MIL-DTL-16938D
a. The searchlight shall be subjected to the action of a salt spray for 200 hours. This salt
spray shall consist of a spray of a 20 percent solution by weight of commercially pure sodium
chloride in distilled water. The spray shall be at 131 °F (55 °C) and shall be applied alternately
with a 3-minute drying period of air at 131 °F (55 °C) producing a 3-minute wet and a 3-minute
dry condition continuously under ultra violet light. Upon completion of the test, the searchlight
shall be washed with fresh water and examined.
b. Careful examination after the salt spray test shall show no damaging effect to the unit
due to the salt spray. In addition, the searchlight shall function satisfactory after the test. Lock
washers shall be thoroughly examined.
4.6.6 Insulation resistance and dielectric strength. Insulation resistance and dielectric
strength tests shall be made, to determine conformance with 3.5.6 and 3.5.7 as follows:
a. Before any other tests.
b. After waterproofness test (see 4.6.2).
c. Twenty-four hours after salt spray test (see 4.6.5).
These tests shall be applied both cold and after the light has reached its maximum operating
temperatures, when operated in an ambient air temperature of 77 °F (25 °C).
4.6.6.1 Insulation resistance. The insulation resistance with 500 volts applied between
each conductor, where possible, without component damage (with the lamp removed) and
between all conductors and the searchlight frame (with the lamp installed) shall conform with
3.5.6. The insulation resistance shall be taken before and after each dielectric strength test.
4.6.6.2 Dielectric strength. A 60 Hz voltage, whose effective potential is 1,240 volts,
shall be applied between conductors, where possible, without component damage (with the lamp
removed) and between all conductors and searchlight frame (with the lamp installed).
4.6.7 Life test. The life test shall include operation for 3,000,000 cycles of the shutter as
a rate of 200 cycles per minute. (A cycle consists of the movement of the shutter from the
completely closed to the completely open positions and return to the completely closed position.)
The shutter shall be attached to the drum for this test, and the lamp shall be burned at rated
voltage throughout the duration of the test. This test shall also constitute a reliability test for the
complete searchlight and failure of any searchlight component (excluding the lamp) during the
shutter operation and salt spray tests shall be deemed a searchlight failure and cause for
rejection. All bearings of the shutter shall be lubricated at intervals of 250,000 cycles. The test
shall be divided into two parts as follows.
a. 1,500,000 cycles of operation of the shutter shall be performed prior to conduction the
salt spray test specified in 4.6.5.
b. 1,500,000 cycles of operation of the shutter shall be performed after conducting the
salt spray test specified in 4.6.5, and the shock test specified in 4.6.3. Care shall be taken to
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