Moving large heavy loads is crucial to today's manufacturing and construction industries. New technology continues to be developed that makes cranes safer. New approaches to crane training and extensive workplace precautions have helped improve safety. But crane accidents continue to happen and there remain significant safety issues to be considered, both for the operators of the cranes and for those working near cranes.
Crane, derrick, and hoist safety hazards are addressed in separate OSHA standards for the general industry, marine terminals, longshoring, gear certification, and the construction industry. We'll be focusing on the construction industry.
Crane Accident Case Study - Boom Failure
A 20-ton steel slab was being unloaded from a low-boy trailer using a 50-ton crawler crane with a 90-foot lattice boom. The crane operator was not experienced with this type of crane and did not know the length of the boom. Additionally, no one had determined the load radius.
As the steel slab was being lifted it moved forward and to the right. This placed a twisting force on the boom. The boom twisted, swinging down, under, and to the right.
Two crew members, about 30 feet away, saw the boom begin to swing. They started to run away from the crane. The boom struck one of the workers on the head, causing instant death. Wire rope struck the other worker, a management trainee, causing internal injuries. He died two hours later at a local hospital.
Bureau of Labor Statistics (BLS) Fatal Crane Accident Data
The most recent BLS data is for 2006. There were 72 crane-related fatal occupational injuries that year. This was a decrease from an average of 78 fatalities per year from 2003 to 2005. These numbers include all fatalities where the source of the injury was a crane, the secondary source of the injury was a crane, or where the injured person was operating a crane.
There were no multiple fatality incidents involving cranes in 2006. There were six multiple injury crane related fatalities in 2005 and eight fatalities in 2004.
In 2006, 30 crane-related fatalities were the result of falling objects. Only nine of the 30 fatalities were as a result of the crane striking a person. The other workers were killed when the load the crane was moving fell, hitting the workers.
The types of cranes most often involved in fatal accidents were mobile, truck and rail mounted cranes, and overhead cranes. Overhead cranes run on a horizontal beam that moves along two widely separated rails and typically use a hook-and-line mechanism. Mobile cranes are typically mounted and travel on top of mobile devices such as trucks or rail cars. In 2006, twenty-six crane fatalities involved mobile, truck or rail mounted cranes. Nineteen involved overhead cranes.
The most common types of workers involved in crane fatalities in 2006 were:
- construction laborers (10 fatalities)
- electricians (8)
- welders, cutters, solderers and brazers (6)
Crane and tower operators accounted for only 3 fatalities.
Twenty-six workers were killed in crane-related incidents while working in the private construction industry in 2006. Most notably, six died working in highway, street, and bridge construction.
Manufacturing (17 fatalities) and mining (7) had the next largest number of fatalities in the private sector.
OSHA Crane Accident Data
OSHA's analysis of crane accidents identified the major causes of crane accidents as:
- boom or crane contact with energized power lines (nearly 45% of the cases)
- under the hook lifting device
- overturned cranes
- dropped loads
- boom collapse
- crushing by the counter weight
- outrigger use, falls and rigging failures
Crane accidents, including fatalities and serious injuries, will occur if cranes are not inspected, maintained and used properly. Many fatalities occur when the crane boom, load line or the load contacts power lines shorting electricity to ground. Other crane accidents happen when workers are struck by the load, are caught inside the swing radius, or when the crane is assembled or disassembled incorrectly. Following these basic guidelines will help reduce the number of crane accidents:
- Cranes must be operated only by qualified and trained personnel.
- The crane and crane controls must be inspected by a designated competent person before use.
- Cranes must be on a firm, stable surface and must be level.
- During crane assembly and disassembly do not unlock or remove pins unless sections are blocked, secure and stable.
- Fully extend outriggers. Barricade all accessible areas inside the crane's swing radius.
- Watch for overhead electric power lines. Maintain at least a 10-foot safe working clearance from all power lines.
- Inspect all rigging prior to use. Do not wrap hoist lines around the load.
- Be sure to use the correct load chart for the crane's configuration and setup, the load weight, and the lift path.
- Do not exceed the load chart capacity while making lifts.
- Raise a load a few inches, hold, verify capacity and balance, and test the brake system before delivering load.
- Do not move loads over workers.
- Be sure to follow signals, and the manufacturer instructions, while operating a crane.
Crane Accident Case Study
A truck driver made a delivery of steel beams to a job site. After positioning his flatbed truck as directed, he stood near the hydraulic crane that was offloading the truck and watched the operation. The steel erection company controlling the crane had secured the area. Instead of barricading the crane's swing radius, walls, vehicles, and two strategically placed employees were used to keep unauthorized personnel away from the crane. The driver was allowed to remain in the secured area because he was a friend and knew the operation.
When no one was looking, the driver apparently walked up to the crane and was crushed between the crane's counterweight and the right rear outrigger. He sustained serious injuries to his chest and internal organs, including his liver, and died later that day.
2010 OSHA Standards for Cranes Used in Construction
In 2010 OSHA issued new standards covering the use of cranes and derricks in construction. The significant number of fatalities associated with the use of cranes and derricks in construction and the considerable technological advances in equipment since the publication of the old rule, issued in 1971, led these new standards. Some of the features of the 2010 crane standards include:
- The 2010 standard addresses key hazards related to cranes and derricks on construction worksites, including the four main causes of worker death and injury: electrocution, crushed by parts of the equipment, struck-by the equipment or load, and falls.
- Significant requirements in the new crane standard include:
- a pre-erection inspection of tower crane parts.
- using synthetic slings in accordance with the manufacturer's instructions during assembly and disassembly.
- assessment of ground conditions.
- Training, qualification, and certification of crane operators.
- Procedures for working in the vicinity of power lines.
- Employers must comply with local and state operator licensing requirements which meet the minimum criteria specified in 1926.1427.
- Written certification tests may be administered in any language understood by the operator candidate.
- When employers with employees qualified for power transmission and distribution are working in accordance with the power transmission and distribution standard (1910.269), that employer will be considered in compliance with this final rule's requirements for working around power lines.
- Employers must use a qualified rigger for rigging operations during assembly and disassembly.
- Employers must perform a pre-erection inspection of tower cranes.
- Operators of most types of cranes to be qualified or certified under one of the options set forth in 1926.1427.
- Employers must pay for all training required for certification of equipment operators.
- State Plans must have job safety and health standards that are more stringent than, or "at least as effective as" comparable federal standards.
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