INCIDENT
For better or worse, the existing supporting piping and ancillary equipment was left in place. One element that had been a problem for some time was the vent condenser piping on top of the vessel. The decomposition reaction would generate flammable gas that would pass through the vent condenser to the flare system.
The problem was solid material in the gas stream that tended to deposit in the piping. Operators had to add a steam line to the pipe to clear obstructions when gas flow restrictions caused pressure in the vessel to climb beyond acceptable levels. When the two operators who were killed went to the vessel, the expected to find this vent was simply blocked and were going to clear it.