Doubly Eccentric Butterfly Valve for Vacuum Leakage Control
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Solution Overview
Problem
Vacuum pressure control apparatuses using butterfly valves face internal leakage issues due to deteriorated elastic seal members, especially in semiconductor manufacturing processes where toxic gases are used, and emergency stops require preventing such leakage to ensure safety.
Innovation Solution
A vacuum pressure control apparatus with a doubly eccentric butterfly valve element and an annular elastic seal member, where the valve element can be rotated to a second valve closed position different from the initial position to maintain a sealed state even if the elastic seal member deteriorates, utilizing a control unit to manage the valve's movement and prevent leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a butterfly valve with an elastic seal member is used to improve conductance and enable pressure control under near atmospheric pressure, then the valve conductance is improved, but internal leakage occurs when the elastic seal member deteriorates
Solution Approach 1:
The butterfly valve element is designed with dual closed positions (first and second closed positions) that can be switched dynamically. The control unit rotates the valve element between these two positions depending on the sealing requirement, allowing the system to adapt to the deteriorating elastic seal member and maintain reliable sealing while preserving high conductance during normal operation
Solution Approach 2:
The valve element's rotational position parameter is changed to have two distinct closed positions instead of a single closed position. By rotating the valve element to different angular positions (first closed position and second closed position), the system changes the sealing contact parameters to compensate for elastic seal member deterioration and prevent internal leakage
2Reliability
If the valve element is rotated to fully close the valve to prevent leakage, then sealing performance is improved, but pressure control capability is lost
Solution Approach 1:
The closed position function is segmented into two distinct positions: a first closed position for normal operation and a second closed position for emergency sealing. This segmentation allows the system to separate the pressure control function (maintained at first closed position) from the absolute sealing function (activated at second closed position), enabling both sealing performance and pressure control capability to coexist
3Object-affected harmful factors
If the elastic seal member is heated to prevent impurity adhesion, then cleanliness is improved, but the elastic seal member deteriorates faster
Solution Approach 1:
The system performs preliminary action by switching to the second closed position before severe leakage occurs due to elastic seal member deterioration. This preventive measure allows the valve to maintain reliable sealing without requiring excessive heating that would accelerate seal degradation, thereby extending the elastic seal member's service life while still preventing impurity adhesion during normal operation
Data Source
AI summary
A vacuum pressure control apparatus includes an annular elastic seal member formed with a valve seat, and a doubly eccentric butterfly valve element configured to come into contact or separate from the valve seat. The vacuum pressure control apparatus is to be placed on a pipe connecting a vacuum chamber and a vacuum pump. The vacuum pressure control apparatus is configured to rotate the butterfly valve element in a first direction from a first valve closed position corresponding to an initial state to change vacuum pressure in the vacuum chamber. The vacuum pressure control apparatus further includes a control unit configured to rotate the butterfly valve element in a direction opposite to a first direction so that the butterfly valve element is moved to a second valve closed position different from the first valve closed position.