5 - Protection concept ‘d’

Abstract

This chapter explains the protection concept “d.” Explosion protection is safety technology at its highest level. A series of pioneering developments and innovative designs have enabled various companies to exploit new, more economical, and safer possibilities and to apply them in many different fields of applications to maximize the gains. Broad specialist knowledge and a well-founded understanding of explosion protection are of benefit to all. The chapter also discusses a widely used protection concept—the flameproof enclosure. The flameproof enclosure is one of the oldest of the protection concepts being considered in various parts of the world as suitable for Zones 1 and 2 areas, dating back to before World War II. It is not possible or desirable to produce equipment with no gaps between the different parts, especially with an electric motor with a revolving shaft. The allowable gap between the different parts is accepted, but strictly defined. The “gaps” help to relieve the pressure inside the enclosure caused by an explosion. Experimental testing is used to establish the “maximum experimental safe gap” for different gases and gas mixtures. It presents the grouping and effect of temperature classification; flameproof enclosures are grouped according to the specified maximum permissible dimensions for gaps between joint surfaces and the surfaces of other openings in the enclosure. The standards quote the maximum permissible dimensions of gaps for the various enclosure groups but, in practice, joints are fit as close as possible and the maximum permissible dimensions are not allowed to exceed under any circumstance.