Electric Valve Actuator Latch Architecture for Fail-Safe Closure
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Solution Overview
Problem
Electric actuators for gate valves in wellheads and Christmas trees face high power consumption and complex fail-safe mechanisms, which discourage their adoption due to energy inefficiency and potential mechanical stress on electromagnets.
Innovation Solution
A simplified fail-safe electric valve actuator design with an integral drive assembly and latching mechanism, utilizing a torsion spring and electromagnetic means for efficient power management and reduced mechanical stress, allowing the actuator to automatically switch to a fail-safe position during power failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional fail-safe mechanism with hydraulic or pneumatic piston and coil spring is used, then the valve can be closed under emergency circumstances, but the structure becomes complex and requires succession of levers for latching and unlatching operations
Solution Approach 1:
The latching mechanism is divided into two independent units: a first latching unit that latches the drive assembly at the fully opened position, and a second latching unit that latches the drive assembly at the fully closed position. This segmentation allows each unit to perform a specific function independently, simplifying the overall structure while maintaining reliable emergency closure capability.
Solution Approach 2:
Instead of using a complex succession of levers for latching and unlatching operations, the invention uses a direct electromagnet-release mechanism. The electromagnet directly engages with the latching unit to hold it in place, and release is achieved by simply de-energizing the electromagnet, allowing the latching unit to move freely under spring action. This inverts the traditional approach from mechanical lever sequences to electromagnetic direct engagement.
2Reliability
If an electromagnet is used to sustain the load of the drive unit and latching mechanism, then the latching can be maintained, but the electromagnet is put under a lot of mechanical stresses
Solution Approach 1:
A latching unit is introduced as an intermediary mechanical element between the electromagnet and the drive assembly. The electromagnet does not directly sustain the load of the drive unit; instead, it engages with the latching unit which then provides the mechanical support and latching function. This intermediary reduces the mechanical stress on the electromagnet while maintaining reliable latching.
Solution Approach 2:
The latching unit acts as a mechanical copy or surrogate for the electromagnet's holding function. When the electromagnet is de-energized, the latching unit maintains the latched position through its own mechanical structure and spring bias, effectively copying the holding function without requiring the electromagnet to sustain continuous mechanical stress.
3Volume of moving object
If the drive unit, return spring and latch are disposed in a same block, then the assembly is compact, but the assembly becomes complex and a part failure can cause the failure of the whole assembly
Solution Approach 1:
The actuator is segmented into distinct functional modules: the drive assembly, the first latching unit, and the second latching unit. Each module can be independently assembled, tested, and replaced. This segmentation reduces the risk that a failure in one component will cause failure of the entire assembly, as other modules can continue to function or be independently serviced.
4Reliability
If a succession of levers is used for latching and unlatching operations, then the fail-safe closure can be achieved, but the number of interacting parts increases leading to higher probability of part failure
Solution Approach 1:
The complex succession of levers is extracted and replaced with a simplified direct-acting latching mechanism. The latching unit can be directly engaged and disengaged by the electromagnet without requiring intermediate lever mechanisms. This extraction of the unnecessary lever system reduces the number of parts and interaction points while maintaining the fail-safe closure function.
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 solution reduces power consumption and mechanical stress, enhancing the reliability and efficiency of electric actuators while ensuring safe valve operation during emergencies by simplifying the mechanism and reducing the number of interacting parts.
Implementation Method 1
a biasing assembly (5) adapted to act on the drive assembly (3) to urge it toward a fail-safe position
Implementation Method 2
electromagnetic means (84), when activated, for holding the first latching unit (7) in the latched position
Data Source
AI summary
Electric valve actuator, comprising: a stem (41, 43) for moving a valve member between open and closed positions; a drive assembly for moving the stem comprising an electric motor (31); a biasing assembly (5) adapted to act on the stem to urge it toward a failsafe position; and a fail-safe shutdown system to allow the biasing assembly to urge the stem toward the failsafe position, comprising a first latching unit (7) mounted movable in translation in the housing and a second latching unit (8) mounted on the housing for latching engagement with the first unit, whereby the stem can be moved free from the action of the biasing assembly in the latched state of the first and second latching units; and the drive assembly and the stem are mounted integral in translation with the first unit (7), which is mounted integral in translation with the biasing assembly.