Hydro-Quebec METAR Inspection Bracelet

Abstract

This paper will present the Gentilly-2 inspection program targeting outlet feeder pipe thinning caused by FAC. The focus of the paper will be on the METAR inspection bracelet development and qualification process, as well as highlights of the 2000 outage inspection campaign. In summary, the '99 inspection campaign allowed personnel to measure wall thickness of 66 outlet feeders totaling 106 elbows. Since the beginning of the inspection program in '97, about 80% of 2-inch outlets and 40% of 2.5-inch outlets have been measured at least once. Collecting high quality data is a challenge, mainly due to lack of space around the pipes - especially for 2.5inch pipes -- and the roughness of feeder pipes at Gentilly-2. Hydro-Quebec developed the METAR Inspection bracelet to improve the quality of inspection data and increase efficiency. The METAR bracelet is a mechanical device that can be attached directly onto the feeder to measure thickness in situ. It consists of 14 ultrasonic sensors, each mounted in its own shoe, attached together in an assembly called a collar. The collar permits each sensor some degree of movement while keeping the proper orientation, perpendicular to the feeder. The collar is held onto the feeder by the frame and kept in position by means of an elastic band. The frame is designed to ease movement and minimize friction. There is a different frame for each feeder size, but the same collar is used. In most cases, inspection can be carried out with only one hand and requires little adjustment by the operator. To date, the bracelet is not motorized and must be moved along the pipes manually. A multi-channel acquisition unit was built for this project based on the R/D Tech p Tomoscan ultrasonic system and Tomoview data analysis software. The system features real-time C-scan from all 14 channels and provides a thickness map of the scanned area for rapid evaluation of minimum wall thickness. The RF waveform is recorded and the sizing technique is based on the zero-crossing method for accurate off-line wall thickness measurement. Accuracy of wall thickness measurement is better than 0.001" for the 2.5 to 4.5 mm thickness range. Finally, a summary of the results and highlights of the 2000 outage inspection campaign will be presented.