Zhaoqing Explosion-proof Electrical Installation

Shenzhen Zhongnuo Testing Technology Co., Ltd. is based in South China, offering on-site explosion-proof construction, safety inspections, renovations, project acceptance, and explosion-proof installation consulting services. We are well-versed in explosion-proof construction standards, boasting experienced construction teams and extensive practical experience. We have served major corporations such as PetroChina, LG, Hanlan Environment, BOE Technology Group, and Sinovac Biotech, earning consistent praise and trust from our clients!
Basic knowledge for explosion-proof electrical construction includes the following points:
Explosive materials classification, grouping, and classification of explosive hazard areas, as well as the delineation of regional scope.
Explosive gases should be classified according to their Maximum Experimental Safe Gap (MESG) or Minimum Ignition Current Ratio (MICR), and grouped by 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 explosion risks are categorized into two types based on the physical state of the explosive substances: gas explosion hazard areas and dust explosion hazard areas; hazardous areas are divided into three zones—Zone 0, 1, and 2—based on the frequency and duration of occurrence of explosive gas environments; hazardous areas are further categorized into three zones—Zone 20, 21, and 22—based on the frequency and duration of occurrence and dust layer thickness of combustible dust/air mixtures.
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 hazard area and the category, level, and group of the 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 categorized into cable wiring and conduit wiring. Electrical wiring should be laid in areas with lower explosion hazards or at a greater distance from the source of release, avoiding locations prone to mechanical damage, vibration, corrosion, dust accumulation, and those with dangerous 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 installed within conduits. For more details, attend training programs 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, during the handover and acceptance of the project. To ensure the electrical equipment remains in good condition and can be used long-term in hazardous areas, continuous supervision and regular inspections should be carried out. 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 requirements. 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 regular inspections should be carried out. Maintenance requirements should propose reasonable remedial measures and equipment replacement procedures.

Selection of cables and wires for explosive environments should comply with the following specifications: (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 lines should be higher than or equal to the working voltage, with U0/U not less than the working voltage. The rated voltage of the neutral line should be equal to the phase voltage and should be laid in the same sheath or protective conduit.
(2) In explosive hazard areas, except within the distribution board, junction box, or metal conduit wiring system, unshielded wires should not be used as power supply and distribution lines.
(3) Copper-core cables should be used in Zone 1. In Zone 2, copper-core cables are recommended except for intrinsically 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 with electrical equipment. Circuits installed in explosive dust environments in Zones 20 and 21, as well as in areas with severe vibration in Zone 22, must use copper-core insulated conductors or cables.
(4) In addition to the circuit of this pressure safety system, the technical requirements for wiring of cables in explosive environments shall comply with the specifications in Table 5.4.1-1.
(5) Technical requirements for piping 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 must comply with the provisions of Tables 5.4.1-1 and 5.4.1-2, as well as the following regulations:
1) The conductor's allowable current 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 delay overcurrent release of the circuit breaker, except for the situation specified in clause 2 of this article.
2) The long-term allowable current for the branch line of 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, it is advisable to use flame-retardant cables. When the installation method employs bridge structures that prevent mechanical damage, plastic-sheathed cables can be used as non-armored cables. In areas where there is no risk of damage from rodents or insects, cables installed in cable trenches in Zones 2 and 22 can be non-armored cables.

Explosive circuit protection should comply with the following regulations (shared by Shenzhen ZhongNuo Testing Technology Co., Ltd.)
In the 1st zone, the phase wires and neutral lines in the single-phase network should be equipped with short-circuit protection, and appropriate switches should be used to simultaneously disconnect both the phase wires and the neutral lines.
(2) For 3kV-10kV cable lines, it is advisable to install zero-sequence current protection, with protective devices in Zones 1 and 21 set to trip.

Basic Standards for Explosion-Proof Electrical Construction (Shared by Shenzhen ZhongNuo Inspection Technology Co., Ltd.)
Explosion-proof electrical installation differs from standard electrical installation due to the increased explosion-proof requirements of its environment. Based on industry standards, an environment where gases, vapors, mist, or dust mix with air under atmospheric conditions and ignite, causing combustion to spread to all unburned mixtures, is termed an explosive environment. An area where a large number or an expected large number of explosive gas environments or flammable dust environments are present, necessitating special preventive measures for the structure, installation, and use of electrical equipment, is called a hazardous area. Explosion-proof electrical installation refers to a task that meets the requirements for explosion-proof electrical equipment, conditions, and personnel, and involves work in explosive environments and hazardous areas, with strong emphasis on safety.
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