The Complex Web of Dryer Safety

The responsibility chain for dryer safety is a complex web of disconnected factions.
By Ron Kotrba | October 29, 2019

No one wants a dryer fire, but their occurrence in the wood and biomass industries is often viewed as an unavoidable cost of doing business. “The problem we run into time and time again is companies that have biomass dryers expect fires and explosions, and they treat them like it’s normal—and it shouldn’t be,” says Becky Long, a design engineer with Thompson Dryers. “Someone has done a great job fooling companies into that assumption.”

Safety equipment such as spark detectors, sprinklers and additional extinguishment or deluge devices, explosion panels and more play vital roles in containing dangers once they manifest, but whose responsibility is it to ensure these dangers do not materialize in the first place? The responsibility chain for dryer safety is a complex web of disconnected factions that ultimately convolute liability.

Dryer manufacturers design and build their equipment with the best intentions, which are then connected through a network of piping and ductwork to biomass or gas boilers to provide heat and steam for drying, and cyclones, baghouses and other emissions abatement equipment. One would be remiss not to mention the obvious infeed and outfeed systems handling the material being dried. Furthermore, sensors and fire safety features and controls add to the complex network of interplay.

Plant operators and maintenance personnel are expected to be properly trained by the dryer manufacturers in order to safely operate and upkeep the equipment to know what to watch for and what conditions to avoid in order to circumvent dangerous situations. Their role as the minute-by-minute overseers of the intricate workings of these highly sophisticated yet potentially hazardous systems should not be understated. These gatekeepers to safety are overseen by plant management.

Then there are the code setters, organizations such as the National Fire Protection Association, that develop and publish standards on fire safety protocols, after which various regulating authorities adopt and enforce. To be clear, those who establish the standards and those who are expected to enforce them are two separate entities with disparate knowledge of the processes—and dangers—at play.

Insurance companies decide who to cover and how expensive premiums will be based on how safe they perceive a plant’s operations and safety procedures to be. They have the power, through refusal to insure or threat of increased premiums, to effect change if they so choose, and if they themselves know what to look for. Third-parties employed as risk assessors or hazard identifiers also provide an important role. But they can shield themselves from liability by the wording of their contracts.

Who then is ultimately responsible for ensuring the safety of dryer operations? “That is a very good question,” says Kevin Ericsson, founder of Cariboo Biomass Consulting Services. “It comes up in my seminars, but there is no easy answer. In front of the dryer there’s a boiler that falls under the boiler codes, or a gas burner that falls under the gas safety branch because, technically, the dryer itself is not meant to produce a gas”—even though syngas can build up in dryers and pose a major fire and explosion hazard. “There’s no code or regulation protecting against syngas in dryers,” he says. “We’re just not there yet. There has to be an incident where there are multiple fatalities before they incorporate these kinds of standards. When you talk with NFPA, they point to the dryer manufacturers. The dryer manufacturers point to the people who produce the boiler or gas burner, and it goes around and around in circles. At the end of the day, with all of the risks, people need to be asked, ‘Would you allow your son or daughter to operate one of these?’ It’s a long, hard question.”

Dryer Companies
One of the main reasons dryers experience fires and explosions to begin with is that too much oxygen is present in the system, according to Long. “We actually recycle exhaust gases,” Long says. “This provides several benefits. One, it lowers the oxygen content. And two, you don’t have to heat up such a high volume of air from ambient temperatures to fill the system, so there’s an energy savings. Not all biomass dryers recycle exhaust gases, and even if they do, it may not be effective. Some plants with recycle loops may not be set up properly.”

Dryer companies have a responsibility to provide adequate training to plant personnel, Ericsson says. “I don’t think all of the dryer manufacturers do this,” he says. “Sometimes it’s just verbal instruction with no documented training process with safety operating procedures, no documentation of what the operators need to do if there’s an upset condition or power failure.”

Upset conditions—those outside of steady-state operations such as power failures, and startup and shutdown situations—are widely viewed as the most dangerous times for dryer operations. Scott Flowers, a professional engineer and a Thompson Dryers electrical and controls engineer, explains what happens during this process. “When a power outage happens, the dryer system turns off,” Flowers says. “If the outage is limited to the motor voltage supply, the PLC will continue to operate, taking any equipment it can still control to a safe state. It will also monitor temperatures and initiate extinguishment functions if conditions require them. However, if the outage takes out all power to the dryer and dryer-related equipment, there is nothing that can be done. Without power, the operator is blind to what is happening inside the dryer system.” 

