Analyses of a Rapid loss of a Steam System During a Power Failure

摘要

NOVA Chemicals' Corunna Ethylene facility has originally been designed to ride through power failure of short duration. Operation of critical rotating equipments with steam drivers along with auto starts on other key equipment was to allow quick recovery of the plant once power supply re-established. The steam system was designed and has always been operated so that it would be unaffected by a loss of power. Power supply to the site has been proven reliable until the year 2000, where only 1 incident had been recorded over 25 years of operations. Since then, 4 occurrences of power losses have been experienced. On 2 of those 4 events, the steam system was lost on low deaerator level and a third event, which could be considered a near miss. Premature losses of the steam system caused a crash shut down of the site leading to damage on a number of process units. Analyses of the water, steam and condensate systems reveals that excessive losses of water along with the duration of the outage are the key contributor to failure of the steam system. This paper presents the key findings from the incidents analyses. Water conservation, steam shedding and proper coordination of emergency shut down activities consistent with reduced capabilities of water supply to the steam system are also discussed.