The alert, issued June 8, highlighted an accident with injury on February 11 involving a scoop with a PDS tramming through a line curtain toward a miner located opposite the curtain.

“The miner was wearing a miner wearable component (MWC) and was on his knees, in the process of ‘spadding down’ the curtain,” MSHA said. “The scoop bucket was in the raised position above the miner, who was able to roll out of the way without being contacted. The scoop operator heard the miner and stopped the scoop.”

The miner, who received a broken leg in the incident, was taken to the hospital for treatment.

Also, on May 19, MSHA officials were visiting another operation where a similar PDS was installed on a continuous mining machine, and it observed erratic operation of the PDS.

“Shutdown zones were found to be set too close to the machine,” agency staff said. “The machine-mounted components would only indicate a warning zone infraction when the MWC was properly indicating that it was within the shutdown zone. This allowed the machine to move.”

As a result of both of these events, MSHA issued best practices for mines to prevent future serious injuries as well as fatalities. At the top of that list: ensuring all PDS are installed and maintained in proper operating condition by a trained person.

Regulators also have stressed pre-operational checks to the specifications set by the systems’ manufacturers, as well as the periodic updating of PDS software.

All warning and shutdown zones should be set by the system’s maker and should be specific to the mine and its company policy. Additionally, both the MWC and the machine mounted components (MMC) should indicate corresponding warning and shutdown zone status.

A video on general inspection procedures for proximity detection devices can be found here.