MIL-DTL-19068B
times by means of the hand pump. After the fifth actuation, the shuttling pressure and leakage
shall then be observed and shall meet the requirements specified in 3.12.4.
4.6.8 Impulse cycling. With a test setup similar to figure 5, the shuttle valve shall be
subjected to a total of 20,000 cycles of operation at a rate of 35 ± 5 cpm. For each cycle, the
directional control valve shall alternately apply a rated pressure of 3,000 psi and then a
backpressure of 75 psi maximum to one inlet port of the shuttle valve. Of the total number of
20,000 cycles, 5,000 shall be performed at high temperature in accordance with the procedure
specified in 4.6.8.1. The remainder of 15,000 cycles shall be performed at intermediate
temperature in accordance with the procedure specified in 4.6.8.2. Surge pressure during the
pressure buildup portion of each cycle shall be 150 ± 5 percent of rated pressure. During this
impulse cycling, internal leakage shall be collected at the unconnected inlet port. The leakage
requirements shall be as specified in 3.12.7.
4.6.8.1 Impulse cycling at high temperature. The valve shall be subjected to 5,000
cycles of impulse at a temperature of 275 °F. Upon completion of these 5,000 cycles, the valve
shall be soaked in hydraulic fluid at a temperature of 275 °F for a period of 1 hour with rated
pressure applied to the valve. The pressure shall then be relieved to approximately 0, and the
valve re-soaked for a period of 1 hour at a temperature of 275 °F. The temperature of the valve
shall then be reduced to a range of 70 to 120 °F and conduct the acceptance test leakage and fluid
shuttling as specified in 4.7.1.3. The temperature of the test setup shall then be lowered to
-65 °F and repeat the test as specified in 4.7.1.3. Both tests shall meet the requirements specified
in 3.12.6.1 and 3.12.7.1 respectively.
4.6.8.2 Impulse cycling at intermediate temperatures. The valve shall then be subjected
to 15,000 cycles of impulse at a temperature of 225 °F. Upon completion of the 15,000 cycles,
conduct the high temperature functioning test as specified in 4.6.7.3 at a temperature of 225 °F.
Reduce the test setup temperature to a range of 70 to 120 °F and stabilize the fluid temperature at
100 °F. Reconduct the test as specified in 4.7.1.3. Both tests shall meet the requirements
specified in 3.12.7.1 and 3.12.7.2 respectively.
TABLE II. Maximum pressure drop.
Valve size
Tube size
Rated flow
Pressure drop
(Dash No)
(inch)
GPM (min)
PSI (max)
-4
.250
1.20
10
-6
.375
3.50
10
-8
.500
6.00
10
-10
.625
10.50
10
10
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