Sometimes overconfidence and poor training can become a fatal combination in the workplace, as a miner’s death in a January 2023 maintenance-related incident demonstrates.
Mine Safety and Health Administration investigators found that the fatal incident was caused in part by a group of miners confident in thinking that they were safely performing maintenance on a jaw crusher, when the reality was far different.
One of the miners was killed when the crusher’s swing jaw moved, pinning him between the back side of the jaw and a toggle block frame. All of the miners in the group performing maintenance thought the crusher had been securely braced from movement due to their misunderstanding of a danger sign.
Crew fails to notice crusher jaw wasn’t blocked
On Jan. 4, 2023, John Ogle reported to work at the Sevierville Quarry in Sevier County, Tennessee. The quarry was a surface limestone mine that used a hopper and jaw crusher for sizing operations.
Ogle was part of a crew of four miners assigned to replace worn parts on the crusher.
The day before, the crew used a chain hoist attached to the bottom of the swing jaw and crusher frame to pull the swing jaw in the direction of the stationary jaw and block it against hazardous motion.
They didn’t notice that the swing jaw’s motion was impeded because it was binding against the left side cheek plate. The crew also failed to notice that the toggle bearing was wedged in the bottom of the swing jaw. Both of these things meant the swing jaw wasn’t actually blocked against hazardous motion.
Miner crushed when swing jaw is accidentally freed
On the day of the incident, the crew continued its maintenance on the crusher, failing to realize that while the swing jaw remained at rest in a nearly vertical position, it wasn’t really blocked.
Ogle and another miner entered the area behind the swing jaw to remove a toggle bearing. The crew attached a chain hoist between a lifting loop Ogle had welded to the bearing and the crusher frame behind the swing jaw.
The miner assisting Ogle moved from the area behind the swing jaw to stretch his legs. As he did this, he heard Ogle ratchet the chain hoist twice, which freed the swing jaw from binding against the cheek plate. The swing jaw moved toward Ogle and pinned him between the back side of the jaw and the toggle block.
Died in the hospital a few hours later
Ogle called for help. One member of the crew called 9-1-1 with his cell phone while the two remaining members tried to release the pressure from Ogle by pulling the swing jaw away from the toggle block toward the stationary jaw. However, they stopped when the 9-1-1 operator recommended that they cease attempting to release the pressure until emergency responders arrived.
When emergency response personnel arrived, they had to use rescue tools to remove Ogle from the crusher. He was transported to a local hospital where he was pronounced dead a few hours later.
They misunderstood context of danger sign
The MSHA investigation revealed that the preferred method for doing maintenance on the crusher would be to remove the jaw before removing the toggle bearing and the toggle assembly.
Because the crew removed three of the four extension bolts on the jaw prematurely, the swing jaw itself was only loosely secured.
The crew thought they were safe, however. Once the chain hoist was released, they thought it was in a stable position because of a flywheel counterweight on the bottom. This flywheel counterweight had black markings on its lower half. A danger sign on the side of the crusher that depicts when the crusher chamber is safe or not safe for conducting non-maintenance work states, “Crusher flywheel can move causing serious bodily injury or death. The black half of flywheel must be on bottom before working on crusher. Refer to operating instructions.”
The manufacturer’s operating instructions explain that when the crusher jams during normal operations, the flywheel must be placed in a “safe” position, as depicted by the danger sign. This was only intended for non-maintenance work such as clearing stuck rocks from the jaw.
Ogle and his crew didn’t review the operating instructions before starting maintenance work on the crusher. They failed to recognize that when the toggle assembly is removed, the lower end of the swing jaw is no longer constrained. The entire swing jaw needed to be secured from hazardous motion regardless of the flywheel’s position. Because they weren’t aware of this, they didn’t block the moveable parts of the crusher, which directly contributed to the incident, according to MSHA.
Hazard was missed because some workers weren’t task trained
Further, Ogle and a miner who conducted a pre-shift safety examination of the area before work continued on the crusher weren’t task trained on this job, so neither of them were able to spot the hazard before an incident occurred.
The other members of the crew were task trained on maintenance of the jaw crusher, but MSHA said that training was inadequate since none of them noticed the hazard.
Employer now has written procedures, proper training in place
MSHA pointed at the failure to block moving parts and lack of training as two of the root causes that led to Ogle’s death.
The mine operator has since created a written procedure for blocking machinery against hazardous motion and trained its miners on the process. It has also revised its training plan to include comprehensive safety procedures for maintenance work, such as:
- task training
- proper crusher examination
- correction of any hazards prior to starting work, and
- blocking of all energy sources.