Grain handlers nagged by dust explosion problem
Booming agricultural exports have focused new attention on an old problem: grain elevator explosions. As the volume of grain exports increases -- China, Japan, Mexico, and others are vying with the Soviet Union for US supplies -- so has the tonnage handled all down the line, from the tiny one-man country elevators to the gigantic Texas and Louisiana export terminals.Skip to next paragraph
Subscribe Today to the Monitor
At each stage -- from the moment when a farmer dumps just-harvester grain into a truck to the point where corn or wheat gushes from an elevator's "marine leg" into a ship's hold at one of the coastal ports -- dust billows up from the flowing grain.
Even when the crop starts its journey from the country elevator, grain dust forms an explosive mixture. By the time the dried grain has passed through another elevator or two after shipment by truck or barge or railroad hopper car, dust levels have increased sharply -- and dangerously.
Elevator operators have been familiar with the risks of grain dust explosions since early in this century and have adopted various means for reducing the risks. But despite the long history, grain dust explosions have become more frequent and more devastating in recent years. Many experts blame the severity of recent explosions on more than just the increased volumes handled by the rapidly expanding export trade.
A chief cause of concern with many grain handlers has been the growing number of government regulations affecting their operations.
Operators remember the days when elevators were open. Passing breezes carried grain dust safely away from the hot machinery used to hoist grain perhaps 200 feet up to be weighed, sorted, and distributed to the elevator's storage bins.
Environmental Protection Agency regulations have changed the system. "Head houses" on newer elevators are tightly closed in to prevent dust emissions into the atmosphere. On older elevators, windows have been sealed up and other measures taken to contain the dust -- resulting in dangerous concentrations of dust inside the elevators.
Government regulations have forced the addition of elaborate dust-collection systems for all parts of the elevator operation. "Good housekeeping" is enforced by far more frequent government inspections so that elevator floors once covered in several feet of grain dust now must be swept constantly. But there remain obvious enforcement problems when government officials can only estimate that there are "somewhere between 10,000 and 15,000" elevators in the United States.
Despite -- or some say at least partly because of -- government enforcement of new regulations, the grain dust explosions continue. In 1979, the first year of relatively accurate record keeping, there were 28 documented elevator explosions and two fatalities. The first half of 1980 brought 26 serious explosions causing eight deaths. In September, two country elevators in Minnesota exploded, killing three persons.
Some take comfort in the fact that there has not been a repeat of the series of blasts at seven grain elevators during the 1977 Christmas period. Those explosions killed 62 people and destroyed two of the country's 81 export elevators.
Yet no one in the industry is satisfied that those explosions have been fully explained -- or that new Occupational Safety and Health Administration (OSHA) standards have removed the risk of similar major explosions in the future.
Government and grain industry experts basically agree on how explosions develop. Grain dust, comprised of tiny particles of broken grain suspended in the air, is explosive. A bare light bulb, overheated machinery, or a spark can trigger an explosion. Usually, an initial small explosion takes place inside a "leg" where grain is being moved by conveyor belt or a chain of buckets. The movement causes dust, and a tiny spark can set off a small explosion. This primary blast can shake the rest of the elevator enough to stir up clouds of dust -- so that a chain of explosions spreads from one part of the elevator to another.
The experts disagree about solutions. Government experts generally feel that it is impossible to eliminate all sources of ignition in an elevator crowded with heavy machinery. The solution proposed by OSHA and the Department of Agriculture is to eliminate grain dust through collection systems and gentler handling methods.Both agencies back pending legislation which would outlaw the industry's practice of mixing filtered-out grain dust back into grain for shipment.
Industry's response is that grain dust itself has all the food value and resale value of whole grain -- and in fact can be handled more safely when it is mixed with grain than when it is separated.
On the basis of their extensive research programs, both Cargill, the Minneapolis grain-trading giant, and the National Grain and Feed Association, advocate reducing ignition sources and educating operators to deal with the unavoidable hazards posed by handling grain.
Accordingly, Cargill's modernized grain export terminal at Chesapeake, Va., incorporates not only new vacuum and venting systems to control dust but a wide variety of automatic monitoring devices to ensure that grain handling machinery doesn't overheat or give off sparks. Cargill has also developed new polyurethane "Toledo" grain buckets which cut down on dust problems.
After two years of studying grain elevator explosions, University of Michigan Prof. C. William Kauffman has concluded that "eliminating the ignition sources is almost impossible. As long as you have grain dust . . . you will have explosions."