Emre Ergun
Head of Sales, Europe
IEP Technologies Gmbh

Combustible dust explosions remain one of the most critical safety threats in grain handling operations. This comprehensive guide helps facility managers navigate the complex selection of explosion prevention and protection systems, offering practical insights to safeguard equipment, processes, and—most importantly—human lives.

The grain handling industry is essential to our global food supply, but it carries a serious and often underestimated risk: combustible dust explosions. Tragic events in recent years serve as a stark reminder that powerful safety measures are not just a recommendation, but a necessity to protect facilities, equipment, and, most importantly, people’s lives.

The Five Ingredients for a Dust Explosion

For a dust explosion to occur, five elements as shown in Picture 1, must be present at the same time. This is often called the “Explosion Pentagon”:

Removing just one of these elements can prevent a disaster. A key first step for any facility is a Dust Hazard Analysis (DHA), which is a professional review to identify high-risk areas and create the best safety strategy. This strategy will involve a combination of prevention (stopping an explosion from starting) and protection (reducing the damage if one occurs). After conducting the DHA, explosion protection and prevention system selection and specification can be done for the high risk process equipment.

Picture 1 – Explosion development inside a vessel

Typical Grain Handling Equipment and Their Risks

Statistics show that certain pieces of equipment are more likely to be the source of a dust explosion. According to industry statistics for the grain industry, bucket elevators, milling systems, dust collectors and storage silos are the most common sites for primary explosions. An explosion in one machine can easily travel through connecting pipes and ducts, causing much larger secondary explosions in other parts of the facility.

The following table details the specific ignition hazards associated with key equipment used in the grain industry and outlines common solutions for explosion prevention and protection:

Understanding the Safety Toolkit

Choosing the right explosion safety solution depends on the specific machine, process interconnections, its location, and the type of material being handled. Here are the key technologies explained simply:

1. Prevention: Spark Detection and Extinguishing

These systems use high-speed infrared sensors to spot sparks or embers traveling through pipes. Within milliseconds of detection, they spray a fine mist of water to extinguish the ignition source before it can reach a machine like a dust collector or silo. Often, this happens so quickly that production doesn’t even need to stop. Type of detector is the key in the overall system selection. Wide viewing angle and wide IR spectrum range detectors such as IEP`s ATEXON SD300Ex detectors can detect through material layers, suitable for high flow applications which are critical in grain handling operations.

Picture 2 – High material flow spark detection applications examples for bucket elevators and transfer chutes. Shown above are ATEXON SD300-Ex wide spectrum and 180o viewing angle spark detectors along with spark extinguishers strategically located at the downstream of the chute.

2. Protection: Explosion Venting

If an explosion does start, venting is designed to relieve the destructive pressure to a level below the vessel strength.

Explosion Relief Vents: These are panels that burst at a predetermined pressure, directing the fireball and pressure wave to a safe area outside. They are a cost-effective solution for outdoor equipment. Impact resistance, vacuum rating are some of the important considerations when selecting explosion vents.

Flameless Vents: When equipment is indoors, you can’t vent a fireball into the workspace. Flameless vents solve this problem. They combine a vent panel with a metal mesh filter that cools the hot gases and quenches the flame, releasing only pressure safely. Size of the vessel, type of material being handled, dust explosibility ratings are some of the considerations when selecting flameless vents.

Picture 3 – Outdoor bucket elevator explosion protection: Explosion relief vents on the elevator head and legs, and eSuppressor type explosion isolation suppressors at the inlet and outlet chutes of the bucket elevators. Dual explosion detection by SmartDS dynamic explosion detectors along with IR-13 flame detectors.

3. Protection: Explosion Suppression

This is an active system that stops an explosion in less than the blink of an eye. Detectors sense the instant a fireball begins to form and rapidly discharge food-safe dry chemical suppressant. This chemical “suppresses” the explosion before it can build to destructive pressures, making it a great solution for indoor equipment or when venting isn’t practical.

4. Isolation: Minimize the Risk of Explosions from Spreading

Isolation is arguably one of the most critical parts of a complete safety plan. It prevents a small, manageable explosion in one vessel from becoming a catastrophic chain reaction by propagating between interconnected vessels.

Passive Isolation: These are mechanical devices, like a weighted flap valve, that are forced shut by the pressure wave of an explosion, automatically creating a barrier.

Active Isolation: These systems use detectors to trigger a high-speed chemical barrier. A device rapidly discharges an explosion suppressant into the connecting ductwork, creating a chemical wall that stops the flame from spreading to other equipment.

Picture 4 – IVE type flameless vents on bucket elevators. IVE’s are specifically designed for bucket elevators providing high efficiency and ease of installation.

A Layered Strategy is the Best Defense

Selecting the optimal explosion protection system is not a “one size fits all” solution. It requires a thorough assessment of process characteristics, material explosibility, equipment geometry, and plant layout.

Expert Assessment by Third Party or Plant Owner: The process starts with a thorough Dust Hazard Analysis (DHA) performed by qualified engineers to identify the true risks which the process owners have to complete this task prior to moving to risk mitigation strategies.

Picture 5 – Explosion suppression system on a vessel using eSuppressor along with additional explosion isolation options 1) Top: Active isolation no the top, 2) Middle: Ventex type passive isolation valve for lower dust load applications, 3) Bottom: IsoFlap passive isolation valve at the inlet pipe.

System Design:  System design must be performed by the safety system manufacturer’s engineers to ensure correct equipment selection and optimal sizing. Such designs require advanced modelling tools which are specific to hardware used in the design.

Certified Solutions: All explosion protection systems must be certified by an independent third party according to ATEX requirements.

System Start up: Explosion protection and prevention systems should go through the detailed commissioning process by the manufacturer’s field engineers in order to ensure systems are installed per the manufacturer’s directions and systems operate as designed. 

Ongoing Maintenance: Safety equipment is only effective if it works. Regular inspections and maintenance by certified system supplier`s technicians are essential to ensure the systems are ready to activate at a moment’s notice.

Picture 6 – Vessel protected by IV8 type flameless vent with eSuppressor type chemical isolation on the inlet pipe.

By combining preventative measures like spark detection with a layered protection strategy of venting, suppression, and isolation, grain handling facilities can mitigate their explosion risks. This integrated approach is the key to protecting personnel, preventing costly damage, and ensuring a safer future for this vital industry.

Table 1: Typical unit operations used in the grain industry with potential ignition sources and recommended protection and prevention methods

References:

 Guidelines for Safe Handling of Powders and Bulk Solids, CCPS, AICHE

 Ref. Instructors Manual, Kirkwood Community College Community Training and Response Center, Susan Harwood Grant Number SH-17797-08-60-F-19, 2010

 ASTM Subcommittee E27.05 on Explosibility and Ignitability of Dust Clouds

 Guidelines for Combustible Dust Hazard Analysis, CCPS

 Journal of Loss Prevention in the Process Industries, 62, 103928

 Guidelines for Choosing an Explosion Protection System, Part-1 and Part-2, Powder & Bulk Engineering, October, November 2011, Emre Ergun

 https://www.ieptechnologies.com/wheres-the-hazard/process-equipment-at-risk/grain-bucket-elevators