Grain Bin Entrapment: What If It Happens to You? A Case Study from an Oklahoma County Elevator
Introduction
A man unloading wheat from a grain bin was trapped for nearly five hours when his foot became caught under the side of a sweep auger motor and he was buried in grain above his waist. The following information was collected from elevator personnel and rescuers involved in this grain entrapment incident. The names and location of the elevator are not listed to protect the privacy of the people involved. This report illustrates how this type of incident could occur at other grain handling facilities, and provides safety guidelines that could help other elevators avoid this type of situation or react more positively if a grain entrapment should occur.
Cause of Entrapment
On January 25, 1994, an Oklahoma country elevator was unloading wheat from a 200,000-bushel, corrugated steel bin. The wheat had drained to a level that exposed the sweep auger and motor installed at the bottom of the bin. Three drain sumps underneath the conveyor from the center to the bin wall near the side entry door were open, leaving an irregular cone of wheat sloping up from the center of the bin on three of the four sides.
At about 11:30 a.m., a worker entered the bin to plug in the sweep auger motor. The
worker stood on top of the motor while unwrapping the cord from around the motor in
order to plug it in. While unwrapping the cord, his foot slipped off the motor into
the grain and slid under the side of the motor. When his foot slipped off the motor
it triggered a grain slide. Instantly, grain began to flow around his leg. His foot
wedged under the motor, and he could not pull his leg out of the grain. As he struggled
to remove his foot, more grain began to flow which buried him deeper in the wheat.
Within a few seconds, the worker was trapped in the sitting position with grain above
his waist.
Emergency Response
Two co-workers were observing the victim as he became entrapped. Immediately all electrical power to the unloading equipment was shut off and secured so that it could not be restarted (locked out and tagged out). One worker went to notify the elevator manager who called the local fire department. The other remained at the grain bin and kept in communication with the entrapped worker. The local fire department notified other surrounding fire departments and emergency rescue teams. Because of the remote location of the elevator, the first fire department rescue team arrived on site about 30 minutes after notification. Area farmers and workers were also notified. Several farmers were already at the elevator.
Elevator employees and farmers at the site tried to decide what to do. They began
collecting material to build a retaining wall around the victim to prevent grain flow
that would submerse the victim further under the grain. One farmer brought an acetylene
torch to cut a hole in the bin.
Fire and rescue teams and a highway patrolman arrived on the site. The patrolman
eventually took control of the assembled personnel outside the bin, while a fireman
took control of the operation inside the bin. The decision was made not to cut a hole
in the bin with a torch for fear of triggering a grain dust explosion or igniting
a fire. Eventually, a tractor front-end loader was used to puncture the side of the
bin to drain the grain out on the ground.
The Rescue Operation
None of the rescue teams had formal training in grain bin rescue operations, but some
had practiced trench rescue operations. They applied the trench rescue techniques
to this bin rescue. Paramedics stayed close to the victim. They informed him of what
was going on, provided high flow oxygen through a non-rebreather mask, and gave him
an I.V. of a saline plasma to maintain body temperature when the victim complained
of being cold. The victim remained calm and in good condition throughout the rescue.
A retaining wall was built on the high sides of the grain out of lumber ranging from
1-inch by-12-inch boards to 4feet by 8 feet sheets of plywood. When the hole was ripped
in the bin wall on the “high” side of the grain with the front-end loader, grain began
to flow out of the bin; but more grain also began to flow down around the victim.
This was caused by both the vibration from the impact of the front-end loader against
the bin and the flow of grain out of the side of the bin. Workers scooped grain away
from the victim and out of the bin. A portable grain vacuum conveyor brought to the
elevator was used to speed up the grain removal process next to the victim, reducing
the manpower needed for hand scooping.
Three sets of retaining walls were finally established at spaced intervals away from
the victim (Figure 1). The vacuum conveyor removed grain from inside the wall closest
to the victim until wheat began to flow underneath the wall. Then, grain was removed
from inside the next retaining wall. This process was repeated until the walls could
be pushed further into the grain, and grain removed again from the wall closest to
the victim. Several people were used to hold the retaining walls against the pressure
of the grain on the back side of the walls. The rescuers attempted to use a round
bale hay gate as a retaining wall, but half of it turned up on end because of the
unequal pressure from the grain.
Figure 1. The initial grain flow trapped the victim’s foot against the sweep auger motor, then
proceeded to bury him above the waist (a). Three sets of retaining walls were established
to prevent further grain flow around the victim and aid in grain removal with a vacuum
conveyor (b).
Rescuer protection was maintained by rotating workers in and out of the bin to give them a rest. Dust masks were worn and changed out periodically to protect against dust inhalation.
The victim was finally freed when all of the grain around his foot was removed, allowing
him to move his foot sideways and pull it out from under the sweep auger motor. The
victim was carried out on a stokes basket and taken to a hospital. The victim suffered
minor tissue damage from the pressure of the grain on his leg and foot, but has no
apparent permanent injury. It took approximately five hours to remove the victim from
the grain bin.
