March/April 2012
Tire processing creates heat, sparks, and dust that together pose a serious fire hazard. Processors have learned that preventive measures, constant diligence, and fire detection and suppression equipment can minimize the risk.
By Diana Mota
In The Wizard of Oz, the scarecrow boasts he’s not afraid of anything except a lighted match, which could send his straw stuffing up in flames. Scrap tire recyclers know that tire materials, when combined with heat- and spark-producing processing techniques, can catch fire even without a match. If you’re a tire processor, “it’s not if you’re going to have a fire, it’s when,” says Max Daughtrey of Four D Corp. (Duncan, Okla.). He should know: He rebuilt his plant from the ground up after a fire triggered by an equipment spark destroyed it in 2000. As Michael Blumenthal, vice president of the Rubber Manufacturers Association (Washington, D.C.), puts it, “There are two types of tire processors: Those who have had a fire, and those who haven’t had one yet.”
Most tire processors have a story like that of Four D, especially if they’ve been in the industry for many years. Mahantango Enterprises (Liverpool, Pa.), which processes scrap tires and other products, also experienced a debilitating fire in 2000. Although investigators never conclusively determined the cause of the fire, which occurred on a day the plant was closed, the company “learned from that experience and many others,” says Vice President Troy Hess. “It made us very passionate about doing everything we can do so it can never happen again.”
Hess’ comment reflects a shift in tire recyclers’ attitude toward fire. Despite the inherent risk, these facilities are not doomed to ashes, nor should recyclers accept that devastating fires are an inevitable part of doing business, they say. “We have the ability to prevent fires,” says Kaytee Moran of equipment manufacturer Columbus McKinnon Corp. (Sarasota, Fla.). With the proper safety equipment and operating procedures in place, “you can certainly minimize the risk.” Like The Wizard of Oz’s scarecrow, tire recyclers are realizing they have the knowledge to prevent and contain fires, which they’ve learned from their own or others’ experiences. Diligent cleaning, maintenance, and temperature monitoring; fire detection and suppression systems; and fire prevention plans and training can keep the potential of fire from becoming a reality, they say.
The Source of the Problem
Tire processing fire risks relate to the physical characteristics of an end-of-life tire and the methods required to separate tire materials: “It’s the nature of the beast,” Daughtrey says. Tires are built to last, explains Allen Wagoner, president of Flamex (Greensboro, N.C.), a manufacturer of fire suppressant equipment. “These tires weren’t meant to come apart.” To grind them into smaller pieces and liberate the tire fiber and steel belting, many recyclers use a high-speed process that results in metal-on-metal contact as the tire wire meets the grinder or granulator’s steel blades. Such contact can create sparks, Blumenthal says. The process also creates tiny dust particles, primarily of tire fiber, which is very combustible material, says Mike Hinsey of equipment manufacturer Granutech-Saturn Systems Corp. (Grand Prairie, Texas). “It’s basically oil products such as nylon and rayon cords. That’s all just fuel for the fire, and the fire is going to follow the fuel trail.” That combination of conditions—dust particles, heat, and sparks—creates a similar fire risk in other industries, Blumenthal points out, thus he asserts that the tire components are not really the problem. “The fire starts for several physical reasons. Limit those reasons, and you limit the incidences and severity of fire,” he says.
Although the risk exists for all tire processors, the finer the material is processed, the greater the risk. Fire “is more predominant in ground rubber operations,” Blumenthal says. “There are more potential causes for fire because you’ve got more complex processing systems and higher speeds that generate sparks and excessive heat.” Even cryogenic operations, which use liquid nitrogen to freeze the rubber until it’s rigid before grinding or breaking it, have a fire risk, Blumenthal says. “That process creates a lot less dust, so the likelihood is reduced, but it’s not eliminated.” In most cases, “you still have to reduce the rubber further [in size] using other equipment.”
At least one company, Colt Inc. (Scott, La.), believes it lowers its risk by using slow-speed shredders, which typically don’t generate sparks or as much heat, and by producing pieces of shred no smaller than 2 inches in diameter. “It’s a business decision we made,” says Kip Vincent, Colt’s president. “The smaller the material, the more likely you are to have a problem just because of the different types of equipment [you must use] to get to that size.”
