Inspection of Generator Components
3angles meets all NDT requirements for the inspection of generators for different OEM’s. Our NDT services for generators typically include the inspection of the following components:
- Rotor forging
- Rotor dovetail slots
- Retaining rings
- Locking rings, snap rings
- Fan blades, fan rings
- Wedges
- Bearings
- Coupling bolts
- Coolers
- Through bolts
- Stator frame
The inspections of the generator components are performed during a major or minor outage. During a major outage, all or most of the generator components will be inspected while during a minor outage the turbine is partially disassembled, and the inspection focuses only on the parts that are accessible or disassembled. During a generator rotor rewind the entire forging including the dovetail slots can be inspected. Typically, this involves a magnetic particle inspection on the rotor periphery using one of its proprietary 10,000 AMP mag machines. A headshot is performed providing a circular magnetic field to find indications in the axial direction. The coil technique is used for creating a longitudinal field finding indications in the radial direction.
Based on design and OEM, generator inspections may require other unique or specialized inspections based on rotor design and configuration. Examples of these inspections are:
Boresonics Inspection: Boresonics inspection examines the forging of a rotor through the bore cavity. The inspection can be performed for straight, step, and bottle bore configurations. Removal and installation of the bore plug(s) and power honing of the bore surface are part of the process. The main bore and/or the collector bore can be part of the inspection.
Periphery Ultrasonic Testing (UT): Ultrasonic testing examines the forging of a rotor from the periphery of the rotor for indications.
Advanced Robotic Inspection: 3angles uses the Advanced Robotic Generator Inspection System (ARGIS), developed by DEKRA, for robotic inspection of generators. The following inspections can be performed without removing the rotor from the stator: visual inspection using 4 cameras, stator wedge tightness test and low flux core test (ELCID) Electromagnetic Core Imperfection Detection.
Automated Inspection of Retaining Rings: 3angles uses its proprietary Automated Inspection of Retaining Rings (AIRR) system. The AIRR system is equipped with ultrasonic (UT) and eddy current (ET) transducers. The ultrasonic measurements inspect the ring ID with emphasis on the shrink fit areas and wall thickness steps. ET is used to inspect the OD surfaces. This system is used when the rings are still mounted on the generator field (rotor out) as well as in-situ when the field is not removed from the stator.
Generator Dovetail Slot Inspection: In many cases, the examinations have been referred to as TIL-1292 examinations. The eddy current testing offered by 3angles uses probes specially designed to target the critical area along the length of the dovetails when properly placed into the dovetail slots.
Bump Test of Stator-End Windings: Bump testing analyzes the natural response of stator end-windings upon excitation from a mechanical impulse.