MIL-DTL-151F
Shock. Fans shall be designed to withstand the shock tests specified in 4.4.13.
3.10
3.11
Mechanical balance and audible noise. Fans shall be dynamically balanced and shall operate without
objectionable noise at rated speed.
3.12
Output. The air output shall be such that the average velocity of the air delivered (see 4.4.7) shall be not
less than 75 feet per minute, when measured at a radius of 5 feet from the center of the fan.
3.13
Terminal boxes. A metal terminal box shall be furnished, mounted as part of the fan assembly. The box
shall be of such size that undue crowding of the connections between the motor leads and the incoming cable will not
result. Each box shall be provided with a 1.26 inch diameter hole to accommodate a size 4, stuffing tube in accordance
with MIL-S-19622. Each box shall also be equipped with a metal cover which shall be secured by machine bolts.
Life. Fans shall operate satisfactorily in accordance with the requirements specified herein at rated voltage
3.14
without showing defects or undue wear, when tested as specified in 4.4.12. At the end of the life period specified, the
wear shall not have exceeded the following:
(a) Commutator: 0.030 inch in diameter.
(b) Sleeve bearings: 0.003 inch in diameter.
(c) Brushes shall not be worn to the extent of causing the fan to become inoperative during the life test (see
4.4.12).
3.15
Dielectric. The insulation shall withstand the dielectric test specified in 4.4.5.
Insulation resistance.
3.16
3.16.1
The insulation resistance shall be not less than 16 megohms when measured in accordance with 4.4.2.
3.16.2
The insulation resistance shall be not less than 2 megohms when measured in accordance with 4.4.10.
3.17
Electromagnetic interference. When required, electromagnetic interference shall be as specified (see 6.2).
3.18
Weight and dimensions. The weight and dimensions of the fan shall not exceed those specified in table I.
Table I. Weight and dimensions.
Projection downward
Weight
from mounted position
Blade diameter
14 pounds
9 ½ inches
8 ½ inches
3.19
Grounding. An electric conducting path shall exist between all exposed metal parts and mounting. In the
case where the fan motor is electrically isolated from the mounting (for example, in rubber grommets for noise isolation
purposes), a stranded wire shall be used for grounding purposes. This wire shall be sufficiently long so that there will
always be slack regardless of the fan position. It shall be of at least the same cross-sectional area as each wire which
supplies power to the motor, and shall be secured in such a manner that it will not become entangled in any part of the
fan assembly.
3.20
Vibration. Fans shall be designed to withstand type I, (environmental) vibration as specified in MIL- STD-167-1.
Designation and marking.
3.21
3.21.1
Designation. The Government designation for the fans shall be shown as type I, type II, type INM or
type IINM. The class of fan shall not be shown.
3.21.2
Identification plates. Identification plates and other designating marking shall be provided in accordance
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