On April 8, 2016, MSHA notified underground coal mine operators of an interference problem between proximity detection systems (PDS) and respirable dust sampling devices when both devices are in use at the same time. MSHA has observed that dust sampling devices function properly. Mine operators who do not have proximity detection systems are not affected by this notice; dust sampling must continue at these mines (and, as will be discussed, at all underground coal mines) as required by MSHA’s final respirable coal mine dust rule.
MSHA’s final rule on Proximity Detection Systems for Continuous Mining Machines in Underground Coal Mines requires that proximity detection systems be installed to prevent interference that adversely affects performance of any electrical system. 30 C.F.R § 75.1732(b)(5).
While investigating reports of interference between PDS and respirable coal mine dust sampling devices, MSHA found that other devices or equipment may also cause electromagnetic interference that adversely affects the performance of the PDS. Devices, other than respirable coal mine dust sampling devices, that can cause interference with a PDS include gas detectors, hand-held radios, and trailing cables. Interference occurs when these devices are placed within several inches of the miner-wearable component of the PDS. This interference can disable the protections designed to stop the machine before a miner is contacted. MSHA is working with mine operators, manufacturers, and the National Institute for Occupational Safety and Health (NIOSH) to identify solutions.
Due to this additional information and to assure maximum protection for miners, MSHA is notifying mine operators with a PDS installed on any equipment that they should identify sources of any electromagnetic interference that adversely affect the performance of the PDS. In making this determination, mine operators should place the miner-wearable component immediately adjacent or as near as possible to electrical devices or equipment used or worn by miners which may include, but are not limited to:
- Gas detectors
- Communication devices
- Respirable dust sampling devices
- Laser range finders
- Trailing cables
- Variable Frequency Drives
If a mine operator finds that any device or equipment interferes with the proper functioning of the PDS, the mine operator should notify the PDS manufacturer and follow the manufacturer’s best practices to address the interference problem. The PDS should not be used until the interference problem is corrected. In addition, mine operators must continue to comply with existing requirements necessary to protect the safety and health of miners such as respirable dust sampling, communication and tracking, methane monitoring, and other relevant standards while the interference problem is corrected.
Mine operators must assure that miners are trained to follow safe work practices around mining equipment, including staying out of the red zone and being alert to the possibility of any interference issues. Training should reinforce the safety principle that, as with any technology, a PDS is intended to provide an added margin of safety for miners and does not replace longstanding safe work practices. Operating equipment with a PDS that is affected by interferences can give a miner a false sense of security. MSHA is continuing to work with its stakeholders to address the interference issue and will provide further communications as appropriate.
If you have questions or concerns, please contact your local district office.