Smouldering Fire Detected in a Hogging Machine

A hogging machine produces hog fuel, which is a type of wood waste. In this particular instance, which occurred in 2016, a smouldering fire developed in one of these machines. When the workers put it out, a piece of burning wood escaped and left the two conveyor outfeeds. The machine was stopped to deal with burning wood but 10 minutes later, another fire broke out in a pile of hog fuel at the outfeed of another conveyor because not all of the material had been collected.

Despite their best efforts, the workers were unable to capture all of the burning mass. The mill yard was filled with flammable materials, so they were unable to put out this second fire. Another hog fuel conveyor caught fire, spreading to several structures and wood waste products. Fortunately, no one was injured, but the spreading fire in the hogging machine caused quite a bit of damage.

2016 Investigation and Recommendations

According to WorksafeBC investigators, the hog machine was inadequately maintained, resulting in a friction fire. They identified three main contributing factors.

The first was hog fuel accumulation under and on conveyors. This hog fuel, sawdust, and wood were very dry in the summer, making them a strong fuel source, so WorkSafeBC recommended regular cleanup moving forward.

The second contributing factor was inadequate training and fire procedures. WorkSafeBC listed a few things that could have been done:

• An employee could have been posted to act as a firewatch during firefighting as well as afterwards to prevent or at least detect the spread of the fire.
• Workers needed the basic skills to fight fires, monitor fire spread, and know when to call the fire department to extinguish the fires.

The third and final factor was that there was no way to detect smouldering fires. In this case, the fire had been detected by a passerby. Investigators stated that smoke detectors could have prevented the fire from spreading.

A Second Incident Occurs

In January 2021, the BC Forest Safety Council released a second Manufacturing Safety Alert. The date and location are not given, but according to that alert, smoke was found inside a hogger. Upon removing the access panels, it was discovered that the blockage in the hogger was causing the grinding, friction, heat, build-up, and smouldering combustion. As an employee used a bar to clear the hogger, a large portion of the room was engulfed in flames. Fortunately, no one was hurt.

One of the most insightful pictures in this Manufacturing Safety Alert shows five workers in the hogger room. They are assembled around the hogger, trying to get it cleared. The top picture shows a flame, which is probably the start of the deflagration. A second picture shows a fireball occupying around 15 per cent or 20 per cent of the room.

The machine is surrounded by fugitive dust, mostly around its base. They don’t go into much detail about what happened except to say there was a deflagration. While clearing the hogger with the bar, the employees may have kicked out the smouldering mass in the vicinity of combustible dust. When the combustible dust was dispersed in the air, there could have been a large flash fire.

Fortunately, there were no injuries. Although the fugitive dust wasn’t enough to cause a pressure rise in the room and destroy equipment, this open-air deflagration directly near the workers was a very dangerous near-miss. It serves as a reminder to be careful when dealing with smouldering masses close to combustible dust.

Recommendations for the Future

In the second alert, the BC Forest Safety Council recommends that when clearing equipment during a potential fire situation, one should always:

• Inspect the area for combustible dust before moving the equipment.
• Ensure the hogger areas are regularly checked for combustible dust to minimize accumulations.
• Review the emergency procedures to ensure they have clear instructions on how to deal with equipment fires.

These measures can control incidents when they do occur, minimize their damage, and save lives.

Sign up at bcforestsafe.org to stay up to date with BC Forest Safety and MAG Group Manufacturing Safety Alerts.

This article originally appeared here and is republished with permission. The article is based on a podcast episode recorded by Dr. Chris Cloney, managing director and lead researcher at DustEx Research Ltd., and was originally released August 9, 2022 on the Dust Safety Science Podcast.

Chris Cloney, PEng., is the managing director and lead researcher for DustEx Research Ltd, a company with a world-wide focus on increasing awareness of combustible dust hazards and reducing personal and financial loss from fire and explosion incidents. 

This article is part of Dust Safety Week 2023. To read more articles on dust safety, click here.

We’ve got tons of great content coming at you this week from our partners, including WorkSafeBC, BC Forest Safety Council, the Wood Pellet Association of Canada, Dust Safety Science, and our sponsor experts.

The Dust Safety Week landing page, hosted on Canadian Biomass, is the year-round hub to learn best practices and find the latest information on wood dust safety.

Find the landing page here and enjoy Dust Safety Week!

Now in its seventh year, Dust Safety Week’s landing page is the year-round hub for forest products manufacturers – pellet plants, sawmills and pulp and paper operations – to learn best practices and find the latest information to keep their operations and operators safe.

Follow along all week as we will highlight feature stories, columns and research reports both from our archives as well as brand-new stories from contributors across Canada.

Find the landing page here, and stay tuned to our websites and social media (#DustSafetyWeek) for more information as we approach Dust Safety Week 2023!

Thank you to our generous sponsors for making Dust Safety Week possible: Biomass Engineering & Equipment, Fagus GreCon, Rembe, Fike and Nilfisk.

WorkSafeBC’s investigation for both incidents pointed to a combination of the concentration of dispersed wood dust in the air and friction from moving equipment. Ineffective dust control measures and maintenance oversight were found at both sites.

It’s an important reminder that complacency can be fatal, especially in industries that process a combustible material.

For the sixth year in a row, Canadian Biomass and Canadian Forest Industries turned the spotlight on dust with our annual Dust Safety Week. Over the past five days, we’ve shared on our website and social channels (#DustSafetyWeek) new and archived content from our partners to highlight best practices when it comes to dust management in wood processing facilities.

Here’s a snapshot of what we learned during the week:

1) Don’t wait for an incident: WorkSafeBC’s Alexandra Skinner wrote about the importance of reviewing dust management programs regularly. She quotes WorkSafeBC prevention field services manager Budd Phillips, who says the pandemic likely drew away resources from proper maintenance and evaluation of those programs. Now, he says, is the time to revamp dust management programs to reflect evolving operational needs.

2) Need to vent? Talk to an expert: Biomass Engineering & Equipment’s Joel E. Dulin shared practical advice on conveyor explosion venting, specifically diving into the questions about whether to choose active or passive mitigation methods or whether or not you can mitigate explosion risks without expert assistance.

3) Fire prevention strategies: Tom Burniston with Fagus GreCon wrote an overview of field-proven automated fire prevention solutions to help protect people, premises and enable uninterrupted process and production in the wood pellet industry.

4) Lessons from the past: DustEx Research’s Rose Keefe shared the story of the Murray Grain Elevator explosion. “… the events that led up to the disaster continue to replicate themselves today, and not just in the grain handling industry. Every year several people are injured and even killed in explosions at sawmills, pellet production plants, and woodworking facilities, and if lessons aren’t learned, more lives and livelihoods are likely to be lost,” she wrote.

5) Deciphering the dust hazards analysis: Jeramy Slaunwhite, a senior explosion safety engineer with Rembe, explained the what, when, why, where and how of dust hazards analysis in facilities that deal with combustible particulate.

6) Stop high-pressure compressed air dust cleaning: John Bachynski with EPM Consulting has a cautionary message for wood processing facilities: stop using high-pressure compressed air to cleanup your mill. Bachynski explains why compressed air blowdowns are the easiest way to blowup your wood manufacturing facility.

Today is the final day of Dust Safety Week 2022, and we’ll continue to share archived content from years past, which hold just as much relevance today. And don’t forget about the Wood Pellet Association of Canada’s webinar on deflagration isolation, happening Monday, July 18.

Dust safety should be top of mind year-round. That’s why our landing page (find it here – or on CanadianBiomassMagazine.ca’s top menu, under Information) is continually updated throughout the year with relevant lessons learned, solutions, and technical information to keep facilities and operators safe.

And I’d like to once again thank this year’s Dust Safety Week sponsors for making it all possible: Biomass Engineering & Equipment, Fike, VETS Group, Fagus GreCon and Rembe.

NFPA (National Fire Protection Association) 664, Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities, restricts the pressure for localized compressed air usage to 30psi and this is only after the surfaces are cleaned as much as practical with vacuum and brushes with minimum dust suspension. However in real life cleanup procedures, mill plant compressed air exceeding 100psi is more likely used. As NFPA is the fire code of Canada, violations to the fire code can cause serious injury and in some cases criminal prosecution.

The main concerns on high pressure blow down for cleanup include:

1. The high-pressure compressed air breaks down the dust particles into smaller particles creating a higher risk of explosion and increased levels of respirable suspended particulates.
2. Dormant dust is not explosive until it has been disturbed, i.e. by the compressed air. The easiest way to create a dust explosion is to use compressed air to suspend combustible dust into a flame/spark. This is exactly what is happening every time compressed air is used to suspend and distribute the fine dust.
3. NFPA (National Fire Protection Association) is recognized by the Canadian fire code and limits the accumulation of combustible dust on flat surfaces to 1/8”. This is recognized as the minimum dust depth required for the suspended dust to create a flash fire/explosion. So consider every time someone using compressed air for cleanup, it only takes a spark to create the sequence of events that can led to a catastrophic explosion.

For explosion risk, inspectors reference primary and secondary explosions. For wood shops and wood processing facilities, dormant dust is not a risk until disturbed and suspended. Once a pocket of dust becomes suspended (this could be as small as a handful of dust), The expanding fireball gains enough energy during expansion to dislodge larger quantities of dust, in some cases catastrophic. This is called the secondary explosion and can and has been deadly in wood processing facilities. The question is why would someone knowingly use compressed air to start the sequence of a catastrophic and deadly dust explosion.

The answer is human nature takes the easiest route. When using compressed air, the combustible dust appears to be cleaned as it “disappears.” This could not be future from the truth. All the compressed air has done is relocate dangerous combustible dust to another area. The combustible dust did not leave the building.

Perhaps education on the science of dust explosions would help. The math is easy, if the suspended dust reaches a concentration of 40 grams/cubic metre, it has reached what is called the minimum explosion concentration (MEC). As it is difficult for the lay-person to identify the air-borne concentration, safety professionals and NFPA have determined that 1/8” of dust depth when suspended can reach the MEC. In reality, the 1/8th inch MEC suspended dust concentration is thick enough that you could not see a 25w bulb six feet away or you could not see beams and columns on the opposite side of the facility. All are good examples, however, when doing cleanup activities and to error on the side of safety, it should be considered that any suspended dust cloud can be explosive and certainly exceeds OSHA’s STEL or TWA for respirable suspended particulate.

How do we solve this problem?

The best way to solve this problem is to install a dust extraction hood at every location where combustible dust is liberated under normal operating conditions. This is also a requirement of NFPA. For this solution, dust is captured at the source and does not leak and deposit to unsafe levels. A properly designed and installed dust extraction system can provide dust capture at the source where no dust levels exceed 1/8” between cleanup. It is expected that some dust will leak into the plant air space even with a properly designed and operating system as the complexity of some capture areas, such as a CNC machine, cause multidirectional dust patterns with sometimes complex moving hoods. It should also be noted that some hoods, for example at head pully of a conveyor, capture nearly 100 per cent of the dust.

In the absence of a properly working dust extraction system, manual cleanup will be required. The best method is by vacuum. The vacuumed dust is captured in an explosion protected enclosure and is physically removed the plant, which 100 per cent lowers the MEC and explosion risk. The main issue with vacuums is the accessibility and cost of larger vacuum trucks. Although perfect for the job, the cost can be prohibitive.

The second best manual solution is to install a vacuum system just for combustible dust. For this system, the vacuum receiver is located outside due to explosion risks and metal piping is distributed throughout the building with connections to which vacuum hoses can be attached. These systems can also be cost prohibitive.

The third solution for manual cleanup is the use of explosion proof portable vacuums, which are less costly than vacuum systems, however, they are heavy and difficult to move around the plant.

The most cost-effective temporary manual cleanup system is the use of portable vacuums (shop vacs). The use of portable vacuums can be safe, providing acceptable operating conditions for the hazardous area classification exist. Hazardous area classification follow three main guidelines.

• Zone 20 would be an enclosure where a combustible dust concentration is normal. For example, inside a dust collector. A shop vac could not be used inside these type of enclosures.
• Zone 21 is where combustible dust layers are above 1/8” and can be easily suspended, shop vacs could not be used.
• Zone 22 is where dust layers are normal under 1/8” and no suspension would result in an explosive suspended mixture.

Shop vacs cannot be used in zone 20 or 21. Shop vacs could be used to vacuum zone 22 areas providing the shop vac motor is in an unclassified area and only the hose is brought into the zone 22 area. In the case where a portable shop vac is the chosen solution it is important to recognize that over 50 per cent of ignition sources in wood manufacturing occur from a hot bearing. If the bearings are covered with dust, this is a perfect condition for a flash fire which can be the catalyst for a catastrophic secondary explosion. So if a shop vac vacuum program results in no dust is on the bearings, the risk of a primary/secondary explosion is significantly reduced.

How do we change human nature?

Once an operator has used compressed air for cleanup, it is unlikely they would be amicable to reverting to a push broom and shovel, even when they have been educated that the air hose is a major hazard. Imagine if a cleanup crew did not have any experience or even knew that an air hose was available for cleanup and they were trained to only use brushes, brooms and shovels, the cleanup would be done many times safer than blowdown.

This exact scenario is unfolding in western Canada, where facilities are successfully eliminating, due to the high risk, compressed air blowdowns and replacing it with manual cleanup with vacuums, brooms and shovels. The new hires have never seen blowdown and hence are quite happy doing the cleanup as trained without compressed air. The problem continues to be the false convenience of operator blowdown versus the harder, more effective manual cleanup, hence the new hires and new methodologies. In some cases, manual cleanup programs have been modified where manual cleanup is faster than blowdown. Considering that high-pressure blowdown does nothing to reduce the potential dust concentrations in the plant, we should consider that the new manual cleanup programs are significantly safer and many times more effective removing the dust from the building versus blowdown.

The methodology and examples described in this article are for illustration purposes only. As with any modified safety program, it is advisable to seek the experience of combustible dust specialists to assist and advise what works best for your facility.

John E. Bachynski, P.Eng, is the president of EPM Consulting Ltd.

There are multiple advantages of a having a DHA performed including due diligence towards ensuring a safe workplace; demonstrating hazard mitigation progress to authorities having jurisdiction; support for developing a plan to address and manage hazards and investment in preventative/protective safety to mitigate higher costs of combustible dust fires and explosions.

A thorough DHA will identify combustible dust hazards (fire, flash-fire and explosion) in both process equipment and plant/processing areas along with possible ignition sources for each hazard and/or area. Recommendations to reduce risk associated with the hazards should be practical and support compliance with industry standards. Practical recommendations can include options for varying levels of risk tolerance, personnel and financial resources, process/facility compatibility and reliability. Limited or overly specific recommendations as well as highly broad recommendations can be misleading, especially with reference to a specific brand or code/standard without any guidance on how to achieve compliance.

Using a common example of an unprotected dust collector located inside a plant, ranges of recommendation examples are as follows:

• Overly specific recommendation: Install Brand ABC, Model XYZ explosion protection system.
• Broad Recommendation: Protect according to NFPA 68/69
• Practical recommendations: Install explosion protection such as deflagration venting with vent ducting, (if close to an exterior wall with safe discharge area), flameless venting or chemical explosion suppression system.

