Throttling Element Seal for Valve Leakage Control
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Solution Overview
Problem
Fluid flow control devices, particularly those used in erosive environments like power plants, face significant leakage and erosion issues due to imperfections in mating surfaces and disruptions in primary seals, leading to inefficiency and damage, with conventional solutions like harder materials or soft seat rings offering limited effectiveness.
Innovation Solution
A seal is introduced that engages the throttling element's outer or inner perimeter to create a redundant seal, independent of actuator force, reducing fluid flow through primary leak paths and minimizing exposure to erosive elements, using a C-shaped or O-ring configuration that can be energized by fluid pressure and formed from various materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a primary seal is formed by pressing the throttling element against the valve seat ring, then the device can close off the fluid flow path, but leakage occurs due to imperfections in the mating surfaces and pressure differentials
Solution Approach 1:
A seal member is introduced as an intermediary component between the throttling element and the valve seat ring. This seal member engages with the throttling element and provides a secondary sealing mechanism that addresses leakage through the primary seal, without requiring modification of the primary seal design itself
Solution Approach 2:
The seal member is configured as a flexible component that can deform to conform to the throttling element surface, creating an effective seal despite surface imperfections. The flexible nature of the seal member allows it to maintain sealing contact under varying pressure conditions
2Strength
If harder materials are used for the seating and throttling element to reduce erosion, then erosion resistance improves, but corrosion susceptibility increases due to chemical treatments and cycling operations
Solution Approach 1:
The seal member is positioned specifically at the sealing interface where erosion occurs, providing localized protection without requiring the entire throttling element or valve seat ring to be made of erosion-resistant materials. This allows the bulk materials to be selected for corrosion resistance
Solution Approach 2:
The system combines different materials with complementary properties: the seal member provides erosion resistance at the sealing surface, while the main body materials can be selected for corrosion resistance, creating a composite structure that addresses both erosion and corrosion concerns
3Reliability
If the throttling element is pressed against the valve seat ring with sufficient force to create a seal, then sealing improves, but actuator force requirements increase and wear accelerates
Solution Approach 1:
The seal member acts as an intermediary that facilitates sealing at lower contact pressures. By providing a compliant sealing surface, the seal member enables effective sealing without requiring the high actuator forces that would be needed to press the rigid throttling element directly against the valve seat ring with sufficient force
4Manufacturing precision
If a cage-style trim is used to guide the throttling element, then flow control precision improves, but a gap forms between the throttling element and cage due to machining tolerances, creating a leak path
Solution Approach 1:
The seal member is positioned to bridge the gap between the throttling element and the cage, preventing fluid leakage through the annular space created by machining tolerances. This allows the cage-style trim to maintain its flow control precision while eliminating the leak path
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 seal effectively reduces or eliminates fluid leakage and erosion, extending the lifespan of valve seats and reducing the reliance on actuator force for sealing, while being less susceptible to damage from entrained particles.
Implementation Method 1
Fluid pressure upstream of the primary seal creates a pressure differential across the seal
Implementation Method 2
Fluid pressure upstream of the primary seal creates a pressure differential across the seal
Data Source
AI summary
A fluid flow control device includes a body defining an inlet, an outlet, and a fluid flow path extending from the inlet to the outlet. A valve seat ring is coupled to the body and defines an orifice through which the fluid flow path passes. A cage is also coupled to the body and defines an interior bore, wherein the cage includes at least one passage through which the fluid flow path passes. A throttling element is sized for insertion into the cage interior bore and movable along an axis between open and closed positions. The throttling element defines a sealing surface oriented substantially parallel to the axis. A seal is positioned to engage the sealing surface when the throttling element is substantially in the closed position, thereby to restrict fluid flow through the valve seat ring orifice.