NDTsi 2001 Session: Major Component Inspection I-IV
Automated System for Ultrasonic & Eddy Current Testing of Hollow Rotors
I. Gaibazzi, M. Sergio, ENEL, Italy; F. Chignoli, T. Cola, E. D'Alessio, R. Garavaglia, CESI, Italy
ABSTRACT
Life assessment programs for extended operation of turbine and generator rotors, have allowed Enel Produzione to achieve a remarkable awareness in damage morphology and localisation, and a wide experience in the performance of non destructive testing (NDT) equipment, procedures, and defect assessment methods. On such basis ENEL Produzione issued the requirements of a novel automated system for the inspection from the bore of hollow rotors, and appointed CESI for the supply of the commissioned system that will be thoroughly described in the paper. The appraisal of the NDT tasks involved in the frame of life assessment of turbine and generator rotors was exploited in a system design, conceived as it is outlined in the followings:
original mechanical device suited for uninterrupted scanning and data gathering along the whole rotor length, up to 14 meters, adaptable to inner diameter in the range 63.5¸330 mm,
effective flaw detection capability near bore and in rotor body accomplished by simultaneous ultrasonic and eddy current testing (UT&ET),
easy installation operation dismantling of system in field, to reduce as much as possible plant unavailability and service costs,
fast delivery of integrity data to shorten the time span before follow-up actions,
modular architecture, to ensure easier maintenance of mechanical device and electronic hardware, and openness to future software upgrading.
The actual system consists of a mechanical inspection device and a computer based equipment. The self-centring scanning device comprises four separate sections (probe head, fine hoop/axial manipulators, coarse axial actuator) terminated with connectors suited for fast and secure mounting:
head with room to accommodate 4 or 8 probes, according to rotor inner diameter,
separate hoop / axial manipulators only move the probe head for automated signal acquisition,
pneumatic device composed with a double acting cylinder actuator, working in synchronism with retracting levers. The device provides the coarse axial move of the front compound - probe head and manipulators. The move is bi-directional and virtually unlimited in maximum path.
An umbilical cable links the inspection device to the electronic hardware driven by an embedded system, and then to the operator station via local Ethernet. The new system, called "SIBAR", allows real-time visualisation of gathered NDT signals, and on-line processing for selection of defect indications. SAFT (Synthetic Aperture Focussing Technique) focalisation is available for improved lateral resolution and better discrimination / sizing of flaw indications. Archiving raw data on CD's allows in depth data evaluation to be carried at any time, and the establishment of a permanent rotor database. The novel system was submitted to extensive testing trials, and afterwards started its service beginning this year, to complement the rotor integrity assessment service package offered by ENEL Produzione. Such offer will address the needs of ENEL's generation plants, as well as other plant owners in the electricity and petrochemical fields.
Publication Source: 3nd International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components, November 14-16, 2001, Seville Spain. Publisher: Tecnatom s.a. - [Homepage]
