Explosion protection temperature class

This marking system correlates the adequate zone on the explosion protected apparatus with traditional data, e.g. group, type of protection and temperature class (see Chapter 5). 

Selection in this chapter is strictly focused on safety related data in the field of explosion protection, neglecting all the other aspects like maintenance or financial considerations (this will be the objective of Chapter 9). Here, selection means the appropriate choice of electrical apparatus according to temperature class and MESG or MIC/MIC (CH4) grouping, taking into account the combustible raw materials and products in the relevant plant. 

IEC and EN Standards ask for marking the type of protection as an abbreviation completed by the classification scheme (temperature class, explosion group) as described in the previous chapter. Table 5.1 gives a survey of the types of explosion protection and their abbreviations. Table 5.2 summarizes the IEC and EN marking code. 

Table 5.5 gives a guideline for the selection of explosion protected electrical apparatus, i.e. the appropriate choice of temperature class and group referring to the hazardous substances in the plant to be considered. Very generally Tower temperature classes do comply with the requirements for... 

Classification and marking of intrinsically safe apparatus concerning explosion groups (I, IIA, IIB, IIC) and temperature classes (T1-T6) are organized in the same way as for, e.g., flameproof enclosure - d (see Tables 4.1 and 4.2, Chapter 4, and Chapter 5 for marking). Some special features, however, which are of importance for type of protection intrinsic safety - i only, will be explained in the following. 

Methyl chloride is classified as a flammable gas, class 2.1, in both the United States and Canada. It bums feebly but forms explosive mixtures with air. The end product of high temperature decomposition may be toxic. For additional data concerning physiological effects, exposure limits, protective equipment, chemical and physical properties, etc., see the monograph on methyl chloride in Part II. 

Non-electrical equipment of the equipment group II, category 2 for explosive atmosphere formed from air and gases, vapours and/or mists, type of protection flame-proof enclosure, permissible explosive atmosphere of the Ex-Group IIB, T-Class T4, ambient temperature (T ) with 0°Cdiffering from the standard values -20 °C < T. -t-TO C ... 

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