Pit Initiation Evaluation for Steam Turbines

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Solution Overview

Problem

Conventional methods fail to predict pit initiation effectively and at a low cost in steam turbine power generation systems, leading to challenges in inhibiting stress corrosion cracking and corrosion fatigue damage.

Innovation Solution

A pit initiation evaluation system that calculates dry-wet alternate time, deposit impurity concentration, and pit initiation data to create a pit initiation evaluation table, allowing for the prediction of pitting corrosion in steam turbine stages using a combination of turbine operating state, dry-wet alternate time, and impurity concentration data.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional monitoring methods are used to detect pit initiation, then measurement precision can be improved, but device complexity and cost increase significantly

Engineering Contradiction:

Improvepit initiation detection accuracyVSAvoidmonitoring system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical/physical sensing systems with a computational evaluation method. Instead of using specialized sensors and monitoring equipment to directly detect pit initiation, the system uses a computer to calculate pit initiation probability based on operational parameters (turbine stage, dry-wet alternate time, impurity concentration), substituting mechanical measurement systems with information processing and mathematical modeling approaches

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary evaluation model that mediates between operational data and pit initiation detection. The model uses dry-wet alternate time and impurity concentration as intermediate parameters to assess pit initiation risk, rather than directly measuring pit formation. This intermediary approach simplifies the monitoring system while maintaining detection accuracy

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If specialized sensors and monitoring equipment are installed to predict pit initiation, then prediction accuracy improves, but cost increases

Engineering Contradiction:

Improvepit initiation prediction reliabilityVSAvoidmonitoring system cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs inexpensive, readily available operational data (turbine stage information, dry-wet alternate time records, impurity concentration measurements) as the basis for prediction, rather than investing in expensive specialized sensors. The system uses data that is already being collected for other operational purposes, making the prediction method cost-effective while maintaining reliability

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The system uses the steam turbine's own operational parameters and existing monitoring data to predict pit initiation, rather than requiring external specialized monitoring equipment. The turbine's operational data serves dual purposes: both for operational control and for corrosion prediction, making the system self-sufficient and cost-effective

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If steam is supplied at different steam flow rates to adjust power output, then adaptability to power demand improves, but dry-wet alternate zone position changes causing unpredictable corrosion

Engineering Contradiction:

Improvepower output adjustment capabilityVSAvoidcorrosion prediction reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent creates a dynamic prediction model that adapts to changing operational conditions. Instead of using fixed corrosion thresholds, the system dynamically calculates pit initiation probability based on the current steam flow rate, turbine stage, dry-wet alternate time, and impurity concentration. This allows the system to maintain reliable corrosion prediction across varying power output conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system accounts for parameter changes in steam flow rate and operational conditions by incorporating these variables into the pit initiation evaluation formula. The model adjusts the evaluation criteria based on the actual operational parameters, ensuring reliable predictions despite changes in steam flow rate and power output requirements

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12025014B2Pit initiation evaluation system, and, pit initiation evaluation method

Publication Date: 2024.07.02 TOSHIBA ENERGY SYST & SOLUTIONS CORP

AI summary

There is provided a pit initiation evaluation system or the like capable of predicting pit initiation effectively and at low cost. In a pit initiation evaluation system of an embodiment, a pit initiation evaluation unit creates and retains, based on a dry-wet alternate time data, a deposit impurity concentration data, and a pit initiation data on pitting corrosion initiated in each of a plurality of turbine stages when an operation is actually performed in the steam turbine, a pit initiation evaluation table presenting a relationship between a dry-wet alternate time, a deposit impurity concentration, and pit initiation. Further, the pit initiation evaluation unit is configured to evaluate, by using the pit initiation evaluation table, pitting corrosion to be initiated in each of the plurality of turbine stages in an operation planned for the steam turbine.