The recommendations of a DHA should assist with understanding options for hazard management not necessarily the engineering for sizing and application of specific explosion protection systems. The goal at this stage is to identify and evaluate hazards and possible solutions with a plan to implement controls. Hazard control methods can be inherent hazard avoidance, engineering controls and administrative/procedural controls.

Inherent hazard management involves modification or removal of material, equipment or actions that prevent a hazardous scenario from occurring. Inherent hazard removal options are often not obvious and require an ”outside the box” perspective of typical processes and procedures. Some examples can include eliminating redundant material handling equipment or vessels and process or material handling changes to avoid unnecessary introduction of combustible particulate; If the fuel is not present, the hazard is controlled.

Engineering controls are considered any type of equipment, new or modified, that either reduces the chance of a combustible dust atmosphere occurring, prevents formation of ignition sources or reduces the consequences of a fire, flash-fire or dust explosion to a tolerable, manageable level. Some examples of engineering controls are explosion prevention, protection and isolation systems, active dust extraction, sensors, monitors and interlocks and physical barriers to limit occupancy in hazard zones. While highly effective at reducing risk, ignition source control alone is not adequate control for explosion prevention according to NFPA 69.

Administrative or procedural controls can include work tasks, operating methods and other human interactions that either reduce the chance of a combustible dust atmosphere occurring, prevent formation of ignition sources or reduce the consequences of a fire, flash-fire or dust explosion to a tolerable, manageable level. Some examples of procedural controls include site smoking policies, manual rotating equipment lubrication schedules, safe compressed air use, hot work programs and manual fugitive dust cleaning.

While arguably not a direct legal requirement of the fire code of Canada or most provincial fire codes, many organizations and authorities are performing and requesting DHAs. The objective and results of a DHA can in some cases satisfy local requirements for hazards identification and control solutions. Unfortunately, in some cases the lengthy DHA report gets shelved or filed and figuratively collects dust because it is not clear how to interpret or proceed with the hazard management recommendations. It can be daunting and intimidating trying to figure out where to start with a collection of NFPA references, technical jargon about combustible dust testing and a lengthy list of safety recommendations. While the simple answer may be to do everything, this is rarely possible due to time and budget limitations.

Most often, once the DHA is completed, the starting point should be developing a plan based on prioritization of hazards and the effort of hazard management technique implementation. The prioritization of hazards can be evaluated by risk assessment that considers the imposed consequences and the likeliness of occurrence.

The five requirements for a dust explosion. Image: Rembe.

A common approach to risk assessment is by applying a scored risk matrix where both the hazard consequences and probability of occurrence are assigned numerical values based on severity and frequency respectively. The corresponding risk ranking can be compared to a risk tolerance threshold. If the risk tolerance threshold is exceeded, it triggers an action to reduce the hazard consequence severity and/or occurrence likelihood through safety controls.

The risk scoring can be used to define priority categories and to organize an implementation plan for hazard management actions. The implementation plan, in turn, aids in planning and budgeting work to to address the most significant hazards with top priority. In some cases, this evaluation can help to identify items where a temporary solution can be considered until a permanent solution can be implemented.

The amount of effort, downtime and cost of hazard management solutions can vary widely and should be considered when developing a post DHA recommendations implementation plan. Some low/no cost recommendations can be implemented almost immediately. Even if ranked as a lower priority than other budget heavy items, the easy fixes help to get the ball rolling, reduce the overall site risks and build a mindset of safety culture. These small fixes can add up and demonstrate starting progress while waiting for budgets, equipment and labour resources. For example, dust explosibility testing is useful and highly recommended for the optimized design and development of explosion protection systems although not a prerequisite to managing fugitive dust accumulation and leaks.

Some of the largest risks from combustible dust are excessive dust layer accumulations in building and process areas which, if suspended and ignited, could create a large catastrophic explosion. Dust accumulation layers are typically a result of fugitive dust leaks in material handling and processing equipment. One of the most effective hazard mitigation strategies is to actively fix and manage fugitive material and dust leaks along with targeted cleaning programs to maintain dust layers below critical thresholds.

Other top priorities should be areas and equipment with a history of sparks, smoulders or fires and inherent heat sources such as mills and dryers. Other top priority items include high consequence hazards specifically on personnel. High consequence examples are explosions in equipment located inside the plant, explosion vent discharges to occupied areas and secondary explosions from unisolated equipment such as dust collectors, bins and silos.

Fire and explosion risks will rarely be completely eliminated but taking the first steps following a DHA to get started with a prioritized plan can quickly start reducing likelihood and potential consequences of combustible dust hazard events.

Jeramy Slaunwhite, P.Eng, is a senior explosion safety engineer with REMBE Inc.

Passive or active mitigation?

Where an explosion hazard exists, the facility owner has the choice to address it with active or passive mitigation devices. Active systems are more complex. These rely on a sensor to trigger a suppressant-containing device and are set up with electrical controls that can include fault modes to prevent unwanted release of the suppressant.

However, the complexity of these systems is a downside, as more can go wrong. Also, technicians may need to clean their conveyors after the suppressant has been released – a chore that can lengthen the downtime of an already disruptive event.

Passive mitigation is simpler and arguably safer than active systems. Jason Krbec, engineering manager at CV Technology, advocates for passive devices for this reason. In an interview with Dr. Chris Cloney on the Dust Safety Science podcast, Krbec insisted passive systems are “readily available” and “failsafe,” which gives them an advantage over tuned, active systems. Passive devices, he said, are “designed to open at a preset pressure. … And once that pressure is exceeded, they open, whether it’s for a deflagration event, explosion event, or a process reason.” In other words, there is no off mode for a passive system. The system is always ready to perform. Its simplicity makes it reliable.

Cloney followed up on Krbec’s point by comparing passive and active systems. “A passive system doesn’t need a controller,” he said. “No wiring. No redundant sensors. If it’s failsafe, it’s even better. It has less chance of things going wrong.”

But simplicity is also the downside of these systems. Because passive systems are designed to open whenever the pressure reaches a certain threshold, process changes that affect airflow may cause the vents to open when a deflagration has not occurred. Vents are getting better in this regard, however. Krbec said vents are configured to higher tolerances nowadays to avoid them opening when they shouldn’t, though expert engineering is required to make a passive system a “set it and forget it” solution.

But those tolerances are only as good as the data a conveyor manufacturer provides about the pressure capabilities of their system. Getting that data takes effort, and not all conveyor manufacturers go through the rigorous testing required to obtain it, which can include computer analysis, field testing, and third-party evaluation.

Engineers who design blast vents for conveyors need accurate information because the pressure characteristics affect the mitigation system’s design. A conveyor with a strong frame, for example, needs fewer and smaller vents than a conveyor with a weaker frame. So, if a conveyor manufacturer provides inaccurate information, such as overestimating the strength of their equipment, the vents designed for it may fail to prevent an explosion.

Can you DIY a mitigation system?

These concerns underscore the fact that mitigation is too specialized to attempt without consulting an expert. Yet we know that wood-industry professionals prefer to do things themselves. If they can strap a solution together, it’s what they do. Large companies are no exception. Plus, they have engineers on staff to handle complex issues.

But the knowledge required to design a reliable mitigation system that conforms to NFPA standards is highly specialized. NFPA 68 alone has some 84 pages of codes, tables, calculations, and exceptions for explosion mitigation devices, and missing one detail can put a facility out of compliance. Worse, it may nullify the system’s effectiveness.

Bernardo Sanson, a sales engineer with CV Tech, spoke to this point on a recent call, saying, “Ventilation requires expertise in the sense you’re required to know and be able to determine the burst pressure of the explosion panels. In the past, they were manufactured without much control for bust pressure. So, without knowing that, you don’t know the side effect a deflagration would have on your conveyor or the atmosphere. That’s only determined with testing. Plus, you have to be compliant with ATEC’s approvals in quality and protocol (as they relate to testing and manufacturing controls).”

Army Test and Evaluation Command approval isn’t likely something a wood processor will get from a panel designed by a staff engineer and manufactured in a company fab shop. Manufacturing intricacies are yet another reason to rely on professionals for this service and not attempt a do-it-yourself solution.

Post-installation care

DIY efforts do come into play post instalment, of course. While passive systems require less care than active systems, they still need attention. As with other systems, plant personnel must know how post-instalment work may affect them and how they wear over time.

According to Krbec, it’s not uncommon for technicians to add insulation to blast panels on their equipment. This is a problem, as insulation adds inertia to the panel and affects how it will perform in the event of a deflagration. The same idea holds for changes to the conveyor the vents protect. For example, replacing a top or bottom panel with material thinner than original equipment manufacturer specifications makes the conveyor weaker. Because the system’s parameters have changed, the vents may no longer adequately protect it.

Adding components around a blast panel likewise can affect how the system performs. Objects placed to the side of a panel may deflect energy up and increase the distance the fireball travels. Changes to the material inside the vessel may also affect the system, as can process changes that add vibrations or alter the air pressure. Due to the complexities associated with mitigation it’s best to consult the blast panel’s manufacturer before making changes.

Plant personnel must also maintain blast vents to ensure they remain functional. Panels must be kept free of debris, snow, ice, and large amounts of dust. They may also need protection from pests and precipitation. Furthermore, panels are not rust-proof, and vibrations will weaken them over time. A panels manufacturer can provide the best estimate for a panel’s expected lifespan.
Because mitigation systems are so nuanced, it’s best to talk to an expert before altering anything that may affect them.

Professionals understand the ins and outs of these systems – what’s required, what to avoid, and how to manufacture devices to code. The forest of information on mitigation and dust safety may be thick, but such experts can help you navigate it. Speak to one to ensure the safety of your facility. It’s the most practical advice you can get.

Joel E. Dulin is the director of marketing for Biomass Engineering & Equipment.

“Tragically, we know too well that if combustible dust is not managed properly, it can catch fire and burn or cause a deflagration and explosion, potentially resulting in serious and life-threatening injuries to workers,” says Budd Phillips, prevention field services manager at WorkSafeBC.

Over the past decade, WorkSafeBC has seen significant progress to ensure the hazards associated with combustible dust are effectively managed, by working alongside industry partners and employers to share and promote tools, techniques and knowledge about wood dust mitigation and control.

However, recent factors such as the COVID-19 pandemic and timber supply issues have impacted plant operations and changed the work environment in many mills and wood processing facilities. In addition, the risks can be hard to spot. Combustible dust can accumulate in out-of-site areas like basements, ceiling beams, and trusses.

“Over the past couple of years, manufacturers have been impacted significantly. Many have had to vary their production levels or reduce their workforce, which may draw resources away from proper maintenance and evaluation of dust management programs — leaving them vulnerable to potential hazards,” Phillips says. “Employers need to stay focused.”

Regular assessment is key

Phillips says now is the opportune time for all employers to revisit their dust management programs. “Dust management programs should be constantly evaluated to ensure they meet the needs of current operations and keep workers safe.”

This begins with a risk assessment to determine what operations are generating dust and where vulnerabilities exist in any given workplace. Find someone qualified – such as a health and safety professional or industry representative – to assess the fire and explosion risks associated with combustible dust.

“Look at your processes, equipment, and buildings to ensure you can accurately evaluate your current handling practices, equipment, fire extinguishing systems, and other dust mitigation efforts,” Phillips says.

Risks should be logged in a comprehensive report that is readable and well-presented. When the risks are clearly defined and understood, optimal controls can been identified, and implemented – typically through a combination of robust cleaning programs and engineering controls – to mitigate dust build-up when it exceeds allowable limits.”

“While cleaning processes are important, there is also a human factor to consider,” adds Phillips. “Ensuring cleaning crews are conducting proper assessments and can keep up with the pace of work can sometimes be challenging in a plant that generates lots of dust.”

Capture dust at its source

Phillips says that high-speed chainsaws can generate 33 pounds of sawdust per minute in multiple locations, which is why capturing dust at its source is critical to a successful dust management program.

Employers should examine ventilation systems to ensure proper airflow and have mechanisms to encapsulate dust such as covering conveyers. Employers should also ensure proper electrical cabinetry is in place and cleaned properly so it does not become an ignition source.

Phillips notes that technology for dust management has improved over the years.

“There are many engineering controls available that extract excess dust more effectively and also help monitor dust levels. For example, some mills have comprehensive monitoring systems that include new sonic fans that help remove dust from high elevation surfaces.”

However, enhanced technology does not replace the need to consistently evaluate dust management programs to ensure they’re sustainable. Plans should be re-evaluated and new risk assessments should be done if any of the following occur:

• Staffing changes
• New or different work duties for staff
• Equipment changes: including new equipment, upgrades, or downgrades.
• Structural changes to the facility
• Operational changes, including changes in production levels or processes.

“The smallest change in personnel or operations could make a difference, so employers must regularly evaluate their programs to ensure they have the capacity required to keep dust levels below the allowable limits,” says Phillips.

Even if nothing changes in a workplace, employers should review their programs at least once a year to ensure they meet occupational health and safety standards, and do not put workers at risk.

Phillips says most employers know their business and are aware of where and when dust is generated. The challenge is determining how best to control it and mitigate it.

Engineers that specialize in ventilation can also provide employers with a detailed assessment of a system’s effectiveness.

Updating legislation to reflect the risk

WorkSafeBC’s prevention efforts, inspection initiatives and collaboration with industry partners have been successful in combating combustible dust in wood manufacturing.

One of the challenges, however, is providing guidance and regulation to support smaller operations and other industries that face similar risks.

“Current legislation does not address all industries that are generating hazardous amounts of combustible dust, like cabinet shops for example,” Phillips says.

Pulp and paper waste, commercial laundry facilities, iron fillings, and sugar plants are just a few examples of the thousands of manufacturers that could experience catastrophic outcomes if dust levels from those products accumulate over certain levels.

“Our current regulations for combustible dust are minimal in terms of what we can require for combustible dust programs, and are limited to specific employers groups,” explains Phillips. “Since our combustible dust strategy was developed in 2012, we realized that there is a significant risk in many industries that needs to be addressed to keep workers safe.”

New proposed legislation changes are being considered right now in B.C., and are currently in the consultation phase, with input welcome from employers, workers, and industry groups. These revised regulations that will become part of the B.C.’s Occupational Health and Safety Regulation providing WorkSafeBC prevention officers with the opportunity to enforce safety programs in a broader range of industries.

A decade of lessons learned

In the 10 years since the sawmill explosions in Burns lake and Prince George, there has been significant progress and tangible improvements in managing hazards associated with combustible wood.

As other provinces across the country embark on their journeys to create combustible dust programs, Phillips encourages collaboration so industry partners and employers all benefit from the lessons learned.

“We owe it to those who lost their lives or were injured to never forget the impact those explosions had on their families, their job sites and their communities – and to remain vigilant in order to prevent a tragedy like that from ever happening again,” Phillips says.

Resources

To support employers in evaluating their dust management plans, WorkSafeBC has developed several resources that are available on their website.

