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Detailed review of a significant arc flash incident at Penhorwood Mine Site in Timmins, Ontario, resulting in equipment damage, fire, and dangers to personnel.
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Significant Potential Incident Arc Flash Timmins, Ontario, Canada March 3, 2011
SERIOUS INCIDENT REVIEW • Equipment: Motor Control Center #1 (MCC Bucket) • Time/Date: March 3, 2011 @ 13:55 • Location: Penhorwood Mine Site • Conditions: Normal Running Conditions • Workgroup: Crushing Operations • Supervisor: Gerry Rondeau • Manager: Ross Byron
Scenario description (maximum reasonable consequence) An arc flash is an electrical breakdown of the resistance of air resulting in an electric arc which can occur where there is sufficient voltage in an electrical system and a path to ground or lower voltage. An arc flash with 1000 amperes or more can cause substantial damage, fire or injury. The massive energy released in the fault rapidly vaporizes the metal conductors involved, blasting molten metal and expanding plasma outward with extreme force. A typical arc flash incident can be inconsequential but could conceivably easily produce a more severe explosion (see calculation below). The result of the violent event can cause destruction of equipment involved, fire, and injury not only to the worker but also to nearby people. In addition to the explosive blast of such a fault, destruction also arises from the intense radiant heat produced by the arc. The metal plasma arc produces tremendous amounts of light energy from far infrared to ultraviolet. Surfaces of nearby people and objects absorb this energy and are instantly heated to vaporizing temperatures. The effects of this can be seen on adjacent walls and equipment - they are often ablated and eroded from the radiant effects.
Risk Score= Consequence × Likelihood • Incident Risk Score • Likelihood = • Consequence = • Maximum Reasonable Outcome (MRO) =
What Happened • Crusher operator enters MCC#1 room to sequence start the crushing plant. • Upon starting rod deck, a loud noise is heard. • Operator investigates the noise. • Operator sees that the panel has been blackened. • He reports incident to Maintenance Supervisor. Immediate Response • Maintenance Supervisor orders to keep systems down. • Investigation begins with Electrician, Crusher Operator and HS Coordinator.
Process review (see notes) • Incident / Injury Management: • Emergency process followed ? YES • Further potential minimized ? YES • Employee statements taken ? YES • Injury management process followed ? YES • Alcohol and Drug Test conducted for all parties associated ? N/A • Notifications (Internal & Government agencies etc) carried out accurately in appropriate timeframes ? YES • Scene: • Supervisor in attendance? YES • Photos taken ? YES • Scene and evidence preserved ? YES • Persons Involved: • Inductions in place and up to date ? YES • Appropriate training up to date ? YES • Experience /familiarity with task ? YES • Pre-existing injury ? NO • Is fatigue / stress a contributing issue ? YES • Procedures, instructions & permits • Safe Work Procedure exists for task ? YES • Safe Work Procedure is adequate (covers task hazards involved) ? YES • Was the procedure for the task followed (as per procedure) ? YES • Has there been a formal risk assessment for the task? YES • Did the risk assessment identify the hazards appropriately ? YES • Permits required for task were in place (attach copy) ? YES
Process review (see notes) • Contractor Management System: • Safety expectations meeting occurred with contractor principals prior to start of contract ? N/A • Safety expectations briefing occurred with contract employees at start of contract ? N/A • Contractors procedures were reviewed for adequacy prior to commencement ? N/A • Accountability for the contractor is clear (defined contract manager) ? N/A • PPE, Tools & Conditions: • Was task specific adequate Personal Protective Equipment (PPE) worn ? YES • Tools/equipment adequate ? YES • Working conditions (light/dark/cold/hot/noise/dust/water/ice/snow) ? NO • Was there a change in task or conditions ? YES • Behaviors & risk psychology: • Was the task a “routine task” ? YES • Risk awareness issue (was the person aware of the potential for something undesirable occurring unknown before the event) ? • Risk Judgment issue (was the person aware of the potential for something undesirable to occur, but underestimated the significance of the event) ? • Risk acceptance issue (was the person aware of the consequence potential, but the positive consequences for the action outweighed the possible negative consequences) ? • Were the critical decisions made consciously or subconsciously ? YES • Do others people perform the same actions or behaviors ? NO • Typically what are the consequences for others who perform the same behaviors ? 8. Supervision: • Adequate coverage ? YES • Experienced in specific task work ? YES • Work Load of supervision ? • Had the supervisor visited the task site prior to the incident ? NO • Was a clear task assignment given for the task (CPQQRT) NO • When last had the supervisor visited the task site prior to the incident ?
Mitigating Factors (i.e. factors that prevented the outcome from being more serious) • The bucket door was closed and secured. • The MCC room is a restricted area.
Contributing / Causal Factors ( list all factors that are believed to have contributed to the incident occurring – from SnapChart TM ) • Multi tasking, electrician called away during a critical part of this task. • Electrician did not perform a Take 5 to reflect on where he was in his task once he came back.
Lessons Learned • There is a right time and a wrong time to step away from an unfinished task. • The electrician was contacted by production because a piece of equipment was causing to whole plant to be down and no production was being made. He chose to leave his task half completed and started working on the equipment. He then came back to his original task in the MCC bucket. • Upon arrival the plate was noticed to be on, so he continued from there. Never coming back to ensure the plate was indeed screwed in.