Flowers says all Thompson Dryers’ biomass dryers have an extinguishment system. “Water and steam valves are typically provided by the owner to meet our specifications,” he says. “We do not recommend the use of fail open water or steam valves. In a power outage situation, water can completely flood a system and surrounding area before power is restored to turn it off. Likewise, a fail open steam valve can completely drain a boiler system. Both of these circumstances can solve some problems but can also create greater ones.”

Thompson Dryers can offer a battery back-up option for control panels, Flowers says. “The backup would be only for monitoring and the operation of key safety features such as the PLC, thermocouples, communications, extinguishment, and so forth,” he says. “We do not provide backup for equipment motors.” Flowers says the effectiveness of a control function backup can be limited by other factors. “If the HMI or communications network are not backed up, the PLC will still be able to do certain functions,” he says, “but the operators will be helpless to make changes or see what the existing conditions are.” He adds that, more often than not, plants prefer to incorporate the dryer controls into an existing control panel or integrate them into their DCS. “In these cases,” Flowers says, “the extent of the battery back-up for dryer functions is limited by the plant’s backup plan.” 

Long says Thompson Dryers remains on-site for a week or two during initial startup of their systems. “We set it up and make sure the control system is doing what we expect,” she says. “During that process, we talk with the operators to make sure they know what is happening. I have a PowerPoint training presentation, which is two to three hours long.” Long says the company does not test operators to ensure they’ve learned the material, but she adds this idea has been discussed internally.

Dryer manufacturers should be expected to run calculations based on equipment in front and back of the dryer, such as the boiler and emissions abatement equipment, Ericsson says. “They need to calculate how much wood fiber at maximum capacity in the form of syngas can accumulate in this dryer, and how much creosote can accumulate in the ducting, to figure out how much energy can be in the dryer, ducting and all the vessels attached, and then engineer explosion panels that will vent all energy safely away from people,” he says. “They should also install more safety interlocks on their dryers and install oxygen analyzers on the recirculation duct.” Ericsson says this would be a good indicator of the accumulation of syngas, an overlooked hazard of biomass dryers. “If oxygen gets below a certain level, it can warn operators this needs attention,” Ericsson says. “If the operator misses the alarm, then when it gets to another level within dangerous limits, the dryer goes into an automatic shutdown and deluges the system.”

Thompson Dryers’ systems “have far fewer explosions” than its competitors, Long says, “but this doesn’t seem to matter to people buying the equipment.” 

Code Setters
NFPA was formed in 1896 at the height of the Industrial Revolution. “The initial impetus was standardization of automatic fire sprinklers,” says Guy Colonna, a chemical engineer and senior director of engineering at NFPA. He says during the late 1800s, in New England, wood processing was in full swing and fires were rampant. “There were a number of manufacturers and insurers, and none could agree on the technical layout for sprinklers, so this lack of standardization brought everyone together to develop the first standard, NFPA 13, and there was agreement that standardization might be applicable to other things.” Since then, the organization has developed more than 300 documents, all of which adhere to certain foundational principals managed by the American National Standards Institute and many of which have been adopted by federal, state and local jurisdictions.

A number of NFPA codes are imperative to the wood and biomass industries, such as 68, 69, 664 and 652, to name a few. “From NFPA’s standpoint, we have some standards that are applicable to some equipment or occupancies, but dryers are not something we have a unique standard directed toward,” Colonna says. He says one source NFPA references is a comprehensive document produced by FM Global, an insurance and engineering company. The document is a data sheet on industrial ovens and dryers, June 2009-6-9. “It discusses fire prevention, temperature controls, specific protections, automatic sprinklers and special precautions,” he says.

Code 652 is NFPA’s standards on the fundamentals of combustible dust. One of the most important additions is that all existing processing facilities that fall under this code will be required to perform a dust hazard analysis (DHA) by Sept. 7, 2020. “I think this will, at least at a minimum, get people talking about it,” Long says of the DHA requirement.

Ericsson says the code setters can get more involved in the engineering and commissioning of new dryers. “They could provide checklists and coaching to owners, engineers and project managers, making sure there are engineered explosion panels in cyclones and ducting, and proper safety interlocks are installed and tested,” he says.

Code Enforcers
Not all states adopt NPFA standards, Colonna says. States that don’t, however, must adopt some codes, such as those by the International Code Council or International Building Council. “But within the ICC staff, there is no expertise on the unique hazards of combustible dust,” Colonna says. “They often refer to NFPA documents, so theoretically all states are expected, one way or another, to conform to NFPA standards. The issue then becomes the level of field enforcement.”

