Shenzhen ZhongNuo Testing Technology Co., Ltd. is based in South China, offering services including on-site explosion-proof construction, safety inspections, renovations, project acceptance, and explosion-proof installation. We are well-versed in explosion-proof construction standards, boasting experienced construction teams and extensive practical experience. We have served major enterprises such as PetroChina, LG, Huanlan Environment, BOE Technology Group, and Sinovac Biotech, receiving consistent praise and trust from our clients!
Basic knowledge for explosion-proof electrical construction should include the following points:
1. Classification, grouping of explosive substances, and categorization, grading, and delineation of explosive hazard areas.
Explosive gases should be classified based on their Maximum Experimental Safety Gap (MESG) or Minimum Ignition Current Ratio (MICR), and grouped by their ignition temperature. Combustible dusts are divided into conductive and non-conductive types based on their conductivity, and grouped by their low ignition temperature. Hazardous areas involving explosive substances are categorized into gas and dust explosion hazardous areas. The hazardous areas are classified into Zones 0, 1, and 2 based on the frequency and duration of explosive gas environments. The hazardous areas for combustible dust/air mixtures are categorized into Zones 20, 21, and 22 based on the frequency, duration, and thickness of the dust layer.
Section 2: Selection of Explosion-Proof Electrical Equipment for Hazardous Areas.
The selection principles for explosion-proof electrical equipment are safety and reliability, as well as economic and reasonable. Selection should be based on the level of the explosive hazardous area and the type, grade, and group of explosive hazardous substances. Refer to the specific selection table in standard AQ3009-2007 for details.
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. Electrical wiring should be installed in areas with low explosion risk or at a distance from the source of release, avoiding locations prone to mechanical damage, vibration, corrosion, dust accumulation, and those with 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 operating voltage of the circuit and not less than 500V. Insulated conductors must be installed within conduits. For more details, refer to 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 after construction. To ensure that the electrical equipment remains in good condition and can be used in hazardous areas for a long period, continuous supervision and regular inspections are necessary. The initial and regular inspections should be entrusted to safety production testing and inspection agencies with explosion-proof qualifications.
Inspections and maintenance of explosion-proof electrical equipment should be conducted by qualified personnel meeting specified requirements. These individuals must undergo training covering areas 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 implemented. Maintenance requirements should propose reasonable corrective measures and equipment replacement procedures.

General Requirements for Explosion-Proof Workshop Design (Shared by Shenzhen ZhongNuo Inspection Technology Co., Ltd.)
4.1 Floor, Interior Wall
Areas producing flammable gases heavier than air or vapors of flammable or combustible liquids, as well as Class B production workshops with dust and fiber explosion hazards, should use non-sparking floors. To prevent sparks, materials such as rubber, plastic, rubber mixed with graphite, or asphalt concrete can be used for the floor.
Interior walls of workshops where combustible dust may settle should be plastered or painted to create easily cleanable (wipeable) surfaces.
4.2 Office, Break Room
For personnel safety, do not establish offices or restrooms in Class A or B production buildings with explosive hazards. If necessary, such rooms can be located outside the workshop, separated from the workshop by non-combustible walls with fire resistance not less than 3.5 hours.
4.3 Electrical Equipment
Electrical equipment in explosion-proof workshops should be selected and installed according to different circumstances, using explosion-proof types such as explosion-proof switches, explosion-proof motors, and explosion-proof lighting fixtures, and absolutely avoiding non-explosion-proof types.
4.4 Lightning Protection Facilities
In facilities and workshops prone to explosion, in addition to installing lightning protection devices on the building itself, it is required to set up grounded lightning rods around the building as per specifications. This ensures that the building is within the protected range of the entire lightning protection system, preventing accidents caused by lightning strikes.

Selection of cables and wires for explosive environments shall comply with the following regulations: (Shared by Shenzhen ZhongNuo Testing Technology Co., Ltd.)
In explosive environments, the rated voltage of insulated conductors and cables used for low-voltage power and lighting circuits should be higher than or equal to the working voltage, and the U0/U should not be less than the working voltage. The rated voltage of the neutral wire should be equal to the phase voltage and should be laid in the same sheath or protective tube.
(2) In explosive hazard zones, except within distribution panels, junction boxes, or metallic conduit wiring systems, uninsulated wires should not be used as supply and distribution lines.
(3) Copper-core cables should be used in Zone 1. In Zone 2, copper-core cables are recommended except for inherently safe circuits. When aluminum-core cables are used, their cross-sectional area must not be less than 16 square millimeters, and copper-aluminum transition joints should be used for connections to electrical equipment. Circuits installed in explosive dust environments in Zones 20 and 21, as well as in areas with severe vibration within Zone 22, must use copper-core insulated conductors or cables.
(4) In addition to the circuitry of this pressure safety system, the technical requirements for cable wiring in explosive environments shall comply with the specifications in Table 5.4.1-1.
(5) Technical requirements for pipeline wiring in explosive environments with voltages below 1000V, excluding circuits of intrinsic safety systems, shall comply with the specifications in Table 5.1.1-2.
(6) In explosive environments, the selection of insulated conductors and cable cross-sections shall comply with the requirements of Tables 5.4.1-1 and 5.4.1-2, as well as the following provisions:
The conductor's carrying capacity should not be less than 1.2 times the rated current of the fuse element and 1.2 times the setting current of the long-time overcurrent release of the circuit breaker, except for the circumstances specified in clause 2 of this article.
2) The long-term allowable current of the branch line for squirrel-cage induction motors with a voltage rating below 1000V should not be less than 1.2 times the rated current of the motor.
(7) When installing overhead or bridge-mounted cables, flame-retardant cables are recommended. Plastic-sheathed cables without armor can be used when the installation method employs bridgeways that prevent mechanical damage. Non-armor cables can also be installed in cable trenches within Zones 2 and 22, where there is no risk of damage from rodents or insects.

Equipment grounding in explosive environments shall comply with the following regulations (shared by Shenzhen ZhongNuo Testing Technology Co., Ltd.)
In accordance with the relevant provisions of the current standard "Code for Grounding Design of AC Electrical Installations" GB/T50065, the following parts that do not require grounding should still be grounded in explosive environments:
1) Non-conductive ground: Metal enclosures of equipment, with alternating current rated voltage below 1000V and direct current rated voltage below 1500V, which are normally not energized.
2) In dry conditions, equipment with alternating voltage not exceeding 127V and direct voltage not exceeding 110V typically has non-electrified metal enclosures.
3) Equipment installed on a grounded metal structure.
(2) In explosive hazardous environments, the exposed conductive parts of the equipment should be reliably grounded. All equipment within explosive zones 1, 20, and 21, and all equipment within explosive zones 2 and 22, except for lighting fixtures, should use dedicated grounding cables. If the grounding cable is installed in the same protective conduit as the phase wire, it should have insulation equal to that of the phase wire. Lighting fixtures within explosive zones 2 and 22 may use a metal pipeline system with a reliable electrical connection as a grounding cable, but not a pipeline for conveying materials.
(3) In different directions of the slope in the explosion hazard area, the grounding main should be connected to the grounding body at least twice.
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