Respirable crystalline silica at bulk material handling facilities has continued to draw attention as information about its presence and dangers increases. This is particularly true in metal and non-metal mining.
What Is Respirable Crystalline Silica?
The most common mineral in the earth’s crust is silica, which is the chemical compound silicon dioxide (SiO2). It occurs in a crystalline or non-crystalline form within rocks such as sandstone, granite, and limestone.
As silica-containing material is crushed, ground, dried, and sized during mining and production for commercial use, it generates large amounts of silica dust. Just a few leading sources of the dust can include:
- excavators, loaders, and off-road trucks
- hoppers and silos
- unpaved haul roads
- bulk material handling load zone
The finest particles of the dust (smaller than 10 μm) are known as respirable crystalline silica. The three main forms of crystalline silica are quartz, cristobalite, and tridymite. While quartz is more common, cristobalite and tridymite are more toxic.
Respirable crystalline silica creates a significant hazard because it can be breathed and travel far into the gas-exchange region of the lungs. Repeated exposure to respirable crystalline silica can cause problematic and even fatal health conditions such as lung cancer, kidney disease, and silicosis, a serious respiratory illness that can continue developing even after exposure has stopped. Early stages of silicosis also can go undetected, and there is no cure once the disease is contracted.
According to the Centers for Disease Control and Prevention, mining is among the occupations with frequent exposure to respirable crystalline silica. Just a few specific job positions with consistent exposure can include drillers, baggers, and loader and crusher operators.
Because of the potential hazards of respirable crystalline silica in metal and non-metal mining, both the Mine Safety and Health Administration (MSHA) and the Occupational Safety and Health Administration (OSHA) have established guidelines for the enforcement of employee safety at mining facilities.
What Is the MSHA Silica Enforcement Initiative?
MSHA has, like OSHA, focused on keeping respirable crystalline silica at or below defined exposure limits at metal and non-metal mining operations. Among other precautions, the administration calls upon mine operators to provide and ensure proper, well-maintained dust control.
Launched in June 2022, the MSHA Silica Enforcement Initiative helps to protect miners’ health by limiting their exposures to respirable crystalline silica. The initiative centers on four main components: inspections, sampling, compliance assistance, and miners’ rights.
MSHA will perform spot inspections for silica at mines in accordance with section 103(i) of the Federal Mine Safety and Health Act. Mines with repeated exposures to silica can be inspected every 15 days at irregular intervals.
For overexposures to particles larger than 100 μg/m3, MSHA can require abatement within a set period and a withdrawal order for unabated exposures. It also can mandate a dust control safety plan if overexposure is found.
MSHA will collect samples of respirable dust from occupations known for high exposure to respirable crystalline silica, including miners involved in overburden removal. MSHA often takes several thousand dust samples each year at U.S. mines.
MSHA will work with primary stakeholders including mining operators and personnel to establish a dust control plan for a safer working environment. It also will remain a source of safety information through its website, phone number, and Educational Field and Small Mine Services staff.
MSHA will help to educate mine workers about their right to report concerns of hazardous working conditions and their protections in doing so.
Controlling Respirable Crystalline Silica: OSHA
As MSHA continues with official measures for controlling respirable crystalline silica in mining, OSHA likewise enforces guidelines for respirable crystalline silica mitigation.
OSHA Standard 29 C.F.R. § 1910.1053 (Occupational Exposure to Respirable Crystalline Silica) requires employers to ensure that no employee is exposed to an airborne concentration of silica greater than OSHA’s permissible exposure limit (PEL) of 50 μg/m3 as an eight-hour time-weighted average concentration.
Mining operators can achieve MSHA and OSHA compliance while maintaining a safer workplace with a proper dust control system supported by complementary dust control technologies.
How to Keep Crystalline Silica Dust Under Control
A respirable crystalline silica safety program at a metal or non-metal mining operation will inform and train personnel on the dangers and risks of silica dust. The program also will include dust control systems that minimize airborne silica dust while maintaining needed mining production.
The engineers at Benetech design, procure, and construct dust control systems for metal and non-metal mining. The MaxZone Safe Plus System reinforces a comprehensive respirable crystalline silica safety program for mining operators by combining technologies that control dust where it originates.
MaxZone Safe Plus System
- MaxZone Plus®
- MaxZone® Modular Skirtboard and Belt Support
A collaboration between Benetech’s engineers and researchers at NIOSH SMRD, Benetech’s new Dustinator™ technology addresses silica dust mitigation to enhance workplace safety and meet or exceed regulatory guidelines for silica dust control.
In particular, it centers on fine particulate abatement for sandmover (and silo) operations and hydraulic fracturing sites. Belt conveyor technologies further control and mitigate silica dust issues in sand, aggregate, and mining material applications. The majority (85%) of the dust and spillage issues occur at the belt conveyor load zones.
MaxZone® Modular Skirtboard and Belt Support System
The MaxZone system provides an economic transfer point and load zone in place of a total system replacement. Its modular format contributes to properly aligned transfer point chutes, centered loading, and a dust-free load zone.
MaxZone Dust Control Components:
- Dust-tight inspection doors
- Belt guards and cleaners
- Internal wearliners
- Peaked or flat hoods
- Dust curtains
- Impact and support beds
- Skirting seal
With the system, metal and non-metal mining operators can mitigate respirable crystalline silica dust by controlling its sources, such as transfer points, carryback, impact forces, material impingement, and material entrapment.
No welding or hot work is required, and the system can be retrofitted to accommodate and enhance an existing system. Its modular design further allows for replacing components without special permits or extended shutdowns.
A flawed material transition onto the receiving belt is often caused by a misaligned transfer point chute. Improper or off-center loading can cause bulk material to load to either side of the belt, creating excess spillage and dust while also threatening to mistrack the belt. Mistracking can then damage the conveyor, cause uneven wear, make the motor work harder, and create safety issues, including respirable silica dust.
If a mining operator is contending with a problematic transfer point but cannot replace a load zone chute because of time and cost, the MaxZone® Plus system supports dust control by combating off-center conveyor loading without chute redesign.
The adjustable side kicker plates and deflector move material forward onto the conveyor belt to correctly center-load the material for a smoother transition onto the moving belt. With 6” removable side panels to suit chute configuration, the MaxZone Plus can be easily installed in an existing MaxZone system. It can be retrofitted to other containment systems as well.
Adjustments to the MaxZone Plus and replacement of wear parts also can both be accomplished externally, which mitigates confined space–entry permitting.
MiniPak Portable Dust Suppression System
Bulk material handling in mining by nature releases dust and makes it airborne. As tons of product are moved each day, operators need a dust suppression system that complements what properly designed load zone components and systems are achieving.
Benetech’s engineers make dust suppression equally effective and versatile. Unlike a system that must be installed, the MiniPak Portable Dust Suppression System is a self-contained, electricity-free enclosure that one person can manually operate.
The system allows personnel to apply Benetech’s non-flammable, non-toxic, non-explosive, and biodegradable chemical agents to silica-containing material on demand wherever needed at the mine, whether in the load zone or by a haul road. This versatility provides a strategic advantage by requiring less equipment at fewer application points for dust suppression that keeps silica dust well below mandated levels.
Benetech: Your Ally in Bulk Material Handling
Benetech takes safety at mines seriously, and our solutions for controlling respirable crystalline silica reflect our commitment to keeping employees safe while contributing to greater production. To learn more about our dust control for respirable crystalline silica mitigation at mining operations, contact us at (630) 844-1300 to speak with a specialist.
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