MIL-DTL-5498G
damage. With the accumulator mounted in a vertical position and with the fluid port down, the
accumulator separator shall withstand 4,500 psi ± 100 psi fluid pressure applied to the gas port
with the fluid port open for two minutes without leakage or damage.
4.6.3 Volumetric efficiency. The accumulator shall be mounted in a vertical position with
the gas port down and with the piston bottomed on the gas end. The accumulator shall be filled
with fluid and the volume of the fluid shall be measured and recorded. Pressure shall then be
applied to the gas port and the piston shall be allowed to travel until it is bottomed on the fluid end.
The volume of fluid exhausted shall be measured and recorded. The volumetric efficiency shall be
determined by the following formula:
Volumetric efficiency percent = 100 X Volume of exhausted fluid
Volume of admitted fluid
The volumetric efficiency shall not be less than 95 percent. With a gas precharge of 500 psi ± 25 psi
and the separator bottom at the fluid end of the accumulator, the fluid pressure required to move the
piston shall not exceed 700 psi. Under 3,000 psi ± 50 psi fluid pressure, the piston shall not bottom
at the gas end.
4.6.4 Fluid immersion. All accumulators shall be filled with hydraulic fluid in such a
manner that all internal parts of the unit are in contact with the fluid. The accumulator shall then
be immersed continuously in hydraulic fluid for a period of 72 hours at a fluid temperature of not
less than 225 °F in a closed container prior to conducting the remainder of the qualification tests
specified. After the 72 hour soak period, the accumulators shall remain in the fluid at normal
room temperature until ready for further testing.
4.6.5 Proof pressure. With the piston in approximately mid-position, completely fill both
ends of each accumulator with fluid and plug the gas end. Fluid pressure shall be applied at the
fluid port until a pressure of 6,000 psi ± 100 psi is obtained and maintained for 5 minutes. There
shall be no leakage of fluid or sign of failure in any part of the accumulator.
4.6.6 Cycling and endurance. With all fluid exhausted, the accumulator shall be
precharged with pure dry nitrogen gas as specified in the steps of table II. The tests for steps 1
through 6 will be conducted in a test rig similar to that shown in figure 2. The tests for step 7
will be conducted in a test rig similar to that shown in figure 3. Fluid shall then be cycled to the
accumulator in accordance with the corresponding pressures and temperatures specified. The
fluid and the gas in the accumulator shall attain the specified temperature before tests are started.
The tests shall be conducted in the order specified. Tests 4.6.7.1 and 4.6.7.2 are performed
between steps 6 and 7. The stabilized gas temperature, the pressure, and the leakage of fluid and
gas shall be recorded and shall not exceed that specified in table II. There shall be no external
leakage or malfunctioning of the accumulator during the test. Only one set of packing gland
seals shall be used throughout steps 1 through 6. A new set of packing glands may be installed
after the leakage test of 4.6.7 (see 4.6.7 a) and as required during the step 7 testing.
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