Repairing Turbine Rotor Dovetails with Segmented Replacement Rings
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Solution Overview
Problem
Current repair methods for turbine rotor wheel dovetails, such as weld buildup and replacement rings, face challenges like defects, high stress concentrations, and limitations in accommodating new dovetail designs, which affect the efficiency and reliability of the repair process.
Innovation Solution
The method involves removing damaged dovetails, replacing them with a forged or cast replacement ring that is welded using partial-penetration welds, leaving a hollow center section to reduce defects and stress concentrations, and allowing for post-weld machining and adaptation of dovetail configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If conventional weld buildup process is used to repair damaged dovetail, then the rotor wheel can be repaired without replacement, but the repair introduces defects such as porosity and slag inclusions and creates high stress concentrations
Solution Approach 1:
The replacement ring is divided into multiple segments that are positioned around the peripheral rim, with gaps between segments that eliminate the need for welding. Each segment is independently installed and secured, avoiding the creation of weld defects while maintaining structural integrity.
Solution Approach 2:
The damaged dovetail portion is completely removed from the rotor wheel, and instead of building up weld material, a separate replacement ring is introduced. This extraction approach eliminates the weld buildup process entirely, avoiding porosity and slag inclusions associated with welding.
2Strength
If full-penetration weld is used to attach replacement ring, then strong joint is achieved, but high stress concentrations and welding defects occur
Solution Approach 1:
The welding process is completely extracted from the joining method. Instead of using welds to attach the replacement ring to the rotor wheel, the segments are positioned and secured through mechanical means, eliminating stress concentrations and defects associated with welding.
Solution Approach 2:
The replacement ring segments may be made from materials with optimal properties for stress resistance, different from the rotor wheel material. This allows each component to be optimized for its specific function without the constraints of welding compatibility.
3Ease of manufacture
If traditional repair methods are used, then existing dovetail designs are maintained, but new dovetail designs cannot be accommodated
Solution Approach 1:
The replacement ring segments can be manufactured with various dovetail configurations and installed based on design requirements. This dynamic approach allows the same basic repair methodology to accommodate different dovetail designs, providing versatility while maintaining manufacturing simplicity.
Solution Approach 2:
Each replacement ring segment can be customized with specific dovetail geometries, materials, or features appropriate for its location and function. This allows local optimization of each segment while using a standardized installation process, balancing adaptability with ease of manufacture.
4Reliability
If replacement ring with gaps is used instead of continuous ring, then welding is eliminated and defects are reduced, but structural continuity is compromised
Solution Approach 1:
The replacement ring is intentionally segmented into multiple sections with gaps between them. This segmentation eliminates the need for welding while maintaining structural functionality through the collective arrangement of segments around the rotor wheel, achieving reliability without compromising essential structural stability.
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
This approach enhances weld efficiency, reduces defects, and enables the accommodation of new dovetail designs, improving the durability and reliability of the repaired rotor wheels by utilizing materials with optimal properties for stress resistance.
Implementation Method 1
welding the replacement ring to the peripheral rim, with weld material applied only within the end grooves
Data Source
AI summary
A method to repair a peripheral portion of a body including: removing a damaged portion from a peripheral region of the body; mounting a replacement ring to the body after removal of the damaged portion; forming an interior groove between the inner surface of the replacement ring and the peripheral surface of the body, wherein the groove is between ridges; welding the replacement ring to the body, wherein weld material is applied only within end grooves, and leaving a void in said center section after the welding of the replacement ring to the body.