Application of Laser Profilometry for Fitness-for-Service Assessment on Pressure Vessel External Corrosion

Abstract

In order to safely extend the life of damaged in-service components, Fitness-For-Service (FFS) assessments are used to evaluate structural integrity. These FFS assessments largely depend upon the quality of the inspection data. Compared to traditional inspection methods such as pit gauge or ultrasonic techniques, laser profilometry provides faster results with higher resolution and accuracy. Improved inspection data enables more precise FFS assessments and leads to fewer unnecessary repairs and non-conservative assessments. This paper examines how laser profilometry measurements were taken of several corrosion areas on the exterior shell of a pressure vessel in order to complete a FFS assessment equivalent to an API 579 Level 2 assessment. The results of the FFS assessment show how laser profilometry data may be used in a detailed structural integrity analysis to consider a vessel safe for continued use. A discussion of how laser profilometry data could also be used for an API 579 Level 3 assessment, using finite element analysis, in areas not acceptable for Level 1, or 2 assessments is included.