U.S. Department of Labor

Mine Safety and Health Administration 4015 Wilson Boulevard Arlington, Virginia 22203-1984

ISSUE DATE: September 1, 1998

PROGRAM INFORMATION BULLETIN NO. P98-22

FROM:          MARVIN W. NICHOLS, JR.
                      Administrator
                             for Coal Mine Safety and Health


SUBJECT:      Hazard Potential To Roof Bolting Machine
                       Operators and Helpers

Scope
This information bulletin applies to underground coal miners, operators of underground coal mines, and Coal Mine Safety and Health (CMS&H) personnel.

Purpose
This bulletin alerts the coal mining industry and CMS&H personnel to a potential hazard to roof bolting machine operators and helpers. The centrifugal force generated during the high speed rotation of free standing drill steel will result in the drill steel bending to a hazardous angle. This hazard was discovered during a recent accident investigation.

Information
As part of a recent accident investigation, testing was conducted to determine what effect high speed rotation would have on drill steel when allowed to rotate freely, standing in a drill head twist-lock chuck, outside of the drill hole. Four different 4-foot sections of 1 1/8 inch diameter steel were tested: two remanufactured steels, an unused new steel, and a used steel. The tests showed that as the RPM was increased, the centrifugal force induced by the rotation caused the drill steel to bend. As the RPM was increased, the drill steel tip would move in an ever increasing rotational arc to approximately 740 RPM. At 740 RPM the steel would permanently deform (bend) near the chuck to an angle of about 30 degrees (see attached photograph). The deformation was nearly identical in all four drill steels tested.

All roof bolting machine operators and helpers should be advised of this hazard potential and instructed to be sure the drill steel has stopped rotating before completely withdrawing the steel from the drill hole.

Background
A roof bolting machine operator was critically injured while withdrawing a drill steel from a drilled hole. The machine operator was violently struck in the head by the drill steel. Investigators observed the drill steel had bent to an angle of about 30 degrees which resulted in a whipping action at the tip of the steel.

Authority
The Federal Mine Safety and Health Act of 1977, Section 103(a).

Issuing Office and Contact Person
Coal Mine Safety and Health, Office of the Administrator Allyn Davis, (703) 235-1915; or Ernest Teaster, (703) 235-1140

Distribution
MSHA Program Policy Manual Holders
Underground Coal Mine Operators
Coal Special Interest Groups

Attachment

Back to Top	www.msha.gov	www.dol.gov
Frequently Asked Questions | Freedom of Information Act | Customer Survey Accessibility | Privacy & Security Statement | Disclaimers
Mine Safety and Health Administration (MSHA) 1100 Wilson Boulevard, 21st Floor Arlington, VA 22209-3939	Phone:    (202) 693-9400 Fax-on-demand: (202) 693-9401 Technical (web) questions: Webmaster On-line Filing Help: MSHAhelpdesk@dol.gov or call (877) 778-6055 Contact Us