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A study to determine factors causing pressure piling in testing explosion-proof enclosures.

Gleim-EL; Marcy-JF
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 4904, 1952 Aug; :1-16
An attempt has been made in this report to predict and evaluate the effect of pressure piling in any given explosion-proof compartment on the basis of its geometry. As a beginning, a simple type of rectangular box that could be divided easily into separate compartments was employed. By extending these tests to more closely represent the more-complicated commercial enclosures taken with their contents, prediction of pressure piling should be made with greater confidence than possible at present. With this in view, continuation of this investigation is planned. Higher-frequency gages will be used to insure greater reliability in the measurement of pressures. Possibility of cavity resonance should be eliminated by the use of flush-type diaphragms. These general deductions are made on the basis of the test results: 1. Pressures of about 125 pounds per square inch are obtainable with openings as large as 8 inches in diameter in a 12-inch-square plate. These pressures are due mainly to high-frequency vibrations. The 50-percent safety margin sometimes provided in commercial enclosures may be reached under these conditions. 2. There is a critical ratio between the size of the hole in the partition plate and the distance of the ignition point from the plate before a vibratory type of explosion can be generated. It would be of considerable interest to determine the extent to which this ratio is independent of the size of the box. 3. Pressure gages, such as those specially designed for detonation studies in gasoline engines, would be used in future explosion tests to insure adequate high-frequency response. A frequency response at least 10 times greater than that of the present gages would be desirable. This need is also indicated from the recent tests by Titman and Haig and Staples.
Mining-industry; Explosions; Explosion-protection; Coal-mining; Underground-mining; Explosion-prevention; Explosive-dusts; Explosive-atmospheres; Explosive-gases; Electrical-equipment; Electrical-systems
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Document Type
Report of Investigations
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NIOSH Division
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Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 4904