Maintenance Man

The victim was leaning over a base lift jack housing. The molded casing catastrophically failed striking the victim in the chest from unknown/undetectable reasons. Cause was catastrophic failure of the housing. Compliance with rules/regs, protective items not a factor, miner proficiency may be a factor, mining equip/systems may be a factor.

On Monday, August 8, 2011, at approximately 10:50 a.m., Keith Baker (Victim), a 41-year old Longwall Mechanic, was struck in the chest by the top of a base lift jack cylinder, resulting in fatal injuries. Baker was conducting maintenance work on the No. 22 Shield of the 11 West Longwall when the accident occurred. Baker was leaning over the base lift jack in the process of evaluating a defective ram cylinder and damaged relay bar at the No. 22 Shield. The shield was lowered from the roof and the incoming pressure turned off in the shield. After the midnight shift on August 6, 2011, the shield was being advanced by the movement of the conveyor by chains connecting the shield to the conveyor. There were no witnesses to the accident. The primary cause of the accident was the mine operator's failure to ensure that the base lift jack cylinder was protected from over-pressurization. No relief valve or other means was installed to protect the cylinder when the shutoff valve in the hydraulic hose was closed.

1. The mine operator failed to assure the safe operating condition of the longwall shields operating on the 11 West longwall. The investigation revealed that modification of the base lift that did not adhere to the original cylinder design. A base lift cylinder, located on the number 22 Shield, was determined to have a rod stroke that exceeded the available travel of the piston in the hydraulic cylinder. The end of the rod is exposed to upward movement of relay bars when the shields are placed in push modes, when shields are advanced, or any similar movement of the conveyor away from the face. This action can impact the structure of the cylinder physically or intensify the internal pressure of the cylinder beyond the designed working pressure. In addition, at an undetermined time prior to the accident, an improper weld repair was made to the cylinder, which reduced the strength of the end cap. The cylinder defect would likely have been prevented or identified by adhering to industry standards in design, proper welding, nondestructive examination, and proof testing of the cylinder in accordance with industry standards after manufacture, the weld repair, and rebuild.

Findings from MSHA's final investigation report, which supersedes the preliminary narrative above.

Activity at time of incident

Machine Maintenance

Subunit / location

UNDERGROUND

Underground location

FACE

Mining method

Longwall

Accident type

Struck by falling object

Source of injury

METAL,(Not Elsewhere Classified)(PIPE,WIRE,NAIL)

Nature of injury

MULTIPLE INJURIES

Body part affected

CHEST (RIBS/BREAST BONE/CHEST ORGNS)

Total mining experience

9 years

Experience at this mine

9 years

Experience in this job

6 years

Degree of injury

FATALITY