MIL-DTL-22706G
penetration, fungus growth, and sunshine. The materials shall meet the environmental
requirements of MIL-STD-810 and shall be verified by the contractor in accordance with 4.4.11.
3.2.1 Protective treatment. Protective treatment shall be applied when materials subject
to corrosion in salt air or other atmospheric conditions are used in the construction of the duct
assembly. Materials shall be protected against corrosion in a manner that shall not prevent
compliance with the performance requirements of this specification. The use of any protective
coating that will crack, chip, or scale, with age or extreme atmospheric conditions shall not be
used.
3.3 Design and construction. The duct and scuff cover assembly shall consist of a length
specified by the contracting activity (see 1.2 and 6.2). An easily replaceable scuff cover (see
figure 1) shall be used. The duct shall be manufactured to ensure that the temperature and
pressure requirements are met when tested as specified in section 4 of this specification. The
typical construction of duct and scuff cover are shown on figure 2. The ends of the duct shall be
designed to be readily connected with MS17833 and MS17835 connectors (see Appendix A).
3.3.1 Duct.
3.3.1.1 Dimensions. The duct shall be of 30-foot or 60-foot length, as specified in 1.2.2.
The duct shall have a uniform wall thickness with a tolerance of + 0.032 inch, exclusive of the
scuff cover. The inside diameter of the duct shall be not less than 3.5 inches or greater than
3.562 inches at standard day conditions (14.7 psi and 70oF). The outside diameter of duct shall
be as small as possible consistent with the requirements specified herein but shall be not greater
than 4.125 inches. The duct construction shall be uniform throughout the length of the duct
assembly so that it shall be possible to cut off a section of the duct at any location and shall be
able to reconnect to any of the standard beaded shank end connectors. No painting or any other
special treatment of the cut surface shall be required.
3.3.1.1.1 Dimensional changes. The duct assembly shall be constructed that it shall not
decrease in length more than two percent nor increase more than three percent when new or after
exposure to any of the environmental conditions specified in 3.4. The inside diameter shall not
decrease more than two percent or increase in outside diameter more than the maximum diameter
specified in 3.3.1.1 after exposure to any of the environmental conditions specified in 3.4.
3.3.1.2 Fabric. The exterior fabric shall be material that is resistant to liquid absorption
and penetration and shall be highly resistant to abrasion (see 4.4.12).
3.3.1.3 Serviceability. The duct assembly shall be able to resist to abrasion (see 4.4.12),
exposure to solvents (see 4.4.10), and shall not leak when in service (see 4.4.3). It shall
withstand continuous flexing when tested with low temperature soak test as specified in 4.4.4.
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