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|  MIL-S-55257C(CR)
skids) shall be raised 18 inches and the shelter shall be allowed to fall
freely onto a hard substantial concrete surface. This inpact shall be
performed four times, once for each bottom edge of the shelter. On com-
pletion of these drops, the shelter assemblage shall meet the require-
ments of 3.16.
4.9 Air tightness test. The shelter facility when subjected to the
following test, shall meet the requirements of 3.16.
a. The air tightness shall be tested by introducing clean dry
air into the closed shelter through an existing appropriate opening (i.e.
drain fixture) to create an internal air pressure that exceeds the exter-
nal pressure by a minimum of six (6) inches of water.
b. A manometer graduated in 0.1 inches or less shall be uti-
lized to measure this differential pressure.
c. The test apparatus shall include an air supply sufficient to
maintain the required air pressure, an air flow regulator and an input
air pressure gage.
d. The shelter facility shall be tested for air tightness by
painting the sealed joints, seams, rivets, etc. of the external modi-
fications with Leak-Tat Formula 372 (American gas & Chemicals, Inc.,
Leak-Tat Division) or equal soap and water solution.
e. To minimize air loss, temporary seals, shims and tape are
permitted to seal the shelter door, blower cover and air conditioner port
openings not being tested.
4.10 Mounting insert tests. Four of each size inserts shall be
randomly selected for test. Each insert shall be tested with an axial
load followed by a torque load in accordance with Table V. After test,
the requirements of 3.19 shall be met. Failure of any insert shall be
cause for rejection of the sample equipment. This test shall be conduct-
ed prior to installation of brackets, racks, etc.
TABLE V
Mounting insert loads
Group B Test
First Article and Group C Test
Insert
Axial (Lbs) Torque (Inch lbs)
Axial (lbs) Torque (Inch Lbs)
Size
23
300
23
0-32
600
I
60
650
60
1/4-20
1300
100
1000
100
2000
5/16-18
20
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