MIL-DTL-22706G
3.3.2 Scuff cover.
3.3.2.1 Dimensions. The scuff cover dimensions shall be as specified on figure 1.
3.3.2.2 Outer jacket. The outer jacket (see figure 1) shall be constructed with moisture
resistant fabric having a maximum regain of 0.5 percent as measured by ASTM-D629. Materials
shall be treated with a moisture resistant compound to meet this requirement. The fabric shall be
of an open construction (weave or braid).
3.3.2.3 Scuff strip. The scuff strip shall be wound with a protective helical coil of
natural or synthetic rubber with a minimum durometer of 60, permanently vulcanized to the
fabric. A bonded strip shall be used between the scuff strip and the fabric. The bonded strip shall
be vulcanized to the fabric so that the fabric, immediately below the bonded strip, is completely
contained within the rubber material. There shall be no exposed fabric threads below the bonded
strip. The last coil wrap at each end of the duct assembly shall be wrapped squarely around the
fabric and vulcanized permantly to prevent separation or raveling of the strip (see figure 1).
3.3.2.4 Scuff cover ends (cuff). Each end of the scuff cover shall be vulcanized with a
5-inch minimum width rubber strip to prevent unraveling of the scuff cover and space for
identification information (see 3.8.1).
3.4 Environmental conditions. The duct and scuff cover as designed shall be able to
operate under the following environmental conditions (see 4.4.11).
a. Exposure to salt sea atmosphere.
b. Fungus growth as encountered in tropical conditions.
c. Radiant energy as found under natural conditions.
3.5 Performance. The duct and scuff cover shall meet the following performance
requirements and shall be capable to operate under the following conditions:
a. Ambient temperature of -65° +5°F when air flowing at 200 +5 pounds per
minute at 100 +2 psia, and 600 +00F, -10°F (see 4.4.4).
b. Ambient temperature of 130 +5°F when air flowing at 200 +5 pounds per
minute at 100 +2 psia, and 600 +00F,-10 °F (see 4.4.9).
c. Static proof pressure of 250 psia at normal ambient temperature of 70oF for 5
minutes with pressure trapped, the static pressure shall not drop 30 psi during that period
(see 4.4.2).
d. A minimum bend radius of 8 inches when the duct is under no pressure and a
bend radius of 30 inches while under pressure of 30 psia (see 4.4.5).
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