Flameproof joint

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

Even with a zero width of a flameproof joint, there will be no flame transmission if the gap is suitably reduced. 

So, cutting edge-shaped joints do prevent flame transmission to the external atmosphere. For the purpose of manufacturing electrical equipment, this fact may be unimportant, but it is very helpful towards an explanation of the working principle of a flameproof joint. 

This simple model indicates that a flameproof joint works in the same way as a rocket. A chemical reaction (combustion) within the combustion chamber... 

Before considering individual types of electrical apparatus, flameproof joints as an essential element of d shall be dealt with. The contents of EN 50018 and IEC 60079-1 are different, depending on the edition of the standard. The requirements are listed in Tables 6.27, 6.28 and 6.29. The values given in these tables are constructional requirements and ensure the flameproofness of an enclosure except for extreme shapes, e.g. long U-shaped pipes for electric heaters. In such cases, the gap shall be reduced to an appropriate value. 

The gap of a joint is the distance between the corresponding surfaces of a flameproof joint. For cylindrical surfaces, the gap is the diametral clearance (difference between the two diameters)... 

Figure 6.85 Longitudinal section drawings of flameproof cage induction motors, indicating the flameproof joints ...

Machining the surfaces of a flameproof joint, gap and width B of joint according to the certificate... 

As Synchronous belt transmission ratio is accurate which can satisfy the requirement of detecting robot flexible mobility. Robot adopts synchronous belt transmission mode with one power output shaft on each side. Compared with all motor driven, it can reduce motor number and the flameproof joint number, optimize the stress distribution of flame-proof encloser, increase internal space improve the AMDR s mobility and safety greatly. Synchronous belt is closed in a confined space, avoiding friction sparks produced, improving the safety of the robot. 

This parabola defines the area of flame transmission through the joint. Its vertex is usually nearby or somewhat below the stoichiometric point. All gases show a behaviour similar to that shown in Fig. 1.3. The knowledge of the vertex MESG values of gas-air or vapour-air mixtures is essential for the construction and use of enclosures, type of protection flameproof... 

The width of a joint is the shortest path through a joint from the inside to the outside of a flameproof enclosure (in a very general sense, it is the length of the flame path)... 

In many cases there will be a certain demand for protective coatings (paints) against corrosion for the joint surfaces. This question should be handled very carefully. Many coatings contain particles (e.g. aluminium) which may adversely affect the flameproof properties of the joint. Tests should be made to ensure the coating s appropriateness for this application. 

Figure 6.101 Flameproof enclosure, coverwith threaded joint.

A typical flameproof enclosure for Group II installation is shown in Fig. 6.101. A cover with a threaded joint enables quick access for replacement... 

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]. 

Obstructions adjacent to flameproof XXX flanged joints are in accordance with... 

Dimensions of joints are an essential characteristic of a flameproof enclosure... 

Machining the surfaces of a joint considered to be flameproof, C gap and width of joint not in accordance with the certificate Dimensions of joint may be outside the requirements of the relevant standard. Joints with changed dimensions shall pass successfully a type test (see Section 8.1)... 

Flameproof equipment is regarded as safe for use when exposed to the risk of explosive atmosphere for which certification has been given. Electrical apparatus, defined as flameproof, has an enclosure that will withstand an internal explosion of the flammable vapour or gas in question which may enter the enclosure. The joints of the enclosure which are designed with clearance gaps to prevent a build-up of internal pressure also prevent any internal explosion igniting vapour or gas surrounding the equipment. The surface temperature of the enclosure must be below the ignition temperature of the vapour or gas in question, hence the importance of the temperature classification referred to above. Flameproof enclosures are primarily intended for use in Zone 1 or Zone 2 classification but not in Zone 0. 

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