ANSI/UL 913, a national intrinsic safety standard, and the U.S. Mine Safety and Health Administration testing procedures specify that intrinsic safety acceptance tests be conducted using a standard tungsten-cadmium electrode configuration. In realistic mining environments, however, sparking seldom occurs that involves cadmium surfaces. Therefore, information defining the probability of spark ignition between more commonly used materials is of much greater value in estimating the probability that explosions may occur. The U.S. Bureau of Mines is conducting research to estimate the degree to which various commonly used materials influence the probability of spark ignition in the standard spark test apparatus. These materials include aluminum, brass, copper, lead, tin, stainless steel, and cold-rolled steel. By comparing currents that give a probability of spark ignition of 10-3, a safety factor may be associated with each material relative to cadmium, which has been arbitrarily assigned a safety factor of 1.00. Results to date are summarized.
Conf. Record of the 1989 IEEE Ind. Appl. Soc. Ann. Mtg., Part II, Cat. #89Ch2792-0, Pp 1536-43