Chemistry and Mechanical Field Assessment Actions for Effective Flow-Accelerated Corrosion Minimisation in Heat Recovery Steam Generators

摘要

The existence or otherwise of flow-accelerated corrosion (FAC) in a heat recovery steam generator is often determined via a field assessment during a plant outage. For a FAC field assessment to be successful pre-reviews of the cycle chemistry and mechanical aspects of the FAC risk factors for a heat recovery steam generator (HRSG) need to be undertaken. This allows for the production of a detailed prioritised list of inspection locations for the HRSG for visual and borescope inspections and for ultrasonic thickness measurements. It also includes an assessment of the effectiveness or otherwise of the cycle chemistry program in relation to FAC minimisation. The use of a prioritised list of inspection locations increases the probability of the early detection of FAC (or the confirmation that FAC is not occurring) so that remedial actions such as cycle chemistry optimisation and engineering modifications to the HRSG can be undertaken to minimise the risk of future FAC failures occurring. The effective management of FAC is a continuous process requiring ongoing cycle chemistry reviews and mechanical FAC field assessments.