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|  MIL-V-5527A
(May 1951)
4.5.5 Static Leakage.- Pressure shall be applied to the valve by means of a hand
pump beginning from a value of approximately 50 percent of the pressure setting to 95 per-
cant of the cracking pressure specified in table 1, in increments not exceeding 10 percent
of the pressure setting. At each increment the pressure shall be maintained constatn for
at least 8 minutes. Time shall not be considered "in" or leakage noted until the beginning
of the third minute after the pressure required by each increment has been applied. The
leakage rate, as noted during the final 6 minutes of each test shall not exceed the rate
of 0.5 cc (approximately 10 drops) per hour. Continue to increase the pressure in suitable
increments until the cracking pressure is determined. For inspection leakage tests, the
procedure noted above may be performed only at a pressure equal to percent of the
cracking pressure. A typical installation for the Static Leakage is indicaated in
figure 2.
4.5.6 Dynamic Leakage and Flow.- Pressure shall be applied to the valve by means of
a power-driven pump, beginning from a value of approximately 50 percent of the pressure
setting to 95 percent of the cracking pressure specified in table I in increments not
exceeding 10 percent of the pressure setting. At each increment, pressure shall be main-
tained constant for 3 minutes with the pump operating continuously. The internal leakage
in the third minute shall be noted and shall be considered the rate of internal leakage.
Following these tests, pressure shall be increased in suitable increments, until cracking
pressure and pressure at rated flow are determined. Flow through the valve shall then be
reduced in suitable increments until the reseating pressure is determined. The pressure
and rate of flow at each increment shall be recorded. The cracking and reseating pres-
sures shall not be below the values listed in table If and the valve shall reseat within
2 minutes after reseating pressure is reached. Pressure shall then be reduced in incre-
ments not exceeding 10 percent of the pressure setting to a value of approximately 50
percent of the valve setting. By-passing of fluid at any pressure below the dynamic-
cracking pressure during increasing pressure or at any pressure below the reseating Pres
sure during decreasing pressure shall not exceed 0.5 cc (approximately 10 drops) per
minute. There shall be no external leakage or chatter duringgg these test. If this test
is used for Inspection test purposes, it may be performed only at a pressure equal to
95 percent of the cracking pressure. A typical set-up for this test is shown on figure 2.
4.5.7 Extreme Temperature Operation.- Extreme temperature tests shall be conducted
on valve (or valves) assembled with parts to the most adverse tolerances conducive to
binding at the temperature tested.
4.5.7.1 Low Temperature and Rapid Warm-Up.- The valve shall be held at a tempera-
0
ture not warmer than -54C (-65 F) for at least 24 hours. At the enc of this period and
O
with fluid at -65 F, the static cracking and reseating pressures shall be determined.
The power-driven pump shall then be started, and pressure obtained at rated flow} through
the valve, shall be recorded. The valvues obtained under the above conditions shall vary, shall be recorded.
not more than +10 percent or -5 percent from those obtained at normal temperature. The
valve shall then be allowed to warm up rapidly and a minimum of five checks for static
cracking pressure, and reseating pressure shall be conducted at approximately equal inter-
vals before the valve warms up to room temperature. The static cracking and reseat
pressures shall not vary more than +10 percent or -5 percent from the values obtained at
room temperature. There shall be non evidence of external leakage or chatter during these
tests l
4.5.7.2 High Temperature Operation.- The valve and hydraulic fluid shall be
subjected to a minimum temperature of 71C (160F) for a minimum period of 6 hours. The
test for Dynamic Leakage and Flow shall then be conducted at this temperature. Operation
shall be within the limits specified for dynamic leakage and flow at normal temperature*
4.5.8 Endurance.- A typical set-up for the Endurance test is shown on figure 3.
The Endurance test shall consist of opening the valve to produce rated flow of the maximum
pressure setting specified in table I, and closing the valve under a reduction of pres-
sure to 60 percent, or less of this pressure setting, for 10,000 cycles. The rate of cycling
shall be between 5 and 35 cycles per minute. After completion of the life cycling and
with the valve setting unchanged, static and dynamic leakage shall be determined. Static
leakage shall not exceed 1.0 CC (approximately 20 drops) per hour. Dynamic leakage shall
not exceed 1.0 cc (approximately 20 drops) per minute.
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