 |
|||
|
Page Title:
Suction unseating of exhalation valve |
|
||
| ||||||||||
|
|  MIL-V-27296C
intercommunication set. The effects on communications shall be determined by listening qualitatively to speech
communication from at least three talkers when using the valve at any altitude between ground level and 32,000
feet. The exhalation valve shall not whistle, chatter, or create noise excessively to a degree which interferes with
communication. The exhalation valve shall not modulate the speech signal because of valve flutter.
* 4.6.17 Acceleration unseating of exhalation valve. The combination valve shall be mounted on a horizontal
centrifuge so that axial acceleration is applied from the mask end to the regulator end of the valve. The valve shall
then be subjected to acceleration from 0 to 9 times the force of gravity. The exhalation valve shall not be unseated
at any acceleration up to nine times the force of gravity.
4.6.18 Suction unseating of exhalation valve. A suction of 10 inches of water (gauge) shall be applied to the
regulator end of the valveand held. A suction of 5 inches of water (gauge) shall be applied to the mask end of the
valve. Leakage through the exhalation valve shall be measured. A maximum leakage of 100 milliliters per minute
will be permissible during this test.
4.6.19 Subjective use. The valve shall be Wed in a type MBU-5/P or MBU-12/P oxygen mask as
applicable, and used by human subjects at any altitude, temperature, or combination altitude-temperature as
specified in 3.6.18 for periods up to 2 hours. The valve shall also be placed in an MBU-5/P oxygen mask
conforming to MIL-M-27274 or MBU-12/P oxygen mask conforming to MIL-M-87163, as applicable, and used by
0
human subjects at a temperature of 0 F for a minimum of 2 hours. This is to insure that both during and after the
test there is no freezing of the valve. High G tests shall be performed with at least 5th and 95th percentile subjects
to determine that the valve will perform Satisfactorily at 3, 4, 5, 6, 7, 8 and 9 times the force of gravity. High
altitude decompression tests which simulate aircraft decompression shall be performed to insure that the subject is
able to breathe both during and after decompression. Subjective use tests are optional tests to be conducted at the
discretion of and by the procuring activity when the valve appears to have performance characteristics that might
be detrimental or objectionable for human use.
4.6.20 Restraint cable retention pin strength. The valve shall be held in place by the cap. A 100 pound load
shall be applied to the restraint cable retention pin at its mid-section perpendicular to its longitudinal axis. The
had shall be applied for 3 seconds.
4.6.21 Valve,installation strength. This test only applies to the MBU-12/P oxygen mask. The valve shall be
installed in a test rig with the bearing washer, both gaskets and flange representative of the nominal thickness of
the hardshell of the MBU-12/P oxygen mask torqued to the nominal torque value as recommended by the valve
manufacter, and set at rim angle of 30 degrees of the longitudinal axis of the valve to the pull angle. Each of 20
valves shall be pulled at a pull speed of 0.30 inches per second until failure or seperation of the valve from the test
rig. The test rig may grip the valve at the surface of the valve where the breathing hose is clamped in place rather
than by being pulled from the restraint cable and retention pin as this may fail before the valve body and cap
separate. Should any of the 20 valves separate with a force of less than 100 pounds, this shall be be cause for failure
of all valves.
* 4.6.22 Reliability test The reliability test shall consist of simulated breathing cycles with oxygen or air as the
test fluid each cycle of the valve shall consist of an inlet breathing flow rate varying from 0 to 50 liters per
minute and back to 0 liters per minute again. The cyclic rate shall be 25 cycles per minute. At least 50 percent of
the reliability testing of the valve shall be conducted under pressure breathing editions at 3.0 inches -4.0 inches
of water (gauge), the remainder being under demand breathing conditions. A failure shall be identified as any
malfunction which could compromise the performance of the valve. The valve shall be tested every 24 hours as
follows:
a. The leakage-Pressure test specified (see 4.6.6) shall be accomplished.
b. The pressure demand operation test specified (see 4.6.8) shall be accomplished.
A test stand conforming to figure 6 need not be used for failure determinations during reliability testing.
11
|
|
Privacy Statement - Press Release - Copyright Information. - Contact Us |
Click
here for thousands of PDF manuals