MIL-PRF-26139D
observed airflow readings to ambient conditions. Pressure lines shall be shown and marked to
correspond with pressure lines on the flowmeter.
3.11.3 Conversion chart. A legible, waterproof chart shall be provided and located on the panel
for converting the airflow from cubic feet per minute to pounds per minute.
3.11.4 Pressure equalization indicator. A rate of climb indicator shall be furnished to indicate
pressure equalization of the tester output and the enclosure being pressurized. The dial face shall
indicate decreasing and increasing pressurization instead of up and down. The indicator shall be
red-lined beyond the 5,000-foot mark, both increasing and decreasing. Some means shall be
provided to prevent damage to the instrument should the rate of increasing or decreasing pressure
exceed the redlined values. A permanent-type, etched or engraved nameplate containing the
following information shall be securely attached to the panel immediately below the indicator.
CAUTION -- DO NOT INCREASE OR DECREASE CABIN PRESSURIZATION AT THE
RED-LINED RATES
3.11.5 Cabin pressure gage. The corrosion-resistant gage shall be accurate to within 1 percent or
less of full scale and shall conform to ANSI B40.1 except as specified herein. The gage shall
provide a range of from 0 to 15 PSI and shall incorporate a means to restore the accuracy of the
gage under all service conditions. The gage shall be suitable for operation from -25° F to 160° F.
The gage shall be of the recess type provided with a mounting flange at the front of the gage. The
mounting flange and dial shall not extend more than 5/8-inch beyond the external surface of the
panel. All gages shall incorporate a safety blowout device to automatically relieve the gage case
should the pressure reach .50 PSI due to gage failure. The pointer shall be adjustable without
removing the gage from the panel.
3.11.6 Discharge air temperature indicator. A remote-reading, dial-type temperature indicator
having a scale range of from -25° F to approximately 200° F and accurate within 2° F
throughout the range shall be furnished. The temperature indicator shall measure the temperature
of the pressurized air on the discharge side of the flowmeter and shall be marked by a red sector
above 120° F. A caution plate containing the following marking shall be securely attached:
CAUTION -- AIR TO CABIN SHOULD NOT EXCEED 120° F.
3.11.7 Pressure gages. The corrosion-resistant gages specified herein shall be included on the
panel. Each pressure gage shall incorporate a safety blowout device that shall relieve the gage
case pressure should it reach .50 PSI due to gage failure. The dial and pointer shall be separated
from the gage movement to prevent rupture through the front of the gage in the event of gage
failure. The pointer shall be adjustable without removing the gage from the panel. All gages shall
be mounted using screws and tapped panel holes to permit removal by one person from front of
the panel.
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