Spark-type explosion-proof electrical equipment mainly includes: electrical components or circuits, enclosures and doors, covers, observation windows, junction boxes, cable leads, joysticks, and shafts. Non-sparking type explosion-proof electrical equipment is mostly used in petrochemical plants or in open space, so the enclosure should be made of non-flammable or flame-retardant and corrosion-resistant materials. The enclosure shall have a certain mechanical strength and meet the protection requirements. For the enclosure with insulated live parts, the degree of protection shall be IP44, and for the enclosure with bare live parts it shall be IP54. However, the protection standard for the enclosure of explosion-proof electrical equipment installed in a room and specially managed and maintained by a person may be IP20 (except for the junction box and exposed live parts on the shell). The door and cover on the shell should be assembled firmly and not easily deformed or damaged. The observation window should be placed in an easy-to-observe position and not easily damaged. Transparent parts of the observation window should be made of glass or other non-flammable or flame-retardant, transparent materials.
The realization of the explosion-proof performance of non-sparking type electrical equipment has a lot to do with the use of junction boxes, connectors, and internal wire connections. Improper handling of these parts will create sparks or arcing during operation of the equipment, posing a risk of igniting explosive mixtures. Therefore, the connection of all components on the circuit of the non-sparking type electrical equipment and the connection between the wire, the cable, and the connector must be firm, safe and reliable, and no loosening or rotation of the cable or the wire due to vibration, etc., and thus overheating or electricity may occur. spark. The connector is a connecting structure composed of a conductive screw, a terminal block and the like. The connector shall have good electrical conductivity and shall not damage the edges and burrs of the conductors. It shall not be permanently deformed and rotate by itself during normal tightening. Insulation members shall not transmit pressure in the connector. For connectors that connect multiple strands of wire, take precautions to prevent strand splitting before connecting. When using aluminum wires, copper-aluminum transition joints should be used to prevent electrolytic corrosion from occurring at the contacts.
The connection of internal wires of non-spark type explosion-proof electrical equipment is also very important. The commonly used connection methods are:
1 Take screws or bolts with loosening measures. This connection method is safe and reliable.
2 The wires to be connected are connected by mechanical extrusion. This connection method has good electrical conductivity.
3 mechanical connection and welding connection and connection.
4 using brazing or welding connection.
The design and manufacture of junction boxes for non-sparking type electrical equipment are to comply with the wiring requirements in the general requirements of section 1 of this chapter and will not be repeated here. In order to ensure that spark-free electrical equipment does not generate arcs, sparks or dangerous temperatures during normal operation, its maximum surface temperature during normal operation shall comply with the maximum surface temperature requirements for Class II electrical equipment in Table 1. The operating temperature range of non-sparking electrical equipment is -20~40°C. Under normal circumstances, the maximum allowable surface temperature of the electrical equipment should be lower than the temperature of the group marked on the electrical equipment. However, for electrical equipment of temperature group T1, T2 and T3, the total surface area in the equipment is not greater than 10cm2 (such as transistors or resistors that limit the power of small power circuits, etc.), and the maximum surface temperature is ignited relative to the actual measurement. The temperature is +50°C (safety margin, the maximum surface temperature of the component is allowed to exceed the group temperature marked on the electrical equipment. For the T4, T5 and T6 group electrical equipment, the total area of ​​the equipment is not more than 10cm2, If the maximum surface temperature has a safety margin of +25°C relative to the measured pilot temperature, the maximum surface temperature of the component is allowed to exceed the group temperature on the electrical equipment.
The realization of the explosion-proof performance of non-sparking type electrical equipment has a lot to do with the use of junction boxes, connectors, and internal wire connections. Improper handling of these parts will create sparks or arcing during operation of the equipment, posing a risk of igniting explosive mixtures. Therefore, the connection of all components on the circuit of the non-sparking type electrical equipment and the connection between the wire, the cable, and the connector must be firm, safe and reliable, and no loosening or rotation of the cable or the wire due to vibration, etc., and thus overheating or electricity may occur. spark. The connector is a connecting structure composed of a conductive screw, a terminal block and the like. The connector shall have good electrical conductivity and shall not damage the edges and burrs of the conductors. It shall not be permanently deformed and rotate by itself during normal tightening. Insulation members shall not transmit pressure in the connector. For connectors that connect multiple strands of wire, take precautions to prevent strand splitting before connecting. When using aluminum wires, copper-aluminum transition joints should be used to prevent electrolytic corrosion from occurring at the contacts.
The connection of internal wires of non-spark type explosion-proof electrical equipment is also very important. The commonly used connection methods are:
1 Take screws or bolts with loosening measures. This connection method is safe and reliable.
2 The wires to be connected are connected by mechanical extrusion. This connection method has good electrical conductivity.
3 mechanical connection and welding connection and connection.
4 using brazing or welding connection.
The design and manufacture of junction boxes for non-sparking type electrical equipment are to comply with the wiring requirements in the general requirements of section 1 of this chapter and will not be repeated here. In order to ensure that spark-free electrical equipment does not generate arcs, sparks or dangerous temperatures during normal operation, its maximum surface temperature during normal operation shall comply with the maximum surface temperature requirements for Class II electrical equipment in Table 1. The operating temperature range of non-sparking electrical equipment is -20~40°C. Under normal circumstances, the maximum allowable surface temperature of the electrical equipment should be lower than the temperature of the group marked on the electrical equipment. However, for electrical equipment of temperature group T1, T2 and T3, the total surface area in the equipment is not greater than 10cm2 (such as transistors or resistors that limit the power of small power circuits, etc.), and the maximum surface temperature is ignited relative to the actual measurement. The temperature is +50°C (safety margin, the maximum surface temperature of the component is allowed to exceed the group temperature marked on the electrical equipment. For the T4, T5 and T6 group electrical equipment, the total area of ​​the equipment is not more than 10cm2, If the maximum surface temperature has a safety margin of +25°C relative to the measured pilot temperature, the maximum surface temperature of the component is allowed to exceed the group temperature on the electrical equipment.
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