.7 and extreme temperature functioning tests as specified in 4.6.7.
4.6 First article method of inspections.
4.6.1 Examination of product. The specimens submitted for the first article tests
shall be carefully examined for any visible defects, and to determine conformance with all the
requirements of this specification and specification sheets. The dry weight of the assembled
valve shall be recorded.
4.6.2 Fluid immersion. Test shuttle valves shall be immersed continuously in hydraulic
fluid for a period of 72 hours at a fluid temperature of 275 °F prior to conducting the remainder
of the first article tests specified herein. All internal parts and external surfaces of the valve shall
be in contact with the fluid during this immersion. After the 72-hour soak period, the shuttle
valve shall remain in the fluid at room temperature until ready for test. It shall not be exposed to
air internally for any appreciable length of time during the test. The valve shall meet the
requirements specified in 3.12.1.
4.6.3 Proof pressure. The proof pressure test shall be performed at a fluid temperature of
275 °F. A proof pressure of 4,500 psi shall be applied twice to each inlet port with the opposite
inlet port open to the atmosphere. Pressure shall be held for 2 minutes each time, and the valve
shuttle shall be actuated between applications of pressure. The valve shall meet the requirements
specified in 3.12.2.
4.6.4 Washout. This washout test shall be performed within a fluid temperature range of
70 to 120 °F using test setup similar to figure 1. A high-surge flow from an accumulator shall be
directed twice alternately to one inlet port in the normal flow direction, and then to the outlet port
in the reverse flow direction. Sufficient time shall elapse between reversals of flow direction to
allow the accumulator pressure to rise to a rated pressure. The accumulator shall have a
volumetric capacity equal to 400 cubic inches and shall have a preload charge of 1,000 psi. The
pump shall deliver the test fluid at rated flow at rated pressure as specified in table II. The
pressure line between the accumulator and the shuttle valve shall be not greater than 4 feet in
length, and the return line from the directional control valve to the reservoir shall be not greater
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