Actuator Return Stop Device for Fail-Safe Valve Positioning
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Solution Overview
Problem
Existing electrical actuators in the oil and gas industry require stronger motors and complex constructions to implement a 'fail as is' mode without energy, which increases costs and complexity.
Innovation Solution
A return stop device with a pot-shaped outer part and a hub part, featuring a wedging mechanism that allows free rolling in one direction and prevents rotation in the other, is integrated into the actuator, enabling 'fail as is' functionality without energy usage and reducing motor strength requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a return stop device is added to enable 'fail as is' mode, then reliability is improved, but device complexity increases
Solution Approach 1:
The return stop device merges the braking function and position-holding function into a single integrated mechanism. The hub part combines the brake drum and position-holding structure, while the wedging member serves both as a brake element and a locking element, eliminating the need for separate braking and holding devices.
Solution Approach 2:
The wedging member is designed to perform multiple functions: it acts as a brake element during normal operation to prevent overs rotation, and simultaneously serves as a position-holding element in fail-as-is mode to maintain valve position without energy consumption. This multi-functionality reduces the overall number of components needed.
2Reliability
If a stronger motor is used to overcome valve-induced rotation, then reliability is improved, but power consumption increases
Solution Approach 1:
The return stop device enables the system to hold position autonomously without continuous energy input. When energy is available, the motor overcomes valve-induced rotation normally. When energy fails, the wedging member automatically engages to prevent retrograde rotation, making the position-holding function self-sustaining without motor power.
Solution Approach 2:
The return stop device acts as an intermediary mechanical element between the motor and the valve. It provides a passive mechanical barrier (the wedging member) that prevents valve-induced rotation without requiring the motor to continuously counteract the valve force, thereby reducing energy consumption during position holding.
3Reliability
If a return stop device is integrated into the actuator, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The return stop device is integrated into the existing actuator structure rather than being added as a separate assembly. The hub part utilizes the existing brake drum structure, and the wedging member is incorporated into the gear shaft assembly, eliminating the need for separate manufacturing and assembly processes for additional components.
Solution Approach 2:
The return stop device is designed as a modular component that can be manufactured separately and then integrated into the actuator. The hub part, outer part, and wedging member are distinct components that can be produced using standard manufacturing processes and assembled together, simplifying production and maintenance.
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 provides a simple, reliable, and cost-effective 'fail as is' mode by preventing valve-induced rotation, allowing unimpeded actuation in both directions without energy consumption, resulting in a robust and compact design.
Implementation Method 1
a wedging member (11) is situated in the free space (10). Rotation of the drive shaft (4) causes the wedging member (11) to transition to a free rolling position, enabling the hub part (9) to rotate relative to the outer part (8). If, however, a respective torque acts upon the drive shaft (4) from the side of the attached valve, then no movement of the wedging member (11) takes place to transition the wedging member (11) to the free-rolling position. Instead, the wedging member (11) stays in the wedging position and a turning back of the drive shaft (4) caused by the attached valve is prevented.
Data Source
AI summary
An electrical actuator (1) especially for operating a valve (2) has at least one electric motor (3), a drive shaft (4) driven by the electric motor (3) and a gear shaft (5) rotatable by the drive shaft (4), which gear shaft is connected to a valve member (6) in a motion-transferring manner. Between the drive shaft (4) and the gear shaft (5), a return stop device (7) especially acting both ways in rotational direction is formed. This return stop device (7) has a pot-shaped outer part (8) and a hub part (9) rotatably supported therein. The hub part (9) is connected to the gear shaft (5) in a torque-proof manner and within at least one free space (10) between the hub part (9) and the outer part (8) a wedging member is arranged. This is only movement into free rolling position by the drive shaft (4) under a rotation of the drive shaft (4). The invention enables an improvement of an electrical actuator to the effect that this is provided with a so-called “fail as is”-device, while having a simple, reliable and cost-efficient construction and without the use of a stronger motor.