MIL-DTL-24402F(SH)
3.5.3.4 Selector valves. Three-way, three-position, directional-control valves shall be incorporated into duplex
filter assemblies. Valve levers or handles shall be provided with a latch or other mechanism to prevent inadvertent
operation. Flow shall not be shut off when shifting from one position to another. With dummy elements installed
and with a flow of at least one-half of the housing s rated flow, the differential pressure across the filter assembly
during shifting shall be not greater than 50 lb/inē. The maximum torque required to change valve positions under
test flow conditions shall be not greater than 40 foot-pounds.
3.5.3.5 Check valves. Duplex filter assemblies shall use check valves to prevent the reverse flow of fluid
through the filtration circuits. Maximum cracking differential pressure shall be 8 lb/inē. Leakage, with the filter
bowls removed and measured at differential pressures of 5 and 3,000 lb/inē, shall be not greater than 0.07 ounces
(2 milliliters [mL]) per minute in each flow passage after completion of pressure cycle testing (see 4.6.1.9).
3.5.4 Welding and allied processes. Welding and allied processes shall be in accordance with
S9074-AR-GIB-010/278 for the filter housing pressure vessel or structural welds, as applicable.
3.6 Performance. Filter assemblies, filter housings, and differential pressure indicators shall perform as
3.6.1 Shock. Filter assemblies and differential pressure indicators shall meet the shock requirements of
MIL-S-901 for Grade A, Class I equipment.
3.6.2 Fatigue impulse. When required by the applicable specification sheet, the filter assemblies and
differential pressure indicators shall withstand, without failure, 10 million impulse pressure cycles in accordance
with NFPA T2.6.1.
3.6.3 Proof pressure. Filter assemblies and differential pressure indicators shall withstand a proof pressure, as
specified in the applicable specification sheet, without evidence of permanent deformation, malfunction, or external
leakage.
3.6.4 Housing pressure drop. The pressure drop through the filter housing at maximum rated flow, with
dummy elements installed, shall be not greater than the value specified in the applicable specification sheet. The
dummy elements may be constructed to minimize element flow loss, but the element end caps shall be solid, except
for the normal hole in the element outlet, and shall comply with the maximum envelope dimensions specified for the
appropriate filter elements.
3.6.5 Burst pressure. Filter assemblies shall withstand a burst pressure as specified in the applicable
specification sheet. The filter assemblies shall not rupture under this pressure. The burst pressure test is required for
those filter assemblies which are not subjected to the fatigue impulse test specified in 4.6.1.2
(see MIL-DTL-24402/1 and MIL-DTL-24402/3).
3.6.6 Vibration. The differential pressure indicators furnished under this specification shall meet the
requirements of MIL-STD-167-1, Type I environmental vibration up to and including 50 hertz (Hz) (see 4.6.1.3).
3.7 Identification.
3.7.1 Filter housing. Each filter assembly shall be clearly and permanently identified by an attached
identification plate containing the following information (except for the fluid symbol, which may be put on a
separate plate alone):
a.
Number and date of this specification.
b.
Filter assembly specification PIN (see the applicable specification sheet).
Manufacturer s part or drawing number.
c.
Manufacturer s name or trademark.
d.
e.
Fluid symbol (see SAE-AS1290).
f.
Relief valve setting, where applicable.
g.
Replacement filter element specification PIN (see the applicable specification sheet).
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