Testing flameproof enclosures

Construction and verification test of flameproof enclosures of electrical apparatus 2148/1993 BS 4683-2/1993 5501-5/1997 -... 

Originally the classification of materials was derived from tests of proprietary explosion-proof (flameproof) enclosures. There were no published criteria. Equipment was approved relative to the lowest ignition temperature of any material in the group (Magison 1987). In about 1965 the U.S. Coast Guard asked the National Academy of Sciences (NAS) to form a panel to classify 200 materials of commerce. The Electrical Hazards Panel of the Committee on Hazardous Materials was formed by the NAS. The Panel studied many ways to estimate the hazard classification of materials. The Panel finally reported to die U.S. Coast Guard in 1970 that no workable, predicdve scheme could be defined, and it then proceeded to assign tentative classifications to the 200 materials. 

Type of protection (Sch)dz indicates that this flameproof enclosure has passed successfully a special type test to avoid the propagation of an explosion inside the enclosure initiated by high current fault arcs to the surrounding atmosphere. This test has been prescribed by a decree of the Supreme Authority in Mines. 

A quite different effect is an arc-induced flame transmission through the joints of a flameproof enclosure. To avoid any misunderstanding these joints do comply with the d-standards and they have been shown to be safe by type testing for the corresponding explosion subgroup and test gas-air mixture. Investigations covering this field have been published in [35] and [56]. 

Remembering the basic principles of flameproof enclosures, two main characteristics of such enclosures shall be proved by type testing they shall withstand the internal overpressure caused by the ignition of a combustible gas-air mixture inside, and they shall prevent flame transmission to the environmental hazardous atmosphere. So, such a test cycle is divided into three parts ... 

Figure 8.1 Explosion test facility for flameproof enclosures.

Figure 8.2 Testing vessel for large flameproof enclosures (according to [17]), the biggest testing facility worldwide.

Construction and verification test of flameproof enclosures of electrical apparatus. 

Tests of the ability of an enclosure to withstand an internal overpressure and for non-transmission of an internal ignition, applied to flameproof - d -enclosures... 

---