Chippers are essential machinery for many arboricultural operations. True, arborists can haul the brush to a landfill and pay a tipping fee, but that gets expensive. It also can require a lot of trips to the landfill, as brush piles are about equal parts air and brush. Some of the older arborists may remember the “poor man’s chipper,” where a worker would stand in the dump box with a chain saw and just keep cutting the brush into smaller, more compact pieces – there’s a safe procedure!
No, chippers can definitely make for a safer and more efficient operation if used properly. There is an art to staging and stacking brush, often the first task a new worker learns. It’s not an easy job, and almost everyone would rather be running a chain saw, either on the ground or aloft, than be the humble brush hauler.
Not only does the chipper operator have a tough, dirty task, but it is also one with numerous hazards. Chipper operations involve exposure to being struck by passing traffic during street-side operations or being struck by falling branches if the chipper is placed within the drop zone. While this violates the ANSI Z133 Safety Requirements, it is all too common a practice, as it certainly reduces the distance to haul the material. However, since the chipper operators are not able to hear the warning that a branch is about to drop over the sound of the chipper, these workers are frequently struck by falling objects – either branches or whole trees – and sometimes bouncing objects, such as when a falling stub ricochets off the tree, onto the fender and then up, striking the worker in the face.
But the hazard source most frequently associated with chipper operations is “compressed-by,” when the worker is pulled into the chipper. These incidents, which may result in total body fragmentation, are the nightmares of tree workers. These are not accidents, of course. No one accidentally stands on the infeed table to kick in brush or pushes their hand (usually the left hand) beyond the plane of the infeed. These are intentional actions with unintended consequences.
No one should ever be standing on the infeed table, feeding brush in from behind the table (always from the side) or wearing loose clothing or gloves that can catch or hook on brush (don’t forget, even a glove with tight wrist straps can have holes that will catch). Some chipper operators trust their luck to the reverse bar or “last-chance” cables, believing that quick action can prevent injury. Quick is an understatement, as a worker can be pulled completely through the chipper, from the infeed table to the chip box, in just over a second. That is not a lot of time to consider what to do to stop the process. If anyone thinks it’s slower, consider this – when a co-worker is pulled through a chipper, the crew sometimes recalls that the chipper momentarily made an odd sound, but almost never do they recall hearing a scream. It happens that fast.
This does not mean these safety devices have not saved lives, they have. Workers have pulled cords in time or co-workers have grabbed the bar quickly enough. However, in these incidents, while lives were saved, fingers, hands or arms were lost.
While the majority of chipper fatalities involve compressed-by incidents, an increasing number are struck-by’s. Not struck by falling limbs because the chipper was staged in the drop zone, or struck by passing traffic, but struck by an object that was pulling into the chipper. In other words, the worker did not go through the chipper, something else went into the chipper and struck them in the process. The rest of this article will focus on struck-by’s involving chippers.
Struck by a limb
We have chipper operators struck by a long limb or log fed into the chipper. Many workers seem to like to see how long a limb or log they can feed into the chipper. If it’s a disc chipper and they are standing on the left side of the unit, they are going to be struck by the wood as it whips to the side. Chipper operators have been smacked in the face, sometimes with only a bruised nose to show for it, but occasionally a worker is struck hard enough that he or she is killed. Still, these incidents are often more embarrassing than life threatening.
Struck by a rope
The more common hazard is being struck by a rope that is being pulled into the chipper. Once the rope is caught by the chipper, it is moving at speeds of more than 100 feet per second – about 70 miles per hour – a speed fast enough to cause serious injury or death to anyone in its path. The caught rope first moves with a slight tug or two as it travels through the feed roller, but then quickly accelerates.
Chipper operators have been struck by the rope and hurled into the side of the chipper from the impact. One worker was standing directly behind the infeed table when the rope was fed in. He was struck by the whipping rope and his head – he was not wearing a helmet – hit the side of the infeed. He died instantly from the impact.
More common is that the rope whips around a part of the body, dragging the worker either into the chipper or against it. Chipper operators, or sometimes crew members merely walking by, have had the rope wrap around their legs, throwing the worker against the chipper infeed. The speed and forces are such that the body extremities are not merely broken but removed. Ropes and winch lines also have wrapped around necks, snapping them when the head hits the infeed table.
Anything in the path of the rope can be lethal. Workers have had extremities severed by striking the outriggers on the aerial lift as the rope pulls them toward the chipper. One horrific incident involved the worker having the rope wrap around his arm, dragging him into the fallen tree and then tearing the arm off at the socket when his forward body movement was blocked by downed limbs.
Chipper manufacturers have installed shear bars into their machines to cut ropes, but they are not 100% effective. A rope might continue to be pulled in, but cut every 6 feet or so in the process. And we have to remember, for the cutters to work, an incident is already in progress. An error has already been made. Keep the work site organized.
These incidents may have been avoided with a little “good housekeeping,” keeping ropes and other rigging gear either bagged or on a tarp when not in use. Too often ropes are just left lying around the job site until it’s time to clean up. This provides ample opportunity for the rope to be caught in brush and dragged into the chipper. Ropes also should be brightly colored so they are easily seen – a green or brown rope is easily missed.
Struck by objects
Not only can objects be pulled in, they can shoot out. The old “chuck-and-duck” chippers were well known and feared for their ability to fling out wood faster than it could be fed in. Heavy rubber curtains help prevent some fragmented debris from kicking out, but they do not eliminate the possibility.
We have had incidents where workers have been struck by fragmented scoop shovels and other metal objects. In one incident, a worker more than 20 feet behind the chipper was fatally struck by a small sliver of metal that penetrated his neck and pierced an artery.
Chippers come with push paddles, but they are frequently absent from the units after a few months. The reason? It was already fed into the chipper. The solution? Get another one. There is no rule saying just one push paddle per chipper. And never install metal bracings on a wooden push paddle. It’s all wood for a reason – this eliminates metal shrapnel!
Chipper manufacturers continue to improve the safety of these essential tools. However, the reason almost all of these safety features work, from bump bars to shear bars, is because a worker has already made a mistake. The best safety feature is the one never used.
John Ball, Ph.D., BCMA, CTSP, A-NREMT (National Registry of Emergency Medical Technicians), is professor of forestry at South Dakota State University and a Board Certified Master Arborist.
This article was based in part on his presentation, “Arborist Safety Update,” at TCI EXPO 2019 in Pittsburgh, Pennsylvania. To listen to an audio recording of that presentation, go to this page in the digital version of this issue of TCI Magazine online, under the Publications tab at http://www.tcia.org/, and click here