MIL-DTL-19068B
4.6.9 Endurance cycling. With a test setup similar to figure 6, the shuttle valve shall be
subjected to a total of 2,000 cycles of shuttling at a rate of 35 + 5 cpm. Shuttling shall be
accomplished by operating the directional control valve in such manner that it alternately applies
rated pressure to the inlet ports. Surge pressure during the pressure application portion of each
cycle shall be 150 ± 10 percent of rated pressure. The valve shall be subjected to the first 500
cycles of shuttling at a temperature of 275 °F. Upon completion of these cycles, the valve shall
be soaked in hydraulic fluid for 1 hour at a temperature of 275 °F with rated pressure applied to
either inlet. The pressure shall then be relieved, and the valve soaked an additional one hour at
this temperature. The temperature of the test setup shall then be reduced to a range of 70 to
120 °F and the fluid temperature stabilized at 100 °F at which the tests for leakage and shuttling
with fluid (conformance) as specified in 4.7.1.3 shall be met and satisfied. Reduce the
temperature of the fluid to -65°F and repeat the test leakage and shuttling with fluid
(conformance) and satisfy the tests as specified in 4.7.1.3. The shuttle valve shall then be
subjected to 1,500 cycles at a temperature of 225 °F. Upon completion of these cycles, conduct
the test as specified in 4.7.1.3 and meet the leakage specified therein.
4.6.10 Shuttling against a closed line. This test shall be performed within a temperature
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range of 70 to 120 F. The test valve shall be set up as shown on figure 7. With shutoff valves
"B" and "C" closed, and shutoff valve "A" open, flow shall be directed through the flow meter
until the air is thoroughly bled from the system. The shutoff valve "A" shall then be closed, after
which it shall be reversed from the position shown in order to direct flow to the emergency inlet
port on the shuttle valve. Allow five seconds before pressure drop reading is taken. Repeat this
test 20 times. It shall meet the requirements specified in 3.12.9.
4.6.11 Surge flow shuttling. The surge flow test shall be performed within a temperature
range of 70 to 120 °F. The shuttle valve shall be set up for test as shown on figure 7 with shutoff
valves "A", "B", and "C" open. The 4-way valve, however, shall be put in a neutral position to
permit the buildup of 3,000 psi hydraulic pressure in the accumulator. The 4-way valve shall
then be cycled 20 times. At the end of each shuttling operation or half cycle, the 4-way valve
shall be returned to the neutral position to again permit the buildup of 3,000 psi hydraulic
pressure in the accumulator. The valve shall meet the requirements specified in 3.12.10.
4.6.12 Pressure drop. This test shall be performed at a fluid temperature of 100 °F.
Hydraulic pressure sufficient to produce rated flow shall be applied to either of the two inlets;
first in the normal flow direction (from inlet to outlet) and then in the reverse direction, from
outlet to the same inlet port. Repeat this procedure with the opposite inlet. Maintain and
observe the pressure and rate of flow very closely. A manometer, or suitable pressure gages,
connected across the shuttle valve shall be used for accurate measurement of the pressure drop.
Pressure drop in both directions shall be measured and shall meet the requirements specified in
3.12.11.
4.6.13 Burst pressure. This test shall be performed at a fluid temperature of 275 °F.
Any test fluids can be used for this test. With the inlet port plugged, the hydraulic pressure shall
be applied at a rate of approximately 25,000 psi per minute until a pressure of 7,500 psi is
obtained. The valve shall withstand this minimum burst pressure for a period of 2 minutes. The
valve shall meet the requirements specified in 3.12.12.
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