According to Section 4.2 of AQ4273-2016 Safety Technical Regulations for Dust Collection Systems in Dust Explosion Hazard Areas, dry dust collection systems must take preventive and control measures based on the explosive characteristics of combustible dust. One or more of the following explosion protection devices should be used to reduce explosion risks:
Explosion Venting Device: Before the explosion pressure exceeds the dust collector and ductwork’s strength, an explosion venting device releases explosion products, preventing equipment damage.
Inerting Device: Introducing inert gas or powder into the dust collector removes the explosiveness of combustible dust.
Explosion Isolation Device: Installed in ducts, this device blocks flames and explosion waves within a limited range.
Explosion Suppression Device: Installed in ducts and/or dust collectors, it instantly injects physical or chemical fire-extinguishing agents to suppress explosion development or spread.
1. Explosion Venting Device
Explosion Venting: The explosion venting opening of a dust collector must meet regulatory requirements. Explosion vent panels should be certified, preferably designed by a qualified third-party institution. Common standards for calculating vent areas include GB/T15605-2008, EN14491-2012, and NFPA 68-2013. National standards for dust collectors now require manufacturers to improve explosion venting and suppression measures.
2. Explosion Isolation Device
Explosion Isolation prevents explosions from spreading to protected areas. The key product is the explosion isolation valve, which is widely used due to its simplicity and reliability. It works by using explosion-generated pressure to move a valve core, blocking flames and pressure waves. The selection of isolation valves depends on dust explosion characteristics and the pressure resistance of the dust collector and ducts. These valves must be installed on the main duct outside the building, with interlocked controls connected to the dust collection system.
3. Explosion Suppression Device
Most explosion suppression devices originate from foreign products. Their main principle is detecting explosions and rapidly spraying suppressants to reduce or stop explosion propagation. They can be installed in any potentially hazardous location, but selection should be based on dust explosion characteristics, as well as the explosion resistance of dust collectors and ducts. These devices must also be interlocked with the dust collection system’s control unit for protection.
4. Inerting Device
When inert gas is used as a medium in a dust collector, internal oxygen levels must be strictly controlled. In a central dust collection system, the flow rate of injected powder should not exceed 50% of the lower explosion limit. After adding an inerting device, an explosion-proof monitoring system should be installed to issue automatic alarms in case of operational abnormalities. To prevent dust explosions or minimize damage if an explosion occurs, explosion venting devices are crucial. Explosion venting is one of the most effective protection methods, as it releases pressure during industrial explosions. A well-designed flameless explosion venting device can safely release pressure while preventing secondary hazards.
The Five Elements of a Dust Explosion
A dust explosion requires five key elements. When all five are present simultaneously, an explosion can occur. Dust explosions generate strong shock waves and flames, and since equipment cannot withstand such extreme pressures, explosions can cause severe damage, leading to secondary or multiple explosions. This highlights the importance of dust explosion protection.
Three Main Explosion Protection Methods
Explosion Venting: Releases explosion pressure in advance through a venting device, protecting equipment from damage.
Explosion Isolation: Uses an isolation valve to block the explosion and prevent flame propagation.
Explosion Suppression: Detects sparks, triggers the fire suppression system, and extinguishes flames instantly to prevent explosions.
Since dust explosions only occur in confined spaces, it is essential to implement protective measures for enclosed equipment handling dust, such as dust collectors, elevators, silos, and dryers.
Explosion Venting for Outdoor Equipment
For outdoor equipment, explosion vent panels can directly release pressure. Using flameless venting provides better environmental protection. However, vent openings should be positioned away from pedestrian pathways or other sensitive equipment to avoid risks.
Functions of a Flameless Explosion Venting Device
1. Flame Capture – Ensures no flames escape, providing a safer operating environment.
2. Prevents Secondary Ignition – Reduces the risk of multiple explosions and equipment damage.
3. Dust Retention – Prevents processed materials from being released into the environment.
4. Pressure Reduction – Cushions explosion pressure peaks, protecting personnel, equipment, and buildings.
5. Temperature Control – Absorbs fireballs while maintaining stable ambient temperatures.
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