![img](MIL-PRF-1900400007im.jpg)
MIL-PRF-19004B
3.11 Sizes. Sizes of CC and X-CC fans shall be limited to those listed in
Table I.
TABLE
I.
Performance of type CC and X-CC fans.
Total Pressure (TP) at stated
volume
3
ft /min
TP (inch H2O)
Fan size
250
¼
1.74
500
½
2.5
900
1
2.5
1200
1-1/2
2.58
1300
2
3.06
1950
3
4.25
2500
4
5.25
3000
5
5.3
5000
6
4.0
4500
8
5.2
7000
10
5.0
3.12 Physical interface dimensions. In order to suit interface requirements,
physical interface dimensions of the type CC and X-CC fans shall be as shown
on Figure 1.
3.13
Fan scrolls and associated parts.
3.13.1
Watertightness.
Scrolls shall be of watertight construction.
3.13.2 Fan scrolls. Scrolls shall be equipped with an inlet designed to
reduce turbulence and noise. The interior of the fan scrolls shall be free of
obstructions.
3.13.3 Rotation. Direction of rotation of impeller shall be indicated on
inlet side of scroll. Discharge and rotation shall be determined by viewing
the fan from the motor end. The rotation shall be designated by the terms
"clockwise" and "counterclockwise". Discharge of a fan shall be determined by
the direction of the line of discharge and its relation to the motor shaft
when the fan is resting on the floor, as indicated in AMCA STD 2406-66.
Unless otherwise specified (see 6.2), fans shall be assembled for top-
horizontal discharge.
3.13.4 Handhole opening. A watertight handhole of sufficient size shall be
provided in the scroll of sizes 1-1/2 fans and larger for cleaning the
impeller.
3.13.5 Flanges. Fan scrolls shall be provided with inlet and outlet flanges
for attachment of ducting (see Figure 1).
3.13.6
When specified in 6.2, a fan bellmouth shall be provided.
3.14 Fan impellers. Fan impellers shall be direct-connected to the motor.
Impellers in fans larger than size ¼ shall be of non-overloading type.
Impellers shall have a safety factor of at least 8, based on the ultimate
tensile strength of the material used.
3.14.1
Balancing.
The impeller shall be statically and dynamically balanced.
3.15 Fan and motor base. The fan and motor bases shall be designed so that
they can accommodate a fan discharge of any possible discharge position
through 360 degrees, without modification as per AMCA 2406-66.
7
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