This paper is based on a 1999 field project utilizing an Ultrasonic Intelligent Vehicle to ascertain internal and external corrosion in 2 x 60"/56" (1524/1422 mm telescopic) parallel internally bare treated seawater pipelines. These 22-year-old pipelines extend approximately 100 km across the Arabian Desert. The objective was to locate and
interpret internal and external corroded locations and derive a cost effective repair solution, which would not jeopardize the safe operation of the pipelines. Both lines were put into operation in mid-1978 using over-the-ditch applied tape wrap supplemented by Impressed Current Cathodic Protection (ICCP) for external corrosion protection. A series of seventeen external pipeline leaks, four within a period of three months in a "subkha" environment (severe moist chloride conditions) indicated both
pipelines were in urgent need of major rehabilitation or partial replacement. In addition to the leaks, a series of "test hole" evaluations confirmed significant disbonding of tape wrap with serious pitting and general corrosion. The tape wrap disbondment shielded the pipelines from receiving adequate Cathodic Protection. This paper discusses (1) seawater injection process (2) pipeline operating history (3) pipeline leaks (4) test hole evaluations (5) pipeline internal cleaning (6) geometry & intelligent vehicle data (7) field anomaly verifications (8) pipeline repair methodology and (9) repair vs. replacement decision economics. This project was the largest diameter pipeline ever assessed by Ultrasonic or Magnetic Flux Leakage non- destructive testing (NDT) technique.
The intelligent vehicle information and on-going pipeline repairs played a major role in cancellation of partial pipeline replacement with cost savings estimated in the region of $40 million (MM) U.S. dollars