Study on LTA Measurement for FFS Assessment

Abstract

FFS assessment technologies for pressure equipment have been studied and standardized in recent 15 years in Japan. FFS assessment of local thin area, LTA, is the most frequently used in process industries. However reliability of thickness measurement of LTA and influence to FFS assessment has not been studied much in the past. Uncertainty of thickness measurements and Remaining Strength Factor, RSF, were investigated on Round Robin Testing using manual UT and additional new technology such as flexi-alley UT and 3D LED system for LTA in pipes, It is recommended to use suitable combination of Manual or mechanized UT and 3D LTA measurement system in case of assessment of critical flaws and decision making for repair and replacement of pressure equipment.

3D Measurement and FFS Assessment for LTA in Pressure Equipment According to WES2820:2015

“…[4]. [5], [6] JWES/WES Task Group on FFS Assessment Procedure issued the FFS assessment procedure for pressure equipment -Metal loss assessment, WES2820, herein after the Standard, on June, 2015 after two years standardizing activities based on FFS assessment standards of LTA developed by PAJ/JPCA FFS Assessment Committee.…”

“…example of mean values vs. standard deviation of thickness reading of the pipe with CUI by UT[5] The various tools measuring corrosion have been studied and developed longtime in US pipeline industries. In recent years, 3D optical measurement system such as laser light-section method, photogrammetry method and 3D…”