I would like share with this forum our recent incident in the DCU.
It happened when we shut down our DCU for cleaning the overhead line of the coke drum.
It happened when the contract worker was about finished with the cleaning work. The 4″ HCGO quench oil line was wating for him to connect to the 48″ overhead line. He stood in front of the 4″ opening nozzle on the overhead line.
Then, a sudden steam blow from the 4″ nozzle on the overhead line (48″) topple and scald the worker.
What is the root cause of this incident?
Why does steam still exist in the coke drum after three days of cleaning work?
Following is our inferential conclusion:
In order to avoid the plugging problem of the switch valve and isolation MOV, we do not stop the steam injection for these valves.
The injected steam condensed and accumulated backwardly in the overhead line.
As the overhead line is well insulated, the condensed liquid actually is a saturated boiling liquid. It could blow out at any time, especially when the liquid level is high.