MIL-DTL-24694A(SH)
4.6 Examination and tests.
4.6.1 Visual and dimensional examination. Valves shall be visually and dimensionally examined to determine
conformance to the applicable specification sheet and any other applicable requirements of this specification.
4.6.2 Proof pressure. A proof pressure of 69 bars (1000 lb/in2) or 200 percent of the maximum possible
pressure setting, whichever is greater, shall be applied to the inlet port of the valve with the return port blocked and
held for 2 minutes. There shall be no external leakage or evidence of permanent deformation. For conformance,
proof pressure shall be applied for a minimum of 30 seconds to assure that no leakage is present.
4.6.3 Performance tests (minimum setting). The following tests shall be conducted with the valve adjusted to
the minimum nominal set pressure specified for its class as identified in the applicable specification sheet. Valves
adjustable to a range of more than one class need only be tested at the minimum setting of the range. Any evidence
of chatter, surging, or squeal under any test condition shall be cause for rejection. Leakage measurements shall be
taken in the third minute of a 3-minute period. For conformance, test time may be reduced to 1 minute.
4.6.3.1 Rated flow differential pressure. The pressure shall be increased until rated flow as identified in the
applicable specification sheet is passed through the valve. The pressure at which this flow occurs shall be recorded
as the rated flow pressure and its value shall be not greater than that identified on figure 1 for a given nominal set
pressure. Fluid temperature shall not exceed 40 °C (104 °F) for this test.
4.6.3.2 Reseat. With rated flow through the valve, the inlet pressure shall gradually be reduced until leakage
not greater than the reseat leakage specified in the applicable specification sheet can be determined. The pressure at
which this leakage rate occurs shall be recorded as the reseat pressure and its value shall be not less than that
identified on figure 1.
4.6.3.3 Internal leakage.
4.6.3.3.1 Decreasing pressure leakage. The reduction of pressure shall be continued, and the leakage rate
observed at a pressure equivalent to 75 percent of the set pressure. Unless otherwise specified (see 3.1), leakage at
this pressure shall not exceed 1 cubic centimeter per minute.
4.6.3.3.2 Increasing pressure leakage. The pressure shall be decreased to zero, then increased to the minimum
reseat pressure. Unless otherwise specified (see 3.1), leakage at the pressure equivalent to reseat pressure shall not
exceed 1 milliliter per minute.
4.6.4 Performance test (maximum setting). The valve shall be adjusted to the maximum pressure setting of its
class (see 3.1) as identified in the applicable specification sheet. Valves adjustable to a range of more than one class
need only be tested at the maximum setting of the highest class. With the valve set at the maximum pressure
setting, the tests of 4.6.3.1 through 4.6.3.3.2 shall be performed. Any evidence of chatter, surging, or squeal under
any test condition shall be cause for rejection. Leakage measurements shall be taken in the third minute of a
3-minute period. For conformance, test time may be reduced to 1 minute.
4.6.5 Vibration tests. The valve shall be mounted on a resonance-free fixture for testing. The vibration input
accelerometer shall be mounted on the fixture close to the mounting point of the valve to the fixture. A second
accelerometer shall be mounted directly on the valve for monitoring resonant frequencies. Valves need not be
pressurized for the tests but shall be mounted in a test block. If a valve is symmetrical about a principal axis,
vibration testing need only be accomplished along two orthogonal axes, one of which shall be the principal axis of
symmetry.
4.6.5.1 Exploratory for resonance frequencies. Resonant frequencies of the valve shall be determined by
varying the frequency of applied vibration slowly throughout the range specified in table II. For frequencies from
4 to 33 hertz, the table vibratory single amplitude shall be 0.25±0.05 millimeter (0.01±0.002 inch). Above 33 hertz,
the table vibratory single amplitude shall be 0.10+0.02 millimeter (0.004±0.0008 inch). The change in frequency
shall be made in discrete frequency intervals of 1 up to 50 hertz and maintained at each frequency for about
15 seconds. From 50 to 2000 hertz, a logarithmic sweep of at least 10 minutes duration shall be made. As an
alternative, a logarithmic sweep from 4 to 2000 hertz back to 4 hertz may be conducted. The total time of the
ascending plus descending sweep shall be not less than 40 minutes.
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