Pressure-Balanced Valve Seal Assembly for Class V Shutoff
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Solution Overview
Problem
High temperature pressure-balanced control valves struggle to achieve ANSI/FCI 70-2 Class V shutoff without pilot operated plug designs, which are costly and introduce stability limitations due to leakage through conventional dynamic seals.
Innovation Solution
A valve assembly with a static seal positioned radially between a seat ring and the inner sidewall of the seat-retainer chamber, combined with a dynamic seal on the plug head, providing a robust seal that maintains pressure balance and achieves Class V shutoff without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional dynamic seal is used in high temperature pressure-balanced control valves, then the valve can maintain pressure balance with simpler structure, but the shutoff capability deteriorates to only Class III or Class IV instead of Class V
Solution Approach 1:
The sealing system is divided into two independent parts: a dynamic seal (piston ring) for maintaining pressure balance during operation, and a static seal (secondary seal) for providing tight shutoff when the valve closes. This segmentation allows each seal to be optimized for its specific function, enabling Class V shutoff capability while maintaining the simplicity of pressure-balanced operation.
2Reliability
If a pilot operated plug design is implemented to achieve Class V shutoff, then the shutoff capability improves to Class V, but the device complexity increases and stability limitations are introduced
Solution Approach 1:
The invention merges the pressure-balancing function and the shutoff function into a single integrated plug design. The plug incorporates both the dynamic seal for pressure balancing and the static seal for shutoff, eliminating the need for separate pilot operated components while achieving Class V shutoff capability.
3Reliability
If a pilot operated plug design is used to achieve Class V shutoff, then the shutoff capability improves to Class V, but the stability of the valve deteriorates due to introduced limitations
Solution Approach 1:
The invention extracts and eliminates the pilot operated mechanism from the valve design, retaining only the essential sealing components. By removing the pilot system with its inherent stability limitations, the valve achieves Class V shutoff capability while maintaining superior stability and response characteristics.
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 assembly provides tight shutoff in high temperature applications exceeding 500° F. with ANSI/FCI 70-2 Class V performance, reducing costs and stability issues by eliminating the need for pilot operated elements.
Implementation Method 1
A static seal is positioned radially between the seat ring and the inner sidewall of the seat-retainer chamber
Implementation Method 2
A dynamic seal is conventionally used to seal between the plug and the sleeve to maintain the pressure in the chamber on the top of the plug head
Data Source
AI summary
Seal assemblies for valves may include a movable seat configured to be disposed in a chamber of a valve. In an initial position, the movable seat is configured to contact a proximal portion of a plug head of the valve at an annular location that is spaced from a distal portion of the plug head during a closing stroke of the plug head. A biasing element is configured to bias the movable seat in the initial position and to enable the movable seat to move in a direction of the closing stroke of the plug head against a biasing force of the biasing element.