Feedwater Sparger Repair Assembly for Weld-Free Nozzle Replacement
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Solution Overview
Problem
Welds in core spray piping and spargers of boiling water reactors are prone to cracking due to high temperature and pressure, making them susceptible to damage and requiring lengthy periods of integrity before repair or inspection during scheduled plant outages.
Innovation Solution
A feedwater sparger repair assembly with a partial cylindrical cover plate, T-bolts, and crimp nuts that allows for the quick replacement or repair of damaged sparger nozzles without welding, by cutting an opening in the core spray pipe and mounting the assembly over it, using a barrel cam to guide the T-bolts into position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If welded spargers are used in core spray piping, then the spargers can be securely attached to deliver coolant water, but the welds become susceptible to cracking due to high temperature and pressure
Solution Approach 1:
The patent replaces the welded mechanical connection with a mechanical fastening system using a cover plate, T-bolts, and nuts. This substitution eliminates the welds that are susceptible to thermal cracking while maintaining secure attachment of the sparger to the core spray piping through purely mechanical means.
Solution Approach 2:
The sparger assembly is segmented into separable components: the sparger nozzle, cover plate, T-bolts, and nuts. This allows the sparger to be independently replaced without replacing the entire piping system, and enables repair during outages without compromising the integrity of the main piping structure.
2Strength
If welds are used to attach spargers, then secure connection is achieved, but repair and inspection can only occur during lengthy scheduled plant outages
Solution Approach 1:
The mechanical fastening system with T-bolts and nuts provides dynamic adjustability and ease of assembly/disassembly compared to rigid welding. This allows rapid installation and removal of spargers during scheduled outages, significantly reducing the time required for repair operations while maintaining secure connection during operation.
Solution Approach 2:
The modular design allows damaged spargers to be quickly removed and replaced with new or refurbished units during outages. The reusable cover plate and fastening system remain in place, allowing efficient recovery and replacement cycles that minimize plant downtime.
3Ease of repair
If traditional welding methods are used for sparger repair, then repairs can be made, but the process is time-consuming and requires complete disassembly
Solution Approach 1:
The repair system is segmented into modular components where only the sparger nozzle needs to be replaced, not the entire assembly. The cover plate and fastening system remain reusable, allowing rapid repair by simply removing damaged nozzles and installing new ones without time-consuming welding operations.
Solution Approach 2:
Replacing welding with mechanical fastening dramatically reduces repair time and complexity. The T-bolt and nut system allows for quick assembly and disassembly during outages, eliminating the need for welding equipment, preparation, and post-weld inspection, thereby significantly improving repair productivity.
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 the easy and rapid repair or replacement of cracked spargers without welding, ensuring continuous reactor operation and reducing downtime during scheduled outages.
Implementation Method 1
a barrel cam that guides rotation of the T-bolts between an insertion position to an installed position
Data Source
AI summary
A feedwater sparger repair assembly includes a cover plate having a partial cylindrical shape and having a nozzle opening and a pair of bolt openings extending through the cover plate. A nozzle is attached to the cover plate and surrounds the nozzle opening. A pair of T-bolts extend through a respective one of the pair of bolt openings and each include a shank having a threaded portion extending from an exterior side of the cover plate and a partial cylindrical head portion disposed at an end of the shank on an interior side of the cover plate. A pair of nuts are engaged with the threaded portion of the pair of T-bolts. The feedwater sparger repair assembly is adapted to be mounted to an opening that is cut into a core spray pipe in order to repair/replace a sparger that becomes cracked.