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Flow Accelerated Corrosion
Flow Accelerated Corrosion (FAC) is the dissolution of the normally protective oxide layer on the inside surface of carbon and low alloy steel piping. The iron oxides that naturally form on the exposed surface of the pipe are removed by mass transfer to the de-oxygenated water flowing over the pipe inside surface at elevated temperatures.
This results in thinning of the pipe wall, which in turn can lead to leaks and potential catastrophic ruptures that adversely impact both personnel safety and plant reliability. FAC process is influenced by the flow rate, pH, oxygen content, temperature and geometry of the piping system. There is a significant temperature and oxygen sensitivity. FAC is most severe at approximately 300oF—far below where many fossil plant piping programs investigate piping integrity. This phenomenon can also cause degradation of other plant equipment such as heater shells, tanks, and other vessels.
As the leading provider of FAC solutions, Altran has evaluated more than half of the nuclear plants and over 150 fossil plants in the United States.
Highly publicized accidents and other less well-known incidents have attracted the attention of utilities, industry groups such as EPRI, as well as regulatory bodies. In 1996, OSHA issued a hazards bulletin discussing FAC in Feedwater piping systems. In recent years, the insurance industry has become interested in the economic impact of FAC in terms of plant downtime, equipment loss, and personnel hazards.
Altran has been involved in addressing FAC since it was first identified as a major issue in the late '80s. Altran offers a methodical approach. The objectives are to minimize cost to the utility and to help ensure that worn components do not escape detection. Altran engineers understand the plant operations and work closely with plant personnel, soliciting input and valuable insights from system engineers, operations, maintenance and NDE personnel. Our approach and experience has enabled us to be successful in identifying locations of significant thinning.
Altran offers a comprehensive approach to assist the utilities with mitigating FAC damage to the plant’s susceptible systems and components. We can show you how to measure the effectiveness of your FAC programs to assure plant safety and reliability.
To identify susceptible systems and components, Altran uses a combination of analytical modeling software such as EPRI's CHECWORKSTM or CHECUPTM, our utility experience combined with engineering design-based staff, and our evaluation methodology. Within the framework of this approach, we offer the following services:
Altran FAC Services
- Plant FAC System Susceptibility Evaluation (SSE).
- EPRI CHECUPTM modeling and model updates.
- EPRI CHECWORKSTM Steam/FeedwaterApplication (SFA) modeling and model updates.
- Development of risk ranking methodology based on susceptibility and consequence of failure.
- Development of Susceptible Non-Modeled (SNM) programs.
- Experienced based evaluations of susceptible piping systems.
- Inspection location selection.
- On-site outage support for FAC activities including Ultrasonic Testing data analysis and component structural qualification, and remaining life evaluations.
- Structural qualification and remaining life predictions.
- Water chemistry studies / material improvement engineering.
- Self-assessments/independent reviews of existing FAC Programs.
Altran is the industry leader in the field of Flow Accelerated Corrosion and has performed program development/enhancement, outage support, and independent reviews for over 150 different nuclear and fossil units.