Practical Ignition Problems Related to Intrinsic Safety in Mine Equipment. Four Short-term Studies.
Litchfield-EL; Kubala-TA; Schellinger-T; Et Al
Four short-term studies of practical ignition problems were undertaken and completed during the course of the Bureau of Mines project "development of specifications for intrinsically safe equipment." Conclusions were as follows: (1) the most easily ignitible mixture of propane-air in a ptb break flash apparatus is approximately 5.2 percent propane; (2) miniature lamp bulbs to be used in intrinsically safe circuits are about as incendive to coal dust-air as to methane-air and should be tested in gas mixtures containing about 7.0 to 7.5 percent methane; (3) the sodium amalgam contained in high-pressure sodium lamps does not present an ignition hazard for coal dust or methane, where the lamps contain no more than 30 milligrams of amalgam; (4) the maximum allowable surface temperature of permissible electrical enclosures should remain at 150 deg. C despite efforts by industry groups to raise the value to 200 deg. C.
IH; Report of Investigations