MIL-PRF-38170H
3.6.8 Dissimilar metal vacuum joints. Any dissimilar metal vacuum joints used in the tank
assembly shall withstand thermal shocks, axial, and lateral vibration as specified (see 4.5.16.1.1).
3.6.9 Shutoff and control valve cycling and leakage. The valves shall withstand a closing torque
of at least 300 in.-lb per inch of nominal size, with the valve bodies at either ambient temperature
or the atmospheric pressure boiling temperature of liquid oxygen or nitrogen. When
subsequently closed with a torque of 60 ± 5 in-lb per inch of nominal size and a pressure of 50
psig applied to the inlet, the valves shall not leak more than 2 cubic inches of free air, oxygen, or
nitrogen gas per hour per inch of nominal size. The valves shall be capable of not less than 2000
cycles of operation when subjected to a differential pressure of 50 psig while closed, including at
least 1,000 cycles at ambient temperature and 1,000 cycles with the valve body at the
atmospheric pressure boiling temperature of liquid oxygen (see 4.5.13.1, 4.5.13.2, 4.5.13.3)).
3.6.10 Line filters. The liquid fill-drain line and the liquid servicing line shall each have a filter
for the filtering of all liquid flowing into and out of the inner shell. Filters shall be of the in-line
configuration conforming to drawing 68B39474. Each filter shall be installed such that it is
readily accessible for inspection, cleaning, or removal. Sintered or powdered material shall not
be used unless provisions are made to prevent media migration. The proper direction of flow
shall be plainly marked on each side of the filter. The filters shall be a non-bypass type and shall
withstand a pressure drop of 50 psi across their elements. Each filter shall remove 98% by
weight of all particles whose smallest dimension is 10 microns or greater (10-micron nominal
rating). The filter shall further remove all particles whose smallest dimension is 40 microns or
greater (40-micron absolute rating). In addition, the filter shall be capable of a liquid oxygen
flow rate of 25-gpm at a maximum pressure drop of 2 psig, and having previously ingested a
minimum of 5 grams of particles of the sizes shown in table II (see 4.5.10).
TABLE II. Particle size distribution.
Size of Particle (microns)
Percentage by weight (± 3%)
10 to 20
36
20 to 40
24
40 to 60
16
Over 60
24
3.6.11 Transportability.
3.6.11.1 Flight and taxiing acceleration forces. The tank assembly shall withstand the air
transport flight and taxiing acceleration forces as described in MIL-HDBK-1791, except that the
lateral loads shall be 3g instead of 1.5g, when empty or filled with liquid oxygen to any level up
to and including design capacity. These same forces shall also apply while the tank assembly is
being transported on a railroad car, ship, or truck (see 4.5.6.1, 4.5.18).
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