Self-Expanding Slip Joint Seal for BWR Jet Pump Leakage
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Solution Overview
Problem
Conventional solutions for Boiling Water Reactor (BWR) jet pump assemblies fail to effectively prevent leakage and flow-induced vibration between the inlet mixer and diffuser, leading to significant damage to jet pump components.
Innovation Solution
A self-expandable and self-tightening slip joint internal seal is introduced, utilizing a flexible metallic seal, such as an E-ring or C-ring, housed within a seal mounting ring, which conforms to varying gap sizes and maintains a tight seal through thermal expansion and contraction, and internal pressure, eliminating the need for machining in some configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional slip joint clamps or restrainer brackets are used to increase system stiffness, then vibration mitigation is improved, but leakage between inlet mixer and diffuser is not prevented
Solution Approach 1:
A flexible metallic seal (E-ring or C-ring) is introduced as an intermediary element between the inlet mixer and diffuser. This seal acts as a mediator that simultaneously addresses both leakage and vibration issues by conforming to the mating surfaces while maintaining system stiffness through its resilient properties
Solution Approach 2:
The patent employs a flexible metallic seal in the form of an E-ring or C-ring that utilizes its flexibility to conform to varying gap sizes and mating surfaces. The flexible nature of this thin-walled component allows it to adapt to thermal expansion and contraction while maintaining a tight seal, thereby preventing both leakage and reducing vibration-induced damage
2Stability of the object's composition
If the inlet mixer is constrained to the riser pipe via restrainer bracket to reduce slip joint FIV, then system stability is improved, but actual leakage between inlet mixers and diffusers continues to occur
Solution Approach 1:
The flexible metallic seal serves as an intermediary component positioned between the inlet mixer and diffuser, addressing the leakage issue directly at the source while working in conjunction with the restrainer bracket system to maintain overall stability
Solution Approach 2:
The seal's ability to change its physical parameters (flexibility, conformance) in response to operational conditions allows it to maintain effectiveness despite variations in gap size, thermal expansion, and vibration, thereby preventing leakage while maintaining system stability
3Force
If slip joint clamps are used to provide additional system stiffness, then vibration mitigation is improved, but the root cause of leakage and FIV is not addressed
Solution Approach 1:
The flexible metallic seal is positioned as an intermediary element that directly addresses the seal integrity issue at the inlet mixer-diffuser interface, while working in conjunction with the clamping system to provide comprehensive protection against both leakage and vibration
Solution Approach 2:
The flexible metallic seal's thin-walled construction allows it to conform to the mating surfaces and maintain seal integrity under varying operational conditions, thereby preventing leakage while the external clamping system provides the necessary stiffness to mitigate vibration
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
The solution effectively prevents leakage and flow-induced vibration, enhancing the durability of BWR jet pump components by providing a reliable seal between the inlet mixer and diffuser, regardless of initial tolerances, and accommodating thermal changes and operational pressures.
Implementation Method 1
maintains a tight seal through thermal expansion and contraction
Implementation Method 2
self-expandable / self-tightening slip joint internal seal that provides a seal between the lower distal end of an inlet mixer and a top portion of a diffuser
Data Source
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AI summary
A method and apparatus for providing a Boiling Water Reactor (BWR) jet pump slip joint internal seal (20) in the interface between an inlet mixer (4) and a diffuser (2) of a jet pump assembly. The internal seal (20) provides an effective means of mitigating leakage and slip joint flow induced vibration (FIV) between the inlet mixer (4) and diffuser (2) to reduce damage to many of the jet pump assembly components that may otherwise be damaged by FIV. A metallic seal (24) of the slip joint internal seal flares out to conform the internal seal to a range of gap sizes, and may be compressed or spring back to nominal dimensions as thermal expansion and contraction occurs. The internal seal is also self-expanding / self-tightening, as the internal seal flares further outward as a result of the internal pressure caused by flowing fluids in an operating jet pump assembly.