Description of Incident
A field flow rate trial to an incinerator at a process plant was initiated, increasing the flow rate from 40 million standard cubic feet per day to 44 million standard cubic feet per day. The trial support team engaged with the shift team on duty and with Control Room Operators to collect data on the trial.
11:00 a rise in incinerator temperature (temperature excursion) was noted by a Control Room Operator, this was followed immediately by flame failure detection from 2 of the 3 operational burners. Inhibits were applied.
- On local inspection, the presence of liquids around the incinerator led to drainage to closed drains, via the incinerator bund.
- The source of the liquids (which were miscellaneous streams feed to the incinerator including condensate) was identified and isolated until the flow of liquid gradually reduced to a stop.
13:15 three shift instrument technicians requested permission to inspect igniters.
14:00 Incinerator restarted.
14:45 the miscellaneous streams feed to the incinerator was opened. A second temperature excursion
occurred with smoke and flame present emerging from the top of the incinerator stack.
- Miscellaneous streams were immediately isolated and the flame and smoke stopped.
14:40 liquids containing high levels of condensate again drained down into the incinerator bund, where the shift instrument technicians were standing.
- Due to the temperature excursion at 14:45 it is highly likely that the adjacent equipment was above the auto-ignition temperature of the condensate (~260 Deg C), there was no ignition.
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