Longwall mechanic Keith Baker, 41, was working at the Century mine in Belmont County the morning of August 8, 2011 when he was struck in the chest by the top of a base lift jack cylinder. He had been working on the No. 22 shield of the mine’s 11 West longwall.

“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 agency said in its just-released report.

There were no witnesses to the accident.

In its probe of the fatal accident, MSHA inspectors noted they found an excessive amount of overtravel in the cylinder’s piston stroke, and a representative number of base lift jacks were inspected along the longwall for comparative damage and condition.

The mine operator, MSHA said, agreed to complete the testing of the remainder of the base lift jacks and also develop safety precautions to prevent a re-occurrence. On August 10, 130 jacks were removed from service or repaired following that review.

“The mine operator failed to assure the safe operating condition of the longwall shields operating on the 11 West longwall,” MSHA concluded in its investigative report.

“[M]odification of the base lift … did not adhere to the original cylinder design.”

Specifically, it said, a base lift cylinder on the number 22 shield had a rod stroke that exceeded the piston’s available travel in the hydraulic cylinder.

As such, the road’s end was exposed to upward movement of relay bars when the shields went into push mode, when the shields were advanced, or when any similar movement of the conveyor away from the face occurred.

“This action can impact the structure of the cylinder physically or intensify the internal pressure of the cylinder beyond the designed working pressure,” investigators concluded.

“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.”

To rectify what MSHA found to be the accident’s root cause, the operator evaluated the cylinders and has since designed and installed hydraulic protection to limit the pressure in the base lift cylinder hydraulic circuit.

All of the design and modifications were reviewed by a professional engineer, the agency noted.

The mine developed safety precautions to prevent a future similar accident and also trained the affected miners on the safety precautions.

As a result of the federal probe, Murray Energy’s Century was issued a 104(a) citation for a violation of CFR 30, Section 75.1725(a).

The Century longwall mine near Beallsville employs 518 persons, 467 underground, and produces about 22,000 tons a day.

A regular safety and health inspection was ongoing at the time of the accident. The previous MSHA E01 inspection was completed June 29, 2011.

The mine’s non fatal days lost incident rate for the first quarter of 2011 was 0.67, versus the national rate of 3.21.