Generator Rotor Blade Root Repair Using Extraction and Split Ring Alignment
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Solution Overview
Problem
Threaded connections between rotor blades and the rotor in generators are prone to fatigue failure due to high cyclic loads, leading to reduced strength and alignment challenges during repair, especially in on-site outages.
Innovation Solution
The method involves removing material from the first section of the rotor root closest to the airfoil, retaining the second section with original threads, and using a split ring for alignment and vibration reduction, allowing the blade to be easily reattached with reduced stress on the remaining threads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first threads on the blade root are removed and re-threaded at a smaller diameter, then the fatigue limit is re-established, but the strength of the root is reduced and the fatigue life is shortened
Solution Approach 1:
The invention extracts only the damaged first section of threads from the blade root, removing material only where fatigue damage has occurred. The remaining second section of threads is preserved intact, maintaining the original root diameter and strength characteristics while eliminating the fatigued portion.
Solution Approach 2:
The invention applies local quality by treating only the affected first section of the root with material removal and re-threading, while leaving the second section unchanged. This localized approach restores fatigue resistance where needed without compromising the overall structural integrity of the root.
2Reliability
If the threads are re-cut at a smaller diameter, then the damaged material is removed, but the alignment of the recut thread with the blade axis becomes difficult and time-consuming
Solution Approach 1:
The invention employs preliminary action by using an alignment tool before re-threading to precisely establish the correct angular orientation of the new threads relative to the blade axis. This pre-alignment step ensures accurate thread placement without requiring complex adjustments during the re-threading process.
3Ease of repair
If the blade is disassembled and reassembled with a securing collar, then the connection can be repaired, but the reassembly process is complex and prone to misalignment
Solution Approach 1:
The invention uses an alignment tool as an intermediary device during the repair process. This tool facilitates precise alignment between the blade root and rotor during reassembly, simplifying the repair process and reducing the risk of misalignment without requiring complex securing collars or multiple assembly steps.
Data Source
AI summary
A method for repairing a blade connection of a generator rotor is disclosed. The generator rotor includes an internally threaded hole formed in the generator rotor and an externally threaded blade root. The method includes the steps of removing the blade from the generator rotor, removing material of a first section of the root extending from an end of the root closest to the airfoil, and screwing the blade back into the threaded hole. Additionally, a reworked blade and a reworked blade generator rotor connection is disclosed.