Brush Shredder

The brush shredder in this incident was hydraulically-powered and had a rotating feed roller equipped with a row of approximately five-inch teeth (Exhibit 1). The forward rotating motion of the teeth grinds and shreds branches. The operator controls the direction of the feed roller with a forward switch and reverse switch. The reverse switch is used to eject jammed branches stuck in the teeth. The feed roller is in a raised position when not in operation and is lowered to the ground when in operation. The contractor owned three brush shredders and provided maintenance records from the last two years for all three machines. Maintenance procedures included inspections of the cutting head assembly, engine compartment, frame structure, and cab; oil changes; and other preventative maintenance tasks. The brush shredder in this incident had been owned by the contractor for two years. The manufacture date for the brush shredder could not be confirmed.

Exhibit 1. Roller and shredder teeth.  

Incident Scene

The weather on the day of the incident was 53 degrees Fahrenheit, with 65% humidity and wind speeds ranging from zero to five miles per hour [Weather Underground 2021]. 

Investigation

At the time of the incident, the laborer was working alone, operating a brush shredder to chop and mulch orchard prunings during the postharvest season in an almond orchard. Postharvest mulching has become a common practice in California’s almond industry, especially in recent drought years because it increases soil organic matter, enhances microbial activity, and improves water holding capacity.

The employer stated that, as part of his training, the victim had been instructed to contact the contractor daily for post-shift safety check-ins as well as to report daily shredding progress. On the evening of February 6, 2021, the contractor did not receive a call from the victim. Neither the contractor nor the employer was able to reach the victim on his cell phone the entire evening.

The next morning on Sunday, February 7, 2021, at approximately 9:45 am, the contractor went to the incident site and found the victim in the middle of a row of almond trees caught in the blades of the brush shredder (Exhibit 3). First responders were notified and found the victim deceased upon arrival.

Exhibit 3: The sheriff arriving at the incident scene.

Cause of Death

The cause of death, according to the death certificate, was traumatic amputation of the legs.

Recommendations

The CA/FACE investigator determined that, in order to prevent future incidents, employers who operate brush shredders should: 

Recommendation #1: Retrofit or purchase brush shredders with an operator presence sensing system (OPSS). 

Discussion: Machines with OPSS have sensors that detect operator presence. An OPSS provides a fail-safe condition when an equipment operator is no longer in the driver’s seat. These safety devices set off an alarm, turn off one or more power sources, and/or apply the brakes to the machine when the operator leaves the seat with the engine on or in gear. If this shredder was designed or retrofit with an OPSS, the blades would not have been able to turn and pull the victim into the shredder mechanism. 

It is possible that the victim exited the cab to attempt to dislodge branches that could not be ejected using the reverse/forward blade mechanism. It could not be confirmed if, under usual operations, brush can remain jammed in the feeder despite reversing the blades. On this machine, there was continued power to the blades if the operator exited the cab while the machine is running. In this incident, brush may have become jammed in the blades and the victim may have been trying to kick these branches loose. He may have lost his balance and was pulled into the roller. 

Recommendation #2: Provide comprehensive worker training including safe work practices, hazard recognition, and how to respond to or avoid unsafe conditions such as a jammed feeder.  

Discussion: Although the employer had an IIPP and the victim had received safety training (mostly OJT) on various farm work tasks, there was no documentation that the victim received formal training in the safe operation of the shredder, or knew how to unjam the feeder. Brush shredder operators should be trained on how to respond to different problems commonly encountered in the field. The training should include testing and evaluation to verify and document an employee’s achievement of skills. Different scenarios should be presented, and solutions discussed. For example, a scenario may involve the actions a worker should take if the usual blade reversal/forward procedures fail to dislodge stubborn brush. Solutions may include manually removing mulch from the blades (this requires lockout/tagout procedures); transporting the machine to a repair shop; or calling the contractor for further direction. An additional scenario may involve a worker losing their balance while kicking branches into the center of the roller’s path. In this situation, a worker should be trained to use a tool to dislodge material. If the victim was given more comprehensive training focused on alternative solutions to different problems encountered in the field, he may not have positioned himself in front of the shredder and been pulled into the blades. 

Recommendation #3: Post clearly visible and language-appropriate safety warning labels both inside the cab and on the outside of the shredder above the feed roller.

Discussion: While safety warning labels by themselves may not prevent injuries and fatalities, they can be an effective tool to complement an existing safety program. Before purchasing warning labels, it is important to consider certain characteristics:

• Visibility: The color/size/font of letters and the contrasting background color will dictate the degree of visibility. The information on the label should be visible to a reader coming from a far distance.

• Attachment Method: The type of method would depend on the adhering surface material. Some surfaces would only require glue while other surfaces will require welding in order to attach a sign.

• Material: Labels used on agricultural machinery have to be able to withstand highly variable environmental conditions (e.g., temperature, UV light, and wind).
  

• Content: An effective label should provide some indication of a problem, followed by a desirable safe action. For example, a sign can state a type of hazard (Example: Danger! Rotating Sharp Teeth), its consequences (Can Cause Amputation or Death), and action needed to avoid this hazard (Do not stand in front of machine while engine is on). Only one message should be contained on a single label so that the label will not be crowded with too much information. 

• Symbols Versus Words: Employers should evaluate whether it is more effective to use symbols rather than words on a label. Signal words commonly used in agriculture may also be good choices to use on a warning label. 

• Location of Labels: Labels should be visible from a distance not obstructed by other parts of the machine. Wider machines may benefit from having two labels, one on each side. Labels should be on both the inside of the cab and the outside of the shredder. Exhibit 4 shows that there were no safety warning labels inside the brush shredder involved in the incident.

• Periodic Inspection of Labels: All labels fade with time. It is important to periodically inspect the labels and replace those that are fading. Exhibit 5 shows the fading label on the outside of the brush shredder involved in this incident. 

• Other Warning Formats: Although a safety checklist is not a label, it serves as a good reminder of safe operating procedures and can be posted next to the control panel. The checklist can include emergency contact information which is especially important since agricultural workers often work alone on the weekends. An available copy of the brush shredder instruction manual may be useful in certain emergency situations and can be stored next to the control panel. Important portions of a manual can be translated to languages used by workers.

• Training: Employers should train workers on how to recognize and interpret posted safety labels. Languages used on the labels should be understandable to workers. Figure 5 shows that the label on the machine involved in the incident was only in English.
  

Exhibit 4. No warning labels were posted on the inside of the cab.

If there were clear and highly visible warning labels on the brush shredder involved in this incident, the victim might have heeded the warnings to not stand in front of the rotating feed roller. Exhibit 5. Faded warning sticker on the front of the shredder.