Abstract
Explosion-proof electrical enclosures contain a variety of organic insulating materials of differing nature and chemical composition. When subjected to thermal and/or electric stress, organic insulators may be potentially hazardous owing to moist tracking and thermal oxidative degradation. Organic materials utilized as cable jacketing, cable insulation, standoffs, insulating boards, and potting compositions were identified and a literature survey performed to obtain the required thermal oxidative and moist tracking data. Thirty representative compositions were procured and subjected to thermal and moist tracking evaluations. Tracking was found to invariably result in ignition or glow of the test specimen. Influence of parameters such as electrolyte strength and composition, temperature, conductor spacing, and electrode material were investigated. Volatiles produced by selected insulators on thermal oxidative and electrical stress were identified, quantitated, and their potential impairment action upon a current interrupter assessed.
