Prepared Discussion of: Comparison of Silentsteam Blowing with Conventional Steam Cycle Cleaning Methods

摘要

I would like to thank the authors for providing a stimulating paper discussing the benefits of steam cycle cleaning and an objective comparison of cleaning methods. Severe damage to main turbine stop valves and high and intermaediate pressure inlet valves and nozzles has been well documented (1). Flaking of magnetite oxides during unit startup is responsible for high levels of particles impacted the turbine. A field study on a 600 MW unit showed significantly higher levels of iron in the steam during startup that lasted after the full load was obtained (2). In the past, steam piping assessments have required removal of tube samples to analyze for deposit buildup and evidence of magnetite exfoliation. Recently ultrasonic testing (UT) has been developed to measure magnetite oxide thickness. Periodic sampling of superheat/reheat piping has been used to confirm the UT results and identify excessive oxide levels.