Avoiding grain entrapment
April 1, 2009
This is the first in a two-part series on grain engulfment. This article focuses on entrapment risk factors and safety tips. The second article, which will appear in an upcoming issue of World Grain, will focus grain entrapment rescue.
Laverne Meier is one of the lucky ones, a grain facility employee from Bern, Kansas who several years ago was pulled to safety after briefly being engulfed inside a grain bin. Meier, who is now retired, said he endured a couple of sleepless nights after the incident before it occurred to him just how fortunate he was to be alive.
“It happened on a Friday, and Sunday morning I was sitting in church, and it dawned on me I could be up front (in a casket) instead of sitting in the pew,” said Meier, who told his survival story at the 2009 GEAPS Exchange in St. Louis, Missouri, U.S. “That’s when it really hit me, and I really got scared. I didn’t realize there was such a low survival rate until some people got in touch with me and talked to me about it. You always think things like that won’t happen to you, but when they do it really makes you stop and think.”
While the grain industry has made progress in safety awareness and prevention, recent statistics indicate that grain entrapments and deaths from entrapments at commercial storage facilities in the United States (U.S.) have risen in recent years.
According to data gathered by Matt Roberts at Purdue University, between 2000 and 2003 a total of 16 entrapments and 14 deaths from entrapments were reported in the U.S. at commercial facilities (non-farm). From 2004 through 2007, the number of entrapments and deaths from entrapments jumped to 45 and 26, respectively, with 19 entrapments and 9 deaths reported in 2007 alone.
At the request of its members, the Grain Elevator and Processing Society (GEAPS) on March 1 held a workshop on “Grain Bin Engulfment: Causes, Human Costs and Prevention” at the GEAPS Exchange.
The workshop included comments from three survivors of grain entrapment, which is the leading cause of job-related fatalities in the grain industry, as well as presentations from safety experts.
Successful managers of stored grain monitor their investment regularly. One way to do this is to enter the bin or send an employee to visually inspect the condition of the grain. One of the most common reasons for entering a bin that contains grain is to break up “caked” or “bridged” grain that is hindering attempts to remove grain from the bin.
But all options to remedy the situation besides entering the bin should be tried first. If it is essential for a person to enter the bin to clear the obstruction, he or she should wear a proper full body safety harness and tether manned by others outside the bin. Failure to take these precautions may prove to be a fatal mistake.
Two of the biggest problems are that people don’t realize how fast grain can move out of a bin and how much force flowing grain can have on a person’s body. When grain is unloaded from a bin, the downward flow pattern immediately transmits to the top grain surface, starting a column of flowing grain. The grain across the bottom and away from the center of the bin does not move. How rapidly the center column of grain leaves a bin depends on the size of the opening and/or the conveyor capacity. The weight of a person standing on the grain forces the grain supporting him or her to flow to the outlet rapidly.
A 6-foot-tall person consists of roughly 7.5 cubic feet in volume. At 41 cubic feet of grain movement per minute, which is the approximate rate of movement of grain being outloaded at a 2,000-bushel-per-hour rate, the entire body of a person this tall can be covered in grain in approximately 11 seconds. In rapidly moving grain, a person would need to free themselves before five second elapsed. Typically, once a person’s knees are covered, they cannot free themselves without some sort of assistance.
Grain may seem like flowing water in that it exerts pressure over the entire surface of any submerged object. However, the amount of force required to pull someone up through grain is far greater than to rescue someone under water. This is because unlike water, which is buoyant, individual grains rub together to create a large friction force.
Even when the grain is only at the knees, there is about five pounds of friction that is added to the weight of the person. A person doesn’t have to sink very much deeper before the weight that must be lifted is nearly doubled. Studies have found that more than 900 pounds of pull is required to raise an adult mannequin covered in wheat or corn.
Even if grain is not flowing from the bin, entrapment can occur if a person walks on grain that has crusted or bridged due to grain spoilage, which is the number one cause of entrapment. Any hollow volume becomes a trap to a person who does not avoid areas where there is no grain support under the surface. Grain crusts rarely become hard enough to support a person. If a grain handler stops the grain from flowing out of the bin before he or she enters, that person may become engulfed anyway when the surface collapses under the person’s weight.
In a similar fashion, victims have died when grain collapsed from a vertical wall in a partially filled bin. If a stack of grain does not flow to the bin outlet, a person may be prone to get a scoop or pole to poke the grain loose. Even though a wall of grain may appear perfectly safe, one scoop of grain may take away the base support and start an avalanche. If you are knocked off balance by the mass of grain, you are likely to be covered and suffocate.
In certain cases, bumping the grain using a pole through one of the bin access covers may release the grain. If you must enter the bin, make sure the following measures are taken:
• A crew is assembled who can rescue you;
• Enter with a body harness and a lifeline manned by at least two other people;
• Lock out and tag out the power source for unloading before entry;
• Start breaking up the hardened grain close to the top of the pile, so when the grain breaks loose the mass of flowing product won’t gain enough momentum to knock you over and there will be less grain to cover you.
A NEW RESTRAINING SYSTEM
Wayne Bauer, safety and security director for Star of the West Milling Co., Frankenmuth, Michigan, U.S., said during the workshop that one point that is often overlooked when it comes to bin entry is the benefits of establishing an overhead anchorage point for the lifeline.
He said Star of the West Milling has designed and installed a restraining system that includes this overhead anchorage point that is secured with a tie-off that allows the rescue crew to provide the person entering the bin with slack, as needed movement, while preventing the person from slipping under the grain if an incident occurs. Bauer discussed this anchorage point design during the GEAPS Idea Exchange held on
March 1. He said the system costs around $200 per bin.
The GEAPS Bin Entry/Tech Rescue (BE/TR) Advisory Committee has been working with GEAPS members, steel bin manufacturers, the Safety and Technical Rescue Association (SATRA) and academia to deal with the recent rash of grain engulfments.
The group has developed a student training manual and has offered a number of training classes in the field during the past five years that are taught by SATRA. The BE/ TR group is encouraging the adoption of new design parameters for the construction of storage space in the future, which should include anchorage points and restraint systems.
The 2009 Bin Entry and Rescue Training includes classes on May 15-16, June 25.19-20, June 23-25 and Aug. 18-20 at Star of the West Milling in Frankenmuth. A class will also be conducted June 1-5 at CHS in Kennewick, Washington, U.S. For more information on the classes, contact Jenny Boeck man at 1.800.888.9596, ext. 213 or firstname.lastname@example.org.