viernes, 18 de diciembre de 2015

CDC - NIOSH Science Blog – Preventing Wood Chipper Fatalities

CDC - NIOSH Science Blog – Preventing Wood Chipper Fatalities

Preventing Wood Chipper Fatalities

Commercial Wood Chipper
Commercial Wood Chipper. Photo ©Thinkstock
Last week, a 19-year-old North Carolina teen was killed after being pulled feet first into a wood chipper (see news reportExternal Web Site Icon).  It was his first day on the job.Self-feeding mobile wood chippers commonly used during tree trimming operations consist of a feed mechanism, knives mounted on a rotating chipper disc or drum, and a power plant. Tree branches and trunk sections fed manually into the machine’s infeed hopper are grabbed by the feed mechanism or chipper knives. The chipper disc or drum, rotating between 1,000 and 2,000 rpm, cuts and propels wood chips through the discharge spout usually into a chip truck. The housing containing the chipper disc or drum is sectioned and includes a removable hood that allows access to machine components for maintenance.
The hazards of working with wood chippers are well known and practical methods exist for preventing fatalities.  Links to various resources are provided below.  This is not a new problem.  How do we prevent another horrible tragedy?
In addition to the hazards of working with this dangerous machinery, we know that certain worker characteristics —such as being an immigrant/foreign-born worker, a worker under the age of 25, or an employee of a small business—can increase an individu­al’s risk for workplace injury or illness (see related blog). We also know that temporary workers face additional risks (see Addressing the Hazards of Temporary Employment). Employers need to have safety and health programs that ensure workers are appropriately trained and supervised before they work with hazardous equipment, such as wood chippers.
At 19, this young man was not prohibited from working with this dangerous piece of machinery. Unfortunately, work-related fatalities involving wood chippers have occurred among young people who are prohibited from this dangerous work because of their age as illustrated in the following case study from Youth@Work-Talking Safety Curriculum:
Terrell was a 15-year-old boy who found work with a landscape company when he moved to Maryland with his family. After only a week on the job, he was told to help grind up tree branches, using a motorized wood chipper. As he fed tree trimmings into the machine, Terrell got tangled in some large branches. The machine pulled him into the feed chute and killed him. A co-worker found his body soon after. He shouldn’t have been doing this work because of his age.

Safety Devices

Some chippers are equipped with safety devices to reduce the risk of being pulled into the chipper knives.
Feed control bars, bottom feed stop bars, panic bars, and emergency pull ropes are designed to stop or reverse the feed mechanism if a worker becomes caught. Feed tray extensions provide a physical barrier between the feed mechanism or chipper drum and the operator. Wooden push bars allow workers to feed short branches into the machine without placing their hands in the infeed area. See OSHA Safety Bulletin: Hazards of Wood ChippersExternal Web Site Icon.


To protect workers from being caught by the chipper feed mechanism, employers should ensure the following:
  • All safety devices and controls, such as emergency shut-off devices, are tested and verified to be functioning properly before the chipper is used.
  • Workers are trained in safe work procedures, including operating wood chipper safety devices and safety controls. These procedures should be based on the manufacturer’s recommendations for each machine.
  • At least two workers are in close contact with each other when operating the chipper.
  • Workers wear close-fitting clothing, gloves without cuffs, trousers without cuffs, and skid-resistant foot wear. Clothing should be kept tucked in.
  • Workers’ hands and feet remain outside the infeed hopper.
  • Workers feed brush and limbs into the infeed hopper butt end first.
  • Workers feeding material are positioned at the side of the machine to allow quick operation of the emergency shut-off device and minimize risk of entanglement in branches. Because of differences among machines, the manufacturer’s operating manual should be consulted for guidance. Safe feeding of some disc-type chippers requires the worker to be on the right side.
  • Workers walk away once the feed mechanism has grabbed the material.
  • Workers lay short material on top of longer material that is feeding or use a longer branch to push it through the infeed hopper.
  • Workers load small raked-up material such as twigs and leaves directly into the chip truck or in trash cans or bags instead of feeding it into the chipper.
  • Workers keep the area around the wood chipper free of tripping hazards.
  • Workers wear hard hats, eye protection, and hearing protection. 
Workers have also been killed when struck by flying hoods covering wood chipper discs or drums. Recommendations on how to prevent this hazard can be found at Hazard ID 8 – Injury Associated with Working Near or Operating Wood Chippers.
Help us spread these prevention recommendations and share your ideas on how we can prevent future tragedies in the comment section below. Do you have suggestions on how engineering controls can make wood chippers safer?
Dawn Castillo, MPH, is the Director of the NIOSH Division of Safety Research
CAPT Cheryl F. Estill, PhD is an Industrial Hygiene Supervisor in the NIOSH Division of Surveillance, Hazard Evaluation, and Field Studies and the Coordinator of the National Occupational Research Agenda (NORA) Services Sector Council.
Robert Harrison, MD, is a Professor of Medicine at UC San Francisco and Chief of the Occupational Health Surveillance and Evaluation Program at the California Department of Public Health. 

Many of the cases mentioned here were identified through the NIOSH-funded FATALITY ASSESSMENT AND CONTROL EVALUATION (FACE) PROGRAMInvestigations conducted through the FACE program allow the identification of factors that contribute to fatal work-related injuries. This information is used to develop comprehensive recommendations for preventing similar deaths.

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