Notice to Underground Coal Mine Operators: Proximity Detection System (PDS) Interference

Posted on: May 2, 2016

On April 8, 2016, MSHA initially notified stakeholders of a possible interference problem between the PDS and respirable dust sampling devices and that MSHA was temporarily delaying its own respirable coal mine dust sampling, and the requirement that coal mine operators conduct sampling, in areas where both the sampling device and the PDS were used at the same time. 

On April 15, 2016, MSHA notified underground coal mine operators that devices or equipment used or worn by miners, including, but not limited to: gas detectors, communication devices, respirable dust sampling devices, laser range finders, trailing cables, variable frequency drives, may cause electromagnetic interference (EMI) that adversely affects the performance of a proximity detection system (PDS).  EMI can occur when the devices or equipment are placed within several inches of the miner-wearable component of a PDS.  This EMI can disable the protections designed to stop the machine before a miner is contacted.

In the April 15th notice, MSHA advised operators to identify sources of any EMI that adversely affect the performance of a PDS.  If any device or equipment interfered with the proper functioning of the PDS, mine operators were to notify the PDS manufacturer and follow the manufacturer’s best practices to avoid the potential for EMI with other electrical systems.  Best practices include maintaining a minimum distance between the PDS miner-wearable component and other electrical devices or equipment, or using some type of shielding.  Mine operators should have completed that assessment and applied measures to prevent PDS interferences.  The PDS should not be used until operators have applied these measures.

As of today, May 2, 2016, mine operators must resume required respirable dust sampling.  Because of the temporary delay in dust sampling between April 8, 2016, and today, MSHA will take into consideration time devoted to resolving PDS interference issues in making decisions about regulatory compliance with the dust sampling requirements in the Dust Rule. MSHA has resumed its own respirable dust sampling.  Mine operators must comply with dust sampling and also must comply with other existing regulatory requirements such as gas sampling, communication and tracking, methane monitoring, and other relevant standards.

As previously noted, 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).  In the preamble to the final rule, MSHA stated that the rule requires the mine operator to evaluate the proximity detection system and other electrical systems, including blasting circuits, in the mine and take adequate steps to prevent adverse interference.  Steps could include design considerations, such as the addition of filters or providing adequate separation between electrical systems.  80 Fed. Reg. 2188, 2195 (Jan. 15, 2015).

MSHA is working with NIOSH, manufacturers, the mining industry, and others to identify additional solutions that mitigate the effect of EMI.  MSHA will keep the mining industry apprised of those solutions.

Mine operators must continue to 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.  As with any technology, a PDS provides an added margin of safety for miners and does not replace longstanding safe work practices and proper training.

Mine operators should consult their PDS manufacturer for further guidance.  For other questions or concerns, please contact Tim Watkins, Deputy Administrator for Coal Mine Safety and Health at (202) 693-9500.