MIL-DTL-24251F
4.5 Method of examination and tests.
4.5.1 Visual and mechanical examination. Shields and associated parts shall be examined to verify that the
materials, design, construction, physical dimensions, marking, and workmanship are in accordance with the
4.5.2 Permeability. The permeability of the tube shield assembly shall be measured with an indicator conforming
to ASTM-A342/A342M to determine conformance with 3.4.
4.5.3 Installation, locking and unlocking torque, or load and removal force.
4.5.3.1 Initial force at 25°C. The force necessary to place, lock, unlock, and remove the shield over the applicable
4.5.3.2 Force at temperature extremes (see 3.5.2). The slug shown on figure 1, the shield and retainer (base) or
adapter shall be conditioned at 85°C ± 5°C for 2 hours after which the test of 4.5.3.1 (at this temperature extreme)
shall be performed within 1 minute after opening the chamber. After completion of the 85°C test, the slug, shield, and
retainer (base) or adapter shall then be conditioned at -55°C ± 5°C for 2 hours after which the test specified in 4.5.3.1
(at this temperature extreme) shall be repeated within 1 minute after opening the chamber.
4.5.3.3 Fatigue test. After the shield is properly installed and removed from the slug and applicable retainer (base)
or adapter 100 times, the tests specified in 4.5.3.1 shall again be performed (see figure 1 and 3.5.3).
4.5.3.4 Installation and removal. The shield with all associated parts shall be installed and removed 25 times over
a mounted tube or proper size. The electron tubes, liner, and coil springs (when used) shall be examined after the
4.5.4 Vibration (see 3.6). The shields and the retainer (base) or adapter (when applicable) shall be tested in
accordance with method 204 of MIL-STD-202. The following details shall apply:
a.
Mounting method: Normal mounting (with a tube in the socket).
b.
Test condition: B.
c.
Electrical load: None.
d.
Measurements during and after vibration: None.
After the test, shields, retainers (bases), or adapters and electron tube glass envelopes shall be examined for
evidence of damage or loosening from the base.
4.5.5 Shock (see 3.7). The shields and the retainer (base) or adapter (when used) shall be tested in accordance
with method 213 of MIL-STD-202. The following details shall apply:
a.
Mounting method: Normal mounting (with a tube in the socket).
b.
Test condition: A.
c.
Electrical load: None.
d.
Measurements after shock: None.
After the test, the shields, retainers (bases), or adapters and electron tube glass envelopes shall be examined for
evidence of damage or loosening from the base.
4.5.6 Heat resistance (see 3.8). The shields, retainers (base), or adapters shall be subjected to an ambient
temperature of 200°C ± 5°C for 48 hours. The shields, retainers (base), or adapters shall then be conditioned for 1
hour at room ambient temperature (see 4.3). At the end of this 1-hour interval, the shields and associated parts shall
be examined for evidence of damage to the body finish (peeling, blistering, chipping, or pitting).
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