Commonly referred to as stoppers or jacklegs, and often called by the brand names Gopher and Wombat, the portable drill should only be used in conjunction with automated roof supports to be in compliance with regulations, the agency said.
While MSHA said that the use of portable drills has decreased over the last few years, careful attention must still be given to their use.
"The use of portable roof drills has two major disadvantages when compared to the use of self-propelled equipment. First, portable roof drills do not have an Automated Temporary Roof Support (ATRS) system.
"In most cases, manually installed temporary roof supports are required when using portable roof drills. As a result, the lack of an ATRS system exposes individual miners to the hazard of a roof fall while installing temporary support."
Secondly, the agency said, material handling and the size, shape and weight of the associated machines must also be considered because of the role they can play in personal injury when carried from location to location along with portable drilling equipment.
It also outlined a March 29 incident where a miner using a portable roof drill following a roof collapse was injured; the worker died from his injuries on April 10.
"The victim was using the portable roof drill to install roof bolts between the tips of the longwall shields and the face in preparation for a longwall move. Although the miner was positioned under the tip of the shield, a rock fell from the roof, hitting the drill and operator, causing him to fall and strike his head, inflicting fatal injuries."
MSHA reminds mines that manufacturers of the equipment have developed roof bolters equipped with ATRS systems that are designed specifically to install roof bolts in preparation for longwall moves. The bolters, it said, are designed to be trammed with the panline just as a longwall shearer would move.
"All of these machines have some form of ATRS that will help reduce the span of unsupported roof from the shield tips to the face while bolting for longwall moves. The use of these self-propelled roof bolters diminishes the need for portable roof drills, reducing the miner's exposure to the fall of unsupported roof and material handling hazards."
