Use qualified welders. Inspect welds and metal components. Train users.
Damaged or defective welds on aerial lifts have caused two fatalities in the mining industry since 2001.
A mechanic died while being lowered in an electro-hydraulic aerial lift. A weld splice fractured on a recently repaired arm of the lift, causing the arm to strike the victim in the head (Figure 1). The weld failed because of poor weld quality from an improper repair.
A welder died while being lowered in an electro-hydraulic aerial lift when the lift arm catastrophically fractured at a critical weld connecting the arm support to its lift cylinder (Figure 2). Undetected cracks existed in the weld and the surrounding metal prior to failure.
Best Practices to Prevent the Mechanical Failure of Welded Connections
Prevent accidents by following proper welding procedures and performing regular inspections for damages or defects.
Only qualified welders should perform all welding.
Determine the service/fatigue life of mechanical systems or parts by consulting with the manufacturer.
Inspect welds following installation and repairs, and periodically during service life.
Train users in the proper operation of lifts – including not exceeding their design capacity.
Routinely examine metal components for signs of weakness, corrosion, fatigue cracks, bends, buckling, deflection, missing connectors, etc.
Use nondestructive test methods to detect cracks that may be indistinguishable to the eye.
Take cracked mechanical components out of service immediately. Small cracks can quickly grow and lead to catastrophic fracture.
Prompted by a fire on a diesel-powered water car in May, the Mine Safety and Health Administration has issued a safety alert addressing fire hazards associated with diesel equipment in underground mines.
According to MSHA, the incident occurred when the vehicle’s automatic and manually activated fire suppression systems failed to function properly. The vehicle had been converted to a water transport vehicle from a personnel carrier. The systems malfunctioned because an actuation hose had been damaged as a result of routing through the engine compartment. Crews extinguished the blaze using a fire hose from the water system near the conveyor belt drive. No miners were injured in the incident.
MSHA offers best practices for fire safety awareness. Among them:
Conduct thorough preoperational inspections and perform required maintenance. Identify and correct obvious fire hazards such as accumulations of combustible fluids or grease, leaking hydraulic and coolant hoses or fuel supply lines, and cracked or blistered flanges on hydraulic and coolant hoses and connections at the hydraulic pump.
Install audible and visible alarms in the cab to alert equipment operators to fires.
Ensure proper design, installation and maintenance of manual and automatic fire suppression systems. Follow National Fire Protection Association standards for dry and wet chemical extinguishing systems – NFPA 17 and 17A, respectively – as well as manufacturer recommendations.
Route actuation and expellant gas hoses away from the engine compartment, heat sources, electrical wires and moving parts, or ensure they have a heat-resistant fire jacket.
Ensure actuation hoses mounted to removable covers are secured in such a manner to prevent damage from wear and potential contact with heat sources.
Electricity has killed three people in the mining industry since August 7, 2019.
An electrician contacted an energized component of a 4,160 VAC electrical circuit while adjusting the linkage between the disconnect lever and the internal components of the panel that supplied power to the plant feed belt motors.
A contract electrician contacted an energized 120 VAC conductor while working inside a fire suppression system’s electrical panel.
An electrician contacted an exposed energized connector while troubleshooting a 995 VAC flooded bed scrubber motor circuit on-board a continuous mining machine.
Prevent Electrical Accidents:
Lockout/Tagout circuits before working on electrical equipment.
Don’t rush. Never work alone. Talk to coworkers and confirm your plan is safe.
Identify and control all hazardous energy sources before conducting any task and follow safe work procedures.
Open the circuit breaker or load break switch to de-energize the incoming power cables or conductors
Open the visual disconnect to confirm incoming power is off
Lockout/Tagout the visual disconnect
Ground the de-energized conductors
Train miners on equipment they may use.
Electricians must know how to de-energize and disconnect electrical systems and equipment.
Always troubleshoot without power first.
If you must troubleshoot an energized circuit, useproperly rated personal protective equipment to prevent hazards. For example, use electrically rated gloves, insulated blankets or mats, and polycarbonate barriers to prevent accidental contact with energized components.
The mining industry has experienced three electrical fatalities since August 7, 2019. The first fatal accident occurred when a 42-year-old electrician with 15 years of mining experience contacted an energized component of a 4,160 VAC electrical circuit. The victim was in the preparation plant’s Motor Control Center (MCC) adjusting the linkage between the disconnect lever and the internal components of the 4,160 VAC panel that supplied power to the plant feed belt motors. Read more»