Ultrasonic Inspection Tool Run on Taps

Abstract A pipeline inspection tool using ultrasonic measurement technology has been developed by NKK Corporation with assistance from Alyeska Pipeline Service Company who is responsible for pipeline maintenance and inspection of the Trans Alaska Pipeline System (TAPS). This ultrasonic tool has succeeded in inspecting the wall thinning of TAPS in June 1989 and 1990. TAPS is 48 - inches in diameter and 1280 kms in length. During the inspection run, a sophisticated encoder condensed ultrasonic data into a compact data recorder to inspect the longest pipeline section of 710 km in one run. After the inspection run, the stored data was monitored by a CRT and processed by the host computer to report a corrosion list. Alyeska has verified the list by excavation. The accuracy of the wall thickness measurement was verified to be 0.2 mm as a standard deviation. The accuracy of the longitudinal and the circumferential location was within ±98 mm from the preceding girth weld and ±10.5 degrees respectively. This paper reports on the ultrasonic inspection pig and the inspection work on TAPS.