Crane safety.
Published in: Concrete Construction
Date: 4/1/2003
By: Warning, Michael
A loaded concrete bucket struck and killed a 50-year-old male carpenter at a municipal construction site during a crane tipover. The victim was removing forms from a newly constructed concrete wall while a concrete finishing crew was filling empty forms about 20 feet away. Concrete being hoisted from street level with a crawler-mounted mobile crane was landed under the direction of a rooftop spotter. As the crane operator hoisted a bucketload of concrete, swung it over the roof, and boomed out toward the empty forms, the crane lost stability, tipping toward the victim. When the crane operator realized what was happening, he radioed a warning to the spotter who relayed the warning to rooftop workers. The victim had started to move when the uncontrolled concrete bucket swung toward him, striking his head and shoulder. Workers notified emergency personnel who responded within minutes, but the worker was pronounced dead at the scene.
Four safety rules were violated and contributed to this tragedy:
1. Employers, crane owners, and operators should ensure that cranes are operated within their safe lifting capacities as recommended by the crane manufacturer’s load chart.
Measurements conducted after the incident indicated that the intended landing site for the loaded concrete bucket was 132 feet from the crane’s center pin. The manufacturer’s load chart lists a capacity of 3620 pounds for this radius. The hoisted load at the time of the incident including the headache ball, 50 feet of load line, rigging fixtures, and the loaded concrete bucket was estimated to be 5110 pounds–1490 pounds over the capacity recommended on the load chart.
2. Crane owners should ensure that monitoring instruments used for guidance during hoisting operations are accurately calibrated and operating correctly.
The LMI [load moment indicator] had been calibrated approximately 5 months before the incident during an annual inspection of the crane. However, during a discussion with the crane rental company’s manager, investigators learned that the LMI had been providing erroneous readouts of lift conditions during and subsequent to the incident.
3. Employers should develop and implement safe work procedures to ensure that workers in or near the landing area of hoisted loads are notified when loads are in the air.
Apparently, the lift was already in progress when the victim arrived at the rooftop work area and began to strip forms from the wall. It is not known if he was aware that a lift was in progress.
4. Employers should develop and implement safe work procedures to ensure that workers and crane operators have a clear and complete understanding of the landing locations before loads are hoisted.
The new landing location may have appeared to the crane operator to be closer to the crane’s center pin than it was. When landing locations are not visible to crane operators and they must rely on signals or radio communications from spotters, extra care should be exercised to ensure that the lift conditions are fully understood by all workers controlling or directing the lift. This could be accomplished at prelift meetings during which the day’s hoisting work, including the swing radius for the intended work areas, would be planned. When switching landing locations, crane operators and spotters should verify that hoisting parameters, such as swing radius, are completely understood.
This incident report is based on investigations conducted by Paul H. Moore, Safety Engineer, NIOSH Division of Safety Research, Fatality Assessment and Control Evaluation Team and Melvin Stallworth, M.S, OHIO FACE Investigator, Ohio Department of Health.
Michael Warning is a construction safety consultant with nearly 25 years of experience. He is the current chairman of the American Society of Concrete Contractors’ Safety Committee.
COPYRIGHT 2003 Hanley-Wood, Inc.