The agency had initially set a November 14 deadline for comments from interested industry parties but that deadline has now been set for November 28. The extension was filed with a viewable notice in the Federal Register Tuesday morning.

The rule, published in the Federal Register on August 31, would strengthen miner protection when working near CM units by reducing the potential for crushing, pinning and striking hazards and incidents.

According to federal data, 30 miners died and another 220 were injured between 1984 and 2010 as a result of becoming crushed, pinned or struck by continuous miners. Two more deaths occurred in 2010 and another has already been recorded this year.

These injuries and fatalities, MSHA noted, could have been prevented with the use of a proximity detection system.

Public hearings regarding the proposal were held October 18 in Denver, Colorado; Charleston, West Virginia on October 20, Washington, Pennsylvania on October 25; and October 27 in Evansville, Indiana.

Plans for the proposed rule were initiated in February 2011, when federal officials published a request for information asking the mining community for input to determine the technological and economic feasibility, training needs and benefits of any suggested regulatory action.

“In response to the RFI, MSHA received stakeholder input to advance the rulemaking process,” assistant secretary of labor for mine safety and health Joseph Main said.

“We know that the technology exists for proximity detection. Some underground coal mine operators already are using it and we know that it saves lives.”

Under the proposal, US underground coal mine operators would be required to equip existing continuous mining machines with a proximity detection system within 18 months from the publication date of a final rule. This, officials noted, would allow operators time to have equipment retrofitted as well as to train miners and supervisors on the technology.

Also, new continuous mining machines would be required to be equipped with the systems within three months of the final rule’s publication date.

MSHA said full-face CMs – those which include integral roof bolting equipment and develop an entry with a single cut, therefore involving less machine movement – would not be included under the proposed rule.

If the proposal were to become law, proximity detection systems would be required to cause a continuous mining machine to stop at least three feet away from a miner unless the machine is remotely cutting coal or rock, in which case it must stop before contacting a miner.

Systems must also provide an audible or visual warning signal when the machine is five feet or closer to a miner (except while a continuous mining machine is cutting coal or rock), provide a visual signal on the machine that indicates the system is functioning properly, prevent movement of the machine if the system is not functioning properly, prevent interference with or from other electrical systems and be installed and maintained by a trained person.

While proximity detection systems are commonly used in South Africa, MSHA to date has approved only three systems for use at US operations.