MIL-PRF-18953C(SH)
3.12.2.2 Aerodynamic stall. Effective stall shall not occur at flow capacities greater than 85 percent of the fan
design as specified in 1.2.2.
3.13 Environmental conditions.
3.13.1 General shipboard design conditions. General shipboard design characteristics shall be as follows:
a.
Power source quality - in accordance with MIL-STD-1399-300.
b.
Able to operate satisfactorily when exposed to soaking atmospheric spray (rain or sea) or seawater.
c.
Perform in accordance with requirements herein in a range of ambient temperatures between -29 °C
and 65 °C. Some special applications may require fans designed to operate in a higher (80 °C) ambient
temperature.
3.13.2 High impact shock resistance. Unless otherwise specified in 6.2, the fan-motor units shall meet the
shock test requirements of MIL-S-901 for Grade A, Class I equipment.
3.13.3 Vibration and balance. Fan-motor units shall be designed such that no damage will occur or
malfunction be caused by the environmental vibrations specified in MIL-STD-167-1. Fan-motor units shall be in
static and dynamic balance. The vibration amplitude shall not exceed the limits for Type II bearing vibration as
specified in MIL-STD-167-1.
3.13.4 Airborne noise. The total sound power levels for the fan-motor unit shall not exceed the levels stated in
Table I when tested in accordance with procedures stated in 4.8.5. Exceeding the total sound power levels specified
in Table I shall be cause for rejection.
4. VERIFICATION
4.1 Classification of inspections. The inspection requirements specified herein are classified as follows:
a.
Qualification inspection (see 4.2).
b.
Conformance inspection (see 4.3).
4.2 Qualification inspection. Qualification inspection shall be performed on Types A and X-A vaneaxial fans
and Types L and X-L tubeaxial fans when qualification is required (see 3.1). This inspection shall include the
examination and the tests as specified in Table III.
4.3 Conformance inspection. Conformance inspection shall consist of the examinations of tests as specified in
Table III. The tests specified shall be performed on each fan-motor unit. Any unit that fails to meet any specified
requirements shall be rejected.
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