An Evaluation System of Tube Wall Thickness of Feed Water Heater Base on the Advanced NDE Technique

Abstract

ABSTRACT The inspection of the tubes of feed water heaters on the wall thickness is generally conducted using the ultrasonic pulse technique. According to the past method, the wall thickness at each measured point is evaluated in comparison with the minimum required wall thickness of the tube, namely it is based on the general metal loss evaluation criteria. However, these tubes often show the local metal loss due to erosion and corrosion. Evaluation techniques and acceptance criteria regarding the locally thinned tubes require many wall thickness data around the local metal loss locations. However, it is inefficient to perform this evaluation work with human power because of the required huge measured data. With recent improvement of the inspection technique, technology enabled faster, larger amount, and more accurate electronic digital data acquisition of tube wall thickness. The authors have developed the systematized evaluation methodology that can transact data acquisition and evaluation simultaneously. This paper describes the logic of evaluation methods and examined algorithms to make them systematized