Preventive Measures
Recyclers and equipment manufacturers consistently name two steps tire processors can take to reduce their risk of fire: keep a clean facility and maintain the processing equipment. Cleaning is the most important preventive measure, Hinsey says. Blumenthal agrees. “Cleanliness is not just next to godliness; cleanliness is next to fire prevention. That’s three-quarters of the battle, if not more.” In Hinsey’s experience, most fires at processing facilities are the result of poor housekeeping. If it was a catastrophic fire, he adds, then most likely “it was made worse by poor housekeeping.” In other words, if a fire does start, a clean facility could mean the difference between a minor incident and a total facility loss.
“Folks sometimes have a hard time justifying spending the labor and hours to keep the plant clean when the money is made shredding tires,” says Tim Landers, director of safety and logistics for Liberty Tire Recycling (Pittsburgh), but it’s essential. Cleaning prevents the buildup of dust that serves as a fire’s fuel. “If you don’t control the dust and fluff, all it takes is a spark to start a fire,” Blumenthal says. That’s why Hess and Daughtrey say their workers clean throughout the day, focusing on areas where fiber and rubber could build up, such as on conveyors or rafters. Don’t forget the ductwork in the dust collection system, Blumenthal says. “Dust and fluff can build up in elbows of the ductwork. With sufficient heat, it could ignite.”
Maintaining and using equipment according to manufacturers’ specifications also is important, Hinsey says. The metal-on-metal contact that comes from processing wire-containing tires takes its toll on shredders and granulators, he explains. Maintenance and proper lubrication will help recyclers avoid equipment breakdowns and the buildup of heat, which can cause a machine fire.
Some recyclers take additional measures to prevent equipment-related fires, such as installing a misting spray over the shredding equipment. The water cools the material as it’s processed and lubricates the shredder blades, Daughtrey says. Hess says he installs his equipment with fire prevention in mind by ensuring it’s easy to maintain, keeping the equipment away from potential fuel sources, and not storing processed material or fluff near it.
Early Intervention
Although cleaning and maintenance can substantially reduce the risk of fire, these recyclers and manufacturers agree they’re just the beginning. Systems that detect sparks and heat and suppress fire are a must, Blumenthal says. Moran recommends using a combination of systems built into tire processing equipment and additional, specialized products.
The systems should cover the entire recycling process, from shredding to steel reclamation to the cleaning stages—anywhere the processed rubber could have an elevated temperature, Hinsey says. The greatest risk of a spark exiting the machine and entering the dust collection system is after the tires have passed through the secondary grinder, he says, when additional processing equipment is separating the steel belting from the rubber. “Once the steel is free, the risk drops dramatically.” Wagoner concurs. “That second process is the most spark-producing and fire-producing process. It takes a tremendous amount of energy to achieve that size reduction.” At this point, Hinsey adds, “the rubber is most likely the hottest it will get.”
A fire suppression system shuts down the processing machinery and sprays the affected area with water if it detects a spark or flame or if the rubber gets too hot, Wagoner explains. At Mahantango, Hess uses a deluge system that will flood key pieces of equipment—the feed conveyor to the grinder, the grinder itself, or the conveyor that carries material away from the grinder—when it detects a spark, he says. (“Most of these grinders are impervious to water,” Wagoner points out, thus the fire suppressant should not damage the equipment.)
Another high-fire-risk point in tire processing is dust collection. Tire processing facilities must have adequate dust collection systems equipped with fire suppression, Hess says. Typically such systems place infrared or ultraviolet sensors in the ductwork of the dust collection equipment. When the sensors detect a spark, they activate a nozzle that mists water within the duct, Hinsey says. “The best systems have another detector after that to make sure no hot spots or embers made it past the water misting area,” he adds, and they activate an alarm on the control panel. He also recommends having detectors and a deluge system in the container that holds the collected dust. “Confined spaces make it easier for a fire to occur and more difficult to detect,” he says.
Just as they do with processing equipment, users must maintain and test their fire suppression equipment, Moran says. Liberty Tire’s Landers agrees. “I can have a good engineered system, but if I don’t operate and maintain it correctly, it’s not going to do what it was designed to do.”
Processors have supplemented these equipment-based systems with additional detection and suppression equipment. For example, the Mahantango staff uses hand-held infrared guns to check and record temperatures of key components such as motors, bearings, grinding shafts, and electrical equipment. The plant’s security system has additional smoke and heat detectors. All of these recyclers have sprinkler systems in their facilities, with the exception of Colt, which operates outdoors, in the open air.
These facilities also have established water supplies they hope will prove sufficient to fight any fire that might get past their first lines of defense. “We have an 8-inch [diameter] water main that runs from one end of the yard to the other,” Hess says. Colt has a 1-acre fire pond and a well that feeds a 2-inch-diameter water line. If there were a fire, “at least we could get some water on it and try and slow it down until the fire department gets here,” Vincent says. Certain members of his staff are trained to operate the fire hoses, he adds. (Blumenthal notes that a facility’s fire response plan should include runoff containment because the water used to fight a tire fire could pick up contaminants.)
