MIL-PRF-83990A
operating temperature and the oven allowed to heat up and stabilize. The thermocouple reading
and the thermostat reading shall be recorded. The thermostat reading shall be within ±10°F of the
thermocouple reading. The process shall be repeated at a temperature approximately 50 percent of
the maximum operating temperature and the thermostat reading verified to be within +/- 10 degrees
F of the thermocouple reading.
4.5.4 Temperature variance test. (Type II ovens only) Four accurately calibrated
thermocouples shall be placed near the corners of the oven to determine the overall temperature
variation. The temperature variation between any two points within the oven shall not be greater
than 10°F. The test shall be conducted at approximately 150 degrees F and at maximum operating
temperature of the furnace.
4.5.5 Heat loss test. The oven shall be operated for a period of time sufficient to allow
complete thermal stability at maximum operating temperature. Then, without altering any controls
or settings, the oven power shall be accurately measured for one hour. The power consumption so
measured and reflected in kW/hour shall not exceed 0.050 kW (171 BTU) per hour per square foot
of oven interior surface.
4.5.6 Cut-out switch test. The oven door(s) shall be closed and the heating elements
energized. The door(s) shall then be alternately opened and closed 20 times. The oven shall cut-
off when the door(s) is/are opened and re-energized when the door(s) is/are closed.
4.5.7 Excess temperature cut-out test. The excess temperature cut out shall be tested by
setting the cut-out at 150 degrees below the maximum operating temperature of the furnace. The
thermostat shall then be disabled to simulate thermostat failure in the closed position and the
furnace operated. Power to the furnace shall be interrupted by the cut-out at the appropriate
setting within +/- 10 degrees F. The test shall be repeated with the cut-out set at 50 degrees above
the maximum operating temperature.
4.5.8 Undervoltage protection test. The oven shall be in operating mode to conduct the
undervoltage protection test. Electricity to the oven shall be interrupted by manually tripping the
circuit breaker. The circuit breaker shall then be reset to the "ON" position. The oven shall not
restart until manually reset.
4.5.9 Dielectric and Insulation resistance test. The circuits of the electrical system excluding
control or recording instruments shall withstand, without damage, for a period of one minute, an
impressed voltage of 1000 volts plus twice the rated voltage. The impressed voltage shall be
applied between all insulated circuits and insulated circuits and the frame. The insulation shall
then be subjected to an electrical resistance test. The resistance between all insulated circuits and
the oven frame shall be not less than one megohm at 500 volts DC.
5. PACKAGING
5.1 Packaging. For acquisition purposes, the packaging requirements shall be as specified in
the contract or order (see 6.2). When actual packaging of materiel is to be performed by DoD
personnel, these personnel need to contact the responsible packaging activity to ascertain requisite
packaging requirements. Packaging requirements are maintained by the Inventory Control Point's
packaging activity within the Military Department or Defense Agency, or within the Military
Department's System Command. Packaging data retrieval is available from the managing Military
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