Shenzhen ZhongNuo Testing Technology Co., Ltd. is based in South China and offers explosion-proof technical consulting services including on-site construction, safety inspections, renovations, project acceptance, and installation. We are well-versed in explosion-proof construction standards, boasting experienced construction teams and a wealth of experience. We have served major corporations such as PetroChina, LG, Hanlan Environment, BOE, and Sinovac, receiving consistent praise and trust from our clients!
Fundamental Specifications for Dust Explosion-proof Construction
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 important. This includes the installation and use of explosion-proof wiring, electrical equipment, dust extraction systems, structural layouts, and explosion-proof venting, all of which must comply with relevant dust explosion-proof standards. Based on a wealth of explosion-proof electrical installation and retrofit cases, Shenzhen ZhongNuo Testing Technology Co., Ltd. has summarized the following points:
4. Explosion-proof electrical equipment
Electrical equipment used in hazardous dust explosion areas shall comply with the relevant standards of GB/T3836. The power design shall be executed in accordance with the provisions of GB50058. Explosion-proof electrical equipment should be selected based on the classification and grade of the explosion hazard area, as well as the category, grade, and group of the hazardous substances.
Options for explosion-proof electrical equipment. Dust explosion-proof electrical equipment with dust-tight construction is used in the 20-zone explosive dust environments, as well as in the 21-zone environments of other explosive dusts, excluding the 21-zone environments for combustible non-conductive dust and combustible fibers. Different types of electrical equipment are selected based on the various ignition temperatures of the dust.
(2) Low-pressure fluid conveying galvanized焊接 steel pipes for piping tubing
(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, and for steel pipes with a diameter of 32mm or more, there should be at least 6 threads.
(4) Flexible explosion-proof conduits should be installed at the following locations: at the motor's entry clamp, where direct connection between the steel pipe and electrical equipment is difficult, and at the expansion joints and settlement joints of the piping system.
(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 Code for Hazardous Areas" categorizes dust explosion areas into 20 zones, 21 zones, and 22 zones.
5. Ventilation and Dust Removal
(1) The dust removal system should be set up in opposing sections according to the process.
(2) All dust-generating points should be equipped with dust collection hoods.
(3) There should be no dust settlement in the air ducts.
(4) Bag dust collectors should be used, with an emphasis on the externally filtered type.
(5) Dust collectors should be installed outdoors. If installed indoors, their explosion relief pipes must directly lead to the outside, be less than 3 meters in length, and a flame arrester should be set according to the properties of the dust.
(6) It is advisable to install isolation valves at the inlet and outlet of the dust collector and set up a temperature monitoring device.
(7) Pulse-jet bag dust collector should use nitrogen, carbon dioxide, or other inert gases as the cleaning gas source.
Fire Protection
(1) Select the appropriate fire extinguisher based on the physical and chemical properties of the dust.
(2) During fire extinguishing, prevent dust from being lifted to form a dust cloud.
(3) If a combustible material generates explosive gas upon contact with water, do not use water to extinguish the fire.
7. Job Safety
When dust clouds can be ignited by sparks 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 that of open flame operations.
(3) All production workshops and storage rooms where dust may accumulate should be cleaned promptly.
(4) Do not use compressed air to blow down the well.
(5) At the workplace, production personnel should not wear synthetic fiber garments or pants next to their skin.

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 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 boards, wiring cabinets, or metal conduit wiring systems, un armored cables 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 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 with 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 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 shall 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 should not be less than 1.2 times the rated current of the fuse element and 1.2 times the set current of the long-time delay overcurrent release of the circuit breaker, except for the situations specified in clause 2 of this item.
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, flame-retardant cables are recommended. Plastic sheathed cables without armor can be used when the installation method employs bridge supports that prevent mechanical damage. Non-armor cables can also be installed in cable trenches in 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 Design of Grounding for AC Electrical Installations" GB/T50065, the following parts that do not require grounding should still be grounded in explosive environments:
1) Equipment with a normal non-electrically charged metal enclosure, for alternating current rated voltages below 1000V and direct current rated voltages below 1500V, on poor conductive ground surfaces.
2) In dry conditions, equipment with alternating voltage not exceeding 127V and direct voltage not exceeding 110V typically has an uncharged metal casing.
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, as well as other equipment within explosive zones 2 and 22 excluding lighting fixtures, should use a dedicated grounding wire. If this grounding wire 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 wire, but not the piping for conveying substances.
(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.

With the development of the global energy and chemical industry, construction in explosive hazardous environments is becoming more widespread, making prevention and acceptance of explosive environments increasingly important.
Especially in flammable dust environments, such as plastic factories, feed/food/grain processing plants, metal polishing workshops, and papermaking/forestry wood flour/fiber dust factories, the demand for explosion-proof installation, design, and retrofitting projects is also on the rise.
In the case of either large-scale or local explosion-proofing, if there are hidden dangers in the quality of the product, installation, or modification.
Our personnel and property security are at significant risk, so we must maintain strict quality control over every process to ensure the reliability and safety of explosion-proof installations and renovations.
Shenzhen Zhongnuo Testing Technology Co., Ltd. offers explosion-proof construction and modification consulting services, boasting a wealth of qualifications and case studies—definitely worth it!
Explosion-proof electrical modifications and on-site explosion-proof construction consulting services for hazardous areas — Shenzhen Zhongnuo Testing Technology Co., Ltd.