• Combustible Wood Dust Management Program Development Guide | WorkSafeBC
• Combustible Wood Dust Mitigation and Control Checklist | WorkSafeBC
• Managing risks in manufacturing workplaces: Assessing risks — Combustible dust | WorkSafeBC

Alexandra Skinner is a manager of government and media relations with WorkSafeBC.

Fagus Grecon
Common causes of fires are heat, sparks, embers, and hot particles. One of the most efficient measures to prevent fire or dust explosion is the early identification of the ignition source. Fagus GreCon’s new DLD 1/9 Spark Detector offers additional protection to industries with new intelligent detection technology (IDT). IDT not only identifies hazardous moving ignition sources before a fire breaks out, but the DLD 1/9 detector is also able to differentiate between dangerous sparks or harmless incidence of extraneous light due to leaky/damaged pipes or an opening of an inspection flap.
www.grecon.us 

IEP Technologies
IEP Technologies provides a complete range of cost-effective industrial explosion protection for explosion protection solutions and is pleased to introduce the IV8 Flameless Vent. The IV8 provides an explosion protection solution for process vessels which are located inside a building or other areas where standard explosion venting cannot be safely employed. The IV8 utilizes a stainless steel explosion relief vent and flame arresting mesh enclosed in a durable carbon steel coated frame. The integrated vent burst detection sensor allows plant personnel to respond accordingly in the event of an explosion within the protected application.
www.ieptechnologies.com 

Kice
Kice Industries has been designing and building dust control systems and equipment for over 70 years, giving them valuable insight as to what works – and more importantly – what doesn’t work. When designing a dust control system, one must consider many factors ranging from the amount of dust emissions being created to the overall layout of the plant they are designing the system for. Every application is unique, and so Kice’s dust control systems and industrial air filtration systems are all designed and constructed specifically to meet clients’ needs.
www.kice.com  

BossTek
A new equipment design has been engineered to provide an unmatched level of mobility and performance, delivering effective particle suppression for new and existing applications.  The DustBoss Atom from BossTek is a fan-less, self-contained unit that incorporates remote control and 4G LTE telematics technologies to deliver an unprecedented combination of suppression and monitoring. The Atom is well suited to biomass handling, bulk material processing, demolition projects, recycling operations, transfer stations, ports/shipping applications, quarrying/crushing, concrete curing and even indoor operations.
www.bosstek.com  

CV Technology
CV Technology’s Interceptor-HRD Chemical Suppression System comes with the advantage of utilizing the latest advances in consumer electronics. The Interceptor-HRD Suppression System is capable of protecting very large dust collectors that are common throughout the biomass industry. The controller of this system is called The CONEX and it features the ability to operate up to eight independent operating zones at a time. A user interface is provided by an LCD screen, push button navigation, and signaling lights on the front of the controller enclosure. The interface includes a searchable data log and electrical lockout key switches for each zone.
www.cvtechnology.com  

Fike
For indoor applications, explosion vents as a form of explosion protection often requires flameless vents. A flameless vent consists of a box with a flame filter which is placed over a vent panel. When the vent opens, the pressure is relieved through the wired mesh of the flameless vent while cooling the flames below their MIT (minimum ignition temperature) so they are extinguished. Fike FlamQuench vents feature a variety of shapes and sizes available, minimizing required surface area on equipment; virtually zero safety distance due to effective particulate retention; and performance validated with many dust types, including fine, coarse and fibrous dusts.|
www.fike.com  

Advanced Cyclone Systems
Advanced Cyclone Systems is a company exclusively dedicated to the development and commercialization of high efficiency cyclone systems, worldwide. The company works in a very close cooperation with its clients in order to design custom made cyclone systems that really solve their unmet needs. ACS became a worldwide reference in cyclones, with over 350 successful installations in 37 countries and with several installations in Canada for biomass boilers applications with companies like KMW Energy, Clermond Hamel, Deltech, Fontaine Lumber, among others.
www.advancedcyclonesystems.com  

Scientific Dust Collectors
Scientific Dust Collectors offers a free third edition publication on dust collection titled, A Scientific Review of Dust Collection – Third Edition . It reviews the history, theory and application of all types of dust collection equipment. This third edition contains updated information on system design, filter media, explosive dust control and additional information on the new standard in measuring dust collector performance: ANSI/ASHRAE Standard 199.  This is the first and only standard as it relates to dust collection equipment, and is a valuable tool in reviewing dust collection equipment for your facility.
www.scientificdustcollectors.com 

VETS Group
VETS Sheet Metal celebrated a century of business in 2021. VETS provides industrial, light industrial and institutional HVAC systems. Whether make up air or cooling MCC rooms or a specialization in dust collection and pneumatic conveying, every application requires a unique approach. VETS’s experienced trades coupled with our specialized in-house Engineering department (P.Eng & E.I.Ts) can help engineer, design, fabricate and install a system that meets or exceeds a plant’s comfort, safety and environmental requirements.
www.vetsgroup.com

Allied Blower
For wood processing facilities demanding larger system capabilities, Allied Blower & Sheet Metal has a certified line of Back Blast Dampers (BBD’s) that reach sizes up to 50 inches in diameter. The BBD can resist a vented dust collector explosion reaching a Pred of five psi (0.35 bar) for dusts with a Kst of up to 200 bar-m/second. This range provides safe operation for a large range of deflagrable dusts used in industry. When comparing the options of using a passive mechanical system or an active chemical suppression system, the mechanical systems are perceived to have less maintenance costs due to simplicity in function, design, training requirements, and the low frequency of inspections.
www.alliedblower.com

We’ve got tons of great content coming at you this week from our partners, including WorkSafeBC, the Wood Pellet Association of Canada, Dust Safety Science, dust safety expert John Bachynski, and others.

The Dust Safety Week landing page, hosted on Canadian Biomass, is the year-round hub for pellet plant operators and sawmillers to learn best practices and find the latest information on dust safety.

Dust Safety Week 2022 is generously sponsored by VETS Group, Biomass Engineering & Equipment, Fagus Grecon, Fike and Rembe.

Find the landing page here and enjoy Dust Safety Week!

Now in its sixth year, Dust Safety Week’s landing page is the year-round hub for pellet plants and solid wood product manufacturers to learn best practices and find the latest information to keep their operations and operators safe.

Follow along all week as we will highlight feature stories, columns and research reports both from our archives as well as brand-new stories from contributors across Canada.

Find the landing page here, and stay tuned to our websites and social media (#DustSafetyWeek) for more information as we approach Dust Safety Week 2022!

Thank you to our generous sponsors for making Dust Safety Week possible: VETS Sheet Metal, Biomass Engineering & Equipment, Fagus GreCon, Fike and Rembe.

In 2018, UBSafe, supported by the BC Forest Safety Council, tested the feasibility of a control system isolating device (CSID) as a lockout alternative at a planer. According to the BC Forest Safety Council, the project successfully established that CSIDs can elevate worker safety using an engineering control which minimizes or eliminates human factors that can lead to serious injury.

Get an in-depth look at this project from those who made it happen at OptiSaw – the one-day education forum for those driving the future of sawmilling – taking place in Kelowna, B.C., on June 9.

Featured presentation: Functional safeguarding of a planer system

UBSafe principal Ian Rood will share the results of the planer system project: a safe, compliant, efficient system that was measured to reduce jam clearing-related downtime by 50 per cent.

Plus, network with our exciting group of sponsors who are releasing cutting-edge technology to the market.

Seat are limited and open only to sawmill management and owners, process engineers, continual improvement managers, optimization staff, researchers and design consultants. Register now for our early-bird rate of $189.

Check out the preliminary agenda, speakers and register online at www.optisaw.com.

According to CBC News, the Ontario Ministry of Labour is now investigating the incident.

In an internal memo to employees, Resolute president and CEO Remi Lalonde said “”We are determined to get to the bottom of what happened as soon as possible, and then take immediate corrective action across all our sites, as appropriate.”

Read the full story here.

No injuries were reported and the mill remains operational as crews investigate, according to local media.

Read the full article here.

“Ten years later, we continue to remember the tragic events at the Babine sawmill explosion that killed two workers and injured many more, and our thoughts are with the families, friends and colleagues on this difficult anniversary,” said Stephen Hunt, United Steelworkers (USW) District 3 director. “There are still many people asking how this tragedy happened and how it could have been prevented. Today we are renewing our call for the provincial government to protect workers.”

In 2019, the B.C. Ministry of Labour contracted Vancouver lawyer Lisa Helps to review the actions by WorkSafeBC and the provincial government in relation to worker safety. Helps released her report later that year, making 11 recommendations to strengthen worker safety, ensure a criminal lens is applied to workplace fatalities and put workers back at the centre of WorkSafeBC.

While the government has made some progress implementing the recommendations from Helps, more needs to be done.

“What happened at the Babine sawmill should never have happened, and while we can’t change the past, we can work to make sure tragedies like these don’t happen again, and if they do, employers are held criminally accountable,” said Hunt. “It’s been over two years since Helps made her recommendations, and the implementation by the provincial government is overdue – it’s time to get going and it’s time for WorkSafeBC to get on with the combustible dust regulation review.”

The United Steelworkers union is renewing its call for the provincial government to implement the recommendations from the Lisa Helps report and to create ongoing training for police officers and Crown counsel for workplace criminal investigations.

“When police are called to a workplace fatality or serious injury, the police need to seize the scene and rule out criminality, not defer it to WorkSafeBC,” said Hunt. “A workplace fatality or injury should be treated no different than a car crash investigation by the police, it should not be a WorkSafeBC issue, and there should be proper workplace-specific training for the officers.”

Since the start of 2022, three Steelworkers in Canada have been killed in workplace fatalities, including one in British Columbia at the Interfor Acorn Division in Delta.

The United Steelworkers has a long history of standing up for the health and safety of workers. The union’s past efforts have resulted in the creation of the Westray Law and a dedicated Crown Attorney for forest industry fatalities.

When a sawmill, like those operated by EACOM, is looking to perform maintenance on its planers, conveyors, stackers, log lines, and other equipment, worker safety must be protected by individually isolating all energy sources through the lockout/tagout process. The de facto standard for sawmills has been to individually lock-out and test all energy sources for each process, which can collectively take upwards of several hours. In addition to the lost productivity associated with this time-consuming process, there is also a risk of making mistakes, with a single missed disconnect leaving the possibility of a catastrophic accident.

A new technology class called control system isolation devices (CSIDs) is now disrupting the status quo.

With CSIDs, non-electrical technicians can quickly and safely lock-out entire circuits from a central master unit, with continuous validation of energy isolation from self-monitoring “smart” disconnects.

This technology offers to enhance the safety of maintenance technicians, while also giving hundreds of productive hours that are currently being lost to administering lockout/tagout back to an operation.

CSIDs differ from stop-button, selector switches, or PLCs with control circuits in that they are not intended to merely stop energy, but rather disconnect the main power of equipment or processes with safety-rated electromechanical devices. They are composed of a central lockout device and energy isolating devices for electrical, hydraulic, and pneumatic circuits located throughout a plant, allowing for simultaneous isolation and monitoring of an entire system of equipment.

Many Canadian regulators have already given the nod to these technologies, and, in the United States, the Occupational Safety and Health Administration is exploring this practice with an open call for feedback from operators and product manufacturers. However, regulations for what constitutes an effective CSID are strict. In WorkSafeBC’s 2019 report “Controlling Hazardous Energy: De-Energization and Lockout,” it is mandated for systems to comply with performance levels for safety as described in ISO 13849-1: Safety-related parts of control systems, and CSA Z460-13: Control of Hazardous Energy. Other bodies also require adherence to standards such as IEC 62061 and 60204 regarding safety of machinery for electronics and design of electrical equipment, amongst other locally relevant standards.

To meet these standards, systems must have components that are control-reliable and safety-rated, utilize hardware rated for millions of cycles without failure, and they must fail-safe in the event of a fault.

Daryl Dominique, CMSE (certified machinery safety expert) and product manager at SafeBox Systems, a vendor of CSIDs, says, “Over the past decade, functional safety standards, regulations, and technology have advanced to the point that CSIDs are now a viable option to improve lockout/tagout. However, while they are a fit for many plants, not all facilities are candidates, and there are many factors that should be considered before taking the plunge.”

Some terms you may come across as you investigate this technology include:

PLe: From ISO 13849-1. Robust safety measures are required for hazards that have severe consequences, occur frequently, and have a high probability of injury should protocols not be followed. For engineered solutions, PLe dictates the highest level of a safety system.

CAT IV Safety: Also from ISO 13849-1, CAT IV system architecture is required for PLe applications. Meeting this level requires continued performance of the safety function in the presence of a fault, detection of faults in time to prevent the loss of the safety function, and that potential accumulation of undetected faults is considered. A system must have independent, self-monitoring safety outputs that operate independently should one fail to avoid any unsafe state. In the event of any discrepancy, the unit will not be able to re-energize before the fault is corrected.

SIL3: IEC 61508’s Safety Integrity Level 3 or SIL3 standard is defined as “freedom from unacceptable risk of harm.” It encompasses the engineered system, in addition to each individual component to validate that a system does not fail to a dangerous state. For a CSID implementation, a SIL3 rating is a necessary condition.

For plants looking to implement and benefit from this technology, there are often pre-start health reviews, internal policies and procedures, employee training changes to be considered, and regulatory approval requirements. As such, it is recommended that a qualified professional be consulted before designing and implementing a system.

Thanks to advances in energy isolation standards and the emergence of CSIDs, plant owners can now enhance the safety of their maintenance teams while reducing downtime of their critical assets.

Marcus Thomson is a business development manager at SafeBox Systems. Reach him at Marcus.Thomson@safeboxsystems.com.

According to CBC News, the victims are Jean Lachance, 51; Mario Morin, 57; and Martin Roy, 50.

Police are investigating the causes and circumstances of the fire, and Quebec’s workplace health and safety board (CNESST) is examining the evidence.

The explosion occurred while workers were trying to put out a fire in one of the plant buildings.

To read the full story, click here.

According to CBC News, the mill’s main building was engulfed in flames. About 70 firefighters fought the blaze for six hours.

Some of the machinery was saved, which means some work can continue, but the mill itself was burned. The cause of the fire is unknown.

To read the full story, click here.

Francis Petit, P.Eng., an engineer with VETS Sheet Metal who specializes in dust abatement systems, shared his expertise in avoiding dust system failures in a webinar called, “Collector catastrophes: Avoiding the top dust system maintenance failures,” on June 25, which wrapped up Canadian Biomass and Canadian Forest Industries’ fifth annual Dust Safety Week.

“The better you know your system, the better you can maintain it without causing catastrophic failures,” Petit said at the beginning of his presentation, adding that the biggest failure is poor system design.

A poorly designed system will lead to increases in costs, maintenance and liability, he said.
Petit cited risks associated with five areas within a dust system: energizing and de-energizing, bad vibration, bearings and sheaves, plugs, and heat trace and water lines.

