Section 7. Electrical equipment of special installations

Electrical installations in hazardous areas. Selection of electrical equipment for hazardous areas. General requirements

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

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7.3.54. Electrical equipment, especially with parts that spark during normal operation, is recommended to be moved outside hazardous areas if this does not cause special difficulties during operation and is not associated with unjustified costs. If electrical equipment is installed within a hazardous area, it must comply with the requirements of this chapter.

7.3.55. The use of portable electrical receivers (machines, apparatus, lamps, etc.) in hazardous areas should be limited to cases where their use is necessary for normal operation.

7.3.56. Explosion-proof electrical equipment used in chemically active, damp or dusty environments must also be protected from exposure to chemically active environments, dampness and dust, respectively.

7.3.57. Explosion-proof electrical equipment used in outdoor installations must also be suitable for outdoor use or have a device for protection against atmospheric influences (rain, snow, solar radiation, etc.).

7.3.58. Electrical machines with type “e” protection are allowed to be installed only on mechanisms where they will not be subject to overloads, frequent starts and reverses. These machines must have overload protection with an operating time of no more than time te. Here te is the time during which electric machines are heated by the starting current from the temperature due to long-term operation at rated load to the maximum temperature according to table. 7.3.7.

7.3.59. Electrical machines and devices with the type of explosion protection “explosion-proof enclosure” in environments with explosive mixtures of category IIC must be installed so that the explosion-proof flange gaps are not adjacent to any surface, but are located at a distance of at least 50 mm from it.

7.3.60. Explosion-proof electrical equipment designed to operate in an explosive mixture of flammable gases or flammable liquid vapors with air retains its properties if it is located in an environment with an explosive mixture of those categories and groups for which its explosion protection is made, or if it is located in an environment with an explosive mixture classified according to Table . 7.3.1 and 7.3.2 to less dangerous categories and groups.

7.3.61. When installing explosion-proof electrical equipment with the type of explosion protection “filling or purging the shell under excess pressure,” a ventilation system and control of excess pressure, temperature and other parameters must be installed, and all measures must be carried out in accordance with the requirements of GOST 22782.4 -78 * and instructions for installation and operation on a specific electrical machine or device. In addition, the following requirements must be met:

1. The design of foundation pits and protective gas pipelines must prevent the formation of unvented zones (bags) with flammable gases or flammable liquid vapors in them.

2. Supply gas pipelines to fans providing electrical equipment with protective gas must be laid outside hazardous areas.

3. Gas pipelines for protective gas can be laid under the floor of premises, including those with explosive zones, if measures have been taken to prevent flammable liquids from entering these gas pipelines.

4. In ventilation systems, devices, devices and other devices specified in the installation and operating instructions for the machine or device must be used to implement interlocks, control and alarms. Replacing them with other products, changing their installation locations and connecting them without agreement with the manufacturer of the machine or device is not allowed.

7.3.62. Electrical devices with oil-filled shells with live parts may be used on mechanisms in places where there are no shocks or measures have been taken to prevent oil from splashing out of the device.

7.3.63. In explosive zones of classes B-II and B-IIa, it is recommended to use electrical equipment intended for explosive zones with mixtures of flammable dusts or fibers with air.

In the absence of such electrical equipment, it is allowed in explosive zones of class B-II to use explosion-proof electrical equipment intended for operation in environments with explosive mixtures of gases and vapors with air, and in zones of class B-IIa - general purpose electrical equipment (without explosion protection), but having appropriate protection shells against dust penetration.

The use of explosion-proof electrical equipment intended for operation in environments with explosive mixtures of gases and vapors with air, and general-purpose electrical equipment with an appropriate degree of enclosure protection is permitted provided that the temperature of the surface of the electrical equipment on which flammable dusts or fibers can settle (when operating electrical equipment with a rated load and without layering of dust), will be no less than 50ºС below the smoldering temperature of dust for smoldering dusts or no more than two-thirds of the auto-ignition temperature for non-smoldering dusts.

7.3.64. Explosion protection of electrical equipment for outdoor ammonia compressor units is selected the same as for ammonia compressor units located indoors. Electrical equipment must be protected from atmospheric influences.

7.3.65. The selection of electrical equipment for work in hazardous areas should be made according to table. 7.3.10 - 7.3.12. If necessary, reasonable replacement of electrical equipment specified in the tables with electrical equipment with a higher level of explosion protection and a higher degree of enclosure protection is permitted. For example, instead of electrical equipment of the “increased reliability against explosion” level, electrical equipment of the “explosion-proof” or “especially explosion-proof” level can be installed.

In areas where the explosion hazard is determined by flammable liquids having a flash point above 61ºC (see 7.3.12), any explosion-proof electrical equipment for any category and group with a surface heating temperature not exceeding the auto-ignition temperature of the substance can be used.

Table 7.3.10. Permissible level of explosion protection or degree of protection of the shell of electrical machines (stationary and mobile) depending on the class of the explosive zone

* Until the electrical industry adopts machines with a shell protection degree of IP54, it is allowed to use machines with a shell protection degree of IP44.

Table 7.3.11. Permissible level of explosion protection or degree of protection of the shell of electrical devices and devices depending on the class of the explosive zone

* The degree of protection of the shell of devices and devices from water penetration (2nd digit of the designation) can be changed depending on the environmental conditions in which they are installed.

Table 7.3.12. Permissible level of explosion protection or degree of protection of electric lamps depending on the class of the hazardous area

* It is allowed to change the degree of protection of the shell from water penetration (2nd digit of the designation) depending on the environmental conditions in which the luminaires are installed.

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

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