During routine facility maintenance of an automatic battery charging system, 6 of 27 nickel cadmium batteries being reinstalled exploded.
Inadequate work procedures in that a probable cause was ignition of accumulated hydrogen gas by a spark generated during the replacement work, and inadequate ventilation of the battery area; a second probable cause was stopped up vent caps, resulting from contaminated electrolyte, which permitted hydrogen pressure build up to an explosive force in the 6 batteries.
Facilities housing battery charging systems need to ensure the ventilation systems are operational, and delivering enough outdoor air to properly ventilate the enclosure.
Operators need to be aware of safe practices and proper battery charging instructions for the nickel cadmium batteries they work on. This information needs to be disseminated to all of the technicians working on the batteries and battery charging systems.
Adequate ventilation of battery charging facilities is addressed in the Lessons Learned Corner on this website.