ISSUE DATE: 4/27/2011 

PROGRAM INFORMATION BULLETIN NO. P11-30

FROM: KEVIN G. STRICKLIN

 Administrator for 

 Coal Mine Safety and Health

 LINDA F. ZEILER

 Acting Director of Technical Support

SUBJECT: Reissue of P05-19 - Use of Mobile Roof Support (MRS) Units for

 Retreat Mining

Scope

Coal mine operators, miners and miners’ representatives, and Mine Safety and Health 

Administration (MSHA) enforcement personnel should have this bulletin.

Purpose

The purpose of this Program Information Bulletin (PIB) is to inform the mining 

community of best practices for reducing accidents related to the use of Mobile Roof 

Supports (MRS) when conducting retreat mining.

Background

On January 13, 2007, two miners were fatally injured when they were struck by a roof 

fall while in the process of moving the MRS units. Since 2000, there have been 13 roof 

fall fatalities while conducting pillar mining. Five of these fatalities occurred while 

moving MRS units. All five of the MRS fatalities occurred because the MRS units were 

not being moved in the proper manner.

Information

MRS have been used in the mining industry for over 15 years, replacing roadside-radius 

(turn) and some breaker posts during pillar recovery. MRS are stronger than posts and 

can be operated remotely. These units provide greater roof support protection and 

eliminate or greatly reduce the need for miners to travel close to the pillar line to install
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posts necessary for conducting retreat mining. If used properly, the MRS units can

provide a safer form of roof support compared to installing posts during pillar mining. 

If not used properly, operating the MRS units and the removal of the units from the 

active pillaring area can be extremely hazardous.

The following Best Practices have been identified as having the potential for preventing 

accidents, injuries and fatalities when using MRS units as roof support during pillar 

mining:

• Onboard, manually-operated controls should be “locked out” or under a “bolted 

down” cover plate to restrict their usage to maintenance and troubleshooting 

purposes only. 

Because onboard, manual controls (sometimes referred to as manual overrides) are intended 

for maintenance and troubleshooting only, their use should be restricted to an outby area, 

between solid coal pillars. To prevent unintended use in an active pillaring area, these 

controls should be “locked out” or under a “bolted down” cover plate. Information on lockout devices or bolt down cover plates for the manual controls should be obtained from the 

MRS manufacturers. Even in an outby area, temporary supports should be installed before 

pressurizing or de-pressurizing the units with the manual controls. Any material, such as 

thin pieces of rock, on top of the MRS that poses a fall hazard should either be removed or 

secured against movement prior to manual operation. Also, any roof damage incurred as a 

result of pressurizing and depressurizing the MRS unit should be addressed before removal 

of the temporary supports.

 

• Umbilical remote controls should only be used for tramming the MRS units 

between solid coal pillars. 

Umbilical remote control requires the operator to physically “plug-in” or retrieve the 

pendent control on the MRS unit. This connection should not be made until the MRS has 

been moved via the radio remote control into a safe location completely out of the active 

intersection following the last lift. Once away from the active pillaring area, the pendent can 

be safely plugged in or retrieved and used for tramming the MRS to the next pillaring 

location. However, the operator should utilize sufficient pendent cable length to maintain a 

safe operating distance and should never use the umbilically controlled unit to displace 

breaker timbers.

• When tramming the MRS units, all personnel should be clear of pinch points

between the units and between the units and the rib.

Under no circumstances should anyone, including the MRS operator, be permitted beside or 

within the turning radius of the MRS units when they are being moved.

• When setting and lowering the MRS, the operator should be positioned in a safe 

location, at least 20 feet away from the units.

A greater distance may be required depending on the MRS working height, immediate roof 

conditions, the amount of accumulated debris atop the units, or the lift being mined. For 
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example, during mining of the last lift the MRS operator should remain out of the active 

intersection. During the setting and lowering process, all personnel should be positioned 

outby the MRS operator. This includes personnel assisting the MRS operator by monitoring 

the pressure gages. 

• While in the active pillaring area, the MRS units should be operated in pairs, 

using the radio remote control.

When moving the mobile roof supports from pillar lift to pillar lift, each MRS should be 

advanced sequentially such that one unit will never be offset more than one half the length of 

its companion unit. The MRS units should be advanced immediately after each lift, and 

should be kept as close as practical to the continuous mining machine during each lift. Upon 

completion of mining in a given pillar, the MRS units should be moved sequentially until 

they are between solid coal pillars. During this process, at least one unit will be pressurized 

against the roof at all times. 

• While pillaring, MRS pressure gages or colored area lights should be used to 

monitor roof loading.

Gages or load indicating lights should be observed to first ensure that the MRS units have 

been properly set against the mine roof. (Mine management should determine a pressure 

level for setting the MRS units). Gages or lights are to be continually observed to ascertain 

if pillaring operations need to be stopped in a specific lift. These gages should be large 

enough to allow remote monitoring. Mining should cease in a lift either at the MRS yield 

pressure or at some lower level dictated by roof conditions (determined by mine 

management). Pillaring operations should also cease if neither the gages nor lights are

operational. 

• Install the MRS cables with break-away cable hangers so that the cable can be 

pulled down remotely.

Use of such devices will prevent personnel exposure to hazardous roof adjacent to the MRS 

units. No hangers should be retrieved from the blocks being pillared.

• Precautions should be included in the Roof Control Plan for supporting the roof 

in the event one of the MRS units becomes inoperative.

Depending on mine-specific circumstances, the roof conrol plan may permit the repositioning 

of one of four units to maintain a pair in the more critical area adjacent to the gob. For 

example, if an MRS unit in the straight becomes inoperative, an outby MRS from the 

crosscut could replace it. Wood supports may provide an acceptable replacement for an MRS 

unit in a breaker setting but should not be used in conjunction with an MRS unit in a radius 

turn post application. It is not advisable to simply substitute wood supports for an MRS and 

continue the same cut plan/lift sequence. 
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• When parking the MRS units for an extended period of time, they should be 

positioned between solid coal pillars outby the active pillaring area. The units 

should remain in contact with the roof to prevent dynamic loading in the event of 

a roof fall.

Pressurizing the MRS against the roof in areas where personnel will later be working or 

traveling may create a hazard by damaging the roof or permanent roof support. Therefore, in 

this circumstance, the MRS units should be pressurized with minimal force (just against the 

roof). Also, the radio remote control units should be stored in a safe area away from the 

machines.

• The roof control plan should include a method for the safe retrieval of a disabled 

or entrapped MRS. 

Train miners before utilizing the plan.

Authority

The Federal Mine Safety and Health Act of 1977, as amended, 30 U.S.C. §801 et seq.; 30 

C.F.R. § 75.207.

Internet Availability

This information bulletin may be viewed on the World Wide Web by accessing the 

MSHA Home Page at (www.msha.gov) and then choosing “Rules and 

Regulations/Compliance Assistance Information/Program Information Bulletins.”

Issuing Office and Contact Person(s)

Coal Mine Safety and Health, Division of Safety

Johnny P. Calhoun, (202) 693-9507

E-mail: calhoun.johnny@dol.gov

Technical Support, Pittsburgh Safety and Health Technology Center

Joseph A. Cybulski, (412) 386-6920

E-mail: cybulski.joseph@dol.gov

Distribution

MSHA Program Policy Manual Holders

Underground Coal Mine Operators

Coal Special Interest Groups