Centric Butterfly Valve Seal Geometry for Low-Torque Sealing
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Solution Overview
Problem
Centric butterfly valves face issues with non-uniform surface pressure and stress concentration due to small annular and circumferential protrusions, leading to reduced sealability and durability, as well as increased open/close operation torque.
Innovation Solution
A centric butterfly valve design featuring an M-shaped section outer peripheral seal part with two linear round-shaped apex parts and a round-shaped valley-bottom part, which are crushed to form two linear seal parts, providing uniform surface pressure and dispersing stress, thus enhancing sealability and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the widths of the annular protrusion and circumferential protrusion are made smaller to reduce open/close operation torque, then the crush margins are decreased and operation torque is reduced, but the surface pressure of the blade portion becomes non-uniform and sealability deteriorates
Solution Approach 1:
The outer peripheral seal part is divided into multiple apex parts (first, second, third, and fourth apex parts) arranged circumferentially. This segmentation allows each apex part to independently contact the inner peripheral surface, creating multiple contact points that distribute pressure uniformly while maintaining small overall width for reduced torque.
Solution Approach 2:
The apex parts are designed with specific local geometric features including rounded contact surfaces and optimized width ratios. The first and second apex parts have different width relationships with adjacent valleys, creating localized variations in contact pressure distribution that ensure uniform overall surface pressure while maintaining small crush margins.
2Force
If the widths of the annular protrusion and circumferential protrusion are made smaller to reduce operation torque, then crush margins are decreased, but stress concentrates on these protrusions and durability deteriorates
Solution Approach 1:
By dividing the seal part into multiple apex parts, the stress that would concentrate on a single small protrusion is distributed across multiple separate contact points. This segmentation reduces the stress burden on each individual apex part while maintaining the small width needed for low torque operation.
Solution Approach 2:
The apex parts are designed with rounded contact surfaces and appropriate width ratios that prevent stress concentration before it can cause failure. The geometric design inherently cushions the stress distribution, preventing the initiation of rupture points that would compromise durability.
3Force
If the annular protrusion and circumferential protrusion are provided with arc-shaped sections to reduce crush margins and operation torque, then operation torque is decreased, but local friction force causes stress concentration and durability deteriorates
Solution Approach 1:
The apex parts feature localized rounded contact surfaces with optimized curvature radii. This local quality design allows the contact surfaces to be smooth and rounded (reducing friction) while maintaining the small overall width of the protrusions (reducing torque). The specific width ratios between adjacent apex parts and valleys create optimal stress distribution patterns.
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 M-shaped section design achieves high seal surface pressure, uniform surface pressure distribution, and improved durability by reducing stress concentration, resulting in enhanced sealability and reduced open/close operation torque.
Implementation Method 1
the M-shaped section part has the two linear apex parts crushed in a fully-closed state
Implementation Method 2
an M-shaped-section outer peripheral seal part is provided at an outer peripheral end of the blade portion of the valve disk to improve sealability
Implementation Method 3
the valley-bottom part has a roundness dimension in a range on order of 1⁄2 to twice as large as the roundness dimensions in the vicinities of the apex parts
Data Source
AI summary
A centric butterfly valve (1) in which top and bottom boss surfaces (19, 29) are formed to be spherical, an outer peripheral end of the blade portion of the valve disk (24) is formed to be an M-shaped section part (29) with round-shaped apex parts (27) and a round-shaped valley part (28) smoothly linked, and the centric butterfly valve has a valve disk (3) having an extended part (41) obtained by successively and slightly extending the spherical surface of each of the top and bottom boss surfaces (19, 20) to a blade portion (40) side.