Wood Chipper Safety: Best Practices

The pull of a chipper is so powerful that an accident sometimes creates a surreal scene — as if the person jumped into the machine.

How does this happen? A wood chipper relies on a powerful motor or engine that creates the incredible torque needed for turning a rotating drum with attached chipper knives. The combination of speed and torque allows commercial chippers to pull in branches at 20 inches per second. As an operator manually pushes brush and tree limbs into a hopper, the feed mechanism and chipper knives grab anything within reach. “Anything” may be tree limbs and brush…or loose jewelry, rope, an arm, fingers or long hair.  

Statistics tell a sobering story. During 2016, three workers died after being caught in a chipper. OSHA logs show that in 2017, one person was killed and at least half a dozen others lost a finger or foot. Most fatalities result from being caught in the chipper; a smaller portion occur when an object kicks back from a chipper and strikes the operator.

To avoid chipper accidents, follow these precautions.

• Suit up for the job. Anyone working near a chipper should wear eye and hearing protection, tight-fitting clothing, a hard hat or helmet and gloves with no cuffs. Work boots with skid-resistant soles can prevent slips and falls near the feed chute. Leave the jewelry at home, and tie up long hair.
• Know the machine. Before operating a chipper, get familiar with the operation of the machine, its safety controls, and proper start-up and shut-down procedures. Know how to stop or reverse it in case of emergency.
• Inspect it before each use or at the start of each shift. Make sure the disk hood is closed and latched. Check the infeed area for foreign objects. Look for missing or loose bolts and pins (every chipper manufacturer specifies torque levels for the knife bolts and nuts). Inspect the knives for wear or damage. Running the chipper with worn or damaged knives can cause the feed to clog and eventually kick debris back through the feed chute. 
• Check the guards. Make sure they’re not missing. Many chipper accident reports cite the absence of guards or malfunctioning safety devices. OSHA’s general machine guarding standard 29 CFR 1910.212 (a)(1) requires that chippers have one or more guard methods to protect workers from rotating parts and flying debris.
• Point the discharge chute away from people. This one’s obvious but still worth mentioning.
• Have someone stand near emergency shutoff devices while the operating is feeding the machine. An operator caught in a commercial wood chipper has very little time to work free or reach and activate a safety device.
• Check the material before you feed it to make sure it doesn’t contain foreign objects.
• Stay free and clear as you feed. OSHA recommends standing to the side of the infeed chute, pushing materials in with a wooden push tool or long branch, feeding branches in butt-end first, and placing shorter branches on top of longer ones (put small debris in the trash, not in the chipper).
• Immobilize the disk or roller when clearing a chute or changing chipper blades.                                                                                                                                                                                                                                            

Chipper manufacturers have introduced a variety of engineering controls — such as feed tray extensions, flexible rubber curtains at the front of the infeed chute, feed control bars that stop or reverse feed rollers, pressure sensitive bottom feed stop bars, panic bars that stop the hydraulic system that operates the feed rollers, and emergency pull ropes that allow operators to reverse feed rollers1 — but engineering controls are never a substitute for human precaution and safe work practices.

Chipper accidents are rarely minor. Amputations can happen in less than half a second. Anyone using one of these machines should be adequately trained, and even experienced operators should never become complacent. Their foot, fingers or life could be at stake.

John Ross has written about industrial, automotive and consumer technologies for 17 years.

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