MIL-DTL-26894D
4.4.6 Low temperature flexibility. An uncoupled 5 ft length of hose shall be bent into a
concave shape so that the ends of the hose are approximately 40 inches apart. A longer
length of hose may also be used by coiling it into a 40-inch diameter circle. The hose shall be
tied to retain the U or circular shape and then exposed to -67 ±2°F for not less than 72 hrs.
While the temperature is at -67 ±2°F, the hose shall then be forced open to an angle of
approximately 90°. The force required to open the hose shall be recorded. Conformance shall
be as specified in 3.4.5.
4.4.7 Low temperature bend. Buffed specimens of the tube and cover, 4 inches long and
0.250 inch wide, shall be clamped in a concave shape between 2-inch wide plates held at
2.500 inches apart. When the plates are brought together so that the distance between the
ends are not greater than 1.250 inches, the bend in the test specimen shall not protrude
beyond the edges of the plates. After 72 hours exposure at -67 ±2°F, the plates shall be
moved rapidly together until the ends of the specimen are not more than 1 inch apart.
Conformance shall be as specified in 3.4.6.
4.4.8 Volume increase. The weight of water displaced by each of three 1-inch by 2-inch
buffed specimens for the tube and cover shall be determined before and after a 24 hours
immersion at 75 ±5°F in the hydrocarbon fluid specified in table II. Conformance shall be as
specified in 3.4.7.
4.4.9 Tensile strength and ultimate elongation. Testing shall be in accordance with ASTM
D412. The tube and cover test specimens shall be obtained from die C. Tube specimens shall
be buffed to a thickness of not less than 0.050 inch. Immersion shall be for 48 hours at 75
±5°F in the mixed hydrocarbon fluid specified in table II. Testing shall be conducted within 5
minutes after removal from the fluid. Conformance shall be as specified in 3.4.8 and 3.4.9.
4.4.10 Pull resistance. A white circumferential line shall be drawn around the hose along
the edge of the coupling at one end of a 15-inch hose assembly. The coupling with the white
marking shall then be held securely in a vise. A pull of not less than 2000 lb shall be applied
by any convenient means to the coupling at the other end of the hose assembly. The 2000 lb
pull shall be maintained for not less than 60 seconds. The jaw separation rate, exerted by the
test apparatus between the couplings, shall be not less than 1 in/min. Conformance shall be
as specified in 3.4.10.
4.4.11 Crush resistance. A 4-foot section of hose shall have its OD measured prior to
testing. Two feet of the hose shall then be rigidly supported on a horizontal plane while a 50 lb
weight shall be attached to the unsupported end of the hose. The weight shall hang freely for
a duration 60 ±10 sec. After 60 sec, the weight shall be detached and the hose shall be
allowed to recover. Recovery time shall be not less than 10 min but not greater than 12 min.
Following the recovery period, the OD of the hose shall then be measured. Conformance shall
be as specified in 3.4.11.
4.4.12 Proof pressure. Except for the individual tests specified under conformance
inspection (see 4.3 and 4.3.1), the test specimen used for the proof pressure test shall be the
same 4-foot section of hose that has already been subjected to the crush resistance test (see
4.4.11). Testing shall be in accordance with ASTM D380. The hose shall be subjected to a
hydrostatic pressure of 350 psi for not less than 3 min but not greater than 5 min.
Conformance shall be as specified in 3.4.12.
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