MIL-DTL-8788F
4.7.9 Bulge resistance test (see 3.5.7). Hoses when subjected to the bulge resistance test shall meet
the requirements of 3.5.7. The four samples prepared for the impulse test (see 4.7.8) shall be checked for
bulging of the inner tube and reduction of fitting nipple inner diameter caused by the attachment of end
fittings. The following details shall apply:
a. Ball gages shall be specified in table VII for the applicable hose size.
b. Without using force or lubrication, the ball shall be placed inside the samples at the bulge gage
inspection point shown on figure 1.
c. Holding the hose in a vertical orientation, the gage is inserted into the end of the hose assembly
at the bulge inspection point C shown on figure 1.
d. The ball gage shall fall through the section at the end of the adapter in the hose under its own
weight without lubrication and without forcing the ball gage through the adapter-to-hose
interfacing section.
TABLE VII. Ball gages. 1/
Hose
Ball
size
Diameter Volume (in3)
Weight (grams) Weight (ounces)
dash
inches (mm)
number
-4
0.132 (3.35) 0.001204259 0.153543075
0.005416078
-5
0.2 (5.08)
0.004188787 0.5340703
0.018838796
-6
0.26 (6.60) 0.009202764 1.173352449
0.041388834
-8
0.35 (8.89) 0.022449279 2.862283014
0.100964171
-10 0.45 (11.43) 0.047712898 6.083394511
0.214585658
-12 0.575 (14.61) 0.099540952 12.69147137
0.447678961
-16 0.781 (19.84) 0.249431534 31.80252055
1.12180211
1/ Steel balls are used to ensure that hoses are free of debris and bulging rubber.
4.7.10 Low temperature flexibility test (see 3.5.8). Hoses when subjected to the low temperature
flexibility test shall meet the requirements of 3.5.8. The following details shall apply:
a. Testing shall consist of two samples of the lengths specified in table I.
b. One sample shall be unaged while the other shall be oil aged prior to testing.
c. Samples shall be filled with fluid conforming to MIL-PRF-5606, MIL-PRF-87257, or
MIL-PRF-83282 and then exposed for 24 hours in a chamber at a temperature of -65° ±2°F
(-53.89°C ± 1.11°C).
d. Size 16 hose may be exposed to a temperature of -40° ±2°F (-40°C ±1.11°C).
e. After the 24 hour exposure and while still at the specified temperature, the samples shall be
flexed through 180° at each extreme travel, considered as one cycle, to the applicable inside
bend radius specified in table I.
f. Each sample shall be subjected to one cycle only, the duration of which shall be no greater than
four seconds.
g. After the flexing cycle (see figure 2), samples shall be removed from the cold chamber and
subjected to the proof pressure test (see 4.7.3).
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