In-situ Examination of Turbine Components (Blade roots and Rotor Steeple and Disk Rim Attachments) of Low-pressure Steam Turbine, Using Phased Array Technology
P. Ciorau, D. MacGillivray, T. Hazelton, L. Gilham, B. Taffs, Ontario Power Generation, Inc.; J. Poguet, Imasonic
ABSTRACT
Three field trials on Darlington unit number 1, number3 and number 4 were performed on ABB LP turbines to inspect blade roots and rotor steeples of L-0 and L-1 stages. The examinations were in-situ performed. One inspection of GE disk-blade rim attachments was done at Bruce B nuclear station. The ultrasonic system uses automated and manual phased array technology, capable of high-speed rate and reliable detection and sizing. The system capability was demonstrated on 1:1 scale mock-ups and reference blocks, using EDM notches. Targets as small as 2 x 0.5 mm on steeple hooks, 3 x 1 mm on blade roots and 1.5 x 0.7 mm on disk rim could be reliable detected. A custom built UT simulation software: Imagine 3D interfaces with SimScan to produce 1:1 2-D/3-D views and generates the spreadsheets with target and probe coordinates and ultrasonic path and angles (refracted and skew) to hit the reference target. The Ray-tracing simulated results w ere validated by experimental measurements. Examination of L-0 blade and rotor steeple grooves was performed with 2 phased array Focus systems under networking. Data analysis was done in real time. Manual phased array was performed on L-1 blade roots (hook 1). Special linear array probes were designed by OPGI and manufactured by Imasonic, to fit the specific geometry and to optimize the beam features for detection and sizing. Accuracy in sizing is±0.5 mm for height, ±1.5 mm for length. Location of indication in 2-D specimen layout is within±2.5 mm space envelope for blade root, and within±4 mm for rotor steeple. Sizing based on Dynamic Depth Focusing board is better for specular reflection of EDM notches on disk attachment. Representative results from the 3 field trials / disk rim examinations will be presented.
Publication Source: 2nd International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components, May 24-26, 2000, New Orleans, Louisiana USA. Publisher: EPRI - [Homepage]
