Publications

Several leaking cases on the piping system in the oil and gas industry are contributed by the failure of flange joints which can cause production shortfalls and increase safety and environmental problems. The flange joint is one of the areas where the conventional Non-Destructive Testing (NDT) technique has limitations to detect the corrosion due to complex configuration. Opening the flange connection for visual inspection on the flange face and its gasket will also be unfavorable due to safety and production reasons. Phased Array Ultrasonic Testing (PAUT), which is an advanced NDT technique that has emerged in the industry, provides wider coverage compared to conventional techniques, hence is chosen to inspect the internal corrosion on the flange face in an on-stream condition. Since the gasket part remains a blind spot, corrosion correlation with the flange face becomes important. This paper shares the experience in developing the strategy, the application of PAUT combined with visual inspection and comparing of results after opening on flange joint by considering age of the facility, fluid corrosivity and flange configuration. The purpose of the analysis is to evaluate PAUT probability of detection (POD), corrosion correlation on flange face and its gasket, and susceptible areas. A statistical approach is used to evaluate the data from 955 actually tested flanges. The results showed that PAUT POD is 82%, and confirmed corrosion correlation between flange face and its gasket. The result also showed that severe corrosion took place on the area which was affected by turbulence flow. It is concluded that PAUT is an effective NDT technique to assure integrity of the flange joint by early detection of corrosion before failure. PAUT can be used also as a screening tool to filter the high number of flange joints that are required to be opened for inspection of the gasket and cost savings are achieved by narrowing the scope of breaking the flanges joints for repair. Keywords: Phased Array Ultrasonic Testing (PAUT), Flange Joint, Internal Corrosion