Two maintenance HVAC technicians unbolted and pulled away the lower portion of the upper cover in order to access the belts in the double squirrel cage unit. They observed that the shaft and fan were "wind-milling." In order to slow down and stop the rotating unit, the technicians attempted to stop the fan from rotating using makeshift tools. While performing this activity the shaft began "wind-milling" again and a technician's hand was pulled into the shaft resulting in amputation of the right index finger tip.
The technicians did not consider closing the associated back draft damper which was open and would have limited the rotation of the fan element.
What Can We Learn?
A Questioning Attitude by either worker would have prompted them to ask “why is the fan wind-milling”.
A Self Check would have prompted a review of the step when the fan continued to wind-mill after their attempt to stop it.
Both workers displayed Overconfidence in their ability to control the fan with makeshift tools.
The rotating equipment created a Physical Environment trap that needed to be mitigated prior to performing the task.
Ask the Right Questions