Sealing Assembly Exploiting Differential Thermal Expansion
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Solution Overview
Problem
Designing large control valves for elevated temperatures is challenging due to differential thermal expansion between components made from different materials, leading to leakage issues, as existing seals are ineffective at high temperatures and cannot accommodate significant thermal expansion.
Innovation Solution
A fluid flow control device with a sealing assembly that exploits differential thermal expansion between the valve body and valve trim assembly, using a gland and sealing assembly to provide a seal by moving from a first to a second compression state, accommodating and utilizing thermal expansion to maintain a tight seal between the valve body and valve trim assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single gasket is used to compensate for differential thermal expansion in smaller control valves, then the seal effectiveness is improved, but the gasket cannot withstand the significant differential thermal expansion in large control valves at elevated temperatures
Solution Approach 1:
The sealing assembly is divided into multiple gaskets (first gasket and second gasket) positioned at different locations within the gland. This segmentation allows each gasket to handle specific portions of the thermal expansion, enabling the assembly to accommodate larger differential thermal expansion in large control valves while maintaining seal effectiveness
Solution Approach 2:
The sealing assembly uses multiple gaskets made of different materials with different thermal expansion coefficients. The first gasket and second gasket are selected to have thermal expansion properties that complement each other, allowing the composite sealing assembly to accommodate differential thermal expansion between the valve body and trim assembly at elevated temperatures
2Adaptability or versatility
If components are made from different materials to optimize performance, then the functional characteristics are improved, but differential thermal expansion between components increases at elevated temperatures
Solution Approach 1:
The sealing assembly is specifically designed to exploit thermal expansion. The gland provides a clearance that accommodates the differential thermal expansion between components made from different materials. The multiple gaskets are positioned to allow this expansion while maintaining sealing contact, converting the potentially harmful differential expansion into a mechanism that maintains seal stability
Solution Approach 2:
The sealing assembly acts as an intermediary between components made from different materials with different thermal expansion coefficients. It absorbs and accommodates the differential expansion through its multi-gasket design and gland clearance, preventing direct stress transmission between dissimilar materials while maintaining the seal
3Reliability
If polymer seals are used between the valve seat ring and valve body, then the sealing is effective at lower temperatures, but the seals become ineffective at high temperatures in excess of 450°F
Solution Approach 1:
The sealing assembly uses multiple gaskets made of different materials including graphite, metal, and other high-temperature resistant materials. This composite approach replaces the single polymer seal with a multi-material system that maintains sealing effectiveness at temperatures exceeding 450°F while accommodating thermal expansion
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 maintains a tight seal at high temperatures, allowing the control valve to operate from -325°F to 1100°F, minimizing leakage and enabling the use of different materials for components, thus enhancing the control valve's performance and longevity.
Implementation Method 1
The movement of the sealing assembly is due to differential thermal expansion between the valve body and the valve cage in a direction parallel to the longitudinal axis and in a direction transverse to the longitudinal axis
Data Source
Figure 1~1A
Figure 2
Figure 3
AI summary
A fluid flow control device includes a valve body (104), a valve seat (132) disposed within the valve body, and a valve cage (136) coupled to the valve seat within the valve body. The fluid flow control device also includes a gland (168) defined by the valve body, the valve seat, and the valve cage. The valve body has a first thermal expansion coefficient and the valve seat and/or the valve cage have a second thermal expansion coefficient different from the first thermal expansion coefficient. The fluid flow control device further includes a sealing assembly (172) disposed within the fluid flow control device to provide a seal between the valve body and the valve cage. The sealing assembly exploits differential thermal expansion between the valve body and the valve cage in a direction parallel to the longitudinal axis and in a direction transverse to the longitudinal axis to improve the seal.