Hinged or Unhinged: How to Operate Equiipment Based on Lab Studies and Incident Investigations

Arc flash and arc blast hazards have two practical considerations from a hazard assessment perspective. First, is the work practice consideration and the second is the risk level consideration. The authors review one scenario using knowledge from recent lab studies in arc blast in simulated motor control center box configurations to provide a practical answer to the question of where to stand. Common practice and common wisdom is to stand to the side of equipment when operating. The oldest idea was to stand using the “left hand” rule. This “rule” assumed that all workers were right handed and that all disconnects were operated from the right side thus the worker was outside the line of fire with no body parts across the door. Some began to believe with the raise concern of arc flash that the worker location should be on the hinged side even if that meant reaching across the door. This paper addresses the thought process from real incident experience and from lab testing for arc blast and arc flash exposure.