With regards to energizing and de-energizing, certain equipment in a dust collection system is energized. This means there is a risk of electrocution when performing maintenance on said energized equipment, he explained.

This risk and others can be mitigated by installing a properly designed dust collection system. In such a system, explosions can be prevented as pressure sensors will detect a rise in pressure and trigger chemical suppression, reducing the oxygen level in the vessel and preventing an explosion from reaching full maturity. Without such equipment, severe injury can occur in the event of an explosion.

Several things can also go wrong with fans, he said, noting that the bigger the fan, the more air flow it generates. If the fan is seeing a lot of dust, over time it can throw the fan wheel out of balance, causing failure through excessive vibration.

“Keep your fan clean and pay attention to vibration,” Petit cautioned.

A badly vibrating fan can create hairline fractures in the duct work. A fan that completely breaks down due to excessive vibration can injure or perhaps kill a nearby worker.

Bearings that are over- or under-greased can also result in failure, contributing to added downtime and halted production, Petit said. Bearings can contribute to an explosion if they’re not given proper care. Belts that are not properly aligned can wear quickly, causing the fan to fail and prematurely wear, leading to dust control issues.

Plugging is another critical risk that needs to be monitored in a dust collection system. To prevent plugging from occurring, duct hoods need to be properly placed in the correct location to capture dust. The objective is to keep dust suspended so that it doesn’t pile up and create plugs. Air flow velocity in the duct work should be kept at a permanent minimum, Petit said.

If plugging is a recurring problem, flex hoses should be checked with their length kept as short as possible to reduce the amount of static.

“If your filters are dirty and you’re trying to save some downtime, don’t replace half the filters,” he suggested. “Replace them all.”

A dirty filter will restrict the air flow and will cause a surge on the new filters, creating plugs.
Dirty filters lead to increased static pressure, Petit said, noting that when they are dirty, fans need to be sped up. When filters are clean, fan speed should be reduced. A constant air flow should be achieved. A fan’s rpm should be 1,200 with new filters and 1,410 with older filters.

Above all, it’s important that plugs be detected before they get out of hand, Petit said. The goal is to catch them before they reach the top of a filter. Otherwise, hours of maintenance will be required before the system can be put back on the grid.

In the end, it all comes back to the design of a dust system. If the collector is constantly plugging, there is a good chance it’s due to poor design, he said. Knowing and mapping a system will help to avoid plugs, which usually take upwards of a month to build up.

“If you can catch it at an early stage, you’re winning the battle,” Petit said.

Proper planning is also critical, especially given the extreme temperatures in some Canadian climates. Sprinkler lines that are allowed to freeze up will fail to do their job in the event of a spark, potentially leading to an explosion. But, proper planning will ensure a dust system will operate effectively for a long time, Petit said.

Good design from the start and proper maintenance are the keys to successful operations, Petit concluded. Correcting maintenance oversights will support a team’s safety as well as the facility and its operation.

Special thanks to VETS Sheet Metal, Fagus GreCon, Biomass Engineering & Equipment, and Fike, for sponsoring this webinar and Dust Safety Week 2021.

Here are four key takeaways from this week:

1) Complacency is a killer

David Murray, co-chairperson of the Manufacturing Advisory Group and the corporate safety, HR and environment manager for Gorman Group, kicked off Dust Safety Week 2021 with an article about preventing dust complacency in the face of competing risks. High-severity but latent hazards are destined to fall off the radar, he said. But, “there are ways to catch lightning in a bottle and maintain control over these risks.” Check out these three complacency-busting tips.

Rembe’s Jeramy Slaunwhite also picked up on this theme, writing that, when it comes to combustible dust explosion protection, “good enough” is not good enough. Explosion protection concepts and systems are only as reliable as their weakest link. “If corners are cut or something is overlooked, it can not only result in a hazardous situation, but also create a false sense of security under the perception of complete, reliable protection.”

Rose Keefe, with Dust Safety Science, took readers back to 1919, when, in a span of five months, four combustible dust incidents in four North American cities took place. She outlined the causes of each event and identified commonalities that can help prevent similar tragedies in the future. The parallels between the events in 1919, just when World War I had ended and in the midst of the Spanish Flu, and the current COVID-19 pandemic, are obvious, and the overall message is clear: as we return to more normal operating conditions and see more workers on site, along with new hires, safety must remain a priority. The changes cannot allow us to lose focus on fire and explosion dangers.

2) Prepare for the worst

One of the best ways to ensure operators and operations do not become complacent is by following best practices, such as the ones outlined by Michele Dyer with the BC Forest Safety Council about fibre pile management. Wood fibre piles, if not managed correctly, can pose a significant fire risk, as microbial growth and biological activity can occur, causing the piles to self-heat over time and triggering combustion, she explained. Consequently, effective management of wood piles and good safety planning is critical. She lays out some best practices for fibre pile storage and control measures to follows.

Another way is to understand what is required of you when conducting a Dust Hazard Analysis (DHA). Brian Edwards, explosion protection consultancy manager for Fike, answered the top five FAQs when it comes to DHAs, including the difference between dust combustibility testing and a DHA, and when a DHA should be completed in the design phase for new projects.

An upcoming webinar, part of the Wood Pellet Association of Canada (WPAC), WorkSafeBC and Canadian Biomass’ Safety Foundation Webinar Series, will also focus on best practices – this time, the best practices for managing combustible dust. The webinar, “Safe handling and storage of biomass, part II,” presented by Jeff Mycroft, regional sales manager at Fike Canada, will focus on the hazards associated with combustible dust, hazard assessment and hazard control and management.

Preparing for the worst also means knowing what to do when an explosive incident happens, not if it happens. VETS Sheet Metal’s Francis Petit, P.Eng., and Erin Rayner provided an overview of blast zones and a few key points to remember when establishing effective blast zones.

3) Standards set the bar

Proper dust safety management also requires an understanding of the applicable safety standards. Biomass Engineering & Equipment’s Joel Dulin gave readers an in-depth look at NFPA 664, Standard for the Prevention of Fires and Explosion in Wood Processing and Woodworking Facility, which was updated in 2020. Although the NFPA doesn’t require operations to be compliant with the revised 664 standard immediately, it does require compliance within a structured timeline, he explains. The code applies retroactively to new and existing facilities, and, therefore, every operation must understand what it requires of them.

Jeffrey Nicholas, managing partner at Industrial Fire Prevention, LLC, also outlined the NFPA standards that apply when classifying combustible dusts and hazardous locations: NFPA 499 and NFPA 70. He also discussed the engineering principle and principle of design outlined in NFPA 664, among other engineering controls.

4) Know your options

Finally, as always, having the right equipment is critical to keeping your facilities as safe as possible. We published our latest equipment spotlight on dust collection and suppression technology. This list includes brief description and photos of some of the latest designs and solutions available to Canadian wood pellet plants and sawmills.

Safety learning never stops

All of these feature stories and more are available year-round on our Dust Safety Week landing page, which will continue to serve as the place to find best practices and information on dust safety.

Thank you to our Dust Safety Week 2021 sponsors and safety partners VETS Sheet Metal, Fagus GreCon, Biomass Engineering & Equipment, and Fike.

Want to get involved in Dust Safety Week 2022? Email Ellen Cools at ecools@annexbusinessmedia.com.

Between May and September 1919, four grain elevators in four different North American cities exploded in similar incidents, killing 70 people and injuring 60 more. This doesn’t look like a coincidence.

The fact that four similar dust explosions occurred over a matter of months raises two critical questions: Why so many? And why did they all happen so close together?

Although these incidents occurred over 100 years ago, the answers are still relevant today. For example, if World War I and the Spanish Flu impacted grain handling practices, those issues may arise again during COVID-19, when social distancing requirements may be reducing the number of workers on site or returning to site and, by extension, attention to safety.

This study examines the factors that may have contributed to these 1919 grain elevator explosions. Identifying commonalities could prevent similar tragedies from happening in the future.

Combustible dust incident #1: the Milwaukee Works explosion

On May 20, 1919, at 11:15 a.m., a dust explosion at the Smith-Parry Grain Elevator in Milwaukee, Wis., killed three men and seriously injured four others.

It was a newer structure, having been built in 1917 to produce animal feed, and included a 100’ by 20’ crib for handling popcorn. Both the mill and warehouse were concrete and considered state-of-the-art for the time.
A 15-year-old boy recalled that he had been moving bags of grain when the explosion shook the elevator building and ignited flames everywhere around him. He escaped by jumping through a grain chute, but seven of his fellow workers weren’t so lucky.

Investigators concluded that the explosion occurred when sparks from machinery friction ignited grain dust.

Once their findings were published, the press quickly moved on to other, more sensational, stories. The incident did not get a lot of attention outside the local press due to the comparatively low death count. During the early 1900’s, injury and death were accepted as occupational hazards in industries like coal mining and grain handling, and unless a lot of casualties resulted, dust explosions did not attract a lot of attention.

Unfortunately, things were about to get worse.

Combustible dust incident #2: the Douglas Starch Works plant explosion

On May 22, 1919, at 6:30 p.m., a small fire ignited cornstarch inside the Douglas Starch Works plant in Cedar Rapids, Iowa. The resulting explosion killed 44 people, injured 30 more, and leveled the entire facility. Over 200 homes in the vicinity were damaged and some debris landed two miles from the site.

The economic loss was equally huge. Founded in 1903, Douglas Starch Works was the largest starch works company in the world by 1914. The plant and its elevator employed 650 to 700 people in 1919, making it a major employer for the city.

At the time, there was very little regulation for factories that handled or produced combustible dust.

The losses from this incident were so high that Iowa citizens demanded more government attention to fire and workplace safety laws. Their concerns were inspired by comments about questionable safety practices at Douglas Starch Works. One day shift worker had told reporters that men in the plant persisted in smoking around the buildings despite supervisor warnings.

Commenting on the explosion in an issue of the National Underwriter, Joseph Hubbell, manager of the National Inspection Company of Chicago, opined that it occurred in the plant’s wet process buildings, where some dry starch may have built up.

“It is now ascertained that projecting air blasts through the doors and conveyors connecting these sections filled them with a starch dust cloud, caused by smashing and upsetting of conveyors, packages, bins, and the like, and went to the end with increasing speed and compression until the building structure gave way.”

On May 27, the coroner’s inquest jury found that the victims had been killed by a “fire of unknown origin followed by an explosion.” No one was ever held criminally responsible for the disaster.

June and July passed without any incidents. Then, on a warm August day in Port Colborne, Ont., a third explosion took place.

Combustible dust incident #3: the Port Colborne Grain Elevator explosion

The Aug. 9, 1919, explosion at the Dominion Grain Elevator in Port Colborne killed 10 workers and left 16 others with serious injuries. Total damage was estimated at $1.5 million Canadian dollars.

Opened in 1908, the elevator played a central role in grain movement throughout the Great Lakes. It was made from reinforced concrete and had a capacity of over two million bushels after more storage bins were installed in 1913.

On the day of the explosion, a fire occurred in one of the lofters used to transfer grain from the lower to the upper system of the elevator’s horizontal conveyors.

Workers put it out, but smelled burning rubber when they returned from lunch. Assuming that a belt in the basement had overheated, they did not investigate.

At around 1:00 p.m., two men saw smoke issuing from the motor of the conveyor in the lofter head area. Fifteen minutes later, a man working on the top floor saw smoke and fire on one of the belts and made it down to the first floor just before an explosion erupted.

The explosion blew apart the top three floors, lifted the concrete roof, and hurled wreckage over a mile away.

Investigators believed that heat from the motor of the jammed conveyor had ignited airborne dust, causing it to explode. However, the law may have also played a role in the Port Colborne explosion.

Canadian regulations prohibited the removal of dry dust from processed grain – if an elevator received 500 tons of grain, the same amount had to be shipped out, even if much of it was grain dust. When the dust leads for the bins in the Dominion Grain Elevator were closed to reduce any product loss, the fans could not clear away airborne particles, creating prime conditions for a dust explosion to occur.

Industry leaders in Ontario were still debating this conundrum when the fourth and final explosion took place.

Combustible dust incident #4: the Murray Grain Elevator explosion

At 2:10 p.m. on Sept. 13, 1919, the Murray Grain Elevator in Kansas City, Missouri was destroyed by a dust explosion that killed 14 men, injured 10 others, and caused $650,000 worth of property damage.

On Sept. 5, 1919, an inspector for the U.S. Grain Corporation found dust accumulated everywhere, along with ignition sources like worn extension cords, carbon filament lighting, and lack of protection on electric light bulbs. There was only one partially filled fire extinguisher on the top floor.

When questioned, the superintendent tried to explain away the dust piles by saying that the dust collector’s fan had recently broken down, but the inspector had personally seen it working. In his report, he wrote, “This plant is dangerous and even though fireproof, will explode if its present condition is permitted to exist.”

On Sept. 12, another inspection took place, but conditions had not improved. Now worried about the possibility of sanctions, elevator management ordered a clean-up the next day, but it was too late.

At around 2:10 p.m., a maintenance man saw blue flames shooting out of electric light wires seconds before an explosion tore the building apart. The force was so tremendous that the entire working shed was blown away and pieces of the 16-inch concrete wall were later found several feet away from the elevator grounds.

Firefighting efforts were delayed because the nearest hydrant was 8,000 feet away. It took over an hour for the fire department to create a long enough hose connection. During that time, the flames had spread from the elevator itself to 30 grain-filled boxcars at the south end of the property.

After inspecting the damage and interviewing witnesses, investigators concluded that the explosion originated in the basement and propagated up through the manlift tower. On Sept. 19, the coroner’s jury ruled that the cause of the explosion was unknown, although the maintenance man repeated his story of seeing blue flames coming out of electric light wires. There were also allegations that someone had lit a cigarette in an area not designated for smoking.

The Murray Grain Elevator explosion appeared to have drawn attention to substandard safety practices in North American grain elevators, because fire underwriters and insurers who had considered fireproofing to be sufficient protection were now re-inspecting facilities for dust explosion hazards. Managers who formerly resented and resisted these intrusions now welcomed them.

What caused these dust explosions in grain elevators?

Although dust explosions in grain handling facilities weren’t rare in 1919, four devastating events over a period of five months is abnormal and raises the question: what caused them?

In this section, we review factors, a few of which are relevant even today, that may have contributed to this string of tragedies or made them worse.

They are:

• Grain elevator construction
• Unsafe work practices
• Current events (in this case, the Spanish flu and conclusion of World War I)

Grain elevator construction

Before 1905, grain elevators were made from cribbed timer or sheet iron on a frame. These structures vented explosions more easily, so they suffered more from fire damage. Believing that the solution was a ‘fireproof’ structure, designers and builders shifted from wood to concrete.

The problem was that an all-concrete grain elevator was a bigger explosion risk than its wooden predecessors. In addition to the three elements of the fire triangle (heat, fuel, and an oxidizing agent), dust explosions require confined space. Although the industry believed that a heavy concrete elevator could safely contain an internal explosion, it was quickly proven wrong.

