Safeguarding Your Workspace: Strategies to Prevent Industrial Dust Collector Explosions

Effective dust collection and explosion protection strategies are essential for maintaining safety and preventing catastrophic incidents in industrial facilities.

• By Todd Willey
• Sep 10, 2024

Industrial dust collection systems properly engineered for your facility enhance safety and efficiency by capturing airborne particles generated during dust-producing processes. This measure ensures cleaner air for personnel to breathe and helps keep products and equipment free from damaging dust.

However, dust collectors themselves pose a significant explosion risk if they lack protective devices. These collectors are essentially closed vessels filled with dry particles. A single spark entering the collector can trigger a catastrophic explosion, endangering personnel safety and causing structural damage and equipment destruction.

Combustible dust is a hidden danger in many industries, including manufacturing, agriculture and metal-working. Materials such as metal powders, organic dusts and plastics can become explosive under the right conditions. Recognizing these hazards is the first step in preventing incidents. Conducting a thorough hazard analysis to assess the types and quantities of dust produced in your facility is essential.

Fortunately, there are ways to mitigate the risks of dust collector explosions. Let’s explore key points on how to protect against such incidents.

Where to Start: Dust Control Standards and Recommendations 

The National Fire Protection Agency is working on a new standard called NFPA 660 Standard for Combustible Dusts. This standard will consolidate all existing NFPA regulations related to combustible dust. By merging six different NFPA standards into one thorough guideline, NFPA 660 aims to simplify compliance. It will offer both fundamental and industry-specific standards for managing combustible dust, advancing best practices to protect facilities from fires and explosions associated with dust.

While awaiting the release of NFPA 660, facility operators should refer to NFPA 652 Standard on the Fundamentals of Combustible Dust. This comprehensive standard outlines the necessary steps for managing combustible dust fires and explosions across various industries, processes and dust types. Under NFPA 652, owners or operators of facilities where combustible dust is present must perform a dust hazard analysis, create a hazard management plan and provide training for personnel whom these hazards may affect.

NFPA 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids offers performance-based explosion protection choices that can increase the safety of your industrial dust collectors. Additionally, NFPA 69 Standard on Explosion Prevention Systems details installation requirements for systems designed to prevent and control explosions in enclosures with flammable concentrations of dusts, vapors, gases, mists or hybrid mixtures. This standard is intended for use by design engineers, operating personnel and authorities having jurisdiction.

NFPA classifies dust according to its potential explosibility, known as the Kst value, as follows:

• ST0: Kst value of 0 = not explosive.

• ST1: Kst value below 200 = weak to moderately explosive.

• ST2: Kst value from 200 to 300 = strongly explosive.

• ST3: Kst value exceeds 300 = very strongly explosive.

In addition, OSHA provides guidance on combustible dust explosion hazards and notes, “In many combustible dust incidents, employers and employees were unaware that a hazard even existed. It is important to determine if your company has this hazard, and if you do, you must take action now to prevent tragic consequences.”

Explosion Protection Solutions for Dust Collection Systems

Let’s explore a few explosion protection devices and systems designed to ensure dust collection systems meet NFPA standards. Active systems aim to prevent explosions by detecting and responding to them before or during an incident. In contrast, passive systems activate in response to an explosion, focusing on controlling the event to safeguard employees and reduce equipment damage.

Active Devices

• Chemical isolation systems are installed in inlet or outlet ducting to react within milliseconds of detecting an explosion. These systems typically consist of an isolation canister, explosion pressure detectors and a control panel. By creating a chemical barrier, they suppress the explosion within the ducting, halt the spread of flames and minimize the pressure surge that could affect process machinery connected to the dust collector.

• Chemical suppression safeguards the dust collector itself. It is often used in conjunction with chemical isolation when safe venting of an explosion is not feasible or when the dust is hazardous or toxic. The system rapidly detects an explosion hazard, triggering the release of a chemical agent that promptly extinguishes the flame before an explosion can occur.

• Fast-acting valves, which close within milliseconds of detecting an explosion, can be installed in inlet or outlet ducting. These valves form a physical barrier within the ducting, effectively isolating pressure and flame fronts from either direction, preventing them from spreading further through the process.

• High-speed abort gates integrated into the inlet or outlet ducting of a dust collection system reroute potential ignition sources away from the collector, thereby averting potential explosions and blocking flames and burning debris from entering the facility via the return air system. A mechanical barrier then redirects airflow to a secure area. A spark detection system, positioned at an adequate distance upstream to ensure ample reaction time, sets the abort gate in motion.

Passive Systems

Passive systems respond immediately after an event to prevent the deflagration from spreading to other areas and causing further damage. Many facility operators prefer passive systems to active systems because they are significantly less expensive and do not require regular recertification. Passive systems control the speed of explosions by releasing pressure once it reaches a certain threshold. Below are commonly used passive explosion protection systems:

• Explosion venting is the most commonly used method for protecting industrial dust collectors. When the dust inside the collector combusts, pressure rapidly increases. In this event, explosion vents open, allowing the pressure and flame front to exit in a safe direction. NFPA 68 – Standard on Explosion Protection by Deflagration Venting outlines specific criteria for these venting systems’ design, location, installation, maintenance and proper use.

• Explosion isolation valves installed in the inlet ducting serve as a mechanical barrier. Their primary purpose is to prevent the explosion flame and pressure from propagating through the ducts and reaching the process area. Normal airflow keeps the flap plate open. However, in the event of an explosion, the sudden pressure wave triggers the flap to close swiftly, effectively containing the flames and smoke within the duct system. 

• An integrated safety monitoring filter safeguards downstream equipment and work areas. It is positioned on top of a dust collector, serving as a flame front barrier. In the event of an explosion in the dust collector, the filter retains the dust inside, preventing the flame front from entering the workspace. The iSMF complies with NFPA-mandated design options and effectively acts as a flame front arrestor for ST1 and ST2 combustible dusts.

• Flameless vents can be placed over a standard explosion vent to suppress the flame front as it exits the vented area, preventing it from escaping the device. This enables the use of conventional venting indoors, even in situations where it might otherwise pose risks to personnel or lead to secondary explosions. However, it’s essential to establish a safe zone around the flameless vent owing to the release of pressure and dust and gases.

• Backdraft dampers placed within the inlet ducting incorporate a mechanical barrier that remains open by the process airflow but swiftly closes from the pressure of an explosion. When closed, this barrier effectively prevents pressure and flame fronts from advancing further upstream in the process.

Conclusion

In industrial manufacturing and processing, controlling dust—especially combustible varieties—is a complex task. To tackle these challenges, implement a tailor-made, high-efficiency dust collection system equipped with appropriate explosion protection technology that adheres to NFPA standards. This strategic approach will help safeguard against risks to humans and prevent damage to both equipment and the facility.

This article originally appeared in the September 2024 issue of Occupational Health & Safety.