Butterfly Valve Clamp Connection for Safe Over-Torque Failure
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Solution Overview
Problem
Butterfly valves face challenges with shaft-to-disc connections that are not strong enough to withstand diverse operating conditions, leading to potential catastrophic failures and loss of flow control, especially when the actuator outside the pressure boundary is over-torqued.
Innovation Solution
A clamp with a unique shape is used to mount the closing member to the shaft, ensuring that the external portions of the shaft fail before the internal components, providing a stronger connection and preventing slippage and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shaft-to-disc connection is strengthened to withstand over-torque conditions, then the reliability of the valve is improved, but the device complexity increases due to the need for a specialized clamp design with unique interface geometry
Solution Approach 1:
The shaft is divided into two distinct segments: an external portion outside the pressure boundary and an internal portion inside the pressure boundary. These segments have different strength characteristics, with the external portion being weaker than the internal portion. This segmentation allows the valve to fail safely at the external portion before the critical internal shaft-to-disc connection, preventing catastrophic failure while maintaining reliability.
Solution Approach 2:
The clamp design incorporates a unique interface geometry with specific engagement surfaces that create a localized strong connection between the shaft and disc. The clamp has a first engagement surface that interfaces with the shaft and a second engagement surface that interfaces with the disc, creating a localized area of enhanced strength at the shaft-to-disc connection point without requiring the entire shaft to be overly complex.
2Object-affected harmful factors
If the external shaft portion is designed to fail before internal components, then catastrophic failure is prevented, but the manufacturing precision requirements increase to ensure proper strength distribution
Solution Approach 1:
The shaft is pre-designed during manufacturing with a deliberate strength gradient built into its structure. The external portion is manufactured to have lower strength characteristics than the internal portion, creating a predetermined failure sequence. This preliminary design ensures that under over-torque conditions, the external portion will fail first as intended, preventing catastrophic failure of the internal shaft-to-disc connection.
Solution Approach 2:
Instead of designing the shaft to be uniformly strong throughout, the design inverts the expected approach by making the external portion intentionally weaker than the internal portion. This inverted strength distribution ensures that the less critical external components fail first, protecting the more critical internal shaft-to-disc connection from catastrophic failure.
3Device complexity
If a traditional shaft mounting method is used, then the device complexity is reduced, but the shaft-to-disc connection may slip or fail under diverse operating conditions
Solution Approach 1:
The clamp serves as an intermediary component between the shaft and the disc, providing a specialized connection mechanism. The clamp has specific engagement surfaces that interface with both the shaft and the disc, creating a reliable mechanical connection that prevents slippage and failure under diverse operating conditions. This intermediary component enables the reliable connection without requiring direct complex integration of the shaft and disc.
Data Source
AI summary
A valve design including a valve body comprising an aperture through the body is disclosed. The valve includes a shaft secured to a disc with a clamping connection.