Flameproof enclosure

For hazardous areas flameproof enclosures alone are recommended, except in areas with moderate intensity of contamination and where such assemblies are located away from the affected area and in a separate well-ventilated room, when pressurized enclosures may also be. safe. The reason for this precaution is that frequent arcing takes place within the enclosure on each switching of a contactor, switch, breaker or an OCR etc. and also during operation of power and auxiliary contactors. 

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. 

The rule described above forms a basis for the secondary type of explosion protection, which results in the avoidance of ignition sources, e.g. by using either a flameproof enclosure of a commutator motor or the pressurized enclosure of a gas analyser, or by limiting the electrical values in intrinsically safe circuits. 

A similar situation exists for the particles generated by fault current arcing in flameproof enclosures after passing the flameproof joints (see Section 6.8). 

In the case of a pressurized enclosure outside, a flameproof enclosure according to EN 50018 may by used in addition to those listed above. 

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. 

Special protection comprises all protection techniques such as powder filling, static pressurization and encapsulation (by plastics materials). At that time, these techniques started their career in the field of explosion protection and advanced to autonomous types of protection described by IEC or European Standards individually. VDE 0170/0171/1969-01 does not contain any specific requirements for these techniques. It has been the decision of the certifying body that an s -apparatus will operate at the same level of safety compared with other well-defined types of protection, e.g. flameproof enclosure d ... 

TGL 30042 has defined a four-zone concept for areas hazardous due to combustible gases, vapours and mists EG 1, comparable with zone 0 EG 2 and EG 3, covering zone 1 EG 4, comparable with zone 2. In contradiction to the majority of standards covering the zone 1 requirements with all types of protection such as flameproof enclosure, increased safety, pressurization, oil immersion, intrinsic safety, powder filling, EG 2 excludes the general application of, e.g., increased safety e, which has been the domain of EG 3. 

The MESG classification relates to flameproof enclosures only. Standards IEC 60079-1 and IEC 60079-1-am 1, EN 50018... 

Electrical apparatus with combined non-intrinsically safe and intrinsically safe components, e.g. a flameproof enclosure with a power supply for intrinsically safe circuits, with a 690 V input, terminal boxes in increased safety, is considered as an associated apparatus (from the intrinsic point of view). In this case, the abbreviation for intrinsic safety is put in brackets ... 

Luminaire for high pressure mercury vapour lamp, flameproof enclosure, terminal box in increased safety, containing the series reactor protected by powder filling, for chemical plants ... 

Cage induction motor, flameproof enclosure, with terminal box in increased safety ... 

High voltage circuit breaker, enclosure and terminal boxes in increased safety, control box has a flameproof enclosure, flameproof vacuum circuit breaker ... 

As a general rule, the access to uninsulated live parts within an apparatus shall be possible only with the aid of a tool. Some types of protection, e.g. flameproof enclosure - d and increased safety - e - require special fasteners complying with the following ... 

When inert gases are used as protective gas, they cause a sort of inertization in the flameproof enclosure. Reducing the oxygen concentration in a gas-oxygen-inert gas mixture down to values of 5... 12% (v/v) prevents ignition of this mixture [2]. So, things move to the safe side. ... 

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