MIL-PRF-24755B(SH)
c. Parts shall be match marked or attached so that reinstallation will be in the same position as originally
installed.
d.
Motor shall be removable using commonly available tools.
3.10 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 -20 °F (29 °C)
and +149 °F (65 °C).
3.10.1 High-impact shock resistance. Unless otherwise specified (see 6.2), the fan-motor units shall meet the
shock requirements of tests specified in MIL-S-901 for Grade A, Class 1 equipment.
3.10.2 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.
3.11 Aerodynamic design parameters. The quantities of blades and vanes shall be chosen to avoid producing
audible tones. The axial distance between blades and vanes shall be chosen with minimum noise amplitude as a
prime consideration.
3.12 Configuration. Fans and motors shall operate in any position on shipboard including vertical (with fan
impeller either up or down), horizontal (parallel to ship's centerline or athwartship), or inclined. Each fan-motor
unit shall be a complete assembly (see Appendix A).
3.13 Sizes. Sizes of vaneaxial high pressure fans shall be limited to those listed in table II.
TABLE II. Fan characteristics.
Vol (ft3/min) 1/ TP (in WG) 2/
Vol (ft3/min)
Fan Size Code Diameter (in)
Length (in)
TP (in WG)
20⅛
101
30
1200
14
1320
12
21⅛
102
31
1800
14
1980
12
21⅛
103
32
2400
14
2640
12
21⅛
104
33
3600
14
3960
12
21⅛
105
35
5400
14
5940
12
NOTES:
1/
Motor speed shall be 3600 revolutions per minute (r/min).
2/
Total pressure in inches water gauge.
3.14 Physical interface dimensions. Physical interface dimensions of the fans shall be as shown on figure 1.
3.15 Fan casings and associated parts.
3.15.1 Watertightness. Casings shall be watertight.
3.15.2 Flanges. Flanges for duct connections shall be provided at each end of the fan casing. These flanges
shall be integral parts of the casing either through manufacture or welding. The flanges shall be drilled as shown on
3.15.3 Directional vanes. Directional vanes shall be provided in the casing.
3.15.4 Fan bellmouth. When specified (see 6.2), a fan bellmouth shall be provided.
6
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