Slow Closing Actuator for Short Throw Valves
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Solution Overview
Problem
Short throw valves, such as quarter-turn ball valves and butterfly valves, are prone to causing water hammer effects when manually operated, leading to potential damage in piping systems due to rapid closure, which existing modifications attempt to mitigate by adding complexity and expense.
Innovation Solution
An actuator system featuring a plate with a guide slot of varying radii and a cam mechanism that controls the handle's rotation, allowing for controlled opening and closing of the valve to prevent sudden flow changes and thus avoid water hammer, maintaining simplicity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If short throw valves are used for controlling water flow, then valve simplicity and reliability are improved, but water hammer effect occurs due to rapid closing
Solution Approach 1:
The guide slot is designed with varying radius of curvature along its length, creating different arc lengths for cam traversal. This dynamic geometric variation controls the valve closure speed - the cam traverses a longer arc in the first region (slower closure) and a shorter arc in the second region (faster closure), enabling controlled slow closing to prevent water hammer while maintaining valve reliability
Solution Approach 2:
The radius of curvature parameter of the guide slot is changed along its length, with the first region having a larger radius and the second region having a smaller radius. This parameter variation directly controls the cam's motion path and the valve's closing speed, transforming the closure characteristic from rapid to controlled slow closing
2Object-affected harmful factors
If multi-turn handle with reduction gearing is added to prevent quick closing, then water hammer effect is avoided, but device complexity and cost increase
Solution Approach 1:
The actuator combines the handle, cam, and guide slot into a single integrated assembly that works with the existing valve stem. This merged design achieves slow closing control without requiring separate multi-turn handles or reduction gearing mechanisms, maintaining simplicity while preventing water hammer
Solution Approach 2:
The cam acts as an intermediary element between the handle and the valve stem. By introducing this intermediate component that interacts with the guide slot, the system achieves controlled motion transmission and slow closing without complex gearing mechanisms
3Object-affected harmful factors
If valve closure speed is reduced to prevent water hammer, then piping system safety is improved, but closure time increases
Solution Approach 1:
The guide slot is divided into two regions with different arc lengths - the first region provides extended traversal for controlled slow closing to prevent water hammer, while the second region provides shorter traversal for faster completion. This partial differentiation of closure phases achieves protection without excessive total closure time
Data Source
AI summary
A valve actuator is disclosed for use with short throw valves. The actuator includes a plate perpendicular to the valve stem that has a slot formed of regions having different radii of curvature centered on the valve stem. An eccentric cam is attached to a handle mounted on the valve stem. The cam extends through the slot and is rotatable for positioning at a radius corresponding to the radius of the different slot regions. When the cam is rotated so that it may traverse a slot region, the handle can be turned to move the valve closing member through an angle subtended by the slot region. This permits the valve to be opened or closed in a step-wise fashion and prevents rapid opening and closing of the valve that can cause a water hammer effect.