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Installation of electrical wiring in explosive environments shall comply with the following regulations (Shared by Shenzhen ZhongNuo Inspection Technology Co., Ltd.)
Electrical wiring should be installed in environments with lower explosion hazards or far from the source of release, and it should comply with the following regulations:
1) When the weight is heavier than air, electrical wiring should be installed at a higher level or directly buried. For overhead installation, cable trays should be used; for trench installation, the trench should be filled with sand and drainage measures should be in place.
2) Electrical wiring should be installed outside the walls of buildings or structures that pose an explosion hazard.
3) In explosive dust environments, cables should be laid in areas where dust does not accumulate easily and is easy to remove.
(2) Holes in walls or floors at different areas traversed by electrical line trenches, cable trays, or conduits should be tightly sealed with non-combustible materials.
(3) When laying electrical lines, it is advisable to avoid areas prone to mechanical damage, vibration, corrosion, ultraviolet radiation, and heat. If avoidance is not possible, preventive measures should be taken.
(4) Conduit wiring can use insulated single-core or multi-core wires without sheath. When the conduit contains three or more wires, the total cross-sectional area of the wires, including the insulation, should not exceed 40% of the conduit's cross-sectional area. The conduit should be a galvanized steel焊接管 used for low-pressure fluid conveyance. The threaded portion of the steel conduit should be coated with lead oil or phosphating paste. In areas where condensation may occur, condensate drainage fittings should be installed on the conduit.
(5) Electrical wiring for piping in explosive gas environments must be properly insulated and sealed, and should comply with the following regulations:
1) During normal operation, all flame source enclosures within a 450mm radius should be sealed off.
2) Steel pipes with a diameter of 50mm or more should be isolated and sealed within 450mm from the incoming junction box.
3) Isolation and sealing should be conducted between adjacent explosive environments, as well as between explosive environments and adjacent other hazardous or non-hazardous environments. When sealing, the inner part of the seal should have a fibrous filling layer as the bottom or intermediate layer, with an effective thickness not less than the inner diameter of the steel pipe, and not less than 16mm.
4) Connection parts for isolation sealing should not be used for wire connections or branching.
(6) Intermediate joints are strictly prohibited in cable lines within Zone 1, and intermediate joints should not be present in Zones 2, 20, and 21.
(7) When terminating cables or wires, if the internal conductors are stranded, the terminals should be connected using a crimped terminal or a splicing sleeve. The connection and termination of aluminum-core insulated conductors or cables should be made by crimping, soldering, or brazing. When connecting to equipment (excluding lighting fixtures), a copper-aluminum transition connector should be used.
(8) Overhead power lines must not cross explosive gas environments; the horizontal distance between overhead lines and explosive gas environments should not be less than 1.1 times the height of the tower. Under special circumstances, after taking effective measures, the distance may be appropriately reduced.

Basic Knowledge and Requirements for Cable Usage in Explosion-Proof Construction Sites (shared by Shenzhen ZhongNuo Inspection and Testing Technology Co., Ltd.)
Installation methods for electrical wiring in explosive gas environments can be categorized into cable wiring and conduit wiring methods.
Note: The installation of inherently safe circuits does not have to comply with the provisions of this article.
7.1 General Provisions
7.2 Electrical wiring should be installed in areas of lower explosion hazard or at a greater distance from the source of release, avoiding locations susceptible to mechanical damage, vibration, corrosion, dust accumulation, and those with hazardous temperatures. If avoidance is not possible, preventive measures should be taken.
7.3 The selected low-voltage cables or insulated conductors must have a rated voltage higher than the working voltage of the line and not less than 500V. Insulated conductors must be laid within conduits.
7.4 Prohibition of overhead lines at 10kV and below crossing explosive gas environments; the horizontal distance between overhead lines and explosive gas environments should not be less than 1.1 times the height of the pole towers.
7.5 Cables and their accessories shall be installed so that their position is suitable to prevent damage from external mechanical forces, corrosion, or chemical influences (e.g., the effect of solvents), as well as from the effects of high temperatures (also refer to 6.1.2.4.4 for this safety circuit). If such conditions cannot be avoided, protective measures shall be taken during installation, such as using conduits or selecting appropriate cable types (armored cables, shielded wires, seamless aluminum sheath cables, mineral insulated metal sheath cables, or semi-rigid sheath cables, etc., to minimize damage).
7.6 Unsheathed single-core wire should not be used for conductive wiring unless installed within a distribution board, housing, or conduit system.

