MIL-DTL-151F
4.3.2 Group B test. Each of the sample fans selected in accordance with table III shall be subjected to the tests
specified herein and the results of the test compared with specification requirements. In the event of any failure to
conform to the specification requirements for the group B test, the contractor shall correct the cause of failure and repair
the deficiency in any fans not yet shipped.
Reference
Group B tests
Output ...................................................
4.4.7
Operation for 4 hours to cause heating .............
4.4.8
Audible noise ..........................................
4.4.9
Insulation resistance ..................................
4.4.10
Low temperature starting ............................
4.4.11
Permeability ...........................................
4.4.14
4.4
Examination and tests.
4.4.1 Visual examination. Each sample fan shall be subjected to a careful visual examination to ascertain that
the structural details and character of workmanship conform to this specification. The selected sample shall also be
checked against the approved master drawings.
4.4.2 Insulation resistance (cold). The insulation resistance of the complete fan shall be measured to determine
compliance with 3.16.1.
4.4.3 Speed. The actual speed shall be determined by any convenient means to determine compliance with 3.9.
The test should be conducted at room temperature. The temperature shall be recorded.
4.4.3.1 Starting characteristics. The time required to accelerate from standstill to full speed shall be recorded.
The fan shall be checked for any tendency to stall.
4.4.4 Power input. The power input at full load shall be measured by any convenient means to determine
compliance with 3.8.
4.4.5 Dielectric test. The fan shall be subjected to a.c. potential of 900 volts for 1 minute applied between the
current-carrying parts and the frame, upon the completion of the tests specified in 4.4.1 through 4.4.3.
4.4.5.1 Capacitor test. Where capacitors are used, the suitability of the installation shall be determined. The
dielectric test shall include the capacitors.
4.4.6 Effect of variations in power supply. All types of fans shall be operated briefly throughout the specified
voltage range to determine compliance with 3.6.
4.4.7
Air movement. The fan output shall be determined as follows:
(a)
The fan shall be mounted on a ceiling whose height is not less than 6-1/2 feet from the floor (see figure 1).
(b)
The ceiling shall be unobstructed within a 10-foot radius of the fan.
(c)
The space in which the fan is mounted shall be free from extraneous drafts.
(d)
The velocity of the air delivered shall be determined at a distance of within 18 inches
From the ceiling and at the specified radius from the fan (see 3.12). The velocity shall be measured with
a calibrated anemometer, velometer, or any other approved instrument. At least eight readings shall be
taken in a like manner at points approximately equidistant from the center of the fan around the
circumference of the circle described by the specified radius.
4.4.8 Operation for 4 hours. Each sample selected as specified in 4.3.2 shall be operated for 4 hours at rated
voltage to ascertain satisfactory operation in respect to the bearings, input, speed, temperature rise, and voltage.
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