MIL-DTL-5508C
rated flow. The pressure drop through the fuse in either the closing or the resetting direction
shall not exceed 25 psi at the rated flow for the fuse.
4.5.7 Extreme temperature operation. The automatic quantity-measuring hydraulic fuse
shall operate to shut off or to establish flow when operated at any temperature from -65 °F to 160 °F
(-54 °C to 71 °C). Extreme temperature tests shall be conducted on the sample fuse assembled of
parts with tolerances most conducive to binding at the temperature tested and shall be performed in
4.5.7.1 High temperature. The fuse shall be subjected to leakage tests and tests for
volumetric capacity at flow rates of 1 gpm, 25 percent of the rated flow capacity, and 100 percent
of the rated flow capacity after exposure to the specified high temperature for a period of six
hours. Fluid flow rate and air temperature shall not exceed that specified in paragraphs 3.6.1 and
4.5.7.2 Low temperature. The tests specified above for high temperature shall be
repeated except that the fuse shall be exposed to low temperature for a period of 72 hours. The
fluid and air temperatures shall be maintained at the required values during the test. Leakage
shall not exceed that specified in 4.5.3 and the volumetric capacity shall be within the limits
specified on figure 2.
4.5.7.3 Rapid warm-up. The low temperature test set up shall be allowed to warm up
rapidly to room temperature and at least five cycles of operation shall be made during the warm-
up period at approximately equal increments of time. The volumetric capacity shall be within
the limits specified on figure 2. The tubing between the transfer cylinder and the fuse (see
figure 4) shall be 1/2 inch size and 12 feet in length to aid fluid temperature stabilization and to
forestall inadvertent closing of the fuse. This length of tubing shall be specified on the
manufacturer's drawings.
4.5.8 Endurance. The fuse shall be installed in accordance with figure 5 and subjected to
20,000 cycles of operation, each cycle to consist of passage of at least 90 percent of the rated
volumetric capacity in the closing direction with the fluid at rated pressure (and reversal of flow
to fully reset the test fuses, where applicable). The means of limiting fluid volume shall then be
removed and 100 additional cycles of full closing and resetting shall be accomplished, the closing
pressure to be the rated pressure.
4.5.9 Acceleration. The apparatus shall be set up in accordance with figure 6.
4.5.9.1 Volumetric capacity. With the fuse bled, in the open position, and installed in a
direction so that acceleration will tend to close it, an acceleration of 12 g shall be developed by
the mechanism. Rated flow shall be applied through the fuse after a minimum time of two
seconds at the acceleration. The volumetric capacity shall not vary from those specified in
4.5.9.2 Leakage. With the fuse mounted in a direction so that acceleration will tend to
open it, 40 psi pressure shall be applied on the fuse in a closed position. An acceleration of 12 g
shall be developed and held for a minimum of two seconds and then stopped. The fuse shall not
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