During work on Tech Area I Laboratory equipment in August 2005, an electrical safety interlock was defeated, and left in a defeated condition for approximately four months. The defeated interlock was discovered when the equipment manufacturer's representative was brought on site for further diagnostics. Subsequently, the equipment was returned to a safe condition. A Causal Analysis Team will perform a review of this event.
This incident underscores the importance of performing zero-energy verification on each phase at the wire termination.
At Lawrence Livermore National Laboratory, a safety switch in service on a 480-volt, 160-amp heater/blower system failed to operate properly when switched to the "off" position. The switch failed such that two of the three blade switches were still closed and electrically connected. Only one of the three blades properly disconnected as expected, although the handle operated normally and there was no evidence of switch failure observed by the operator.
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