MIL-DTL-27166F
4.6.1.1 Cycling.
The cycling procedures are used in the operating life performance test (see 4.6.2) and in
preparation for the cracking, reseal, leakage, and flow rate tests, to be performed in the order
listed. For cracking, reseal, leakage, and flow rate test preparation, the valves shall be initially
cycled 10 times in order to normalize operating conditions. The procedure for each valve type is
as follows:
4.6.1.1.1
Types I and II.
Air pressure shall be applied to the inlet port of the valve with the outlet port open to the
atmosphere or suitably vented. The pressure differential shall be uniformly increased until an
air flow of at least 20 percent of the rated flow rate is reached. The air pressure shall then be
reduced to zero differential. The cycle shall be accomplished in 3 to 10 seconds.
4.6.1.1.2
Type III.
One complete cycle shall consist of the cycle detailed in 4.6.1.1.1 accomplished in each
direction of flow.
4.6.1.2 Cracking, reseal, leakage, and flow rate.
The valve shall be cycled (see 4.6.1.1) in preparation for cracking, reseal, leakage, and flow rate
tests. The valve shall be placed in a test cell so that required pressure differentials can be
applied. Suitable gauges or manometers shall be connected to the cell to determine the
pressure differential across the valve to within ±5 percent of the actual values. For reseal,
cracking, and leakage testing, a gas flowmeter, capable of measuring a flow rate of 0.061
±0.006 cubic inch (1.0 ± 0.1 cubic centimeter) of standard air per minute, shall be connected in
series with the valve test cell so that all air flowing through the valve flows through the
flowmeter. For valve flow rate testing, a flowmeter capable of measuring the specified valve
flow rate ±5 percent shall be connected in series with the valve test cell. A suitable regulator or
throttling valve shall be used to control the test pressure so that test conditions are maintained
to within ±5 percent of specified values during the test. Test results shall be reported in
standard air conditions. For reseal and leakage tests, an indicated flow of 0.061 cubic inch (1.0
cubic centimeter) of standard air per minute through the valve, or the reseal pressure to be less
than the specified reseal pressure shall be an indication of failure and cause for rejection. For
cracking tests, failure of the cracking pressure to be within the offset range of the specified
reseal pressure shall be an indication of failure and cause for rejection. For flow rate tests,
failure to develop at least the specified flow rate at a differential pressure of 1.5 psi (10.3 kPa)
greater than the specified reseal pressure across the valve in the flow direction shall be an
indication of failure and cause for rejection.
4.6.1.2.1
Types I and II cracking and reseal.
Initially, the valve shall be in the closed state with an applied pressure differential of 0.0 psi (0.0
kPa) for a period of at least five (5) seconds. The pressure differential shall then be increased
until the flow rate is slightly greater than 0.061 cubic inch (1.0 cubic centimeter) per minute. The
pressure at which the valve cracks shall be measured. The valve shall then be subjected to the
pressure differential causing the specified flow rate. The pressure differential shall be
decreased until the valve flow rate is slightly less than 0.061 cubic inch (1.0 cubic centimeter)
per minute. The pressure at which the valve reseals shall be measured. Failure of the valve to
crack within the offset range (see 3.6.2) of the specified reseal pressure, or to reseal at or above
the specified reseal pressure shall be cause for rejection.
4.6.1.2.2
Types I and II leakage.
The valve shall be subjected to a pressure differential of 10.0 psi (68.9 kPa) which tends to
produce flow in the non-flow direction. Observation for leakage shall then be made.
10
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business