Downloaded from https://www.everyspec.com MIL-STD-81OC 10 March 1975 L METHOD 510.1 OUST (FINE SAND) 1. PURPOSE. The dust test is used to ascertain the ability of.equipment to r-he effects of a dry dust (fine sand) laden atmosphere. This test simulates the effect of sharp edged dust (fine sand) Particles, UP to 150 microns in size, which may penetrate into cracks, crevices, bearings, and joints. This test is”applicable to all mechanical, electrical, elec- tronic, electrochemical,and electromechanicaldevices for which exposure to the effects of a dry dust (fine sand) laden atmosphere is anticipated. However, this method “isnot applicable to Southeast Asian dust conditions.
1.1 General effects. General e“ffects, resulting from the penetration of dust can cause a variety of damage such as fouling moving parts, making relays inoperative, forming electrically conductive bridges with resulting shorts. and acting as a nucleus for the collection of water vapor, and hence a source of possible corrosion and malfunction of equipment. 1.2 Many items, such as rifles, vehicles, and helicopters, wil1 encounter sand particles up to 1,000 microns,as opposed to the 149 micron maximum for 140-mesh silica flour sand tests,that would require a much coarser formula- tion than that cov”eredby this method. 2. APPARATUS.
The test facility shall consist of a chamber and accessories to “controldust concentration,velocity, temperature, and humidity of dust laden air. In order to provide adequate circulation of the dust laden air, no more than 50 percent of the cross-sectionalarea (normal to air flow) and 30 percent of the volume of the chamber shal1 be occupied by the test item(s). The chamber shal1 be provided with a suitable means of maintaining and veri- fying the dust concentration in circulation. A minimum acceptable means for doing this is by use of a properly calibrated smoke meter and standard light source.
dust laden air shal1 be introduced intO the test sPace in such a manner as to allow it to become approximately laminar in flow before it strikes the test item. 2.1 Dust requirements. The dust used in this test shall be a fine sand (97-99 percent by weight Si02) of angular structure, and shall have the following size distiibution as determined by weight, using the U.S. Standard Sieve Series: a. 100 percent of this dus’tshal1 p“issthrough a 100-mesh screen b. 98 *2 percent of the dust shall pass through a 140-mesh screen 510.1-1 METHOD 510.1 D 10 March 1975