96/00986 Mechanical apparatus for use in potentially explosive atmospheres formed by gases, vapours and mists

Abstract

Abstract Only in Germany to date have mechanical apparatus for use in potentially explosive atmospheres been type-tested and formally approved under the ‘Verordnung uber brennbare Flussigkeiten (VbF)’ (Ordinance for Flammable Liquids). In the near future, however, the new EC directive ATEX 100a will require all EC member states to issue formal certificates of conformity based on a type-test by a notified body or on declarations of conformity by the manufacturer not only for electrical equipment as hitherto but also for non-electrical apparatus. For this reason, there is great interest at present as to how the required explosion protection of non-electrical apparatus can be achieved. Based on the long-standing experience of PTB in the type-testing of mechanical apparatus for use in potentially explosive atmospheres, this article discusses the requirements for the safe design and construction of a number of typical apparatus of this type, in particular those for use in zone 0. For equipment with rotating parts which constitute the majority of explosion-protected mechanical apparatus, the necessary explosion protection can be achieved merely by good design and construction and only in exceptional cases is it necessary to employ types of protection such as flameproof enclosures or pressurization. This is exemplified for a number of typical apparatus such as design of shafts and bearings, shaft passages for stirrers, ventilators and gas pumps, submerged pumps and drum pumps, as well as internal combustion engines and fork lift trucks.