Grain dust explosions
September 1, 2009
Grain elevator explosions are not a new problem. They have been documented as far back as the late 1800s, and experts are convinced that grain elevator explosions have occurred ever since large quantities of grain have been stored.
In a presentation at GEAPS Exchange 2009 in St. Louis, Missouri, U.S., Ron Demaray, president/chief executive officer of Horton, Kansas, U.S.-based RCI Safety, noted that while dust explosions are still a threat to the grain industry and those who work in it, some progress has been made in reducing the number of incidents and fatalities associated with them. He pointed out that from 1958 through 1993, there were 395 grain elevator explosions in the United States, for an average of 11.29 per year. From 1994 through 2008, there were 130 explosions for an average of 9.29 per year. Unfortunately, 17 explosions were reported in 2008 — the highest total during that 14-year period — serving as a grim reminder that more work needs to be done to educate employers and employees at grain storage and handling facilities about dust explosion prevention.
From a regulatory standpoint in the United States, a turning point occurred in December of 1977 when five grain elevator explosions in seven days killed 59 people, injured 48 others and resulted in millions of dollars of damage. As a result of these tragedies, the U.S. Department of Agriculture requested that the National Academy of Sciences (NAS) conduct a symposium to begin studying the problem. Late in 1978, the Occupational Safety and Health Administration (OSHA) commissioned the NAS to study these explosions further to make recommendations to the industry.
Demaray said grain elevators explode because each element of the “fire triangle” — oxygen, fuel (dust) and an ignition source — is present.
“The fire triangle requires all three elements be present in a confined area before an explosion can occur,” Demaray said. “If you take away one of the elements, an explosion cannot take place.”
Many contend that the causes of dust explosions are fairly well known among members of the grain industry, so why do these often fatal incidents continue to happen?
“The failure of our industry is not our lack of knowledge about explosions, but in our failure to develop an effective safety and health management system,” Demaray said. “(Government) regulation drives many companies initially to develop a systematic and focused safety and health management function. However, the companies who truly have first-class safety and health management systems understand that merely complying with regulation is insufficient when striving for a zero-injury or incident culture.”
Demaray said a successful safety and health management system consists of four elements:
management commitment and employee involvement; hazard analysis of the facility; controlling those hazards; and employee training.
MANAGEMENT COMMITMENT/EMPLOYEE INVOLVEMENT
Management commitment starts with allocating enough employee time and committing the financial resources to make a facility safe, Demaray said.
“Safety improves employee morale and protects your most valuable asset — employees,” he said. “A superior safety and health management systems correlates with business excellence in quality, efficiency and profitability.”
A safety team or committee should involve management and employees in task and hazard analysis.
“Employee involvement is necessary in a first-class safety and health management system because they know the facility they work in better than anyone else and employees understand the systems and the processes involved,” he said. “Their input to hazard analysis and task analysis is essential for success.”
Demaray said employee participation also helps them buy into the overall program, since a program can only become fully integrated into a facility when employees at all
levels are engaged in it and have confidence that it is effective.
This element is critical to identifying potential causes of grain elevator explosions. It helps to identify the location of the hazards and the critical tasks associated with moving grain with bucket elevators and conveyors.
Demaray suggests using a flow diagram to chart grain movement through the facility.
“This is a very simplified flow diagram and should be expanded to include all steps in the process of receiving grain, storing or processing grain and shipping grain,” he said.
Welding and cutting rank as the second on the list of causes of grain elevator explosions, said Demaray, noting that welding and cutting contributed to a recent grain elevator explosion in Arizona.
If you don’t have a job task analysis and hazard analysis created for procedures that are conducted in a grain elevator, then Demaray suggest that you start by identifying a safety team to write a list of tasks or jobs at your facility. Then prioritize those tasks, putting at the top those that are critical to the operation, such as welding and cutting inside the facility.
Because of the high degree of risk when welding and cutting, a safe and efficient process needs to be completed. This leads to the next element of a better safety and health system — controlling hazards.
Designing the task out of the operation should be the first means of controlling a hazard in your workplace. Obviously, some tasks must be done in a hazardous location, so it is critical to analyze each step of the task and ask, “Can we eliminate this step or task, and in doing so, can we eliminate the risk associated with the hazard?”
“We know grain dust contributes to explosions by providing fuel,” Demaray said. “Our hazard analysis of job tasks within the priority housekeeping areas should determine how you will keep the area free of dust buildup and not create a hazard while doing so. The OSHA Grain Handling Standard 1919.272 addresses the requirements, but it is up to your safety team to determine the safest and most efficient way to deal with dust in your facility.”
The standard requires that priority housekeeping areas are identified and cleaned regularly to keep dust from accumulating beyond 1/8 of an inch thickness within 35 feet of any bucket elevator, on floors of enclosed areas containing grinding equipment, and on floors of enclosed areas containing grain dryers located inside the facility.
When removing the hazard isn’t possible, the next step is engineering a control of the hazard in the process. In grain elevators, this means installing dust control systems, plugging leaks in spouts and using proper equipment for explosive atmospheres. A good example of engineering control, Demaray said, is adding blast doors to bucket elevators and
structures. Protecting employees by guarding equipment hazards is an engineering control but may simply be replacing belt or chain guards. Evaluation of opportunities to utilize engineering controls should be part of the safety team responsibilities, he said.
The last element of a first-class safety and health management system is training employees.
“More and more people in this industry tell me we are in a deficit situation when it comes to finding qualified workers,” Demaray said. “In fact, training is required for simple tasks like dumping grain and moving grain within the facility. Do we assume the new employees know how explosive grain dust is and what causes explosions? Without a written and documented training program for all new employees, I would be very afraid of the outcome.”
He said documenting attendance, training materials and quizzes to show employee understanding is important for demonstrating that companies value their employees and their safety and health.
“Observing, analyzing, measuring, reporting and implementing are individual opportunities to contribute to the building of a first-class safety and health management system for your company,” he said. “Don’t wait for an earth-shattering event before building and refining your safety and health management system.”