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Based on the basic requirements of GB 15577 "Safety Regulations for Dust Explosion Prevention," in the construction and renovation of explosion-proof measures for dust explosion-prone areas, the following five main explosion-proof measures can be adopted (shared by Shenzhen ZhongNuo Inspection Technology Co., Ltd.).
Anti-knock
1. Definition: An explosion suppression technology that, in the event of an explosion within an enclosed space where combustible dust and gaseous oxidizers or air are present, allows the enclosed space to withstand the high explosion pressure without being destroyed.
2. Purpose: By enhancing container wall thickness and improving material, external damage is minimized even in the event of a dust explosion.
3. Basic Requirements:
When producing and handling powdered materials that can cause explosions, if there is no explosion suppression device and no pressure relief measures, all process equipment should be designed to be explosion-proof and capable of withstanding the overpressure generated by internal explosions without rupture.
(2) The connection parts between various process equipment (such as pipes, flanges, etc.) should have the same strength as the equipment itself. For connections between high-strength and low-strength equipment, explosion-proof devices should be installed.
(3) Equipment for explosion-proof pressure and shock resistance shall meet the requirements of GB/T 24626.
Explosion Relief
1. Definition: A suppression technology that, upon an explosion occurring within the enclosed package, allows the high temperature, high-pressure combustion products, and unburned materials generated by the explosion to be released through pre-set weak points in the package before the explosion pressure reaches the package's limit strength, thereby preventing the package from being destroyed.
2. Objective: To reduce explosion damage by setting up explosion relief devices.
3. Methods: Two explosion relief methods are available – with flame and without flame.
4. Basic Requirements:
When the strength of the process equipment is insufficient to withstand the overpressure generated by internal dust explosion under actual working conditions, explosion relief ports should be installed. The relief ports should be directed towards a safe direction, and the size of the relief ports should comply with the requirements of GB/T 15605.
(2) Equipment for dust explosion hazards installed indoors should be vented to a safe outdoor direction via pressure relief ducts. The pressure relief ducts should be as short and straight as possible, with a cross-sectional area not less than that of the relief port, and their strength should not be lower than the strength of the protected equipment container.
(3) For equipment inside the room that cannot vent explosion to the outside through pressure relief ducts, flameless explosion relief caps should be installed.
(4) Process equipment with inline pipelines should be designed to withstand at least 0.1 MPa of internal overpressure.
Section 3: Explosion Suppression
1. Definition: In the initial stage of an explosion, extinguish the flames and suppress (prevent) the development of dust explosion through physical and chemical actions.
2. Objective: To pre-detect and extinguish fires, as well as suppress explosions, by setting up explosion suppression devices.
3. Basic Requirements:
Process equipment with a risk of dust explosion should be protected with explosion suppression devices.
(2) If a monitoring-type explosion suppression device is used, it should comply with the requirements of GB/T 18154.
(3) Explosion suppression system design and application should comply with the requirements of GB/T 25445.
Four, Explosion-proof
1. Definition: Technology that prevents the spread of an explosion through physical and chemical actions after an explosion occurs.
2. Purpose: To prevent the spread of flame through pipes or other passages
3. Basic Requirements:
(3) Equipment and facilities with dust explosion hazards that are interconnected by pipelines should ideally be equipped with explosion suppression devices on the pipelines.
(2) Equipment and facilities with a dust explosion hazard, interconnected by pipelines, should ideally be equipped with explosion-proof devices. The shutdown direction should align with the direction of explosion propagation.
Five. Inertizing
For processes such as crushing, grinding, drying of powders, and pneumatic conveying through pipes within sealed containers, inert gases like nitrogen, carbon dioxide, halogenated hydrocarbons, argon, helium, and steam, or inert dusts such as fire extinguishing powder, chemical dry powder, and mineral rock powder are introduced. This is to dilute combustible components and reduce the oxygen content in the environment.

In recent years, with the continuous development of society and the increasing prominence of safety accidents, people's awareness of safety production has been on the rise, and the treatment of potential hazards in dangerous environments is urgent.
In various industrial sectors in our country, such as oil, chemicals, ports, coal, and others, there may often be leaks or spills of flammable and explosive gases, liquids, dust, and fibers during production, processing, transportation, and storage. When these substances mix with air, they can form explosive mixtures. If the concentration of the mixture reaches the explosive range, any ignition source can trigger an explosion and severe incidents like fires. In extreme cases, chain reactions can lead to major accidents. Therefore, equipment used in such hazardous environments must be certified with explosion-proof capabilities. The use of all explosion-proof environment equipment must be installed and adjusted by experienced engineering companies in strict accordance with explosion-proof construction specifications and acceptance standards before being put into actual production use. This ensures the maximum safety requirements for all stages of the production process.

Equipment grounding in explosive environments shall comply with the following specifications (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 shall still be grounded in explosive environments:
1) Equipment with a normal non-electrified metal housing, where the alternating current rated voltage is below 1000V and the direct current rated voltage is below 1500V, on poor conductive ground surfaces.
2) In dry conditions, equipment with alternating current rated voltage of 127V or less and direct current voltage of 110V or less typically has metal enclosures that are not normally charged.
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 atmosphere zones 1, 20, and 21, as well as other equipment in zones 2 and 22, except for lighting fixtures, should use specialized 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 atmosphere zones 2 and 22 may use a metal piping system with reliable electrical connections as a grounding cable, but not the pipeline 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 no fewer than two points.

Selection of cables and wires for explosive environments shall comply with the following specifications: (Shared by Shenzhen ZhongNuo Testing Technology Co., Ltd.)
(1) In explosive environments, the insulated conductors and cables used for low-voltage power and lighting circuits should have a rated voltage higher than or equal to the working voltage, and U0/U should not be lower than the working voltage. The rated voltage of the neutral line should be equal to the phase line voltage, and they should be laid in the same sheath or protective tube.
(2) In explosive hazard zones, except within distribution boards, wiring cabinets, or metallic conduit wiring systems, unshielded 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 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 within Zone 22, should use copper-core insulated conductors or cables.
(4) In addition to the circuit 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) The technical requirements for steel pipe wiring with voltages below 1000V in explosive environments, 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 shall comply with the provisions of Tables 5.4.1-1 and 5.4.1-2, as well as the following requirements:
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 delay overcurrent release of the circuit breaker, except for the circumstances specified in item 2 of this clause.
2) The long-term permissible current for the auxiliary branch of squirrel-cage induction motors with an impeding voltage of less than 1000V should not be less than 1.2 times the motor's rated current.
(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.
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