With the explosions at Douglas Starch Works, Dominion Grain Elevator in Port Colborne, and the Murray Grain Elevator, the elevators not only blew apart, but pieces of the concrete structure were found miles from the site. Without proper venting, the force of each explosion caused irreparable damage.

Despite these tragedies, faith in the invincibility of concrete elevators continued for years.

The Armour Grain Elevator in Chicago, touted as the ‘world’s biggest elevator,’ was considered so safe that its owners deemed insurance unnecessary. Their confidence was misplaced: in 1921 the elevator experienced a grain dust explosion so intense that 40 of its loaded concrete silos shifted six inches on their foundations. Six people died and losses were estimated at $3 million.

Investigations into the root causes of these explosions gradually led to improvements in elevator design, such as venting and isolation of more hazardous equipment. Unfortunately, these safety measures came too late for the victims of the 1919 explosions.

Unsafe work practices

During the early 20th century, only a small number of workers (many of them part-time or seasonal) were needed to operate a large grain elevator. Quick processing of high volumes of grain was essential to realize a return on investment. Consequently, cleaning and maintenance went by the wayside because it siphoned away necessary labour without boosting profits.

Other problems that contributed to grain dust fires and explosions then and now include:

• Welding or cutting operations in poorly-ventilated areas
• Open flames, including matches used to light cigarettes
• Improper attention to slipping elevator belts
• Dust coming into contact with hot surfaces like bearings
• Friction sparks from machinery or tramp iron (which caused the Milwaukee Works explosion)
• Electric arcs from static, surges, cable damage, or improperly applied electrical equipment (which is believed to have caused the Murray Grain Elevator explosion)

In 1919, National Fire Protection Association (AFPA) guidelines were treated as optional and likely to be ignored if implementation was expensive.

This tunnel vision continues to be a problem today. Cost often takes priority over safety when implementing fire and explosion safety measures, and until this practice stops, the danger will never be overcome.

Current events

World War I

When the United States entered the war in April 1917, over 4.7 million men and women served in the regular U.S. forces, National Guard units, and draft units, with around 2.8 million serving overseas. By the time peace was declared, 115,600 had been killed and 200,000 wounded.

In Canada, more than 650,000 Canadians and Newfoundlanders served: out of this number, over 66,000 died and more than 172,000 were wounded.

These soldiers surely included skilled agricultural workers who understood the fire and dust explosion risks in grain handling facilities. Whoever replaced them may not have had the same level of knowledge and experience.
At the same time, demand for wheat increased. Farmers were encouraged by the government to ‘Win the War with Wheat.’ The crops were not just for Americans – a lot of them went to Europe, where the war had drastically impacted wheat production. Demand for output, combined with a workforce impacted by the war and Spanish flu (see below) conceivably resulted in safety missteps that proved fatal.

The Spanish Flu

Several comparisons have been made between the COVID-19 and Spanish Flu pandemics. Both are respiratory illnesses caused by a virus, transmitted through close contact, and spread across the world within months, killing millions.

Pandemics of this magnitude affect workforces everywhere. Illness-related deaths and absences, combined with social distancing, can result in a workplace with fewer skilled workers who understand the dangers of their specific industry.

With the Douglas Starch Works and Murray Grain Elevator explosions, there were allegations of smoking in high-risk areas, something that experienced and aware workers probably wouldn’t have done. Minutes before the Dominion Grain Elevator exploded, men returning from lunch smelled something burning but failed to investigate.

Lessons learned

Jess McCluer, vice-president, safety and regulatory affairs at the National Grain and Feed Association (NGFA), observed one important commonality between all four incidents.

“There wasn’t any type of program in place to mitigate ignition sources, i.e. smoking, sparks or explosion hazards [such as] dust accumulation,” he says. “Further, there wasn’t any type of plan to address the heated bearings in many of the conveyors i.e. preventative maintenance.”

These mistakes shouldn’t be blamed on the workers. Then, as now, they carried out their duties under the direction of elevator management. With demand for wheat being high despite personnel shortages due to the war and the pandemic, safety may have taken a back seat to production and profit.

Conclusion

Regulations and safe work practices are necessary to encourage conformance to appropriate standards in grain elevator design and construction. Industries and countries without appropriate and enforced regulations may continue to see combustible dust incidents.

Although design changes and advanced protection systems now mitigate losses in grain elevators in North America, COVID-19 has affected the industry globally, much like World War I and the Spanish flu pandemic did. Due to social distancing, many locations have fewer workers on site and, as we return to wrk, see an increase in new personnel to replace those who have died of COVID. The changes in routine and inexperienced new hires may contribute to a lack of focus on fire and explosion dangers.

Although we can’t totally escape conflict and disease, we can prevent them from affecting safety in industries handling combustible dust. We can also work together on an international basis to encourage appropriate standards and safe work practices around the world. Ensuring that safety remains a priority at all times can lessen the human cost of these tragic events.

Sources

Periodicals

• Wausau Daily Herald (Wisconsin)
• Decatur Herald (Wisconsin)
• Portage Register-Democrat (Wisconsin)
• The Cedar Rapids Gazette (Iowa)
• Ottawa Journal (Ontario)
• Kansas City Star (Missouri)
• Kansas City Times (Missouri)

Publications

• The American elevator and grain trade. (1917). Chicago: Mitchell Bros. & Co
• Proceedings of conference of men engaged in grain dust explosion and fire prevention campaign, conducted by United States Grain Corporation in cooperation with the Bureau of Chemistry, United States Department of Agriculture. (1920). New York: U.S. Grain Corporation.

Rose Keefe is a technical writer for the DustEx Research family of services including DustSafetyScience.com.

Dust Safety Science aggregates their reports twice a year, and this most recent report includes all incidents we’ve captured from Jan. 1, 2020, to Dec. 31, 2020. These are broken into fires and explosions occurring both in North America and internationally.

The following table compares the number of incidents, injuries and fatalities entered into the database since we started recording.

Loss history – United States

Loss history from dust explosions in the United States over the last five years is given in the following table. This data has been collected in the incident database and reported in the combustible dust incident reports, from 2016 to 2020.

This data gives an average of 31.8 dust explosions per year, 29 injuries and 2.6 fatalities over the last four years. Note that dust fires are excluded in this analysis.

2020 global loss overview

In 2020, 70 per cent of the fatalities recorded occurred due to dust explosions. Of the injuries, 73 per cent occurred due to explosions and 27 per cent occurred due to fires.

Some of the more severe incidents include:

• Five injured in food recycling dust explosion (Rose Hill, N.C.)
• One killed, three injured in dryer explosion (Belle, W.V.)
• One killed, four injured in feed plant explosion (Shanxi, China)
• One killed, four injured in dried sludge explosion (Bristol, UK)

Limited information has been available for damages from dust explosions and fires. From the information that is available the following incidents resulted in more than $1,000,000 in losses:

• Wood chipping fire causes $2 million in damages (Ramseur, N.C.)
• Paper products fire causes $2 million in damages (Mooresville, N.C.)
• Sawmill destroyed by fire (Cap-Pelé, N.B.)
• Food plant fire causes $3 million in damages (Sibley, Iowa)

Materials involved

In reviewing the global incident data, food and wood products made up over 75 per cent of the combustible dust fires and explosions recorded.

These materials also resulted in 57 per cent of the injuries and 40 per cent of the fatalities. A breakdown of the fires, explosions, injuries and fatalities for each type of material is given as follows:

The one fatality from metal dust and two injuries involved aluminum alkyl, while three of the injuries involved titanium. The other injuries from metal dusts involved four incidents where the type of metal was not specified.

Two fatalities occurred in an explosion where unspecified raw materials were being added to a reactor, one fatality occurred when smashing unspecified chemicals in a tank, four fatalities occurred during a dried sludge explosion and one occurred in a bleach powder drier explosion.

Industries involved

As shown in the historical data, wood processing, wood products, agricultural activity and food production make up a large portion of the overall fire and explosion incidents. Since 2017, wood and wood products have ranged from 21 to 28 per cent of the incidents, while agricultural activity and food production has ranged from 33 to 44 per cent.

As shown in the detailed incident breakdown, the “other” category includes pulp & paper, high schools, and educational facilities. Industries not broken out in the detailed breakdown include incidents in metal recycling, rail maintenance, display stand manufacturing, jewelry, surfactant manufacturing, plastic bottle manufacturing, chemical processing, phosphate production, waste treatment, composites manufacturing, and textiles.

Combined, the overall “other” category of industries makes up 28 per cent of the injuries and 50 per cent of the fatalities reported in 2020. Wood and wood products, agriculture and food processing, and automotive and metalworking make up 19 per cent, 43 per cent and eight per cent of the injuries, respectively. Wood and wood products, and agriculture and food processing make up 30 per cent and 20 per cent of the fatalities, respectively.

Equipment and causes

In 2020, storage silos demonstrated the highest percentage of combustible dust incidents with 30 fires and 13 explosions reported. This is a higher percentage than the 2017 and 2018 reports, which found that dust collection systems had the highest percentage of incidents. In 2020, only 13 per cent of the fires and explosions occurred in dust collection systems.

As demonstrated in previous reports, storage silos had the largest number of injuries. This is followed by other storage (e.g., small bins, hoppers and storage buildings), dust collection systems, dryers and elevators. The breakdown between fires, explosions, injuries and fatalities for different pieces of equipment are summarized in the following table for 2020:

Although equipment labeled under, “Other,” only had 13 per cent of the total incidents, these incidents resulted in 22 per cent of the injuries and 30 per cent of the fatalities. Some of these included a spark that ignited varnish vapours and sawdust while doing maintenance on a staining machine, an explosion and fire in the ducting and mill of a pellet manufacturing process, an explosion of a combination of titanium and calcium powder in a chemical processing unit, a dust fire and a dust explosion while using a welding machine in a dusty area, an explosion in a raw material feed tank into a reactor, and an explosion in a plastic extruder system.

For more information or to download a copy of the report, visit www.dustsafetyscience.com/2020-report.

Disclaimer

The contents of the incident reports are generated using publicly-available news articles and resources. The data is provided for informational purposes only and is not meant as a replacement to professional guidance. Due to reliance on third-party news agencies, incomplete articles, and limited analysis methods, DustEx Research Ltd. and its subsidiary Dust Safety Science makes no warranties or guarantees to the accuracy or completeness of the information provided.

This is a question I often found myself asking as new wood pellet and biomass plants started sprouting up all over the United States and Canada. I didn’t say this to be rude, but to point out potential combustible dust and ignition issues.

For decades, we have been making wood flour in the forest products, wood and secondary wood products sectors, especially in the MDF (Medium Density Fiberboard) and other related industries. Yet there seemed to be little technology transfer, especially when it comes to engineering controls for fire and explosion prevention and protection. Every engineering firm and large equipment manufacturer seemed to think they could build a wood pellet plant. So, naturally, many of the designs are different. Some are built with the proper engineering controls designed in, but others’ fire and explosion protection seemed to be an afterthought. My job is to help prevent these fires and explosions. This is what keeps me up at night.

In my job, I get the opportunity and privilege of making site visits to many of these wood pellet operations, as other various types of combustible dust processes. Often, there is a disconnect from safety theory to actual practice. I go through many variations of safety orientation at these plants and will often see posters that say, “safety first,” all the while walking around on layers of combustible dust!

What if I told you combustible dust could be just as flammable or explosive as gasoline? Or if I told you combustible wood dust bin explosions are just as powerful as grain elevator explosions? Would that change how you view combustible wood or biomass dust?

There are established and reputable conveyor companies who dismiss the idea of building a conveyor that is dust tight. However, if a plant had a combustible gas leak, they would not continue to operate. Instead, they would shut down and fix the leak before starting back up. Or if they had a fuel, gasoline or other flammable liquids spill, they understand that their first responsibility would be to evacuate the area, fix the problem and clean up the mess. Yet, when it comes to combustible dust, we seem to be blind to the potential hazard. Because we work around it every day, a level of complacency tends to develop. So, training and housekeeping is critical to preventing fires, explosions and the catastrophic secondary explosions.

Complacency kills

Another thing that makes me cringe is hearing someone say, “That’s the way we have always done it,” or, “Fires are just part of the process.” This is complacency, lack of education to the hazard, and, really, a lack of respect for the danger of combustible dust. Plants change. Machinery wears over time, products change, specifications change. Change management, constant improvement and training are critical to stay on top of safety.

Combustible dust layers on equipment and machinery, walls, floors, on the rafters, cable trays, conduit and piping are an indication of this complacency and of a potential combustible dust incident. Often after touring plants that have layers of combustible dust on surfaces, I find they have indeed had previous fires or explosions. Understand, if you are having fires and explosions, no matter how minor, they are potential precursors to a bigger event. A deflagration is simply a fast-moving fire. And a combustible dust fire is simply a failed explosion, you just haven’t gotten the recipe right yet!

Any time you move or manipulate a combustible product, you are creating friction and heat as well as combustible dust, and therefore have the potential for fires and explosions.

The Fire Triangle and Explosion Pentagon

Courtesy Fagus GreCon

There are three main areas of concern for creating fires in the biomass process – dryers, hammer mills, and pelletizers. Conveyors and other moving machinery are also a concern. These processes create friction and heat, which is one leg of the Fire Triangle. The other two are oxygen and fuel. So, you inherently have all the ingredients for a fire in your biomass process.

If your dust is in an enclosure that contains a dust cloud such as a bin or dust collector, you not only have all the ingredients for a fire, you also have the additional ingredients needed for a deflagration: combustible dust in suspension in a confined area or vessel. If you are storing wood dust or pellets in enclosures, and/or you have dust collectors, you have all the ingredients necessary for an explosion.

Courtesy Fagus GreCon

Heat, friction and mechanical sparks cause many of these fires and explosions. According to the 2016 National Fire Protection Association (NFPA) report, “Fires in Industrial or Manufacturing Properties”:

• U.S. fire departments responded to an estimated average of 37,000 fires at industrial or manufacturing properties each year, with annual losses from these fires estimated at 18 civilian deaths, 279 civilian injures, and $1 billion in direct property damage.
• Structure fires accounted for 20 per cent of the fires, but 47 per cent of civilian deaths, 82 per cent of civilian injuries, and 69 per cent of direct property damage.
• Heating equipment (14 per cent of total) and shop tools and industrial equipment (also 14 per cent of total) were the leading causes of structure fires in industrial or manufacturing facilities.
• A mechanical failure or malfunction was a factor contributing to the ignition of one in four structure fires (24 per cent) in industrial or manufacturing properties, accounting for 23 per cent of civilian injuries and 21 per cent of direct property damage.

The controlling document for protecting wood biomass and wood pellet plants and processes is NFPA 664 Standard for the Prevention of Fires and Explosions in Wood Processing and Wood Working Facilities (for agricultural-based biomass, see NFPA 61 Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities). NFPA 664 requires a dust hazard analysis (DHA), to identify and mitigate all potential combustible dust and ignition hazards.

The primary areas of concern for explosions are enclosed vessels such as bins and hoppers, dust collectors and storage silos, and secondarily enclosed conveyers such as bucket elevators. To protect these facilities, use the Hierarchy of Controls.

