Thermal-Release Shaft Sealing Ring for Uniform Pump Leakage Control
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Solution Overview
Problem
The existing shaft sealing structures for primary coolant circulation pumps in nuclear power plants face issues with uniform heat transfer and mechanical strength distribution, leading to potential leakage due to non-uniform contact and temperature differences, which compromise the reliability and safety during station blackout conditions.
Innovation Solution
A shaft sealing structure featuring a sealing ring with removed parts for continuous ends, a movable pressing member, an elastic member, a support member that buckles at elevated temperatures, and a communicating portion for uniform heat transfer, ensuring consistent contact with the rotation shaft and preventing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat is transferred from high-temperature primary coolant to the locking/unlocking means, then the mechanical strength decreases and the piston is released, but the heat transfer is not uniform in the circumferential direction causing non-uniform release and potential leakage
Solution Approach 1:
The locking/unlocking means is divided into multiple independent locking elements arranged circumferentially. Each locking element can respond independently to heat transfer, allowing for more uniform circumferential release behavior. The segmentation enables each element to be optimally sized and positioned for heat exposure, improving overall uniformity of the release process.
Solution Approach 2:
A heat transfer enhancement structure is introduced as an intermediary between the primary coolant and the locking/unlocking means. This intermediary structure distributes heat more uniformly across the circumferential direction, ensuring that all locking elements receive comparable thermal energy and release at similar times, thereby improving sealing reliability.
2Strength
If the locking/unlocking means uses material with high flowability to reduce mechanical strength at elevated temperatures, then the piston can be released, but the material may flow out from its installed position causing deformation and loss of function
Solution Approach 1:
The locking/unlocking means employs materials with different local properties: the bulk material has high flowability for reliable release, while the peripheral regions have enhanced structural characteristics to prevent outward flow. This local differentiation allows the material to exhibit release capability where needed while maintaining positional stability at critical boundaries.
Solution Approach 2:
The locking/unlocking means uses composite material construction combining a base material with high flowability characteristics and a reinforcing component with high structural stability. The composite structure enables the material to soften and flow for piston release while the reinforcing component prevents excessive deformation and material ejection, maintaining functional reliability.
3Reliability
If the sealing ring is made of PEEK resin to provide sealing function, then the sealing performance is improved, but the resin softens at high temperature requiring the locking/unlocking means to remain at its installed location without elution
Solution Approach 1:
The locking/unlocking means is designed with pre-planned thermal response characteristics that activate before the sealing ring material reaches its softening temperature. The locking elements begin to release at a lower temperature threshold, creating a cushioning effect that prevents the sealing ring from being subjected to high temperatures that would cause softening and loss of sealing performance.
Solution Approach 2:
The system replaces reliance on the sealing ring material's high-temperature stability with a thermal-triggered mechanical release mechanism. Instead of depending on the PEEK resin to maintain strength at high temperatures, the design uses temperature-sensitive locking/unlocking means that actively release the piston before the sealing ring reaches critical temperatures, substituting material property reliance with active mechanical control.
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 ensures uniform temperature distribution and mechanical strength across the sealing structure, allowing for reliable and smooth operation by maintaining consistent contact with the rotation shaft, even under high-temperature conditions, thereby enhancing safety and reliability during station blackout scenarios.
Implementation Method 1
a support member configured to support the pressing member at the retracted position against the elastic force of the elastic member, and to allow the pressing member to move to the pressing position at a predetermined temperature or higher
Implementation Method 2
an elastic member configured to bias the pressing member toward the pressing position by elastic force
Implementation Method 3
a communicating portion configured to communicate between an outer circumferential portion of the rotation shaft and an outer circumferential portion of the support member
Data Source
AI summary
A shaft sealing structure for a rotation shaft, includes a sealing ring having ends formed by removal of its part. The ends abutting each other are continuous in the circumferential direction when the sealing ring is reduced in diameter to a radially inner side. The sealing ring is provided along the circumferential direction of the rotation shaft so as to be contactable with an outer peripheral surface of the rotation shaft. The structure also includes a pressing member configured to be movable between a pressing position and a retracted position; an elastic member configured to bias the pressing member toward the pressing position by elastic force; and a support member configured to support the pressing member at the retracted position against the elastic force, and to allow the pressing member to move to the pressing position at a predetermined temperature.