To prepare for CK-2 stoppage, production was properly shut down
(14:05). After the heater for the exhaust gas piping connected to the
pre-carbonization furnace (hereinafter referred to as “PCB”) was turned off
(14:12), four day-shift workers started cleaning the inside of PCB exhaust
gas header to remove adhering deposits (hereinafter referred to as
“scale”) according to the machine stoppage plan (made in a preparation
meeting for the machine stoppage and approved by the section manager
and team leader) (14:45).
Meanwhile, a DCS monitor (one not of the above-mentioned four
workers) noticed unusual temperature rise in the PCB exhaust gas piping
and reported it to the group leader (14:55).
A maintenance engineer for the electrical system, who was in the
process of rechecking the site, found smoking around the area where the
piping passes through the wall of the plant building (15:23). The
maintenance engineer together with the day-shift workers and the group
leader, who were summoned to the site, extinguished the smoke by using
two fire extinguishers (15:25 – 15:50).