The Hierarchy of Controls

The hierarchy of controls include Administrative, Engineering, and PPE. Administrative controls such as housekeeping, hazard communication and management of change (MOC) are a primary level of prevention. For example, changing from softwoods to hardwoods or adding a dryer to the process necessitates hazard analysis, hazard communication and MOC.

Personal protective equipment (PPE) and gear are the easiest controls to apply. Most of us know that when operating in areas where there are potential fire and explosion hazards, proper PPE must be worn. Safety glasses, hardhat, hearing protection, gloves and steel toed boots are the most common. When working around processes where there is potential for combustible dust fires and explosions, you should also consider adding fire resistant clothing (FRC). While this article focuses on combustible dust, this also applies to processes with flammable gasses, other flammable products, and hybrid mixtures.

Engineering controls

Engineering controls include area classification. Two documents are used for the classification of combustible dusts and hazardous locations: NFPA 499 and NFPA 70, Article 500 of the National Electrical Code (NEC). Also refer to NFPA 77, NFPA 79 Electrical Standard for Industrial Machinery, and NFPA 499.
Class/division hazardous locations are another engineering control facilities should use. Hazardous locations are locations where electrical equipment might present an ignition hazard. Class II Hazards are combustible or conductive dusts that are present (or may be present) in quantities sufficient to produce explosive or ignitable mixtures.

Division refers to the probability of hazardous materials. Division 1 has a high probability of producing an explosive or ignitable mixture due to it being present continuously, intermittently, or periodically from the equipment itself under normal operating conditions. Electrical equipment in these areas must meet the criteria for explosion proof rating. Division 2 has a low probability of producing an explosive or ignitable mixture, and is present only during abnormal conditions for a short period of time – such as a container failure or system breakdown. See NFPA 652 Standard on the Fundamentals of Combustible Dust requirement for a Dust Hazard Analysis (DHA). NFPA 652 requires all such facilities to perform a dust hazard analysis and risk assessment for each process that handles or creates combustible dust.

An engineering principle outlined in NFPA 664 is to isolate, segregate and separate the various hazardous parts of the process from each other. As an example, there is a design of a hammer mill process that uses a plenum between the mill and the dust collector, thus creating a bomb. It is preferable to have a choke in between these two areas, like a screw conveyor or airlock, and to remove the dust collector to a remote location outside the building, thus isolating a potential explosion or deflagration.

Another principle of design found in NFPA 664 is layered protection systems for fire prevention, fire protection, and explosion protection. NFPA 664 Chapter 8 applies to processes and systems such as mechanical conveyors, pneumatic conveyors, classifying, and dust collection systems. Conveyors and ducts with a fire hazard are required to have fire prevention and/or fire protection.

Fire prevention is typically spark detection. Spark detection and extinguishing systems are a primary tool to prevent sparks from propagating into fires by detecting and suppressing sparks or embers in the incipient stage. Spark detection systems are typically applied to mechanical conveyors, pneumatic conveyors and dust collection systems. Fire protection is typical deluge and sprinkler systems. We may also utilize other types of hazard monitoring equipment such as bearing temperature, heat detection, spark, ember, flame, smoke, CO detection, and emissions monitoring, as well as other types of suppression, control and isolation devices. Interlocking machinery, conveyors, fire dumps, and proper sequencing of shutdowns are also critical engineering controls.

Vessels and dust collectors with a deflagration hazard are required to have explosion protection and isolation. Mechanical or chemical isolation of these vessels and dust collectors is also required (see NFPA 68 Standard on Explosion Protection by Deflagration Venting, and NFPA 69 Standard on Explosion Prevention Systems).

Explosion vents have to be engineered based on the explosive characteristics of the dust, thus dust testing is required. Venting needs to vent to a remote area away from buildings, machinery and people. Blast radius areas should be defined. Bins inside the building can be vented outside provided the distance to the exterior wall is short enough. Alternately, indoor explosion vents, also called “flameless venting” can be utilized. These flameless vents use a mechanical or chemical flame barrier to suppress the flame front, but still emit a pressure wave.

Where explosion venting cannot be used, chemical explosion protection and isolation must be used. Explosion protection systems consist of an optical and or pressure sensor, a control panel and chemical canisters strategically located on the vessel and connected ducting.

After implementing the above, you have now created layers of protection based on the hierarchy of engineering controls, best practices, and applicable codes and standards.

So, there you have it. A brief overview of how to protect your wood pellet and biomass operation from fires and explosions. With proper analysis, design, and engineering and administrative controls, training, and housekeeping, you plant can be made safe.

You can reduce the probability of risk, as well as the severity of any consequences, maintaining safety and business continuity as well as a safe environment for employees and stakeholders, and safeguarding your reputation in this industry.

Reference codes and regulations

• The International Fire Code (IFC)
• The International Building Code (IBC)
• Local building codes
• National Fire Protection Association (NFPA), particularly the following codes:
  • NFPA 68, Standard on Explosion Protection by Venting
  • NFPA 69, Standard on Explosion Prevention Systems
  • NFPA 70, National Electrical Code, (particularly the sections on area classifications)
  • NFPA 77, Standard on Static Electricity
  • NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous Locations for Electrical Installations
  • NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids
  • NFPA 652. Standard on the Fundamentals of Combustible Dust
  • NFPA 664, Standard for the Prevention of Fire and Explosions in Wood Processing and Woodworking Facilities

Other resources

Insurers such as FM Global have their own requirements. See the following FM Global Property Loss Prevention Data Sheets:

• FM 7-10, Wood Processing and Woodworking Facilities
• FM 7-11, Belt Conveyors
• FM 7-17, Explosion Protection Systems
• FM 7-73, Dust Collectors and Collection Systems
• FM 7-76, Prevention and Mitigation of Combustible Dust Explosions and Fire
• FM 7-78 Industrial Exhaust Systems
• FM 8-27, Storage of Wood Chips

Jeffrey C. Nichols is a managing partner at Industrial Fire Prevention, LLC. Industrial Fire Prevention specializes in helping protect industrial manufacturing processes, pneumatic and mechanical conveying, and dust collection systems from combustible dust fires and explosions. For requests for more information, please contact info@industrialfireprevention.com.

In the event of an explosion, creating a clear and efficient pathway for the resulting fire and possible subsequent deflagration to exit the building in the safest, most direct path possible while avoiding key equipment and personnel is crucial. Enter the blast zone.

[Editor’s note: This article is part of Dust Safety Week 2021. Find more articles here.]

When speaking about dust management systems, a blast zone is an area, either outdoors or indoors (depending on the system), that allows for the safe expulsion of an explosion that has happened within a system without putting workers, vehicles, equipment, or other buildings in danger. Typically, these areas are marked by paint on the floor or cement and further defined by fencing and signage.

However, sometimes they are not as obvious as they should be, or, even worse, they increase the danger of an explosion by venting directly into a raised catwalk or solid interior wall.

An explosion with Rembe Targo Vent. Photo courtesy Rembe Inc.

A few key points to remember when establishing effective blast zones:

1. Think it through

A risk assessment of the blast zones should be performed and documented by a qualified and knowledgeable Professional Engineer when adding to or making changes to a system.

2. Once a blast zone, not always a blast zone

Blast zones should be re-evaluated each and every time there is a change in the process or operation to confirm that it is still safe and effective.

3. Between a blast and a hard place

Consider additional or alternate methods to suppress or efficiently release an explosion depending on the space and type of dust collection system in your facility. Dust system technology is always evolving and changing. There are options to enhance the safety of a dust system such as chemical suppression coupled with spark detection. If the system is indoors with compressed space requirements, use a ventless explosion panel to quench and diffuse any possible explosion while continuing to utilize the space around the collector.

Finally, employing a directional vent such as a Rembe Targo-Vent to effectively direct any explosion away from occupants or equipment could be a solution.

Erin Rayner is the marketing and business development officer for VETS Sheet Metal. Francis Petit, P.Eng., earned his Bachelor’s degree in Mechanical Engineering from the University of Sherbrooke, Que., and has developed a specialization in dust abatement systems including fire and explosion protection. He has more than 10 years of experience in design, engineering, and installation of dust collection and industrial HVAC ventilation systems.

The hazardous result of this biological, physical and chemical reaction generates smouldering pockets that can endure continuously for months, creating gaps and fire pockets that can collapse under any weight. These smoulders can even lead to surface fires and open flames when exposed to oxygen such as wind, exposure from another fire or from other ignition sources close to the piles.

[Editor’s note: This article is part of Dust Safety Week 2021. Find more articles here.]

Effective management of wood piles and good safety planning can help decrease the risk of internal fires caused when fibre piles self-heat, causing combustion. The risk of spontaneous ignition increases if the raw material or solid biofuel is initially moist, the stored volume is large and the ambient temperature is high. Follow the best practices in fibre pile management and control methods below developed by *Shahab Sokhansanj, Ph.D., and *Fahimeh Yazdan Panah, Ph.D., to help mitigate the risks of spontaneous fibre pile fires to help keep workers safe and your fibre protected.

Storage

• Fibre pile storage should preferably be located on dry, level ground on an asphalt or concrete surface close to the transport road
• The dry, level ground should be free of stumps, stones and large residues
• The storage area should be located in an area higher than the transport road(s) to avoid rainwater saturating the storage pile from the water accumulating on the road(s)
• Outside storage piles should preferably be covered to avoid precipitation or the accumulation of moisture
• Store dry fibre piles (<20 per cent moisture content) to avoid microbial growth
• Different types and qualities of fibres, such as hog fuel and wood chips, should never be mixed and should be stored separately
• Fibre piles should preferably be stored in small piles
• Store fibre piles for a short period of time
• Ensure fibre pile storage management controls are in place with inventory and timeline management as essential control measurement
• Store the material such for FIFO (First In-First Out)
• Avoid compacting the material – (i.e.) running heavy equipment on the material
• Use these rules of thumb:
  • FIFO (First In-First Out): store the material to ensure it is transported first in-first out to reduce the risk of some material sitting in the pile for an extended period of time
  • Raise piles in elongated stacks using this rule of thumb: base width twice the height of the stack
  • Fibre pile typical heights:
    • clean wood chips without bark: 15 metres,
    • chipped forest residue: 15 metres
    • bark: seven metres
    • sawdust: six metres

Control measures

• Use a Forward Looking Infrared (FLIR) camera or thermal imaging camera to identify hot spots early
• Monitor the temperature at several different locations in the bulk
• Measuring the CO concentration in the air above the fuel surface is one possible method for detection of activity in the fuel bed
• Other detection methods include multi-gas detectors and sensitive “electronic nose” detectors
• Understand the signs of an on-going self-heating process to detect the hazard – the first sign is often a sticky and irritating smell
• Initiate firefighting if the smell or sight of fire is sensed from the storage pile such as the smell or sight of smoke (not steam or water vapour) or if flames or embers are spotted. Use trained fire fighters or contact the local fire department to safely expose and extinguish fibre pile smolders/fires
• Ensure workers do not climb up on and equipment does not scale or drive on a fibre pile that is suspected of self-heating
• Restrict public access to fibre storage areas
• Follow all established safe work procedures regarding fibre pile storage
• If you suspect the pile is self-heating
  • Don’t go on top; instead, seek help and advice from your supervisor
  • Check to see if your safe work procedures follow a process; if there is no procedure in place, ask your supervisor for help

To learn more about fibre pile management, visit the Wood Pellet Association of Canada.

Resources

BCFSC Fibre Pile Management Crew Talk
WPAC Safety Alert: Fibre Pile Fatality

*Dr. Shahab Sokhansanj (PhD, MSc) is an adjunct professor of chemical and biological engineering at the University of British Columbia Faculty of Applied Sciences.

*Dr. Fahimeh Yazdanpanah (PhD, PMP, P.Eng) is the research and technical development director for the Wood Pellet Association of Canada, founder of Spark Biomass Consulting Inc. and former research associate for the Biomass and Bioenergy Research Group (BBRG) at the University of British Columbia.

Michele Fry is the director of communications for the BC Forest Safety Council.

After publishing the standard, the NFPA began updating other standards to align with it. Its Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities (NFPA 664) was revised with these updates in 2017 and again in 2020. The 2020 edition represents a major overhaul of the standard with changes to its layout and material additions related to, among other subjects, hazard management. In the chapter dedicated to this subject, NFPA 664 details what the NFPA considers inherently safe designs for equipment that handles cellulosic dust.

[Editor’s note: This article is part of Dust Safety Week 2021. Find more articles here.]

While the NFPA doesn’t require owners get their operations in compliance with the revised 664 standard overnight, it does require them to get in compliance within a structured timeline. Existing, uncompliant systems are not “grandfathered in.” NFPA 652 8.7.4 states:

Where equipment deficiencies that affect the prevention, control, and mitigation of dust fires, deflagrations, and explosions are identified or become known, the owner/operator shall establish and implement a corrective action plan with an explicit deadline.

This code applies retroactively to both new and existing facilities (8.1). This means that as wood-processing facilities conduct their dust hazards analysis (DHA) every five years (664 7.1.6, ref. 652 chapter 7, also applied retroactively) and identify equipment or processes that are not inherently safe, they must create and implement a plan to address problem issues. The codes we shall discuss, therefore, apply not only to new installations but also to those already in place.

When is there a risk for an explosion?

When it comes to NFPA 664, you should first understand that if an operation hasn’t completed a DHA, a deflagration risk exists by default (4.1.3.2). It’s thus necessary for wood-product manufacturers to complete their DHAs as required. Otherwise, they risk having the fire marshal shut them down or their insurance company drop their coverage. An assumption of risk flows throughout the standard, with one portion stating explicitly that owners should, “Assume that all wood waste in an enclosed dust collector is potentially deflagrable, unless a dust deflagration test demonstrates it is not (A.9.3.3.1).” The same section of code identifies other assumptions. Unless otherwise proven, the NFPA considers a deflagration risk to exist when:

• The mean dust size is 500 microns or less.
• At least 10 per cent of the dust mixture contains dust 80 microns or less in size.
• The dust is produced from fine cutting, such as sanding (1).
• The dust is created from sawing or machining hardwood (3).
• The dust is created from sawing or machining fiberboard (4).

The NFPA does not usually consider dust created from sawing or machining softwood deflagrable unless it accumulates (2). However, NFPA 664 states that any cellulosic dust poses a risk when it accumulates to an average of 1/8-inch on all upward-facing surfaces in a building compartment (4.1.3.1). These concerns apply only to materials that haven’t been evaluated.

But, according to the standard, the NFPA does not deem fire and deflagration hazards to exist in systems that handle only green material (9.3.3.1.3) (NFPA 664 defines green material as wood with a moisture content of 25 per cent or higher (3.3.17).). The NFPA does, on the other hand, consider dry material a risk (9.3.3.1.4). It also deems risk existent if part of a dust handling system is combustible, whether or not the material is dry or green (9.3.3.1.4), examples being a rubber conveyor belt or a baghouse filter that can burn. The agency, likewise, always considers a suspension a risk when the material is concentrated at 25 per cent above its minimum explosible concentration (9.3.3.1.5).

