MIL-DTL-13444H
4.7.8 Ozone resistance (see 3.6.5). Type I hose covers when subjected to ozone test in accordance
with ASTM D380 shall meet the requirements of 3.6.5. The following details shall apply:
a. The hose outer cover elongated 12.5(, shall be exposed for a period of 168 hours at a
temperature of + 100°F ± 2°F (+37.78°C ± 1.11°C) to an ozone concentration maintained at
50 ± 5 parts of ozone per hundred million parts of air.
b. During the duration of the test specimens shall be examined daily for cracking, visual
examinations shall be made without and with 7Xmagnification, except areas covered by tape
or twine. The first observable cracking shall be recorded.
d. After required exposure to ozone, the specimen shall be visually examined without and with
7X power magnification to determine conformance to 3.6.5.
4.7.9 Vacuum collapse resistance (see 3.6.6). Hose specimens when subjected to vacuum shall
meet the requirements of 3.6.6. The following details shall apply:
a. A piece of 36 inch (0.91 m) long hose shall be wrapped around a mandrel having a diameter as
specified in table X.
b. While bent around the mandrel, hose less than 1/2 inch (.500 inch) (12.70 mm) nominal size
shall be subjected to an internal vacuum equivalent to 20 inches of mercury (0.68 bar); hose
1/2 inch (.500 inch) (12.70 mm) and larger shall be subjected to an internal vacuum equivalent
to 10 inches of mercury (0.34 bar).
c. While vacuum is being applied, two readings spaced 90° apart shall be taken on the outside
diameter of the hose. The readings shall subsequently be averaged and the decrease
calculated as a percentage of the original outside diameter.
TABLE X Vacuum collapse resistance mandrel diameter.
Mandrel diameter
Hose size
inches (mm)
Fraction
Inches
Metric
1/8
.125
3.18
3.5 (88.90)
3/16
.188
4.78
4.0 (101.60)
1/4
.250
6.35
4.5 (114.30)
5/16
.313
7.95
5.5 (139.70)
3/8
.375
9.53
6.0 (152.40)
13/32
.406
10.31
7.0 (177.80)
1/2
.500
12.70
7.5 (190.50)
5/8
.625
15.88
9.5 (241.30)
3/4
.750
19.05
11.0 (279.40)
7/8
.875
22.23
12.0 (304.80)
1-1/8
1.125
28.58
15.0 (381.00)
1-3/8
1.375
34.93
16.0 (406.40)
1-13/16
1.813
46.05
20.0 (508.00)
19
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