Stability, visibility crucial in preventing industrial truck overturns, collisions
October 14, 2008
According to the Bureau of Labor Statistics, in the U.S. nearly 100 workers are killed and another 20,000 are seriously injured annually in forklift-related incidents. Knowing how they occur and studying the events that lead up to them can go a long way in preventing typical accidents.
Editor's Note:The information in this article came from three sources: Combilift USA; National Institute for Occupational Safety and Health (NIOSH) Publication No. 2001 – 109 (June 2001), "Preventing Injuries and Deaths of Workers Who Operate or Work Near Forklifts"; and Occupational Safety & Health Administration (OSHA) standard 29 CFR 1910.178, Appendix A. In this article, the terms industrial truck, lift truck, industrial lift truck, and fork lift are used interchangeably.
Nimble and versatile, industrial lift trucks are indispensable for moving loads of tube or pipe from place to place in a manufacturing plant. Whether used by tube and pipe producers or fabricators, industrial trucks move loads of various shapes and sizes and can accommodate many plant layouts.
The downside is that, used improperly, industrial trucks are dangerous. Each year in the U.S. nearly 100 workers are killed and another 20,000 are seriously injured in forklift-related incidents. The worst accidents, those that result in fatalities, fall into four categories: overturns (which cause 22 percent of industrial truck fatalities); workers struck by an industrial truck (20 percent); workers crushed by a lift truck (16 percent); and falls from a lift truck (9 percent).
A training program for industrial truck operators is the first step in injury and fatality prevention. NIOSH recommends that all operators adhere to the following guidelines:
While in Motion:
A review of the events that led up to a few truck-related fatalities reveals specifically how these types of incidents can be prevented.
Overturn. The president of an advertising sign company was killed while using a sit-down forklift to unload steel tubing from a trailer. He was driving the forklift about 5 MPH beside the trailer on a concrete driveway with a 3 percent grade. He turned the forklift and it began to tip over. He wasn't wearing a seat belt. The victim jumped to the driveway, and when the forklift overturned, the victim's head and neck became pinned under the forklift's overhead guard. A subsequent inspection revealed that infrequent maintenance contributed to the incident.
Overturn. A shop foreman was fatally injured after an overturn. The victim was turning while backing down an incline with a 4 percent grade. The forklift was transporting a 3-foot-high, 150-pound stack of cardboard with the forks raised approximately 60 inches off the ground. The foreman wasn't wearing a seat belt. He was found with his head pinned under the overhead guard.
Overturn. A forklift driver was pinned under the overhead guard after the forklift fell off a loading dock. The forklift was not equipped with a seat belt.
The loading dock had large cracks in the surface and was in need of extensive repair. It was raining when the victim left the storage building to lift a load from the back of a pickup truck. Evidence indicates that either the forklift was too close to the edge of the loading dock (which crumbled) or the right front tire was caught in a large crack in the loading dock, causing the overturn.
Excessive Speed. A punch press operator was fatally injured as a result of a forklift traveling in reverse at high speed toward the victim's work area. The forklift struck a metal scrap bin, propelling it toward the machine; the bin hit the press and rebounded toward the forklift. There it was hit once again and shoved back, crushing the victim against the press.
Fall. A worker was fatally injured after falling from and being run over by a forklift. While the operator was driving the forklift, the victim was riding on the forks. As the operator approached an intersection, he slowed down and turned his head to check for oncoming traffic. When he turned his head back, he could not see the victim. He stopped the forklift, dismounted, and found the victim underneath the right side of the forklift.
Fall. A maintenance manager fell 7 ft. from a safety platform that had been elevated by a forklift. The victim had been raised in a steel-framed, cage-type safety platform that had not been secured to the forklift. The victim removed a fluorescent light bulb from its fixture and stepped to one side of the safety platform. When the victim shifted his weight from the center of the platform to the outer edge, the safety platform toppled off the forks. The victim fell, struck his head on a concrete floor, and was subsequently struck by the steel safety platform.