Standards for conveying systems

Understanding where risks for fire, flash fires, and explosions exist are necessary because it is in these locations that 664’s standards for inherently safe material handling equipment apply. Conversely, these standards do not apply where there are no identifiable risks. An owner needn’t install a conveyor that’s compliant with 664’s standards for dust control if it’s outdoors and handling green material, though there are other reasons an owner may wish to do so, of course (reducing clean-up, for example).

As for conveyance systems in at-risk areas, NFPA 664 lists a slew of requirements. Among these, the standard states all ducts and enclosed mechanical conveyors must be designed with at least one of the following methods to mitigate explosions (9.7.1.1):

• Strength to withstand the maximum, unvented deflagration pressure (1).
• A listed deflagration-suppression system (2).
• Relief vents and ducts (3, 5).

Indoor systems may vent through flame-quenching devices (4), and all systems must be able to withstand the maximum, unvented deflagration pressure of its relief or suppression system if equipped with these devices (2-5).

The code does allow some flexibility around the strength of the conveyor if the conveyor is outdoors. Owners may conduct a risk analysis in such scenarios and install a conveyor with a weaker box, but the conclusions of the analysis must be acceptable to the local regulatory official (6).

NFPA 664 also stipulates that conveyance systems handling explosive dusts mustn’t leak dust. On this point, there is some ambiguity between standards 664 and 652. NFPA 664 states these systems must be designed to “minimize fugitive dust emissions” (9.3.6.1.2). Meanwhile, 652 states, “Housings for enclosed conveyors (e.g., screw conveyors and drag conveyors) shall be of metal construction and designed to prevent the escape of combustible dusts (9.3.6.1.2, emphasis added). NFPA 652 also states, “Where the equipment cannot be designed for dust containment,” it must have a dust collection system in place (9.3.2.2). The words “minimize” in 664 imply conveyors do not have to be IP-65-rated dust tight, which would require a tightly enclosed system like motor housing. The only places where the standard mentions “dust tight” in relation to conveyors is for removable covers and hatches (9.3.15.1.2) and for bearings and bushings (9.3.6.1.4). Nowhere does the code state that conveyors as a whole be dust tight.

It’s also worth noting that NFPA 652 9.3.15.1.1 does not state the degree to which systems must prevent dust from escaping. The gist of the NFPA’s standards is that conveyors mustn’t leak any volume of dust that could constitute a hazard or build up to the point of creating a hazardous situation. Small openings in conveyors, such as rivet holes or gaps for plastic expansion, appear acceptable. Systems with any meaningful leakage will likely require dust collection, however (and those that leak large volumes will certainly require it).

Another area of concern with conveyance systems is their ability to isolate fires. NFPA 664 (9.7.2.1.1) and 652 (9.7.4.1, 3) require conveyance systems with identified risks be designed so fires not propagate to processing systems upstream. An example of such isolation devices is a flop gate, which enables a conveyor to quickly dump material.

Other requirements for mechanical conveyors include:

• Design, installation, operation, and maintenance that prevents the buildup of excessive heat (9.3.6.1.1).
• Unless impractical, bearings and bushings that are outside the equipment (9.3.6.1.5).
• Shaft seals located where shafts penetrate equipment walls (9.3.6.1.6).

Standards for screening

Beyond setting standards for conveyance and processing equipment, NFPA 664 also stipulates manufacturers screen bulk, cellulosic material before processing it. “Wood stock must be inspected for foreign materials […] prior to being processed,” it states (9.4.11.1). Also, “Foreign materials […] capable of igniting wood waste and wood dust shall be prevented from entering the wood and dust process equipment” (9.4.11.2). These codes are targeted at metal contaminants because they can create sparks within processing equipment.

While the standard doesn’t specifically mention screening in Chapter 9, a note accompanies 9.4.11.2 in the appendix that lists screeners, along with magnetic separators and grates, as a system capable of removing metals from the material stream. Even without the mention of screening in the appendix, 9.4.11.1-2 all but requires it due to the nature of the task.

Safe systems

While any category of conveyance system can be designed to meet the standards outlined in NFPA 664, it’s worth noting that some systems are inherently safer than others.

Among the least safe are bucket elevators, according to Jack E. Osborn, member of the Correlating Committee on Combustible Dusts, which created standard 652 and the most recent version of 664. In a recent edition of Powder & Bulk Solids, Osborn wrote, “Fully enclosed bucket elevators represent one of the highest hazards and risk types of equipment when handling and conveying combustible materials. Deflagration event records confirm that bucket elevator bearings and belt-and-pully alignment represent consistent ignition source risks,” (“Is Your Facility Dust Compliant?” Vol. 39 (No. 5), 26-27). Osborn reached this conclusion after studying cross-industry data for years as part of his duties as a committee member at the NFPA.

According to Osborn, pneumatic conveyance systems constitute some of the safest systems when, he stressed, they are designed properly. But it is also true that mechanical drag conveyors are among the safest solutions for handling deflagrable dust – when designed properly.

Both pneumatic systems and mechanical conveyors have their downsides, as do bucket elevators (beyond their safety record). But all these systems will wear, and any effectiveness they have containing dust when first installed will diminish over time. Owners, as stated in 664, must therefore maintain their equipment to ensure it continues to operate safely.

The maintenance aspect of safety means that as owners and managers purchase new conveyance systems, they should consider how quickly a given system will wear and how easily crews can perform maintenance on it. The faster a system will wear and the more difficult the maintenance, the less likely it will receive the care it needs to meet NFPA 664’s criteria. Owners and managers do well to identify reliable systems that minimize downtime and which are designed to ease maintenance.

Commitment from management is key to safety. Yet while some wood processors have begun requiring NFPA-compliant conveyance systems, many mills prefer not to make such an investment, which can be significant. The alternative, though, is what happened recently to a shavings manufacturer in New York. In 2013, the mill experienced a catastrophic fire, which burnt down the operation. That fire came only five years after a previous fire incident. After rebuilding, a third fire occurred in April 2021. The business frequently had such incidents, the owner said (WWNY. “Firefighters battle blaze at Berry Brothers Lumber,” wwnytv.com, accessed April 27, 2021). Unkept machinery and a lack of safety systems will put any mill at risk of a similar event.

There are enough loopholes in the NFPA codes that a mill owner may get by with systems that don’t meet the standard (after all, it is the owner who conducts the DHA, and it’s a local-level fire marshal who conducts the inspections), but insurance companies aren’t going to turn a blind eye to repeated incidents – we can assume the insurance premium for Berry Brothers Lumber increased after the third major fire in less than fifteen years. Indeed, we’ve seen insurance companies already begin to make changes in what they will and will not insure among wood product industries. Many will no longer cover rotary dryers, for example.

Yet, the onus for change ultimately does not come from the insurance companies or even machinery suppliers. It rests with the operation owner (664 4.1.2). How quickly the NFPA’s requirements are adopted, and thereby how quickly risk is mitigated at wood processing facilities, depends on the priority management assigns compliance.

Joel Dulin is the director of digital marketing and sales co-ordinator for Biomass Engineering & Equipment.

This article is intended to answer some of the most common questions received by the consultancy team at Fike Corporation and those which may be valuable to the Canadian biomass industry.

1. Are Canadian facilities required to complete a DHA?

DHAs are required by several National Fire Protection Association (NFPA) standards. The National Fire Code of Canada, as well as most provincial fire codes, reference various NFPA standards for combustible dust. However, these references are typically not mandates, which means facilities may not be required to comply with specific sections of the NFPA standards.

That said, the purpose of a DHA is to identify hazards at a facility and help develop a strategy for minimizing risks. The focus of a DHA is the safety of your operations, regardless of the regulatory requirements. Therefore, DHAs are always highly recommended for facilities which handle combustible materials because it could ultimately save someone’s life.

2. What is the difference between dust combustibility testing and a DHA?

Dust combustibility testing is commonly mistaken for a DHA. Dust testing consists of laboratory analyses of the dust to determine if the material will burn in air, and, if so, how energetic is a flash-fire, how sensitive is the dust to ignition, what is the minimum concentration of dust needed for an explosion, etc.

Dust testing is used to determine the hazards and properties of the material, but it does not look at the process. A full DHA looks at the processes, equipment, and occupancies where the dust is handled or generated. A dust test does not satisfy the need for a full DHA, unless the dust is found to be non-combustible.

3. Do I need to test my wood dust as part of the DHA?

Decades of empirical data on the combustibility of wood dust is available in several resources. Some variability exists between various species of wood, but the most important factors that affect the combustibility of wood dust are moisture content and particle size.

If you know those two values at various stages of the process, an experienced professional should be able to complete your DHA. However, there may be times where testing may be useful, such as determining if a specific conveying stream presents a deflagration hazard. Your DHA professional will be able to advise when dust testing can be useful.

4. For new projects, when in the design phase should a DHA be completed?

A DHA should be completed as early in the design process as possible. Once a conceptual process flow and/or general arrangement of equipment has been established, a preliminary DHA can be performed.

The DHA should be used to determine where fire and explosion protection systems are required, so it is important that this is determined prior to finalizing specific equipment selections. Determining whether explosion protection is required for a piece of equipment after a purchase order has been issued will certainly delay a project.

5. Can I perform my own DHA or is an outside expert required?

A DHA will be led by a “qualified person,” as defined by NFPA 652 3.3.39: “a person who, by possession of a recognized degree, certificate, professional standing, or skill, and who, by knowledge, training and experience, has demonstrated the ability to deal with problems related to the subject matter, the work, or the project.”

It is possible for a qualified person to be employed by the facility and serve as the DHA lead. Even so, the DHA lead will also require the assistance of the facility’s subject matter experts: engineers, operations managers, maintenance managers, and more. Each of these experts can provide insight to specific areas of the DHA. For example, a maintenance manager can describe the preventative maintenance programs and various failure modes that could be potential ignition sources.

Most facilities have the experts to contribute to the DHA but usually don’t have the qualified person to serve as the DHA lead. In these common scenarios, the assistance of an outside combustible dust safety expert is required to ensure the DHA is performed accurately, potential hazards are reliably identified, and a usable action plan is developed from the findings.

Brian Edwards has a degree in civil and environmental engineering from Georgia Tech, and he is a licensed Professional Engineer with over 20 years of experience as a consultant to industry. Brian is the explosion protection consultancy manager at Fike, where he uses his decades of experience managing combustible dust hazards to assist their customers. He is a member of the NFPA, and has previously sat the committees for NFPA 61 and 664.

A dust explosion is a highly chaotic event with many influencing variables. The predictability of dust explosions does not necessarily follow a simple mathematical scale factor. Explosion protection systems must be designed and tested for the range of expected conditions and application parameters under which is it to be applied. Outside the range of tested conditions and parameters, there is reduced confidence that the protection system will perform as required.

[Editor’s note: This article is part of Dust Safety Week 2021. Find more articles here.]

For this reason, it is important that explosion protection systems are correctly selected and applied for the specific application within the certified tested parameters. Considering the potential effects and hazards of a dust explosion, performance uncertainty in the protection system simply cannot be tolerated. NFPA standards for explosion protection systems^2,3 requires testing and certification for most explosion protection equipment. Some examples include flameless explosion venting devices, explosion isolation valves and active protection systems. These devices must be independently tested by a credible organization according to a published set of testing procedures. This ensures an unbiased reliability of the equipment to perform under the range of tested conditions.

Application, installation and maintenance of explosion protection devices must strictly follow acceptable sizing calculations³, the manufacturers’ certification, installation and maintenance requirements in order to guarantee reliable performance and protection.

Some influencing factors for certified flameless vents include: dust type and characteristics, protected volume, design pressures and device efficiencies. Certification parameters for explosion isolation devices include the above-mentioned influential factors but also include connection pipe parameters such as: installation distances, elbows and fittings, dust concentration, conveying air velocity and pressures.

Figure 2 – obstructed vent panels

Vent panels must be installed so that they can freely open, and the effects of venting discharge must be taken into account. The release of a pressure wave and a fireball must be considered so that residual damage or harm is avoided. Compromised vents such as the obstructed ones shown in Figure 1 above reduces the system’s venting efficiency and reliability. Vent ducts, directional venting, and flameless venting can be used to help manage the safety zone of a vent discharge. The Rembe Targo Vent shown in Figure 2 provides directional vent discharge to manage safety zones.

When vent ducts are used to direct the venting effects to a safe exterior area, additional calculations and considerations must account for the reduced efficiency imposed by the duct. Unlike a standard duct for air movement, a deflagration vent duct is a passageway for a turbulent combustion event. Unburnt dust is projected from the vent into the duct, causing a propagating fireball. Excess turbulence and restrictions from the vent duct can create back-pressure on the relief vent which, if not considered, can

Figure 3 – Poor vent duct design example

reduce venting efficiency and risk vessel over-pressurization. Any accessories such as screens or weather covers added to the end of vent ducts and duct bends must also be accounted for as potential resistance to primary explosion venting. The vent duct shown in Figure 3 is not compliant and would likely result in compromised relief venting, equipment over-pressurization and damage.

The design, materials and construction of explosion vents have an impact on the performance and reliability of protection. Hinge-style doors are inherently higher in mass, which has a direct impact on the venting efficiency. Mechanical components on vent doors such as hinges, springs and latches can add additional friction resistance, especially if corrosion and deterioration occur. Care must also be taken to ensure venting devices do not detach and become projectiles. Venting systems must be carefully designed and documented to ensure the opening pressure tolerance is in accordance with the protection system design. Unapproved vent coverings can lead to equipment failure as shown in the Figure 4 example.

Another factor that must be considered is the recoil force resulting from an explosion venting event. The rapid discharge of combustion gases and material through the vent opening causes an opposing thrust force on the vessel. This recoil force must be calculated and evaluated against the geometry and integrity of the vessel

Figure 4 – Failed bunker from a plain metal sheet vent covering

and footings. For example, a 36-inch x 36-inch vent with an internal venting pressure of only two PSI will result in recoil force on the vessel of more than 3,000 lbs. At 10 feet from the ground, this is 30,000 ft-lbs of torque applied to the footing anchors. The protection system must not be the cause of a catastrophic failure!

The science and knowledge of explosions and protection systems is continuously evolving and expanding with experience, testing, and statistics of past events. Publications such as the NFPA standards^1,2,3 serve to guide the industry on the fundamentals of explosion safety. A DHA and associated explosion protection solutions led by competent, qualified person(s) will not only apply the fundamental intentions of the NFPA standards but also evaluate the risk based on the relevance, severity and probability of actual hazards while also considering the consequences to personnel, property and process integrity. A reliable explosion protection system in the event of a dust explosion can mean the difference between clean-up and maintenance activities or injury and extended downtime. Where industrial safety is concerned, any compromise can increase the risk and severity of hazard consequences.

