Electrical installations in hazardous areas. Electrical apparatus and devices

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 7. Electrical equipment of special installations

Electrical installations in hazardous areas. Electrical apparatus and devices

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

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7.3.68. In hazardous areas, electrical apparatus and devices can be used, provided that the level of their explosion protection or the degree of protection of the shell in accordance with GOST 14255-69 correspond to Table. 7.3.11 or higher.

7.3.69. In hazardous areas of any class, electrical connectors can be used provided that they meet the requirements of Table. 7.3.11 for appliances that spark during normal operation.

In explosive zones of classes B-Ib and BIIa, it is allowed to use connectors in a sheath with a degree of protection IP54, provided that they break inside closed sockets.

The installation of connectors is allowed only to turn on periodically operating electrical receivers (for example, portable lamps). The number of connectors should be limited to the minimum necessary and they should be located in places where the formation of explosive mixtures is least likely.

IS circuits can be connected with general purpose connectors.

7.3.70. Clamp assemblies are recommended to be moved outside the hazardous area. If it is technically necessary to install assemblies in an explosive zone, they must meet the requirements of Table. 7.3.11 for stationary devices that do not spark during operation.

7.3.71. Fuses and switches for lighting circuits are recommended to be installed outside hazardous areas.

7.3.72. When using devices and devices with the type of protection "intrinsically safe electrical circuit" should be guided by the following:

1. The inductance and capacitance of intrinsically safe circuits, including connecting cables (the capacitance and inductance of which are determined by the characteristics, calculation or measurement), must not exceed the maximum values specified in the technical documentation for these circuits. If the documentation prescribes a specific type of cable (wire) and its maximum length, then their change is possible only if there is a conclusion from the testing organization in accordance with GOST 12.2.021-76.

2. Intrinsically safe circuits may include products that are provided for by the technical documentation for the system and are marked "Included ...". It is allowed to include in these circuits commercially available general-purpose sensors that do not have their own current source, inductance and capacitance and satisfy clause 4. Such sensors include commercially available general-purpose resistance thermometers, thermocouples, thermistors, photodiodes and similar products built into protective shells.

3. A circuit consisting of a commercially available general-purpose thermocouple and a galvanometer (millivoltmeter) is intrinsically safe for any explosive environment, provided that the galvanometer does not contain other electrical circuits, including scale illumination.

4. Commercially available general purpose switches, keys, terminal assemblies, etc. may be included in intrinsically safe circuits provided the following requirements are met:

a) other, spark-hazardous circuits are not connected to them;

b) they are closed with a lid and sealed;

c) their insulation is designed for three times the rated voltage of the intrinsically safe circuit, but not less than 500 V.

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

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