Evaluation and Lessons Learned
The elevator workers, emergency rescue team members, and other personnel involved in this rescue are to be commended for their success in rescuing a healthy worker from a grain bin entrapment incident. Many things were done which aided in the success of the operation:
- Good communication between the paramedics and victim helped calm the victim and allowed for proper medical attention and care.
- Electrical power to unloading equipment was shut off and secured immediately to protect the victim and rescuers from accidental start up.
- The use of retaining walls to prevent additional grain flow around the victim kept the grain level below the victim’s shoulders, which aided in breathing.
- The grain vacuum conveyor was valuable in expediting grain removal.
- Rescuers helped ensure their safety by wearing respiratory protection and rotating workers.
- The cooperation of all involved in the rescue allowed the victim to be removed safely.
The grain elevator where this incident occurred is taking action to prevent similar occurrences. Managers are having a stand made for workers to use when they are in the bin. This will keep them out of the grain while plugging in the sweep auger. This stand will straddle the sweep auger and provide protection for workers by keeping them above both the grain and auger.
Knowing that a grain dust explosion was not a threat when using a cutting torch to
cut steel covered with grain would have assisted the rescuers. A confined space with
specific dust concentrations, as might be found in an operating grain leg or grain
dump pit, is required for combustion of grain dust. This is not the case along the
side of a filled grain bin. Hard red winter wheat typically contains a maximum of
0.6 pounds of dust per ton of grain. Concentrations of dust required for explosions
with wheat dust are at least 50 grams of entrained dust per cubic meter of space.
For explosions to occur, the dust must be entrained or uniformly suspended in the
space. Most loose dust in stored wheat settles under the fill point and sifts to the
bottom. Wheat against a bin or tank sidewall has very little grain dust and the dust
is not entrained in the air, so there is no threat of a dust explosion.
Even though a dust explosion is not a risk when using a cutting torch, grain could
catch fire and smolder or burn slowly under the right conditions (high temperature
and relatively low moisture). The grain in this bin was in good condition and cool,
so a fire was unlikely. However, a fire extinguisher or water hose should be on hand
to put out any fires that could occur when a cutting torch is used to cut bin wall
openings. Knowing that a dust explosion could not occur would have allowed a hole
to be cut quickly in the side of the bin with a cutting torch or saw. The speed with
which grain can be removed is more important the deeper the victim is buried in the
grain.
A second factor which could have expedited the rescue was previous training on grain
bin rescue operations. Grain elevators and local fire departments need to work together
to practice on-site rescue operations and educate employees and rescuers about proper
actions and techniques to use in case a grain entrapment occurs. Elapsed time is vital.
Knowing the proper course of action can reduce rescue time and give workers and rescuers
confidence in the difficult decisions they must make during a bin rescue emergency.
Grain elevator workers should have needed rescue
equipment on hand or know where it is located and how to acquire it quickly.
Several personnel at the site commented that no one immediately took charge of the
rescue operation. Elevator employees and farmers on site first began the rescue operation.
As more people and multiple fire and rescue teams arrived, each had different ideas
on how to rescue the entrapped victim. Several courses of action were discussed and
considered before a chain of command was finally established. A state highway patrolman
took charge of the personnel outside the bin, and a fireman took charge of the operation
inside the bin.
Establishing effective command and control is essential in minimizing rescue time
and conducting a successful rescue operation. Lack of a well-defined authority can
hinder the efforts of rescue workers. Information on the status of the victim, resources
available, and current activities taking place must be quickly and accurately conveyed
to the rescue team upon arrival. The rescue team should then establish an
incident command post and assign an incident commander.
Emergency rescue teams should be familiar with the Incident Command System, a standardized
emergency management system developed to organize and manage all the functions required
to deal with an emergency situation.1 This system is designed to allow the leader
to command the incident and to prevent the incident from commanding the leader. An
incident commander should be assigned quickly to establish a final authority for all
decisions. Specialists and those familiar with the site should act as advisors to
the incident commander to assist in making decisions about the rescue operation.
Failing to establish leadership and command roles is a common problem with rural
rescue operations and occurs when more than one jurisdiction or agency is involved
in an incident. Mutual aid agreements between rescue teams in the same response area
can define roles and responsibilities to reduce the potential for disagreements and
problems and minimize response time.
Elevator managers should check with local emergency rescue teams and assist them
in pre-incident planning. A pre-incident plan involves developing and maintaining
a
written plan for response to and management of a rescue.1 It allows information to be gathered and for as many decisions as possible to be
made before an incident occurs. This will help the rescue team in managing the incident,
rather than simply reacting to it. Once again, practicing a rescue operation on site
with multiple rescue teams is invaluable training for both the elevator and rescue
personnel, and it enhances total
community preparation for when an incident does occur.
1Robert A. Worsing, Jr., MD, Rural Rescue and Emergency Care (Rosemont, IL: American Academy of Orthopedic Surgeons, 1993) 15-19.
Training for fire departments, emergency response teams, and elevator personnel is available through Oklahoma State
University’s Fire Services Training Division in Stillwater, Oklahoma. (http://www.osufst.org)
Carol L Jones, PhD, PE
Stored Products Engineer