Downloaded from https://www.everyspec.com MIL-.STD-81OC 3. PROCEDURES for evaluating equipment item shal1 be ulaced in the chamber in its normal ~ueration t)ositionin accordance with General Require- ments, 3.2. The test item ~hall.be ~xposed to a simulated rain at a rate ~f 2 +0.s inches per hour for 10 minutes. The rate of rainfall shall then be raised to 5 *1 inches per hour ,andheld at this rate for 5 minutes. The rate shall then be reduced to 2 +0.5 inches per hour for the next 15 minutes. Starting 5 minutes after the initiation of the rain, the wind source shall be turned on adjusted to produce a horizontal wind velocity of 40 miles per hour (3,500 feet per minute).
The wind source shall be maintained at this velocity ,for15 minutes after which the wind source shall be turned off. 3.1 Procedure I (cycling). used outdoors under blowing The procedure is intended rain conditions. The test NOTE: If specified in the equipment specification, the test item shal1 be operated during,the last 10 minutes of the 30-minute rain. Each of the sides o“fthe test item that could be exposed to’blown rain shall be subjected to the rain for a period of not less than 30 minutes, for a total test duration of not less than 2 hours.
At the conclusion of the test period, the test item shal1 be removed from the test chamber, operated, inspected, and results obtained in accordance with General Requirements, 3.2. The protective cover or case shall, where possible, then be removed and the test item inspected for compliance with General Requirements, 3.2. I 3.2 Procedure II, For simulation of steady-state rainfall. Step 1 - Place the test item ii the chsmber in accordance with General Requirements, 3.2.2 and orient in such a manner as to allow impingement of the rain on the item normal (90° ) to its hori- zontal plane.
Step 2 - Produce a simulated falling rain in the test chamber stabilized at a constant rate of 2 fO.5 inches per hour. Step 3 - Reorient the test item to an angle of 45° from the horizontal plane of step 1 and.index the item around its center axis periodically to allow exposure to rainfall of all the,significant surfaces of the test item. Step 4 - Expose the test item to the simulated falling rain for”a total time of not less than 2 hours, which shal1 represent the sum of equal exposure periods in the orientation modes of steps 1 and 3. METHOD 506.1 506.1-2 J