Downloaded from https://www.everyspec.com MIL-STD-81OC 3.3.2 Performance of test. The test shall be conducted at sea level or laboratory ambient as follows: Step 1 - The test chamber shall be sealed. The ambient chamber temperature shal1 be at least 25°C (77”F). Sufficient fuel vapor and air shal1 be introduced and circulated throughout the test enclosure and test chamber to assure a uniform mixture. The interior of the test enclosure shall then be isolated from the chamber atmosphere. Step 2 - explosion shall occur. The test shall be repeated twenty times unless a failure occurs.
Ample time shall be allowed between internal enclosure explosions for replacement of The mixture in the enclosure shall be ignited and an burnt gases with fresh explosive mixture. If the internal enclosure explosions produced did not cause a main chamber explosion the explosivenessof the fuel vapor and air mixture in the test chamber shall be verified. If an explo- sion does not occur the test shall be considered void and the entire procedure repeated. 3.3.3 Failure criteria. The test’item (sealed or unsealed as applicable) shall”be considered as failing the test for the following: a. Discharge of flame to the test chamber from the interior of the test enclosure. b.
Ignition of explosive mixture in the test chamber. c. If the internal case explosion causes a main chamber explosion, the test item shall be considered to have failed the test and no further trials need be attempted. d. After burning, immediately after the explosion within the test enclosure, caused by the ignition of explosive mixture entering the test enclosure as a result of cooling of the products of the original explosion. e. Rupture or permanent distortion of the enclosure. Deformation Of flat surfaces shall be checked and recOrde.d. 3.4 Procedure IV 3.4.1 Preparation for test. The test item shall be placed in the test chamber in accordance with 3.1.1 of procedure 1.
The suspected components to be tested for thermal ignition shal1 be instrumentedwith thermocouples operating in a range of 65° to 260”C (150” tO 500”F). METHOD 511.1 511.1-10