Smoke and heat radiation occurred in a lead-acid battery manufacturing plant. An oven for drying electrodes coated with a mixture of lead oxide and minium had been shut down for a month at the time of its restart.
An employee noticed the release of smoke and sounded the alarm. The General Services Manager disconnected the workshop’s gas and electrical supplies. The emergency services were alerted as a precautionary measure. They checked that the burner was secured and that the air circulation temperature in the combustion chamber had returned to an acceptable level. As a precautionary measure, traffic in the street in front of the site was stopped for 1 hour. From the environmental perspective, the consequences were limited to the release of smoke inside the workshop for 1 hour.
Three of the five ovens in the workshop were returned to service in the afternoon. The fourth oven underwent an operational verification of the safety temperature sensors before being restarted a few days later. The incriminated oven was switched off for a week, and its power (gas and electricity) was locked out.
The causal analysis revealed that the origin was an uncontrolled rise in the oven’s temperature due to:
- a malfunction of the safety temperature sensor located in the oven’s air supply duct;
- a malfunction of the servomotor controlling the combustion chamber burner;
- the combustion chamber fan was switched off when the emergency stop was activated when the smoke appeared. This did not dissipate the energy that had accumulated in the oven.
The operator decided to replace the burner and combustion chamber safety sensors on ovens 1 and 2. Smoke detectors, slaved to the fire panel and gas disconnection system, were installed. Instructions were developed for intervention operations and the disconnection of power sources in the event of a fire. Technicians were given specialised training in its application. The burner on the incriminated oven was inspected and the servomotor was repaired by adjusting the installed capacity.
