Fail-Safe Actuation System with Decoupled Safety Circuit
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Solution Overview
Problem
Existing fail-safe actuation systems for hydraulic or pneumatic pistons, such as those used in wind turbines, cannot reliably move actuators into a safe position in case of pump blockage or circuit defects, compromising safety and operational reliability.
Innovation Solution
A fail-safe fluid-based actuation system with a safety circuit that automatically connects a pressurized tank to the actuator's first chamber, decoupling from the working circuit, and includes a short-circuit fluid connection between chambers to ensure movement into a safe position, even if the working circuit fails, using a switching valve and check valves to prevent fluid loss and ensure redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the pump and circuit elements are used for actuation, then the actuator can be controlled during regular operation, but the system cannot rely on these elements in case of pump blockage or line defects
Solution Approach 1:
The system is segmented into working and safety circuits with completely separate pumps, control valves, and fluid pathways. The working circuit handles normal actuator control with the working pump and control valves, while the safety circuit with its dedicated safety pump and safety control valves handles emergency positioning. This segmentation allows easy operation during normal conditions while ensuring reliability during failures.
Solution Approach 2:
The system changes operational parameters by switching between working circuit mode (normal pressure, normal flow) and safety circuit mode (emergency pressure from safety tank, emergency flow path). The switching valve and associated control mechanisms enable this parameter change, allowing the system to transition from regular operation to fail-safe operation based on system state.
2Loss of substance
If the safety circuit is completely decoupled from the working circuit, then fluid loss is minimized and pressure is maintained, but the system complexity increases
Solution Approach 1:
The hydraulic system is segmented into two completely independent circuits with separate fluid pathways, pumps, and control valves. The safety circuit is fully decoupled from the working circuit, meaning fluid in the safety pressure tank cannot leak into the working circuit and vice versa. This segmentation minimizes fluid loss by containing potential leaks within each separate circuit while maintaining the necessary complexity through dual independent systems.
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 system reliably moves the actuator into a safe position, maintaining safety and operational integrity even during failures like pump blockages or circuit defects, by utilizing the energy stored in the tank and decoupling from the working circuit, ensuring minimal fluid loss and maintaining pressure for actuation.
Implementation Method 1
a tank (7) that holds pressurized fluid and that, in the failure state, is automatically connected to the first chamber (3)
Implementation Method 2
a drain valve (9) that, in the failure state, is moved into the through-flow position in order to drain fluid out of the second chamber (4)
Implementation Method 3
check valves to prevent fluid loss and ensure redundancy
Implementation Method 4
a short-circuit fluid connection (36) is provided between the first and second chambers (3, 4) that, in the failure state, is through-connected in order to generate a short-circuit flow between the first and second chambers (3, 4)
Data Source
AI summary
A fail-safe actuation system comprising an actuator having first and second chambers, a working circuit with a motor/pump device configured to actuate the actuator in an operative state, and a safety circuit configured to move the actuator into the safety position in a failure state, the safety circuit having a tank that holds pressurized fluid and that, in the failure state, is automatically connected to the first chamber via a switching valve, and having a drain valve that, in the failure state, is moved into a through-flow position in order to drain fluid out of the second chamber, the safety circuit configured such that, in the operative state, an inflow into the actuator—in a manner that is decoupled from the tank—is established by the working circuit, and, in the failure state, an inflow from the tank into the first chamber—in a manner that is completely decoupled from the working circuit—is created by the safety circuit, whereby a short-circuit fluid connection is provided between the first and second chambers that, in the failure state, is through-connected in order to generate a short-circuit flow between the first and second chambers.