Contractor Safety Share

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Worn Insulation Causes Arc!

Two employees were tasked with installing, testing, and energizing a 480V temporary power skid. They placed the temporary skid and performed an inspection that included removing the cover of the wire trough to ensure all the wires were connected.  Then they ran approximately 80 feet of wire to a junction box in the ceiling that had 3-phase 480v wires fed from an MCC, but these wires were not connected to the MCC yet.  They made up the joints in the junction box and then proceeded to the penthouse.  There, MCC1 was locked out and they landed the wires from the ceiling junction box in that bucket.  They then conducted a successful continuity check from phase to phase and phase to ground.  They removed the locks and energized the circuit.  Back at the power skid, a carpenter heard a popping sound and saw a blue spark come from the front of the panel.  He notified his foreman and the foreman notified the electrical foreman.  The carpenter foreman stationed one of his employees at the skid to keep people away until the electricians could get there and identify the problem.  MCC1 was locked out and the skid examined.  A 1/8 inch hole was observed on the cover of the wire trough.  The cover was removed and one of the splices inside the trough was found to be burnt.  It was determined that a small hole had been worn through the insulating tape that was wrapped around one of the splices.

Factors to consider at your site and/or project include, but not limited to the following:

1.      When was the last time the piece of equipment was used

2.      Develop a formal inspection process that includes a more robust testing process

3.      Are better insulating materials available to use on temporary installations

4.      Are temporary power skids properly stored and protected


Consider this example as you complete today’s work activities.

Safety Flash Action Items:
  • Date Contractor Safety Flash posted for all employees to review: _______________
  • Safety Talk meeting date: _______________
  • Full employee attendance and participation at safety meeting to review this incident (documentation required).
  • Employees understand urgency in protecting themselves and others.
  • Supervisors and Employees are clear which items shared in this Safety Flash are mandatory.
  • Employees/Supervisors will focus on recommended actions during future work activities of a similar nature.
Contract Firm Management Rep Signature____________________

THINK about the hazards associated with your particular work, and the steps that can be taken to increase safety on your job.
If you have questions about this CONTRACTOR SAFETY FLASH, please contact


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