Colonna says enforcement begins with original plan reviews for new facilities. “Existing facilities may not get inspected as regularly, but this depends on many things,” he says. “Another issue is, some of this stuff is fairly complicated technically. One thing we do in states that adopt NFPA codes is we provide training for enforcement officials. In certain states, I have done combustible dust training. I’ve assisted them in implementing Chapter 7 DHAs to help them know what to look for in explosion venting designs. Not every state adopts these at the highest level, but the codes may get swept in [through ICC or IBC codes]. Those states don’t necessarily invite us in. They may get fire code training, but not in detail on specific pieces of it like the industrial standards. It all varies, and jurisdiction is part of it.”

If the presiding state or local fire marshal and responding fire departments can identify any hazards present and work with plants to correct them—such as proper explosion venting—then everyone will benefit, Long says. “The fewer fires and explosions you have,” she says, “the happier everyone will be all around.” She adds that it would be beneficial to know how far from explosion panels is safe so the plant can properly mark “no carry” zones.

Ericsson says while fire departments are sometimes invited to the mill and shown the equipment, when the boots hit the ground and an actual fire occurs, many times “they’re like a deer in the headlights” and look to staff on where the fire is and what to do, he says. “The only thing they often know about the equipment is basically whether the sprinkler systems work properly, and if they have accessible connections to hydrants. Fire departments do not know enough about the specific fire protection equipment.” To improve this, Ericsson says plants should involve them during installation and commissioning, to help educate them. “They are generally unfamiliar with the whole realm,” he says.

On preventing fires, Ericsson says the code enforcers need to have educational opportunities put in front of them on how biomass dryer systems work. “That’s not included in any fire department training,” he says. “We need to be educating the fire marshals and chiefs to a level where they can come in and speak with authority on whether the plant or dryer is being commissioned properly.”

At a plant where Ericsson was recently providing consulting services, the spark detection on the outlet of the dryer kept tripping, getting second-stage deluge aborts. “I questioned whether the fire protection system was commissioned properly, and no one was able to produce commissioning records—they just went off of fan curves,” he says. “My question is, if there was a fire or explosion and there was a significant event, the insurance companies would get involved and they will start digging into this. If they can’t produce documentation, the mill owner will be liable. It will come down to that. Fire departments, regulators, project managers—they just don’t know enough about drying equipment. I’ve talked to lots of naysayers who say you don’t need this or that because it costs extra money. But when you’re standing on the end of a fire hose dealing with a dryer fire that could explode any minute, it ramps the game up.” 

Plant Personnel
In addition to too much oxygen present in the system, the other main reasons for dryer fires, according to Long, are dirty ductwork and operational problems such as poor shutdown and startup sequences, upset conditions, operator error, and variable moisture content in incoming material to be dried.

The fundamental place for operators to start in terms of upset conditions is when the dryer is up and running. “When talking about upset conditions and getting back up and running, they should look at the process the same way,” Colonna says. “It’s overlooked. Everyone is in a hurry to get back to production vs. getting back to the original startup scenario. From what I’ve observed, startup is the place we break down. If the plant has shut down for whatever reason, they take care of what caused it to shut down and then jump back in without doing a good startup assessment—a process safety management (PSM). A number of PSM elements are useful guidance. One element is a pre-startup routine. In my mind, having looked at a number of incidents, people jump ahead and skip safety steps in their startup routine, which becomes a problem. If I have a fire detection and suppression system and I lose power, if I don’t go back and recheck that my pre-deflagration system is still active, then this is where failures can occur.”

Proper maintenance, and having qualified personnel performing maintenance, are critical considerations, Colonna says. “It gets into management of change,” he says. Repurposing equipment made for other industries without performing hazard analyses is also a failure of management of change. “I’ve seen this extensively,” Colonna adds.

Dryer manufacturers recommend certain maintenance procedures in various service intervals. “For our systems, we recommend replacing drum seals every one to two years, or as needed,” Long says. “Airlock blades should be replaced or refurbished every couple of years too. From an equipment longevity perspective, having smooth rolling surfaces on the dryer tire and trunnion wheels improve how long the dryer lasts. And from a fire and explosion perspective, the airlocks under cyclones—if those are letting air through and you’re getting dust carryover, then any dust carryover has the potential to be hazardous in the right concentrations. Also, flanges in duct work seals should be siliconed or welded. We typically tell installers to run silicone between, but if they’re never removed, then they could be welded. Doors on cyclones get opened a lot too, but we recommend never opening them during operation. Some plants don’t see this as a risk. But it lets a lot of oxygen in. They also need a gasket or silicone put back on every time they’re opened. If nothing else, it is reducing cyclone efficiency. Any oxygen in the system, however, is increasing the risk of fires and explosions.”

