Eddy Current Probe for Gas Turbine Corrosion Detection
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Solution Overview
Problem
Corrosion pitting in gas turbine rotor blades, caused by corrosive elements like Chlorides and Sulphides, leads to cracks and potential breakages, resulting in costly outages in LNG plants, as existing detection methods are ineffective in identifying corrosion pits without disassembling the turbine system.
Innovation Solution
An Eddy Current (EC) probe device with a primary coil driver, measurement coils, band-pass filters, and signal processing unit is used to detect signal amplitude changes from corrosion pits on gas turbine rotor blades, allowing for in-situ detection without disassembly, utilizing sensitive receiver designs and reference data for accurate identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional detection methods are used, then corrosion pits can be detected, but the gas turbine system must be disassembled which causes downtime and loss of productivity
Solution Approach 1:
The patent replaces mechanical disassembly-based detection methods with an electromagnetic field-based eddy current detection system. The probe device uses electromagnetic induction to generate eddy currents in the turbine blades, allowing corrosion detection without physical contact or disassembly, thus maintaining gas turbine availability while achieving accurate corrosion pit detection
Solution Approach 2:
The patent introduces an intermediary probe device that can be accessed through the existing gas turbine structure without full disassembly. The probe includes a detection head with coils that generate electromagnetic fields to detect corrosion pits, serving as a mediator between the external inspection system and the internal turbine components
2Productivity
If in-situ detection is implemented, then gas turbine availability is maintained, but detection precision for early-stage corrosion pits is reduced
Solution Approach 1:
The patent employs a nested probe structure where the detection head with measurement coils is inserted through the gas turbine's air intake path. The probe can be accessed and operated in-situ without removing turbine components, nesting the detection system within the existing turbine structure to maintain availability while enabling detection
Solution Approach 2:
The patent uses parameter changes in the electromagnetic field (frequency, amplitude, phase) to enhance detection sensitivity. By analyzing changes in eddy current parameters caused by corrosion pits, the system can detect early-stage corrosion with sufficient precision even in the constrained in-situ environment
3Productivity
If the gas turbine operates continuously, then productivity is maximized, but corrosion pitting progresses undetected leading to catastrophic failure
Solution Approach 1:
The patent enables preliminary detection of corrosion pits during routine operation or scheduled maintenance intervals without shutting down the turbine. By detecting corrosion early in its development stage, the system allows for timely intervention before cracks propagate and cause catastrophic blade failure, thus maintaining both productivity and reliability
Solution Approach 2:
The patent implements a feedback mechanism where detection results are analyzed and used to determine subsequent actions. The signal processing unit analyzes eddy current responses to identify corrosion pits, providing feedback that triggers maintenance decisions, creating a closed-loop system that balances continuous operation with preventive maintenance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables early detection of corrosion pits, preventing crack initiation and propagation, thus avoiding catastrophic failures and reducing downtime and costs associated with gas turbine outages.
Implementation Method 1
a primary coil driver operable to generate a magnetic field
Implementation Method 2
An Eddy Current (EC) probe device with a primary coil driver, measurement coils
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
Methods and apparatuses for detecting corrosion in one or more blades of a gas turbine system includes a detection head having a shape that conforms to a surface geometry of a filet section of a gas turbine blade, whereby the detection head is operable to move along the axial length of the filet section for detecting corrosion pitting. At least one coil device located within the detection head induces a first magnetic field within an area of the filet in contact with the detection head. A receiver device is adapted to detect a signal corresponding to a second magnetic field received from the area of the filet exposed to the first magnetic field, where the second magnetic field is generated by induced currents in the area by the first magnetic field. A signal processing device then processes the detected signal for correlating a corresponding amplitude of the detected signal with the presence of corrosion pitting in the area such that the presence of corrosion pitting is determined without any casing disassembly of the gas turbine system.