Tag Archives: MSHA

Martin Engineering on controlling belt conveyor dust at the source

Bulk handling, Mineral processing, Mining equipment, Mining services, , ,

The conveyor technology experts at Martin Engineering are responding to the US Mining Safety and Health Administration’s (MSHA) new dust emissions final rule by offering simple, make-sense solutions for staying compliant.

Often, these rule changes cause a ripple effect internationally and serve as a template for similar policies worldwide. Martin engineers have dedicated years to reducing conveyor-borne dust by designing accessories and engineered solutions that improve workplace safety and production efficiency. In this article, Martin Engineering experts offer field-tested advice and methods that have delivered measurable results for mines and bulk handlers around the world for decades.

On August 1, 2024, the MSHA final rules came into effect. MSHA measures the dust personal exposure level (PEL) in a time weighted average (TWA) by a personal dust monitor carried by trained workers throughout their eight-hour shift. The volume is measured in micrograms (μg) in cubic meters (cubic metres). The final rule establishes a new PEL of 50 μg/cu.m for a full-shift exposure, calculated as an 8-hour TWA, and an action level of 25 μg/cu.m. These standards also apply to miners diagnosed with or showing early signs of pneumoconiosis (aka – black lung).

MSHA mandates operators seek to install or repair equipment that offer engineering controls which control or eliminate sources of dust. This is supplemented with administrative controls (signs, policies, etc). Temporary personal protective equipment (PPE) is also required for exposures above the PEL but is not considered a long-term solution.

Conveyor loading zones

Conveyor belt dust is largely generated at the loading and discharge zones. Passive dust reduction means no machinery or electricity such as air cleaners, pumps or HAVC are needed. Passive dust reduction strategies include:

A well-designed and -sealed transfer chute offers field-tested passive dust reduction
  • Fully enclosed transfers – Completely enclosing the loading, stilling and settling zones contain the dust. Items like dust curtains and dust bags control airflow and capture dust;
  • Shorter or sloped loading – Transfer chutes that minimise the impact of cargo on the belt reduce the amount of turbulence and volume of dust within the loading zone;
  • Belt training – Belt training when entering and leaving the loading zone ensures centered belt loading and minimises material shifting. It also controls belt drift for less spillage and dust along the run; and
  • Preventing belt sag between idlers – The belt can dip slightly between idlers, creating gaps that release dust and fines. Using an impact cradle with shock-absorbent polyurethane bars reduces strain on the belt and creates an even belt plane. Cradles can extend along the entire length of the stilling zone.
Cradles reduce dust emissions by creating a sealed environment between the belt and skirting

Lower belt speeds

Many sources suggest belt speeds of 2 m/s or less for reducing dust generation. However, with lower belt speeds, the belt width must increase to convey the same tons-per-hour creating a capital cost vs operating cost dilemma. The Conveyor Equipment Manufacturers Association (CEMA) Classification and Definitions of Bulk Materials (ANSI/CEMA 550-2003) lists miscellaneous properties of bulk materials that benefit from lower belt speeds:

  • B-1 Aeration-Fluidity;
  • B-6 Degradable-Size Breakdown;
  • B-8 Dusty; and
  • B-20 Very Light and Fluffy

Idler spacing and belt tension

Managing belt tension so the sag between idlers is minimised reduces the number of escape points for fugitive spillage and dust from material trampling and splash. Splash is material spread after impact on the belt during loading. Material trampling is the particle-to-particle movement created by the change in the bulk material profile as it goes over the idlers. The higher the belt tension, the lower the trampling loss.

Similar to turbulent air caused by impact, at a critical speed, bulk material moving over idlers loses contact with the belt at the idler and is launched into the air, falling back onto the belt at a slightly lower speed and releasing dust. Keeping the belt sag to 1% between idlers is a frequent specification.

Idler spacing is critical to controlling belt sag. To reduce gaps where spillage and emissions can escape and retain an even belt profile in the loading zone, idlers should be placed as closely together as possible. Outside of the loading zone, CEMA has some recommendations based on volume and belt width.

