Safety Technical Specifications for Dust Removal Systems in Dust Explosion Hazardous Locations

1 Scope

This standard specifies the requirements for explosion protection measures, maintenance, inspection, and testing of dust removal systems used in dust explosion hazardous locations.

This standard applies to the design, manufacture, installation, acceptance, use, and maintenance of dust removal systems in dust explosion hazardous locations.

This standard does not apply to dust removal systems used in chemical plants, mining, tunnels, fireworks and firecracker production facilities, and civil explosives production facilities.

2 Normative References  The following documents are indispensable for the application of this standard. For dated references, only the dated version applies to this document. For undated references, the latest version (including all amendments) applies to this document.

GB 2894 Safety Signs and Guidelines for Their Use

GB 7231 Basic Identification Colors, Identification Symbols and Safety Signs for Industrial Pipelines

GB 12158 General Guidelines for Preventing Electrostatic Accidents

GB 12476.1 Electrical Equipment for Combustible Dust Environments - Part 1: General Requirements

GB 12476.2 Electrical Equipment for Combustible Dust Environments - Part 2: Selection and Installation

GB 15577 Safety Regulations for Dust Explosion Prevention

GB/T 15605 Guidelines for Dust Explosion Venting

GB/T 16758 Classification and Technical Conditions of Exhaust Hoods

GB/T 17919 Guidelines for Explosion Protection of Dust Collectors in Dust Explosion Hazardous Locations

GB 50019 Design Code for Heating, Ventilation and Air Conditioning

GB 50057 Design Code for Lightning Protection of Buildings

GB 50058 Design Code for Electrical Installations in Explosive Hazardous Environments

AQ 7005 Safety Requirements for the Use of Woodworking Machinery

3 Terms and Definitions

The following terms and definitions apply to this document.

3.1 Dust

Solid fine particles that can settle in the atmosphere under their own weight, but can also remain suspended in the air for a period of time.

3.2 Combustible dust

Dust that can burn or smolder in the air and can form an explosive mixture with air at atmospheric pressure and normal temperature. 3.3 Dust explosion hazardous area

A location where combustible dust, oxidizing gases, and ignition sources are present.

3.4 Dedusting system

A device composed of a dust hood or dust cabinet, ductwork, fan, dust collector, and control device, used to capture solid particles in a gas-solid two-phase flow.

3.5 Explosion-proof devices

Devices that employ technologies to prevent and control dust explosions, avoiding the formation of dust clouds or potential ignition sources, and rendering combustible dust incapable of combustion or explosion, such as explosion venting, inerting, explosion isolation, and explosion suppression devices.

4 General Principles

4.1 The dust explosion hazards existing in the production and processing system should be identified and assessed, and the selection of dust collectors should meet the following requirements:

a) When using dry dust collectors for dust removal, bag filter and/or cyclone dust collection processes should be adopted.

b) For dust from mechanical processing of aluminum and magnesium products, and other dust suitable for wet dust collectors, water washing or water curtain dust collection processes should be used when selecting wet dust collectors.

c) Electrostatic precipitators should not be used.

d) The dust collection system should not use gravity settling dust collection methods mainly based on settling chambers; dry tunnel-type structures should not be used as dust collection ducts.

e) When using single-unit bag filter dust collectors for mechanical processing of wooden furniture, the requirements of AQ 7005 should be met.

4.2 Dry dust collection systems should adopt measures to prevent and control dust explosions according to the explosion characteristics of combustible dust, and select one or more of the following explosion-proof devices to reduce the explosion risk:

a) Explosion venting device. Before the explosion pressure reaches the explosion resistance strength of the dust collector and ductwork, the explosion products are discharged through the explosion venting device to prevent damage to the dust collector and ductwork.

b) Inerting device. Inert gas or powder is introduced into the dust collector to render the combustible dust non-explosive.

c) Explosion isolation device. An explosion isolation device is installed on the ductwork to block the flame and explosion wave within a certain range.

d) Explosion suppression device. Explosion suppression devices should be installed on the ductwork and/or dust collectors.  At the moment of an explosion, physical and chemical extinguishing agents are injected into the ductwork and/or dust collector to suppress the development or propagation of the explosion. For dust collectors and ductwork containing toxic, corrosive dust, and combustible dust, explosion venting devices should not be used for pressure relief; instead, explosion suppression devices that inject fire-extinguishing gases or powders into the dust collector and ductwork should be used.

4.3 The dust collector casing shall meet the following requirements:

a) The casing shall be made of steel; if other materials are used, they shall be flame-retardant and anti-static, and aluminum materials should not be used.

b) The design strength of the casing shall be able to withstand the large explosion pressure generated after implementing explosion protection measures. Casings located inside buildings shall be made of steel and have a welded structure.

c) The angles between the panels of the square casing shall be rounded.

d) The internal surface of the casing shall be smooth. Steel casings shall be treated with anti-corrosion measures, and aluminum coatings should not be used.

4.4 Dry dust collectors should operate with continuous ash discharge and continuous ash conveying. Sedimentation chambers should not be used for dust treatment.

4.5 Dust collectors in areas with aluminum-magnesium dust and wood product dust explosion hazards should operate under negative pressure; if other dust explosion hazard areas use positive pressure for dust conveying, reliable measures to prevent ignition sources should be taken.

4.6 Aluminum-magnesium dust should not be combined with iron dust or other types of combustible dust in the same dust collection system. The dust collection system should not be connected to systems containing...