The six incidents described in the previous section reveal that preventing injuries and fatalities requires more than a simple training plan. Routine inspections, maintenance, and repairs; knowledge of the hazards associated with elevating and transporting workers; and a thorough understanding of industrial lift truck stability can go a long way in preventing safety incidents.
Inspections, Maintenance, and Repairs. OSHA requires that industrial trucks be examined at least daily; if the truck is used around the clock, it must be examined after each shift. When defects are found, they shall be immediately reported and corrected.
The American Society of Mechanical Engineers (ASME) and the American National Standards Institute (ANSI) state that inspections and maintenance must cover the brakes, steering mechanisms, control mechanisms, warning devices, lights, governors, lift overload devices, guard and safety devices, lift and tilt mechanisms, articulating axle stops, and frame members.
Avoiding Pedestrians. Keeping workers away from aisles, installing safety equipment, and developing facility-specific rules and training can go a long way in helping industrial truck drivers avoid pedestrians.
First, review the facility's floor plan and the overall working environment to maximize safety. Install the workstations, control panels, and equipment away from aisles when possible. Install physical barriers to ensure that workstations are isolated from aisles traveled by forklifts where practical. Evaluate intersections and other blind corners to determine whether overhead dome mirrors could improve the visibility of forklift operators or workers on foot. Do not store bins, racks, or other materials at corners, intersections, or other locations that obstruct the view of operators or workers at workstations.
Second, separate forklift traffic from pedestrian traffic where possible. For example, limit some aisles to workers on foot only and others to forklifts only. Also restrict the use of forklifts near time clocks, break rooms, cafeterias, and main exits, particularly when the flow of workers on foot is at a peak (such as at the end of a shift or during breaks). Finally, make every effort to alert workers when a forklift is nearby. Use horns, audible backup alarms, and flashing lights to warn workers and other forklift operators in the area. Flashing lights are especially important in areas with high ambient noise levels.
Third, conduct routine inspections. Ensure that workplace safety inspections are routinely conducted by a person who can identify hazards and conditions that are dangerous to workers. Hazards include obstructions in the aisle, blind corners and intersections, and forklifts that come too close to workers on foot. The person who conducts the inspections should have the authority to implement prompt corrective measures.
Finally, enforce safe driving practices such as obeying speed limits, stopping at stop signs, and slowing down and blowing the horn at intersections.
Guidelines for Elevating Workers. NIOSH offers these guidelines for lifting workers:
Combined center of gravity Source: Combilift USA
The factors that make a lift truck stable are based on the center of gravity and the stability triangle.
First, every object has a center of gravity. This is the imaginary point about which the weight of the object is evenly distributed. Most objects have a fixed center of gravity. However, on a lift truck, it is much more complicated. The lift truck has a center of gravity and so does the load. The result of these is a combined center of gravity (seeFigure 1) that lies somewhere between the two.
Furthermore, the combined center of gravity isn't fixed—it moves:
Second, the wheels of a lift truck form the stability triangle.1Keeping the load located over the stability triangle is key in keeping the load and the truck stable.
Increasing and Decreasing Stability. Without a load, the truck's center of gravity is close to the rear wheels (see Figure 1). Putting a load on the truck platform increases its stability because the combined center of gravity moves closer to the middle of the stability triangle.
As long as the combined center of gravity is located behind the front wheel and over the machine's wheel base, the truck will not tip over. On the other hand, as the combined center of gravity gets close to the edge of the stability triangle—from raising the mast, making a turn, or driving down an incline, for example—the stability decreases. This can lead to:
If the combined center of gravity shifts to a point outside the stability triangle, the truck will tip over.
The load and the truck are just two components in stability. Another is the surface the truck operates on. Cracks, crumbling edges, and other defects on loading docks, aisles, and other operating surfaces can lessen stability and cause an overturn.
1. According to OSHA, nearly all counterbalanced powered industrial trucks have a three-point suspension system. In other words, the vehicle is supported at three points. On a three-wheeled truck, the three points are the three wheels. On a four-wheeled truck, the truck's steer axle is attached to the truck by a pin in the axle's center; this pin and the two nonsteering wheels form the triangle (see Figure 2).
Three-point suspension system