Best practice: Enclose the system

The amount of dust that can become airborne is directly proportional to the volume and speed of the airflow through the transfer point. If the openings in the chute work are restricted to the practical minimum, the inward airflow is restricted. A useful dust control strategy is to capture the material shortly after discharge and keep the stream coalesced as tightly as possible to reduce induced air. Extend enclosures apply dual skirting to seal the enclosure and use dust curtains to control airflow and allow dust to settle back into the material stream.

Martin Engineering concludes: “Conveyor transfer points have a history of being drafted rather than designed. Design tools and material flow modelling software helps reduce dust emissions in the transfer point design phase. How the conveyor is operated and maintained also has a significant effect on dust generation and release. In initial conveyor system designs, emphasis is commonly placed on maximising production. But experts recommend operators engage in feasibility studies on how the conveyor systems create and emit dust with the goal of improving air quality and workplace safety while still increasing operational efficiency.”

MSHA looks to accelerate tech uptake in underground ‘gassy’ mines

Automation, Coal technology, Communications in mining, IoT, Mining equipment, Mining policy, Mining safety, Mining services, Mining software, , , , , , , , , , ,

The US Mine Safety and Health Administration (MSHA) has proposed revisions to its standards that could speed up the testing of electric motor-driven mine equipment and accessories in underground “gassy” mines in the country.

Under the proposed rule, during a one-year transition period, mine operators could use equipment and accessories that meet either 14 voluntary consensus standards (VCS) or the existing MSHA approval requirements.

After that period, operators would be required to use the consensus standards for equipment and accessories covered by consensus standards, MSHA said.

“The proposed rule would improve the efficiency and effectiveness of the product approval process and promote the use of innovative technologies for improved mine safety and health,” it added.

Rich Nolan, National Mining Association president and CEO, said the industry had long advocated for updates to the standards.

“Current standards have resulted in a backlog of superior technologies awaiting MSHA approvals, even as those technologies are being used successfully in mines elsewhere around the world or by other occupations in the US,” he said.

“The proposed updates will allow us to provide the best available protection for miners through a more efficient and effective process.

“Put simply, this translates into people being safer sooner.”

The 14 VCS have been developed by the American National Standards Institute, the International Society of Automation, UL LLC and the International Electrotechnical Commission. They contain general and specific construction and testing requirements for equipment used in explosive gas atmospheres, explosive dust atmospheres or hazardous locations. The agency will accept tests from these organisations in lieu of MSHA’s standards, the NMA said.

Examples of equipment covered by the regulations include portable two-way radios, remote control units, longwall mining systems, portable oxygen detectors, miner-wearable components for proximity detection systems, and powered air-purifying respirators.

“NMA and its members have tenaciously worked for this change to streamline the process by which MSHA approves and certifies equipment for use in gassy mines,” the NMA said.

(Photo courtesy of Peabody Energy Inc)

Paringa Resources in ramp-up mode at Poplar Grove coal mine

Coal technology, Energy minerals, Explosives and blasting, Mine operation news, Mineral processing, Mineral project development, Mining equipment, Mining services, , , , , , ,

Paringa Resources says production ramp-up at its Poplar Grove coal mine in the Illinois Coal Basin of Kentucky, US, has begun with the commencement of higher productivity, continuous underground mining operations.

Raw coal is being brought to the surface and has been processed by Poplar Grove’s coal handling preparation plant (CHPP), the company reported.

The commencement of mining using company-operated equipment follows approval from the US Mining Safety and Health Administration (MSHA) for the recently amended development ventilation scheme, the company said.

Mining to date at Poplar Grove has been undertaken by Paringa’s mining contractor as part of the bottom development using drill and blast techniques. These development activities have included creating a void for the installation of underground infrastructure at the bottom of the slope and a turnout area to enable the efficient movement of underground mining equipment. “This mining activity has produced raw coal which has been run through the CHPP as part of the testing and commissioning of the surface infrastructure,” Paringa said.