Basic knowledge for explosion-proof electrical construction includes the following points:
Explosive materials classification, grouping, and classification of explosive hazard areas, including the division of regional scope.
Explosive gases should be classified based on their Maximum Experimental Safe Gap (MESG) or Minimum Ignition Current Ratio (MICR), and grouped by their ignition temperature. Combustible dusts can be divided into conductive and non-conductive types based on their electrical conductivity, and grouped by their low ignition temperature. Hazardous areas with explosive risks are categorized into two types: gas explosion hazardous areas and dust explosion hazardous areas. These areas are further divided into three zones (0, 1, and 2) based on the frequency and duration of the presence of explosive gas environments. Hazardous areas with combustible dust/air mixtures, as well as the thickness of dust layers, are categorized into three zones (20, 21, and 22) based on the frequency and duration of their occurrence.
Two: Selection of explosion-proof electrical equipment for hazardous explosive areas.
The selection principle for explosion-proof electrical equipment is safety and reliability, economic and reasonable. It should be selected based on the grade of the explosive hazardous area and the category, level, and group of explosive hazardous substances. Refer to the specific selection table in standard AQ3009-2007.
Section 3: Installation of electrical wiring and explosion-proof electrical equipment in hazardous explosive areas.
Installation methods for electrical wiring in explosive gas environments can be divided into cable wiring and conduit wiring methods. Electrical wiring should be laid in areas with lower explosion risk or at a greater distance from the source of release, avoiding locations prone to mechanical damage, vibration, corrosion, dust accumulation, and hazardous temperatures. When avoidance is not possible, preventive measures should be taken. The low-voltage cables or insulated conductors used must have a rated voltage higher than the working voltage of the circuit and not less than 500V. Insulated conductors must be laid within conduits. For more details, you can attend training courses on explosion-proof electrical installation, maintenance, and repair.
Four: Inspection and maintenance of explosion-proof electrical equipment in hazardous areas.
To minimize the ignition hazard of electrical equipment in hazardous areas, initial inspections should be conducted before the equipment is put into operation and during the handover acceptance of the project. Continuous supervision and regular inspections should be carried out to ensure the electrical equipment remains in good condition for long-term use in hazardous areas. The initial and regular inspections should be entrusted to safety production testing and inspection institutions with explosion-proof qualifications.
Inspections and maintenance of explosion-proof electrical equipment should be conducted by qualified personnel meeting specified criteria. These individuals must undergo training covering topics such as explosion-proof types, installation practices, relevant regulations and procedures, as well as the general principles of hazardous area classification. They should also receive appropriate continuing education or regular training and possess relevant experience and trained qualifications. Continuous supervision and periodic inspections should be conducted. Maintenance requirements should propose reasonable corrective measures and equipment replacement procedures.

Basic Dust Explosion Proof Construction Standards
In facilities where explosive dust is present, such as flour mills, feed factories, grinding workshops, and plastic production plants, the requirement for explosion-proofing on-site is particularly important. Explosion-proof wiring, installation and use of explosion-proof electrical equipment, dust removal systems, architectural structure layouts, and explosion-proof venting must all comply with the relevant dust explosion-proof standards. Based on a wealth of explosion-proof electrical construction and retrofitting cases, Shenzhen Zhongnuo Testing Technology Co., Ltd. has summarized the following points:
1. Structure and layout of the building
Process equipment with a risk of dust explosion or buildings (structures) with combustible dust should be separated from other buildings (structures), and the fire protection distance should comply with the relevant provisions of GB50016.
(2) The building should be a single-story structure, with a lightweight roof design preferred.
(3) Structural requirements for multi-story buildings are as follows:
A. Multi-story buildings are recommended to use frame structures.
B. Buildings without frame structures should have explosion relief openings installed on the walls in compliance with requirements.
C. If windows or other openings are used as blast relief vents, they must be calculated and ensured to effectively release blast during an explosion.
(4) Evacuation route requirements are as follows:
The work area should have evacuation routes, and the number and location of these routes should comply with the provisions of GB50016.
B. The door should open outward and no threshold should be installed.
C. Detailed road signs and emergency lighting should be set up for evacuation routes.
2. Process Equipment
If there are process equipment with a dust explosion risk in the factory building, they should be located on higher floors and close to the exterior walls.
(2) Equipment with explosive hazards should be located in outdoor open areas outside of buildings.
(3) Equipment or devices in direct contact with dust (such as light sources, heating sources, etc.) should have surface temperatures lower than the corresponding low ignition temperature of the dust.
(4) In areas where combustible dust is present, the transmission mechanisms of the equipment and installations shall comply with the following regulations:
The bearings of the process equipment should be dust-proof and sealed. If overheating is possible, a detector capable of continuously monitoring the bearing temperature should be installed.
B. Belt drive is not recommended. If belt drive is used, a speed difference sensor and an automatic anti-skid protection device should be installed. In the event of sliding friction, the protection device should ensure automatic shutdown.
(5) At the feeding point of the process flow, magnets, pneumatic separators, or screens capable of removing impurities mixed in the material should be installed to prevent the impurities from colliding with the equipment.
(6) Effective measures should be taken to prevent sparks from being generated when metal powders such as aluminum, zirconium, or powders containing these metals come into friction with stainless steel.
(7) For protective stopping in case of explosion, several power supply control boxes capable of interlocking with each other should be installed according to the size of the workshop. In emergencies, they should be able to promptly disconnect the power supply of all motors.
(8) Joints, inspection doors, baffles, and explosion vent covers of process equipment should all be sealed tightly
(9) The equipment housing should be made of non-flammable material
(10) The moving parts of the equipment should operate smoothly without any scraping, bumping, jamming, or rubbing.
(11) When the strength of the process equipment is insufficient to withstand the overpressure generated by internal dust explosion under actual operating conditions, explosion relief openings should be installed, and the size of these openings should comply with the relevant provisions of GB/T15605.
(12) The explosion relief port should be located near potential ignition sources, and it should be as close to the top or upper part of the containment structure as possible. It must not vent towards flammable and explosive hazardous areas to prevent igniting others, and it must not vent towards public areas to avoid causing injury from the explosion.
3. Lightning and Static Electricity Protection
Dust explosion hazard areas should adopt corresponding lightning protection measures in accordance with the relevant provisions of GB50057. When static electricity hazards are present, the following regulations should be followed:
(1) All metal equipment, casing of devices, metal pipes, brackets, components, parts, etc., generally use antistatic direct grounding. For those that are not convenient or prohibited by the process from direct grounding, grounding can be achieved indirectly through conductive materials or products.
(2) Equipment directly used for containing electrostatic powder, such as conveyance pipes (belts) for the powder, should be made of metal or antistatic materials.
All metal pipe connections should be bonded together.
(4) Operators should take anti-static precautions.
(5) Avoid using methods that involve direct grounding metal conductors or screens in contact with rapidly flowing powders to dissipate static electricity.
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