Butterfly Valve Stem Seal Assembly for Thermal Cycling Leakage
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Solution Overview
Problem
Valves face leakage issues due to demanding environmental and operating conditions, such as thermal cycling, high temperatures, vibrations, and pressure changes, which degrade traditional stem seals, leading to fugitive emissions and operational hazards.
Innovation Solution
A butterfly valve with a dual stem seal assembly that includes a primary and secondary seal system, utilizing a force transmitting member to expand radially and create multiple seals, along with a secondary sealing assembly between the body and flow element, to prevent leakage and detect leaks before they occur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional single stem seal is used, then the device complexity is low, but the reliability of preventing leakage under demanding conditions deteriorates
Solution Approach 1:
The stem seal assembly is divided into multiple independent seal elements (primary seal, secondary seal, tertiary seal) arranged in series along the stem. Each seal element can independently prevent leakage, and the segmentation allows each seal to be optimized for specific operating conditions while maintaining overall sealing reliability
Solution Approach 2:
The patent incorporates multiple backup seal elements that activate if primary seals fail. The redundant seal arrangement provides beforehand cushioning against seal failure, ensuring that if one seal degrades or fails under thermal cycling or vibration, other seals remain intact to prevent leakage
2Reliability
If multiple seal assemblies are implemented, then the reliability of preventing leakage improves, but the device complexity increases
Solution Approach 1:
Multiple seal elements are merged into a single integrated stem seal assembly that functions as one cohesive unit. The seals are arranged concentrically around the stem and are simultaneously actuated by stem movement, combining multiple sealing functions into a unified structure that reduces overall complexity
Solution Approach 2:
The stem seal assembly is designed to perform multiple functions simultaneously: the primary seal prevents leakage under normal conditions, the secondary seal provides backup protection, and the tertiary seal offers additional redundancy. Each component serves multiple purposes including sealing, supporting the stem, and accommodating thermal expansion
3Reliability
If traditional sealing means are used, then the ease of manufacture is high, but the reliability under thermal cycling and vibration deteriorates
Solution Approach 1:
The seal elements are designed with specific material properties and geometric parameters that allow them to maintain sealing integrity under thermal cycling and vibration. The seals incorporate compliance features and are positioned to accommodate dimensional changes due to temperature variations while maintaining contact pressure
4Reliability
If a robust multi-seal system is implemented, then the reliability under demanding conditions improves, but the ease of manufacture deteriorates
Solution Approach 1:
The seal elements are arranged in a nested configuration where secondary and tertiary seals are positioned inside or adjacent to the primary seal assembly. This nesting allows all seal elements to be housed within a compact space and facilitates assembly by allowing components to be installed in a sequential, nested manner
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 under demanding conditions, maintains sealing integrity, and detects leaks proactively, reducing operational risks and compliance issues.
Implementation Method 1
the force transmitting member is configured to transfer an axial load to the second pusher, which causes the first and second energizer to expand radially to create a secondary and tertiary seals
Data Source
AI summary
A butterfly valve capable of preventing leakage under demanding environmental and operating conditions. The valve includes two stem seal assemblies. The stem seal assemblies include a first pusher, a first energizer, a second pusher, a second energizer, and a force transmitting member. The force transmitting member is configured to transfer an axial load to the second Pusher, which causes the first and second energizer to expand radially to create a secondary and tertiary seals between the stem seal assembly and valve stem. In addition, the force transmitting member is configured to transfer an axial load to the first pusher which creates a primary seal.