Material Storage Risks
After tire material exits any stage of processing, “it’s critical that you get the rubber back down to the ambient temperature before you stockpile or package it,” Hinsey says. Four D’s Daughtrey concurs. If the processing material has “any heat to it, don’t leave it in a confined space,” he says. “If it sits there long enough, it will [catch] fire.” Once the material cools down to room temperature—due to air movement or the passage of time—the risk evaporates, they say, and it’s safe to package it. Blumenthal recommends using heat sensors around the bags or piles of processed material. Hess uses infrared sensors and 6-foot-tall thermometers to probe his piles three days a week, and he records the temperatures. More compact, dense piles create heat, he says. “Rubber is a good insulator. The heat will grow and grow and grow. The goal is to get [to hot material] before it becomes severe.” He cautions that pouring water on a pile of overheated rubber can actually make the situation worse by driving oxygen into the pile and increasing the temperature. Instead, he recommends moving the material around or spreading it out to help cool it down. “You’ve really got to pay attention,” he says.
Heat primarily is a problem in piles of crumb rubber consisting of pieces smaller than three-quarters of an inch, Hess notes. That’s one reason why Colt only stores lightly processed material—pieces 4 inches or larger—that’s cooled with water by the time it leaves the processing line, Vincent says. “We do cut down to 2 inches, but we move all that out to end markets.” He experienced a fire in a pile of more finely processed tire rubber mixed with larger pieces at a different facility in 1988, before he took the helm at Colt, he says.
Preparation and Diligence
These recyclers emphasize the role staff training plays in fire prevention and detection. “We talk about being alert,” Hess says, such as by keeping an eye open for sparks that could start a fire—or by using your nose. “When you smell something [burning], one of our procedures is to find the source of the smell.” They remind workers of common-sense safety practices, such as not welding or smoking near the processing line or tire piles. “I’ve heard of fires starting from people using torches to cut something on a conveyor belt,” Vincent says. “It’s that easy to do something wrong.” Landers provides each of Liberty Tire’s 39 plants with a written safety plan that contains fire prevention information tailored to that site because “each of the facilities has different risks.”
ISRI’s Scrap Tire Processors Chapter recently developed a tire processing facility fire-safety manual to help companies prevent and prepare for a fire. The manual is a compilation of best practices and recommendations from various industry stakeholders, including processors and equipment manufacturers. “When the guidelines were put together, it was interesting hearing how others do things,” Hess says. “It’s a great tool from a technical and common-sense approach. You can’t beat experience” as a teaching tool, he says. (For a copy of the manual, e-mail Jonathan Levy, ISRI’s director of member services, at jonathanlevy@isri.org.)
For some processors, training includes outreach to first responders. “Most fire departments don’t know how to fight scrap tire fires, so it’s in the processors’ self-interest” to educate them, Blumenthal says. Once tires catch fire, it’s difficult to put the fire out, Moran says. “It’s a tough fire to contain.” In some cases, the solution is to smother the tires with dirt, she notes. Daughtrey says he tries to have members of his fire department out to the facility at least once a year to make them aware of his plant’s layout and operations. Insurance companies can provide fire prevention advice as well. “We work hard with our insurance carrier,” says Don Rea, president of Liberty Tire Recycling. “Sometimes you need that outside eye.”
The Risk Remains
“Today’s tire recycling plants are less likely to have a fire than a plant in the mid-’90s,” Hinsey says. “The industry has gotten smarter; insurance companies, more demanding.” In the beginning, processors weren’t cognizant of where fires could occur, nor did they have the technology to arm themselves against fires, he says. He cautions, however, that “it’s still the greatest threat to their business—the possibility of a fire destroying their plant or hurting their employees.”
With the right equipment, procedures, and “good, old-fashioned common sense,” processors can do much to avoid a fire, Moran says. But the problem is not likely to go away for the industry or any single tire processing facility. “You can’t rule out the possibility [of fire], but you can mitigate the probabilities,” Blumenthal says. “It’s a constant threat. The day you think you have everything under control is the day you have a fire, because the conditions are always there.”
Diana Mota is associate editor of Scrap.
Tire processing creates heat, sparks, and dust that together pose a serious fire hazard. Processors have learned that preventive measures, constant diligence, and fire detection and suppression equipment can minimize the risk.