US fossil FAC work and Nuclear Chekworks Compatibility
Flow Accelerated Corrosion (FAC) Inspection using a modern digital portable C-scan Ultrasonic system

Topics :

FAC prediction tools
Non-Destructive Examination methods

ABSTRACT :

Flow Accelerated Corrosion (FAC) is a very serious problem in Power Generation facilities. It is an increased rate of corrosion or material dissolution caused by the fast flow of a fluid on an unprotected material surface. FAC often occurs in liquid and liquid-steam carbon steel piping at temperatures between 120°F - 550°F (35°C - 290°C). The turbulent flow of the liquid is generally at velocities greater than 10 f/sec.

FAC results in the thinning of carbon and low-alloy steel components, mostly of carbon steel piping and tubing. It is a mass transfer process in which the protective oxide (mostly magnetite) is removed from the steel surface into the flowing water. The material wear rate depends on the steel composition, temperature, flow velocity and turbulence - and on water and water droplet pH and oxygen and oxygen scavenger concentration.

To detect and size FAC, critical piping and elbows must be tested with ultrasonic's to determine remaining wall thickness. Currently, this is being done with conventional thickness gages using point measurements. This process is time consuming and provides a limited amount of manual data. This paper describes the use of a Portable digital Cscan system to greatly increase the efficiently and accuracy of testing critical structures for the presence of FAC.