Failure to provide proper training and block equipment against hazardous motion resulted in the death of a contractor mechanic who was struck by the counterweight of a hydraulic excavator.
The U.S. Federal Mine Safety and Health Administration (MSHA) found that the contractor didn’t task train the mechanic on how to disassemble the major components of the excavator and didn’t have procedures in place for controlling potentially hazardous motion.
Counterweight fell as last bolt was removed
On Dec. 16, 2022, Thomas Hild was working as a mechanic at the Signal Peak Silica of Atascosa mine in Atascosa County, Texas. Hild was employed by Stout Excavating Group LLC, a contractor that provided excavating and hauling services.
At 7:30 a.m., Hild, a co-worker and their supervisor began disassembling the major components of a hydraulic excavator for transportation to Kermit, Texas. They removed the tracks, upper boom and bucket earlier in the day. Later in the afternoon, Hild backed his service truck close to the rear of the excavator’s 27,227-pound counterweight and then climbed onto the truck’s back step. He did this so he could get access to the bolts securing the counterweight to the excavator.
At 4:29 p.m., the co-worker and supervisor stood out of sight about 10 feet away while Hild removed the last bolt from the counterweight. They heard a popping noise and went to where Hild had been working. The co-worker and supervisor found the counterweight lying on the ground near an injured Hild, who had been struck by the falling counterweight.
Police arrived at 4:32 p.m. Emergency medical services showed up at 4:51 p.m. Hild was pronounced dead at 6:18 p.m.
Important anchor bolts were missing
The excavator involved in the incident was a Caterpillar 390F. MSHA investigators found a copy of the manufacturer’s operating manual in the cab, which contained step-by-step instruction on how to remove the counterweight.
Investigators brought in representatives of Holt CAT, an authorized Caterpillar dealer, to aid in looking the excavator over for defects. They found that two anchor bolts were missing from the counterweight, which were important for supporting the counterweight during the assembly and disassembly processes. No other defects were found.
MSHA investigators also determined that Hild didn’t engage the lift cylinder on the excavator to block the counterweight from hazardous motion before removing the final mounting bolt.
Co-workers felt mechanic lacked experience to perform task
Based on his training records and interviews with co-workers, investigators learned that Hild had more than one year of experience working as a mechanic for Stout. He participated in the assembly of the counterweight on the excavator in the past, but had a limited role and was more of an observer at the time.
The MSHA investigators also learned that Hild and his co-workers were called by two more experienced Stout employees and asked to wait for them to arrive before attempting to remove the counterweight. These more experienced employees were concerned because they knew Hild lacked experience with the disassembly process.
The supervisor told investigators that Hild was familiar with the disassembly procedure but wouldn’t confirm that Hild had ever removed the counterweight from the excavator before.
MSHA interviewed Stout management and learned that their mechanics received no task training. Instead, the company relied on the mechanics to look at the manufacturer operating manuals for their training. None of Stout’s management acknowledged assigning the counterweight removal task to Hild.
Company now task trains all of its employees
Based on its investigation, MSHA determined that the root cause of the incident was that Stout:
- failed to provide task training on disassembling the major components of the hydraulic excavator, and
- didn’t ensure that equipment was blocked against hazardous motion.
Stout has since properly task trained all of its employees on the duties assigned to them. The company has also held safety meetings with all of its employees to retrain them on existing procedures and requirements regarding blocking equipment against hazardous motion.
