MIL-PRF-17773C(SH)
4.6.19 Degree of enclosure. Switches shall be tested in accordance with MIL-E-2036 for Class I enclosures, as
supplemented by MIL-STD-108, to determine the effectiveness of the enclosure as specified in 3.4.41. The switch
enclosure shall be subjected to a water sprinkle rate of 6.9 in/hr (1000 cubic inches per hour per square foot of area
covered) for a 12 minute (8 minutes operating and 4 minutes off) minimum in each of five different orientations;
vertical and inclined 45 degrees forward, backward, to the right, and to the left. Failure of the equipment to operate
satisfactorily or accumulation of water within the enclosure shall be cause for rejection. Additionally, the unit shall
not be a hazard to personnel in case of minor water intrusion.
4.6.20 Ambient temperature. Switches shall be designed for continuous reliable operation within specified
limits over an ambient temperature range of 32 to 122 °F (0 to 50 °C). The switch shall not be damaged nor shall
the operational performance be degraded when restored to operating temperature range after exposure for long
periods, 24-hour minimum, in a non-operating air temperature range of 13 to +140 °F (25 to +60 °C). Test shall
be conducted in accordance with MIL-STD-202.
4.6.21 Humidity. Switches shall be subjected to humidity testing in accordance with MIL-STD-202.
4.6.22 Pressure. Switches shall operate within the specified performance limits while subjected to an
atmospheric pressure from 24 to 36 inches of mercury in accordance with MIL-STD-202. The ABT shall reliably
operate within specified performance limits after exposure to an atmospheric overpressure of 2 atmospheres (14.7
psi positive differential on the ABT).
4.6.23 Temperature rise. Switches shall be subjected to a temperature rise test. The test shall be conducted
with the switch carrying rated current, with control circuit energized. Component temperature rises shall be
measured by the resistance method or by thermographic equipment. Sufficient thermocouples (or equivalent
temperature sensors) shall be installed on representative current-carrying parts such as coils, contacts, and terminals.
Temperature rises shall be measured at the hottest point where current-carrying parts are closest to insulating
material. The test shall be conducted in accordance with MIL-E-917.
4.6.24 Inclined operation. Switches shall be tested for inclined operation in accordance with MIL-E-917.
4.6.25 Shock. Switches shall be subjected to shock tests in accordance with MIL-S-901 for Grade A, Class I,
Type A equipment with weight classification as required by the weight of the equipment. The ABT shall be tested
in the same mounting configuration as the one chosen for shipboard installation. The tests shall be conducted with
the switch carrying current, at rated voltage and frequency. Control circuits shall be energized as in actual service.
An oscillograph shall be used to check the closed contacts for excessive contact bounce and to check the open
contacts for momentary closures. Switch mounting shall be as specified for standard mounting for bulkhead
mounted equipment in accordance with MIL-S-901. Fuses (or other indicators which provide a positive indication)
shall be connected in a manner to detect any momentary shorting between live parts or live parts and ground. The
bus transfer switches being tested shall not be reconditioned or adjusted during the testing. Switches shall fail the
test if it cannot perform its intended operating functions during and after such tests or if one or more of the following
occurs during the tests:
a.
Contact occurs between live parts and the enclosure.
b.
Enclosure door opens.
c.
Structural parts are damaged or loosened.
d.
Functional parts are damaged or loosened.
e.
Inadvertent transfer of load due to the force of shock blow.
f.
Main line contacts have contact bounce in excess of 0.02 second per bounce.
g.
Closed auxiliary contacts momentarily open or open auxiliary contacts momentarily close.
Note: The switches shall be thoroughly examined after the tests to determine whether there is evidence of items c
and d above. The vibration test shall follow the shock test.
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