Alarm root cause analysis for water level monitoring in high and low pressure heaters of power plants

In order to ensure the safe and economic operations of thermal power plants, heater water levels of high pressure (HP) and low pressure (LP) heaters are important process variables to be monitored in industrial alarm systems. This paper proposes multiple factors affecting heater water levels, and the ways performing the root cause analysis for corresponding alarms. Combining with the operating data of a large-scale 300 MW power generation unit in 2015, the number of each cause is summarized for a large amount of alarms of HP and LP water levels. The results show that excessive movements of control valves are the main causes of alarms for the #7 and #8 low pressure heaters, and changes in power generation load are the main causes of alarms in the #6 low pressure heater. Those analysis results may help operators to obtain the root causes of alarms promptly and take suitable corrective actions to remove alarms for the safe and efficient operation of the high and low pressure heaters.

I. Introduction

Regenerative feed water heating system is adopted usually in power plant to improve the economy of unit, because it can enhance the feed-water temperature of boiler, and reduce exhaust steam into condenser [1]. For regenerative heater of surface type, high water level will submerge condensing bundles, decreasing effective heat exchange area, but low or no water level will lead to entrance of part steam into next heater, excluding low pressure steam extraction and decreasing quality of steam ([2], [3]). Therefore, monitoring the water level of regenerative heater is necessary to maintain safe and economic operation.