Shenzhen Zhongnuo Inspection & Technology Co., Ltd. is based in South China and offers explosion-proof technology consulting services including on-site construction, safety inspections, renovations, project acceptance, and explosion-proof installations. We are well-versed in explosion-proof construction standards and have experienced construction teams with ample experience. We've served major enterprises such as PetroChina, LG, Huanlan Environment, BOE, and KeXing Biotechnology, receiving consistent praise and trust from our clients!
Shenzhen ZhongNuo Testing Technology Co., Ltd. offers explosion-proof engineering construction services for hazardous explosive areas.
1. Explosion-proof Site Inspection and Consultation
2. Explosion-proof engineering construction and renovation on-site
3. Explosion-proof Construction Acceptance
4. Explosion-proof electrical installation, maintenance, and renovation
5. Explosion relief walls, doors, and windows installation
6. Dust Removal Equipment Installation and Renovation Construction

Selection of cables and wires for explosive environments should 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 U0/U should not be 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 tube.
(2) In explosive hazard zones, except within distribution panels, wiring cabinets, or metal 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, it is advisable to use copper-core cables, 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 environment 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 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) The technical requirements for pipeline wiring in explosive environments with voltages below 1000V, excluding circuits of intrinsic safety systems, shall comply with the specifications of 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 requirements:
1) The conductor's allowable current-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 delay overcurrent release of the circuit breaker, except for the circumstances specified in clause 2 of this article.
2) The long-term allowable current for the branch line of squirrel-cage induction motors with voltage 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 bridge supports that prevent mechanical damage. 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-armor cables.

Basic knowledge for explosion-proof electrical installation includes the following points:
1. Classification, grouping of explosive substances, and categorization, grading, and delineation of explosion 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, classified by their conductivity, can be divided into conductive and non-conductive types, 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 based on the frequency and duration of explosive gas environments: Zone 0, Zone 1, and Zone 2. Hazardous areas with combustible dust/air mixtures are categorized into three zones based on the frequency and duration of the mixture and the thickness of the dust layer: Zone 20, Zone 21, and Zone 22.
Section 2: Selection of Explosion-Proof Electrical Equipment for Hazardous 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 the 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. Electrical wiring should be installed 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 laid inside conduits, etc. For more details, refer to training programs on explosion-proof electrical installation, maintenance, and repair.
4. 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 for long-term use in hazardous areas, continuous supervision and periodic inspections should be carried out. Initial and periodic 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 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-proof measures on-site is particularly crucial. The installation and use of explosion-proof wiring, electrical equipment, dust removal systems, architectural layout, 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:
4. Explosion-proof electrical equipment
Electrical equipment used in dust explosion hazard areas must comply with the relevant standards of GB/T3836. The power design should be executed in accordance with the provisions of GB50058. Explosion-proof electrical equipment should be selected based on the grade of the explosion hazard area, as well as the category, level, and group of the explosive substances.
Options for explosion-proof electrical equipment. In addition to dust explosion-proof electrical equipment with dust-tight construction for the 21区的 environments with combustible non-conductive dust and combustible fibers, dust explosion-proof electrical equipment with dust-tight construction is used in the 20 zone of explosive dust environments and other 21 zones of explosive dust environments, with different electrical equipment selected based on the varying ignition temperatures of the dust.
(2) Galvanized Welded Steel Pipe for Low-Pressure Fluid Transportation
(3) Connections between steel pipes, steel pipes and electrical equipment, and steel pipe accessories should be made using threaded connections. Soldering with sleeves is prohibited, and the following requirements must be met: The threading should be smooth, complete, and free of rust. Power composite grease or conductive anti-rust grease should be applied to the threads. Do not wrap with hemp or insulating tape, nor apply other paints on the threads. For steel pipes with a diameter of 25mm or less, there should be at least 5 threads. For steel pipes with a diameter of 32mm or more, there should be at least 6 threads.
(4) Explosion-proof flexible conduits should be installed at the following locations for steel pipe wiring: at the motor's incoming line clamp, where direct connection between the steel pipe and electrical equipment is difficult, and where the pipeline passes through the expansion joints or settlement joints of the building.
(5) Mobile electrical equipment is not recommended in Zones 20, 21, and 22. If mobile electrical equipment must be used, YC or YCW rubber cables should be selected for the wiring.
AQ3009-2007 "Electrical Explosion-Proof Safety Regulations for Hazardous Areas" classifies dust explosion hazardous areas into 20 zones, 21 zones, and 22 zones.
5. Ventilation and Dust Removal
(1) Preferably, the dust removal system should be set up in a relative opposing manner according to the process sections.
(2) All dust-generating points should be equipped with dust collection hoods.
(3) There should be no dust settlement in the ductwork.
(4) Baghouse dust collectors should be used, with the external filter type being given priority.
(5) Dust collectors should be installed outdoors. If installed indoors, the explosion relief pipe should directly lead to the outside, with a length less than 3 meters, and a explosion-proof device should be set up based on the properties of the dust.
(6) It is advisable to install isolation valves at the inlet and outlet of the dust collector, as well as temperature monitoring devices.
(7) Pulse-jet bag dust collector should use nitrogen, carbon dioxide, or other inert gases as the cleaning gas source.
6. Fire protection
(1) Select the appropriate fire extinguisher based on the physical and chemical properties of the dust.
(2) When extinguishing fires, prevent dust from becoming airborne to form a dust cloud.
(3) If the combustible material generates explosive gases when in contact with water, do not use water to extinguish the fire.
7. Job Safety
When dust clouds can be ignited by sparks produced from collisions, measures should be taken to prevent collisions from occurring. Additionally, explosion-proof tools should be used during maintenance.
(2) Do not use rotating grinding wheels and rotating cutting disks for grinding and cutting without equivalent protection measures to those for open flame operations.
(3) All production areas and storage rooms where dust may accumulate should be cleaned promptly.
(4) Do not use compressed air for downhole blowing.
(5) At the workplace, production staff should not wear synthetic fiber garments or pants that are too close to the body.
explosion-proof electrical transformation in hazardous explosive areas and on-site explosion-proof construction consulting services - Shenzhen ZhongNuo Testing Technology Co., Ltd.