Downloaded from https://www.everyspec.com M1L-,STD-81OC 10 March 1975 METHOD 506.1 RAIN 1. PURPOSE. The rain test is conducted to determine the effectivenessof prot~covers or cases to shield equipment from rain.. This test is applicable tO equipment which may be exposed to rain under service conditions. Where a requirement exists for determining the effects of rain erosion on radomes, nose cones, etc., a rocket sled test facility or other such facility should be considered. Since any test procedure evolved would be contingent on requirementspeculiar to the test item and the facility employed, a standardizedtes~ method. procedure ,forrain erosion is not included in this test 2.
APPARATUS 2.1 Procedure 1. Rain chamber with wind source. ,, 2.2 Procedure II. Rain chamber. 2.3 Chamber. The rain chamber shall,havethe capability of producing falIing rain and for procedure I a facility for producing wind blOwing a.tthe rates specified herein. The chsmber temperature shall be uncontrolled, except as regulated by water introduced as rain, throughout the test period. The rain shall be produced by a water distribution device of such design that the water is emitted in the form of droplets having a diameter range between O.5 and 4.5 millimeters. The temperature of the water shall be between and 3S° C (52° and 95”F).
The water distribution shall be’such that,with the wind source turned off, the rain is dispersed completely over the test item and an”additional test area to accomplish the wind blown rain effects on the equipment. The wind source shall be so positioned with respect to the test item that it will cause the rain to beat directly, with variations up to 45° from the horizontal, and uniformly against one side of the test item. The wind source shall be capable of producing horizontal wind velocities up to 40 “milesper hour. The wind velocity shall be measured at the position of the test item, prior”to placement of the item in.the chamber.
No rust or corrosive contaminants shall be imposed on the test item by the test facility. (A recommended method of”measuring raindrop size is the flour pellet method as referenced in “The Relation of Raindrop Size to Intensity”by Laws and Parsons, Transactions of the American Geophysical Union, part II, PPs 452 tO 459, -1943). 506.1-1 METHOD S06.1 10 March 1975