Long adds that plant personnel should be checking the moisture of the inlet feed and temperature of the outcoming dried product. “If it’s getting hotter coming out, this may indicate something is wrong,” she says.

Plant personnel need to understand what hazards might be present in their process associated with their equipment, and the material running through their equipment, Colonna says. “This starts with a hazards assessment or analysis,” he says. “Secondly, they need to continue to look for solutions that drive them toward mitigating the hazards initially and embed this in their process and procedures, whether this is a new type of dryer or whatever—be open to looking at that kind of change in technology that brings greater safety to this industry.”

In addition to proper training, Ericsson says plant management needs to raise the bar on operator qualifications and commitment to public safety. “On maintenance days in many of these plants, the control room fills with people who stand around and talk,” he says. “The professionalism that’s needed is not always there in dryer operations yet. They are operating equipment that can—and will—kill someone if they’re not careful.”

“The biggest problem we’ve found is operator turnover,” Long says. “We can spend time training them, but if they’re there only for a month, then the person replacing them may have no training.”

Long says in college she worked at a nuclear power plant, where operators were required to have two years of training. “Biomass dryer operators require nowhere near what nuclear power plant operators require,” she says. “Society doesn’t view biomass dryers as they do nuclear power plants.”

Many times, fire incidents are kept under the radar, according to Ericsson. “If a fire or dust explosion occurs, and it’s enough to pop an explosion panel, sometimes they’ll just put the panel back on, button it up and it doesn’t get reported,” he says. In British Columbia, any open flame that occurs in a mill must be reported to WorkSafeBC. “Still,” Ericsson says, “there is room for improvement on  this requirement.”

Third Parties
Whether it’s insurance companies, risk assessors or consultants, third parties play an important role in fire safety. Long says it’s entirely possible that, with the DHA requirement in NFPA 652, insurance companies may start dictating how facilities are operating their dryers. “I’m speculating, but with insurance companies it’s a numbers issue,” she says. “If the DHA shows they have to replace a cyclone and it’s below the cost of the deductible, they may not worry about it. But if they have to replace their entire system, the insurance companies might have something to say about that or spike their rates. The DHA is going to be a fairly big deal as of next September.”

Insurance companies should be more involved, according to Ericsson. “Today, they mostly deal with sprinkler systems and those kinds of regulations that have to be followed—testing the system, checking fire hydrants, fire extinguisher checks, all that,” he says. “Insurers want to see work orders and check sheets to make sure proper maintenance is being done. What I’ve noticed is they don’t know enough about [spark detection and suppression devices] or their required maintenance. In my course, I get into the meat and potatoes of all this. Insurance companies don’t know enough about dryer fire protection. It’s easy enough for some people to pull the wool over their eyes.”

Insurance companies such as FM Global have field engineers. “If they’re going to insure your facility, they come in and assist you with performing a DHA or help you review it if you’ve already conducted one,” Colonna says. “They help you be aware of the consensus standards. FM Global sits on committees. They’ll encourage people to make sure they follow the relevant standards. They’ll say, ‘If you want me to insure you and sweeten the insurance premium, then it is requested that you comply. If not, we won’t insure you, or we’ll charge you higher premiums.’”

Thompson Dryers employs BakerRisk. “That’s been our way to ensure we’ve done our homework,” Long says. With inspections, however, come liability. “If I make the recommendations and then there’s a fire, the first thing they will look at is recommendations made,” Ericsson says. “So, what some consultants can do is word their contract by saying these ‘recommendations’ are a draft only and can only be implemented by mill staff, and the mill staff must decide whether to implement them.”

Ultimately, there is a fine balance between producing and the cost of money and time to install, maintain and test equipment. “Time is of the essence,” Ericsson says. “If the press is not going up and down, then they’re losing thousands of dollars a minute. Maintenance days have to be precisely managed. When you talk with plants about spending money on fire protection, if there’s a lot of hidden costs in the maintenance of those systems, then the people who run the budgets for those plants say they want them to be safe but, at the end of the day, they have to produce.” 

Ericsson emphasizes the importance of educating people. “The heightened sense of education is just not there yet,” he says. “I feel strongly that, as the biomass industry grows, we will see more and more explosions. The imperative won’t be there until there are numerous fatalities, unfortunately.” 

Author: Ron Kotrba
Senior Editor, Biomass Magazine
218-745-8347
rkotrba@bbiinternational.com