Accelerated Stress Corrosion Cracking Evaluation for Steam Turbines
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Solution Overview
Problem
Existing methods for evaluating stress corrosion cracking in steam turbines, such as JP 2001-305043 A, face challenges in accurately predicting the cracking due to temperature and wetness differences between the test environment and the actual operating environment, and require a similar duration for test piece and actual equipment, making them inefficient for quick and reliable evaluation.
Innovation Solution
A stress corrosion cracking evaluation method that uses a sample with higher sensitivity than the evaluation object material, housed in a sample box within the steam turbine, to acquire a sample breakage time and estimate the breakage time of the steam turbine based on this, accounting for operational conditions like temperature and wetness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a test piece is produced from the same material as the evaluation object part, then the evaluation reflects actual material behavior, but the test period becomes as long as the actual service life, making the evaluation inefficient
Solution Approach 1:
The patent changes the material parameter by using a test piece with different material properties (higher sensitivity to stress corrosion cracking) than the actual evaluation object. This allows the test to proceed at an accelerated rate while still providing meaningful data for predicting the behavior of the actual component, thereby reducing test time without sacrificing evaluation relevance.
Solution Approach 2:
The patent performs preliminary action by using a test piece that experiences stress corrosion cracking faster than the actual component would. This allows the evaluation to be completed in advance of what would otherwise be required, enabling predictive maintenance planning before actual failure occurs in the service component.
2Ease of operation
If the test environment is assumed from the operating environment, then the evaluation is simplified, but temperature and wetness differences reduce evaluation accuracy
Solution Approach 1:
The patent applies feedback by using the test results from the accelerated stress corrosion cracking test to continuously refine and update the predictive model for the actual component. The test data provides feedback that allows correction and improvement of the evaluation methodology, accounting for environmental differences between test and operating conditions through iterative refinement.
Solution Approach 2:
The patent introduces an intermediary relationship between the test piece and the evaluation object by using a predictive model or conversion factor that translates results from the accelerated test to the actual service condition. This intermediary allows accurate prediction despite environmental differences, bridging the gap between simplified test conditions and complex operating conditions.
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 quick and accurate quantitative evaluation of stress corrosion cracking in steam turbines, allowing for timely maintenance planning and preventing equipment malfunction.
Implementation Method 1
it is known that Stress Corrosion Cracking (SCC) occurs because a constituent member is exposed to moist steam under a high-temperature environment for a long period of time
Data Source
AI summary
In a stress corrosion cracking evaluation method for a steam turbine, a sample having a high sensitivity is housed in a sample box of the steam turbine, and a sample breakage time is acquired. Then, based on the sample breakage time, a breakage time of the steam turbine is estimated.