MIL-PRF-39019F
4.8.8.2 Seal (used for group A inspection) (see 3.11). Circuit breakers shall be immersed to a depth not exceeding
10 inches in tap water which may contain a wetting agent. The manufacturer may, with approval of the qualifying
activity, use an alternate liquid provided there is verification that it is equivalent to tap water. In case of dispute, tap
water is the referee. During immersion, observation shall be made for any visible air bubbles indicative of leakage
emanating from the circuit breakers, either in the form of continuous stream or as bubbles emanating at regular
intervals. Bubbles which are determined to be the result of entrapped air on the exterior parts of the immersed circuit
breakers shall not be considered a leak.
4.8.9 Panel seal (see 3.12). Circuit breakers shall be secured by their normal mounting means to a suitable test
jig. A suggested test jig is shown on figure 3. The test jig shall be immersed in a water-filled glass container
containing a wetting agent, with the circuit breaker completely submerged. An air pressure of 15 pounds per square
inch shall be applied to the test jig for approximately one-half hour. The circuit breaker and connection to the test jig
shall be observed for any visible air bubbles indicative of leakage, either in the form of a continuous stream or as
bubbles emanating at regular intervals. The test shall then be repeated by applying air pressure in the opposite
direction by reversing the cover.
Circuit breaker
Wire size
capacity (amperes)
(AWG designation)
Less than 6
18
7 to 10 inclusive
16
11 to 15 inclusive
14
16 to 20 inclusive
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Ammeter: Accuracy within .5 of 1 percent.
FIGURE 2. Suggested calibration test circuit.
4.8.10 High temperature and low temperature operation (see 3.13). Circuit breakers shall be conditioned for 2
hours at -40°C ±2°C, at which temperature the calibration test shall be performed in accordance with 4.8.6.2. Without
a warming period, circuit breakers shall then be conditioned for 1 hour at -55°C ±2°C at which temperature the
calibration test shall be performed in accordance with 4.8.6.2, except the percent of current needed to trip the circuit
breaker shall be 150 instead of 135. While still maintained at -55°C ±2°C, the insulation resistance test shall be
performed in accordance with 4.8.4. Circuit breakers shall then be conditioned for 2 hours at 100°C ±2°C, at which
temperature the calibration test shall be performed in accordance with 4.8.6.2. While still maintained at 100°C ±2°C,
the dielectric withstanding voltage and insulation resistance tests shall be performed in accordance with 4.8.3 and
4.8.4, respectively. Circuit breakers shall be examined for evidence of mechanical damage. Circuit breakers shall
then be subjected to the seal test and panel seal test in accordance with 4.8.8 and 4.8.9, respectively.
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