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MIL-P-27431B(USAF)
condition shall be evidenced by the extinguishing of the heater indicator light and a
sharp drop in wattage.  With pressure still applied to the heat exchanger inlet, the
flow shall be shutoff downstream from the connected filler valve, allowing the outlet
pressure to build up.  Evidence of any of the following conditions shall constitute
test failure and cause for rejection:
a. An elapsed time of more than 10 minutes for the heating element to
thermostatically cut off.
b. A maximum power drain of more than 1500 watts.
c. An effluent gas temperature of less than 220F after 10 minutes from
first application of power to the heating element.
d. An outlet temperature of more than 250F at any time after first
application of power to the heating element.
e. An effluent flow rate of less than 300 or more than 400 liters of
standard gas per minute.
f. Failure of the heater indicator light to cycle on and off coincident
with application and removal of power at the heating element.
4.6.5 Performance test (long method).  The performance test shall consist of
eight 5 hour runs conducted with heat exchanger gas inlet pressures and ambient
temperatures according to Table I.  The inlet gas temperature shall be controlled to
within 5F of the specified ambient temperature throughout each run.  In addition to
maintaining the specified ambient temperature throughout each run, all unit
components, excluding carrying case, shall be soaked at the specified ambient
temperature for at least 4 hours before starting the run.  The purging unit
components shall be assembled and instrumented as shown on Figure 3.  The 115 5V,
60 or 400 cycle single phase power shall be applied to the power cable and the-toggle
switch turned on.  Flow rate, inlet, outlet, and surrounding ambient temperatures,
inlet pressures, elapsed time, and applied wattage shall be measured throughout each
run.  The elapsed time at which the heating element reaches each thermostatic cut-off
and cutin temperature shall also be recorded.  This condition shall be evidenced by
the extinguishing or lighting of the heater indicator light and a corresponding sharp
drop or increase in wattage.  Once every hour during each 5 hour run, the gas inlet
pressure shall be reduced to 0 psig for a period of 5 minutes and then restored.  The
electrical power shall not be removed during this period.  Any of the following
conditions observed during the course of any test run shall constitute test failure
and cause for rejection:
a. An elapsed time of more than 10 minutes for the heating element
to reach the specified temperature and thermostatically cut off. An
elapsed time of 30 minutes will be allowed for runs one and two.
b. A maximum power drain of more than 1500 watts.
c. An effluent gas temperature of less than 220F within 10
minutes from first application of power to the heating element except
that during runs 1 and 2 at -30F ambient , the limits are 220F within 30
minutes.
d. An outlet temperature of more than 250F.
11

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