Inspection Detail

Inspection: 977249 - Airco Carbon Div Of Boc Inc

Inspection Information - Office: Buffalo Area Office

Investigation Summary

EMPLOYEES IN MAIN CONTROL ROOM WERE ENGAGED IN BALANCING THE PLANT'S ELECTRICAL LOAD. THIS WORK IS NORMALLY DONE BY ONE PERSON. THE PROCEDURES ARE TO REDUCE THE LOAD ON A PANEL; ELECTRICALLY TRIP THE CIRCUIT BREAKER; AND ACTIVATE THE KIRK INTERLOCK BY OPENING THE LOWER CUBICAL DOOR, PUSHING IN THE LOCK RING AND REMOVING THE KEY. ACTIVATING THE KIRK INTERLOCK MANUALLY TRIPS THE CIRCUIT BREAKER, IF FOR SOME REASON IT HAD NOT ELECTRICALLY TRIPPED OUT, AND THEN IT MECHANICALLY PREVENTS ANY FURTHER ELECTRICAL ACTIVATION OF THE BREAKER. THE KEY IS THEN PUT INTO THE LOCK ON THE OUTSIDE OF THE UPPER PANEL TO UNLOCK THE MANUALLY OPERATED PHASE CHANGE SWITCH IN A NO LOAD CONDITION. IT WAS DURING THIS PHASE CHANGE THAT THE ARC OCCURRED FROM THE 12,500-VOLT POWER SUPPLY LINE. BOTH EMPLOYEES WERE BURNED BY THE FLASH THAT CAME THROUGH EQUIPMENT OPENINGS IN THE PANEL. IT WAS DETERMINED AFTER THE ACCIDENT THAT THE KIRK INTERLOCK WAS NOT FUNCTIONING. IT WAS IMMEDIATELY ADJUSTED.

Keywords: BURN, ELECTRIC ARC, INTERLOCK, CIRCUIT BREAKER