References

1. National Fire Protection Association, NFPA 652 Standard on the Fundamentals of Combustible Dust – 2019
2. National Fire Protection Association, NFPA 68 Standard in Explosion Protection y Deflagration Venting – 2018
3. National Fire Protection Association, NFPA 69 Standard on Explosion Protection Systems – 2019

Jeramy Slaunwhite, P.Eng, is a mechanical engineering graduate from Dalhousie University in Halifax, N.S., with over 13 years of applied engineering experience. Jeramy has developed expertise in manufacturing, consulting and governmental environments in fields including material handling, industrial ventilation, mechanical building systems, energy conservation, and project management. Jeramy’s career focus on industrial combustible dust assessment and design has developed his exceptional familiarity with the NFPA standards for combustible dust safety. Jeramy joined Rembe Inc. in 2018 as their North American explosion safety consultant where he applies his combustible dust knowledge on explosion safety solutions and technical support for various industries and applications with a focus on NFPA compliance and risk management methodology. In addition to being an active member of the NFPA technical committees for agricultural dust and wood materials processing, Jeramy has extensive experience with performing combustible dust hazard assessments and explosion safety engineering design work throughout the western Canada forestry industry.

It is easy to miss that sandwiched in between all of these terrible statistics were those of the tragic 2012 B.C. sawmill dust explosions. If this is an article about combustible dust, why start it out with a “Where’s Waldo” search exercise for that topic? Simply put, to hint at why high severity but latent hazards can be destined to fall off the radar. Fortunately, there are ways to catch lightning in a bottle and maintain control over these types of risks, and this article will discuss some of these complacency-busting tips.

David Murray, corporate safety, HR and environment manager, Gorman Group, and chairperson of the Manufacturing Advisory Group. Photo courtesy David Murray.

Before learning how to address complacency towards combustible dust risk, it is important to understand how safety risks get managed. Famed economist Lord Lionel Robbins defined his specialty as, “the science which studies human behaviour as a relationship between ends and scarce means which have alternative uses.” There is a strong correlation to that definition of economics and how many safety professionals manage risk. Using economic principles to analyze the laundry list of tragedy above through a safety lens may help us decide where to place the “scarce means” that are available to tackle each “end”. Shouldn’t money and effort be prioritized towards the largest cause of occupational death? If so, we ought to drop what we’re doing and focus on preventing asbestos exposures in businesses. How about the injuries that cost the most financially? Those would be overexertion and musculoskeletal injuries, which would mean safety programs need to spend a lot more time on ergonomic control measures.

[Editor’s note: This article is part of Dust Safety Week 2021. Find more articles here.]

Two B.C. WPM safety groups, the B.C. Forest Safety Council (BCFSC) and the Manufacturing Advisory Group (MAG), have chosen a traumatic injury prevention mandate that centres around a Serious Injury and Fatality potential (SIFp) initiative. Regarding that mission, the statistics suggest these safety groups should focus on preventing workers from being caught inside live machinery and from being struck by mobile equipment or spilled loads. Those are indeed categories that are on the short SIFp priority list, but it may come as a surprise that so, too, is combustible dust. The following complacency-busting tips will explain how and why the BCFSC and MAG are ensuring the insidious dust hazard remains targeted and B.C. WPM businesses are continuing to effectively safeguard against the risk of combustible dust explosions.

Complacency-busting tip #1: Climb and stay at the top of the hazard control hierarchy

It may sound like a boring tip, but the most effective, fundamental practices often are. The hazard control hierarchy order of elimination, engineering, administrative, and personal protective equipment (PPE) has been historically used to control wood dust risks in the inverse order. Rules requiring workers to wear gloves and safety eyewear served to protect against slivers and dust in eyes, and almost every worker in the WPM industry started their career wielding a shovel to clean-up sawdust, an example of an administrative control. In the 2012 sawmill explosions, the first control measure that was ramped up across the B.C. industry was an increase in manual sawdust clean-up. Because of the substantial cost and sophistication required, engineered control measures such as dust extraction systems and baghouses were slower to be expanded upon, but, over time, this has happened. The number of manual clean-up workers can change over time and, therefore, so too can that administrative control measure’s effectiveness. Although a more costly upfront investment, a maintained engineered dust control system pays the business back in peace of mind, knowing the combustible dust risk is comprehensively addressed.

Complacency-busting tip #2: Keep honest by adopting and maintaining an audit cycle

No matter which control measures a business chooses in their combustible dust safety program, it is important to confirm that they have adequately addressed the risk now and over time. Another unexciting but most effective way to confirm this is through a tailored dust audit, and ensuring that that audit’s cycle is maintained. The BCFSC/MAG combustible dust audit does just that – and this can be utilized as a standalone audit or included under the broader MAG-SAFE audit.

Complacency-busting tip #3: Catch lightning in a bottle and don’t lose momentum

This tip is about reaching people’s hearts. In 2012, the deaths and injuries caused by the two mill explosions affected our B.C. industry differently – these were people from our industry family who suffered in a catastrophe unique to our sector. The long-term statistics may not have met a threshold that typically drives our actions, but our reaction then was to never forget this tragic year and our behaviours today demonstrate that we haven’t and we won’t. Our industry safety groups continue to keep combustible dust as a priority, our WPM businesses maintain what is required to prevent a reoccurrence, and we honour those lost and injured in 2012 with commemorations like the annual Dust Safety Week.

A former colleague of mine had a personal reason that drove him to campaign for charitable funding towards a specific disease, and he was quite accomplished in his efforts. One thing that he attributed to his fundraising success is the idea that although all charities exist for great causes, they are like businesses – each competes against others for every scarce dollar. My take-away from that was how good business practices can solve problems; they can help one charity raise more money than another, or, in our case, help address a seemingly impossible safety challenge. What may be missed in the technical economics approach mentioned at the beginning of the article is how critical it is to also connect emotionally with these issues – it’s that emotional tie to combustible dust that has caused our industry to catch lightning in a bottle and not let it go.

References

1. Industry health and safety data. WorkSafeB.C.. (2020, December 9). www.worksafeB.C..com/en/about-us/shared-data/interactive-tools/industry-health-safety-data
2. Robbins, L. (1984). An Essay on the Nature and Significance of Economic Science. doi.org/10.1007/978-1-349-17510-9
3. Combustible Dust Safety. B.C. Forest Safety Council iCal. (n.d.). www.B.C.forestsafe.org/combustible-dust-safety/

David Murray, CRSP, is the corporate safety, HR and environment manager for Gorman Group and chairperson of the Manufacturing Advisory Group.

CFI: So, 100 years, that’s a big milestone. Can you give me a brief overview of VETS’ Group and its history?

Erin: VETS was founded in 1921 by World War I veteran Fred Rayner, our great-grandfather. Fred had immigrated from the UK to Canada before World War I, but went back to the UK to fight in World War I. He was injured in the war and he met a nurse, who he convinced to move back to Edmonton. They had just had their first child. He was actually a carpenter by trade, and he was working at a place called Barry’s Sheet Metal. At the time there were party lines – a shared phone line system where, for example, two rings was your house, three rings was my house, and in theory I wasn’t supposed to pick up your house’s ring, but lots of people did. Fred’s wife was eavesdropping on the party line one day and overheard that there would be some layoffs at Barry’s Sheet Metal, and Fred’s name came up. So, she chimed in and said, “Don’t worry about it, tell him he quits, and send him home.” So, his wife quit on his behalf and he got home and presumably she said something along the lines of, “I guess you better find a job because you’ve got kids to feed.” That’s how he started the business. Due to his injuries, he wore leg braces most of his life, but that didn’t seem to stop him from rolling sheet metal under his arm and riding his bicycle from residential jobsite to jobsite installing the VETS Supreme Furnace, which is a gravity furnace he patented.

So, VETS got its start in residential construction. Fred’s son Alan then took over the business and the focus changed to commercial and institutional construction. Then our father, David Rayner, took over. He took over the business and he did some pretty incredible things when it came to custom fabrication. He changed the company’s focus from construction to custom fabrication, with a focus on safety. He also modernized the company, bringing in computers, etc. By doing so, he was able to govern the business through two pretty intense recessions and maintain the status quo for years.

By this point, Sean and I were doing what we called our “externship.” We both got away from the family business, and lived and worked in Toronto in totally different industries until our dad got sick. When we got that call, we both packed up and came home. Sean and I spent six months in the company together full-time at that point. But before this, I was working at the CBC, and going from a major company to the family HVAC business in Edmonton was a 180-degree turn. So, I stepped away for about a decade and just recently came back.

CFI: So, Sean, since taking over the company, what’s changed?

Sean: I was 24 when I took over, and, interestingly enough, my grandfather was 24 when he took over as well. Erin and I came back to the business, which she decided wasn’t what she wanted to do. She helped me put together a business plan to present to my mom and dad, who had been given less than two years to live. It was a plan for purchasing the company and taking it into the future. Once that was in place, Erin left and went on to do her own thing.

The company under my dad’s tenure was pretty stable. It did between $1.8 and $2.4 million per year for around 30 years, and it didn’t fluctuate a whole lot. We did custom job shop manufacturing and small industrial ventilation projects. But, I learned relatively quickly that if I wanted to pay for the business and earn a living, it was going to have to grow. So, we set to growing both sides of the business – trying to grow our custom fabrication side as well as our industrial ventilation side. Given the boom times of the mid-2000’s in Alberta, the industrial ventilation side started to grow relatively quickly. In about five years, we went from $2 million per year to $10-$12 million per year and had moved away from job shop fabrication, focusing almost exclusively on industrial ventilation.

That part of the business is really the core part of the business today, though we have gotten in and subsequently out of a number of different things as we continue to evolve today. We got into the HVAC service business through acquisition and that part of our business is thriving and doing well today. In 2016, we bought a company in British Columbia to grow our reach and depth into the industrial wood market in that area. We were manufacturing industrial ventilation systems and dust collection systems before that, but this acquisition really made us a player in that market in western Canada. Today, dust collection is the strongest side of our business; it’s where we put most of our focus and energy and where we have success. It’s a big part of what we do.

CFI: What was it like when VETS first got into the wood products industry?

Erin: I think there’s some really obvious synergies between VETS and the organizations that we work with in the industry. There’s a grounded-ness in the wood industry. The general mentality is, “If we have a problem, let’s work together to solve the problem.” That’s where our teams thrive – helping to solve problems. I call it the “partnership perspective.” We have an expertise and understanding in an area where there’s a lot of risk, especially for the wood processing industry, when it comes to dust collection and explosive dust. We’re able to sit down at the table with those folks, and understand where their priorities are and how we can support them to have a safer more community-focused grounded workflow.

Sean: It’s been a challenge bringing that approach into the industry because I think people have felt taken advantage of in the past, maybe not feeling like they received what they paid for. But, I think that’s changing. In all types of construction, you really need to have the best of all of your stakeholders in mind, whether it’s your customer or your supplier, and you have to be willing to work together to get there. I think that’s still relatively new in this side of the business.

But, we’ve always had a consultative approach. I’ve always said we’re going to do everything openly and honestly. We’re not in this business to get rich off of one customer; we’re here to build a lifetime of relationships. We’re 100 years old, and that’s part of it. We’ve said that to customers recently who still seem to be holding their cards close to their chest. I say to them, “This is our 100-year anniversary this year; I want to still be doing business with you in 100 years. So, don’t worry, I’m here for you.”

CFI: What are some of the advantages and disadvantages to being a family-owned and operated business?

Sean: Statistically, very few companies have been around 100 years. Being family-owned and feeling the connection to the history and the legacy, not just for the Rayners, but for the employees, has been really beneficial. It has given us a level of continuity in all things that is really hard to find in private enterprise, although the wood industry has a lot of old and successful family businesses.

Erin: That’s one of the immediate commonalities between VETS and the wood products industry. In a room full of wood industry people, there’s an inordinate number of family businesses present, typically.

Sean: We’ve been very present the last few years at the Alberta Forest Products Association (AFPA) annual conference, and I remember sitting at the table this past year – which was a much different experience, very spread out, a small group – and we just talked family business. Having that common ground, regardless of industry, that’s always fun to discuss.

But, we’re actually planning a big change. A number of years ago, I was considering the idea of employee ownership. Ownership mentality is one of our core values and, looking back over our history, we’ve had several families with multiple generations involved in the business. So, we’re actually in the process of rolling out an employee share ownership plan here at VETS to try and take us forward through the next 25, 50 or 100 years as an organization with commitment and buy-in at a different level from our employees.

CFI: The wood products industry has changed quite a bit just in the last five years, with more and more companies aware of the importance of dust safety. How has VETS positioned itself to navigate these changes and different challenges?

Erin: One of the biggest pieces would be a focus on education. Further to what Sean said, we’re not in this business to get rich off of one customer. The idea has always been to educate our customers. And as the education has progressed, customers are realizing what they’re facing, the possible consequences of it, and that not just anybody can provide a solution that will keep them safe. So, I think that’s definitely been good.

Sean: I think that’s a different approach, one that’s kind of inherent within us. When we acquired the company in B.C., we hosted one of the wood dust safety seminars, which Dalhousie University would usually put on and charge $2,000 a head. We came in and I said, “I’m going to pay for the whole thing, and I’m going to invite people to it, because I want them to be aware of the challenges that they’re facing and understand them.” The guys from the company that we bought thought I was bonkers. The old-school mentality of the industry was, “Show them nothing, tell them nothing. This is your livelihood.” And I said, “No, it’s better if more people know what the risks are and how to mitigate them. And I’m just going to do such a good job that they want to use me, and I’m going to be open about it.”

CFI: So, where do you see the industry going in the short-term with regards to dust safety?

Sean: From a dust side, I expect that the customers who take it seriously are going to continue to do so and are going to continue to get tighter and tighter with their compliance. And with those who haven’t, we’re going to see an increased level of knowledge and understanding with the regulatory bodies that are going to push them more to do so. We’re seeing that mostly in B.C. and a little bit more here in Alberta. We’re seeing WorkSafe and WCB starting to push the issue more. I think it’s a good thing for everyone.

CFI: What are the plans for VETS in the coming years?

Sean: Pre-pandemic, we were looking at how we continue to develop as a regional player. We do think we bring a value-driven approach that we can deliver further afield from where we currently operate. I really want to put a lot of intention and effort about how we can mix technology with our business to address the needs of the customer. We need to work with some customers on that to give them a product and an offering that makes sense. That’s long-term, trying to figure out what our customers need and how we can use technology to make our delivery better.

This interview has been edited for length and clarity.

No injuries were reported and the cause of the fire is being investigated, reports Global News. Production at the sawmill has been paused while clean-up is underway, and production will resume once it is deemed safe.

To read he full story, click here.

The government is investing $5.3 million to help small and medium-sized forest sector businesses offset the cost of setting up sanitizing stations, providing enhanced cleaning, additional worker training, measures to increase physical distancing, and the purchase of personal protective equipment.

The funding will be provided through the federal Forest Sector Safety Measures Fund.

Both levels of government deemed the forestry industry an essential sector due to its role in supplying essential forest products for hygiene, medical supplies, food packaging and shipping materials.

For information on program eligibility and timelines, visit ontario.ca/forestsafetyfund.