Downloaded from https://www.everyspec.com b MIL-STD-81OC 3.2.2 Performance of test. The test shall be accomplishedthree times at altitudes between sea level and 5,000 feet. as follows: Step 1 - The chamber shall be sealed and the internal pressure reduced sufficientlyto simulate an altitude between ground level and 5,000 feet. The ambient chamber tempera- ture shall be at least .25° C(77”F). An explosive mixture within the chamber shall be obtained by following the procedure set forth in procedure 1. Steu 2 - The internal case ignition source shall be energized in order to cause an e~plosion within the case.
Tie occurrence of “anexplosion”within the case may be detected by use of a thermocouple inserted in the case and connected to a sensi- tive galvanometersoutside the test chamber. If ignition of the mixture within the case does not occur immediately, the test shal1 be considered void and shall,be repeated with a new explosive charge. Step 3 At least five internal case explosiorisshall be accomplish- ed at the test altitude selected.
If the case tested is small (not in’excess of one-fiftieth of the test chamber volume) and if the reaction within the case upon ignition is of an explosive nature without continued burning of the mixture as it circulates into the case, more than one ) internal case explosion, but not more than five, may be produced without recharging the entire chamber. Ample time shall be allowed between internal case explosions for replacement of burnt gases with fresh explosive mixture, within the case. .Ifthe internal case explosions produced did not cause a main chamber explosion, the explosiveness of the fuel-air mixture in the main chamber shall be verified.
If the air-vapor mixture in the main chamber is not found to be explosive, the test shall be considered void and the entire procedure r,epeated. 3.2.3 Failure criteria. If the internalcase explosion causes a main chamber explosion, the test item shall be considered to have failedthe test aridno further trials need be attempted. 3.3 Procedure III 3.3.1 Preparation for test.’ The test enclosure and test item shall be prepared for test in accordance with 3.2.1 of procedure 11: 511.1-9 METHOD 511.1