An operator reports a high level alarm (LAH-12) displayed at the control room for the last 13 hours of operation, in this sour water stripping tower unit (where sulfide-laden water is “stripped” of sulfur compounds by the addition of hot steam). Over that time period, the sightglass (level gauge LG-11) has shown the liquid level inside vessel C-406 drifting between 2 feet 5 inches and 2 feet 8 inches:
Identify the likelihood of each specified fault in this process. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for all measurements and symptoms in this process.