Explosion in an electrostatic precipitator

An explosion occurred in an electrostatic precipitator whilst it was being accessed for maintenance.
The explosion caused an inspection hatch cover, which had been unbolted, to be blown off and created a fireball which engulfed an electrician causing minor injuries.

The sequencing of the shutdown tasks was fundamentally flawed as the spades were introduced immediately prior to the opening up of the vessel, after the 1.5 day steam purge and 3.5h cooling period.

Leakage past the inlet gate valves would allow a flammable atmosphere to develop as the main constituents of coke oven gas are hydrogen, methane, carbon monoxide etc.
The exact source of ignition cannot be established, the probable source was pyrophoric deposits in the vessel.

INITIATING cause: probably leakage of the combustible gas mixture (hydrogen, methane, carbon monoxide) ignited by pyrophoric deposits.
ROOT cause: mistakes in the maintenance procedure, specifically lack of gas detection step.

Electrostatic precipitator of a coking plant

The facility was under maintenance.

it seems that the truck was left burning.