(148d) Causes and Future Prevention of a Firebox Overpressure Event

During normal cracking operation of an ethylene furnace in one of Saudi Chevron Phillips plants, the induced draft inlet damper suddenly went to the closed state at full firing rate. There was no furnace trip for this condition by design. This led to high firebox pressure with hot flue gas coming out of the peep doors and resulted in damage to the firebox structure and surrounding instrument cabling and lighting. This paper will go through the details of the incident, the learnings from the incident investigation and some corrective actions implemented.