Section 7. Electrical equipment of special installations

Electrical installations in hazardous areas. Classification and marking of explosion-proof electrical equipment according to GOST 12.2.020-76*

Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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7.3.31. Explosion-proof electrical equipment is divided into levels and types of explosion protection, groups and temperature classes.

7.3.32. The following levels of explosion protection of electrical equipment have been established: "electrical equipment of increased reliability against explosion", "explosion-proof electrical equipment" and "especially explosion-proof electrical equipment".

Level "electrical equipment of increased reliability against explosion" - explosion-proof electrical equipment in which explosion protection is provided only in a recognized normal mode of operation. Level sign - 2.

Level "explosion-proof electrical equipment" - explosion-proof electrical equipment, in which explosion protection is provided both in normal operation and in case of recognized probable damage determined by operating conditions, except for damage to explosion protection equipment. Level sign - 1.

The level of "especially explosion-proof electrical equipment" is explosion-proof electrical equipment, in which, in relation to explosion-proof electrical equipment, additional means of explosion protection are adopted, provided for by standards for types of explosion protection. Level sign - 0.

7.3.33. Explosion-proof electrical equipment can have the following types of explosion protection:

The types of explosion protection that provide different levels of explosion protection differ in the means and measures for ensuring explosion safety, specified in the standards for the corresponding types of explosion protection.

7.3.34. Explosion-proof electrical equipment, depending on the field of application, is divided into two groups (Table 7.3.5).

7.3.35. Group II electrical equipment with types of explosion protection "explosion-proof enclosure" and (or) "intrinsically safe electrical circuit" is divided into three subgroups corresponding to the categories of explosive mixtures according to Table. 7.3.6.

7.3.36. Electrical equipment of group II, depending on the value of the limiting temperature, is divided into six temperature classes corresponding to groups of explosive mixtures (Table 7.3.7).

Limiting temperature - the highest temperature of the surfaces of explosion-proof electrical equipment, safe in relation to the ignition of the surrounding explosive atmosphere.

Table 7.3.5. Groups of explosion-proof electrical equipment by area of ​​its application

Table 7.3.6. Subgroups of electrical equipment of group II with types of protection "explosion-proof enclosure" and (or) "intrinsically safe electrical circuit" *

* Sign II is used for electrical equipment that is not subdivided into subgroups.

Table 7.3.7. Temperature classes of electrical equipment of group II

7.3.37. The marking for explosion protection of electrical equipment in the following sequence includes:

• sign of the level of explosion protection of electrical equipment (2, 1, 0);
• Ex mark indicating compliance of electrical equipment with explosion-proof electrical equipment standards;
• sign of the type of protection (d, i, q, o, s, e);
• sign of a group or subgroup of electrical equipment (II, IIA, IIB, IIC);
• sign of the temperature class of electrical equipment (T1, T2, T3, T4, T5, T6).

Explosion protection markings may contain additional signs and inscriptions in accordance with the standards for electrical equipment with certain types of explosion protection. Examples of marking explosion-proof electrical equipment are given in Table. 7.3.8.

Table 7.3.8. Examples of marking explosion-proof electrical equipment

Explosion protection level	Type of explosion protection	Group (subgroup)	Temperature class	Explosion protection marking
Electrical equipment of increased reliability against explosion	Type "e" protection	II	T6
	Type "e" protection and flameproof enclosure	IIB	T3
	intrinsically safe electrical circuit	IIC	T6
	Shell purge under pressure	II	T6
	Flameproof enclosure and intrinsically safe electrical circuit	IIB	T5
Explosion-proof electrical equipment	Flameproof shell	iia	T3
	intrinsically safe electrical circuit	IIC	T6
	Filling the shell under pressure	II	T6
	Type "e" protection	II	T6
	Quartz shell filling	II	T6
	Special	II	T6
	Special and flameproof shell	IIA	T6
	Special, intrinsically safe electrical circuit and flameproof enclosure	IIB	T4
Particularly explosion-proof electrical equipment	intrinsically safe electrical circuit	IIC	T6
	Intrinsically safe electrical circuit and flameproof enclosure	IIA	T4
	Special and intrinsically safe electrical circuit	IIC	T4

See other articles Section Rules for the installation of electrical installations (PUE).

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