The mining contractor’s last piece of work is to undertake 80 ft (24 m) of development mining via drill and blast over the next month, which will occur in tandem with Paringa’s operational teams.

The next underground mining development activity is the connection of the return and intake air shafts to establish the permanent ventilation system. The connection is being made by Paringa-owned continuous miners in the coal seam, from the turnout to the base of the intake shaft and then to the base of the return shaft. This mining is producing raw coal for processing and subsequent sale to Paringa’s cornerstone customer LG&E. Paringa commenced this activity using the recently commissioned company-operated mining equipment, it said.

Paringa said: “The bottom area ground conditions look good with slightly less water and a more competent roof than was expected, although initial mining with the continuous miner has encountered an area of very hard rock which will slow advancement marginally only in the very near term.

“Once the permanent ventilation system has been established, the company will commence a typical underground room and pillar mining sequence. All other underground infrastructure, including the bottom sump, temporary slope belt tailpiece and tramp iron magnet, will be commissioned in the coming month to enable the commissioning of the ventilation system needed to begin the room and pillar mining sequence, subject to customary MSHA permanent ventilation system approvals.

The company is targeting delivery of first processed coal to LG&E in the second half of March, and has progressed initial shipments activities, including a 2019 shipping schedule and invoicing and payment procedures.

On surface, the CHPP is fully commissioned and has been run several times, processing raw material from the mine, with feed comprised of raw coal and waste rock material, Paringa said. “The proportion of raw coal in the plant feed will significantly increase in the coming weeks as mining activities continue using the company operated continuous miner in the coal seam as part of establishing the permanent ventilation system.”

Initial raw coal stockpile development has commenced using material produced by company-operated mining equipment, conveyed from the underground mine portal to the preparation plant stockpile area.

All other surface infrastructure including the workshops, bath house and river dock has been commissioned.

MSHA checking up on coal dust in US mines

Energy minerals, Mine ventilation, Mineral commodities, Mining policy, Mining safety,

The US Mine Safety and Health Administration (MSHA) is re-examining its own coal dust rule to see if it is providing miners with the necessary protection they need.

MSHA, via a request for information (RFI) in the Federal Register, is soliciting comments, data, and information from industry, labour, the US Department of Health and Human Services’ National Institute for Occupational Safety and Health, and other stakeholders related to the rule entitled ‘Lowering Miners’ Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors’.

The organisation is also seeking information and data on engineering controls and best practices that mine operators find effective to achieve and maintain required respirable coal mine dust levels, particularly those practices that can be replicated throughout mines nationwide to achieve similar results.

MSHA said: “Due to the significant latency period between exposure and disease, MSHA anticipates the agency will not likely be able to fully evaluate the health effects of the rule for a decade or more.”

David Zatezalo, MSHA Assistant Secretary, said the study had been initiated to determine if the rule was meeting its intended result, and warned mining companies that the organisation had “no intention of rolling back the protections afforded to coal miners under the final dust rule”.

The new rule, which originally took effect on August 1, 2014 and has since been updated, sought to:

  • Lower the concentration of dust in the air that miners breathe and improve sampling practices
    to better reflect actual working conditions and protect all miners from overexposure
  • Increase sampling and make use of cutting-edge technology developed for the mining environment to provide real-time information about dust levels
  • Provide a common sense phase-in over a two-year period to give the industry the time it needs to
    adjust to the new requirements, acquire monitoring equipment, and obtain compliance
    assistance from MSHA.

On August 1, 2016, Phase three of MSHA’s respirable dust rule went into effect. This saw the concentration limits for respirable coal mine dust lowered from 2 mg per m³ of dust to 1.5 mg/m³ at underground and surface coal mines, and the concentration limits for respirable coal mine dust lowered from 1 mg/m³ to 0.5 mg/m³ for intake air at underground mines and for part 90 miners (coal miners who have evidence of the development of pneumoconiosis).