Pneumatic Drive System for Control Valve Positioning
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Solution Overview
Problem
Pneumatic drive systems for control valves in process plants face challenges in achieving rapid and precise position control, often resulting in overshooting and delayed responses due to pneumatic power transmission, which can lead to unsafe operating states and difficulties in regulating process media.
Innovation Solution
A pneumatic drive system with a current-to-pressure converter that generates two independent pneumatic actuating signals with different pressure and timing characteristics, allowing for rapid displacement and fine-tuning of the control valve position, using high and low air flow rates to overcome static friction and prevent overshooting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single pneumatic control signal is used to actuate the control valve, then the system structure is simple, but the position control precision deteriorates due to overshooting and delayed response
Solution Approach 1:
The single pneumatic control signal is segmented into two independent control signals with different characteristics (first control signal for rapid displacement, second control signal for fine-tuning). This segmentation allows the system to achieve both fast response and precise positioning by applying different control strategies at different stages of valve actuation.
Solution Approach 2:
The control system dynamically switches between different control signals based on the valve's position and operational requirements. The evaluation unit dynamically determines which control signal to apply, creating a dynamic control strategy that adapts to the real-time state of the system, thereby improving both response speed and positioning accuracy.
2Speed
If high pneumatic pressure is applied to move the control valve quickly, then the response speed improves, but the risk of overshooting and dangerous operating states increases
Solution Approach 1:
The system dynamically adjusts the pneumatic pressure applied to the valve based on real-time evaluation of valve position and operational state. High pressure is applied only when needed for rapid displacement, then switched to low pressure for fine-tuning, creating a dynamic pressure control strategy that maintains both speed and safety.
Solution Approach 2:
The control system employs periodic evaluation and switching between different control signals in a structured sequence. The evaluation unit periodically assesses the valve state and switches between high-pressure and low-pressure control modes, creating a rhythmic control pattern that ensures safety while maintaining responsiveness.
3Ease of operation
If the control valve is used to regulate process medium, then the regulation function is achieved, but vibrations are induced making precise control difficult
Solution Approach 1:
The control system dynamically adapts its control strategy based on the operational state of the valve and process medium. By continuously evaluating the valve position and adjusting the control signal accordingly, the system can maintain precise control even when vibrations are present, reducing their impact on control accuracy.
4Force
If greater force is applied to release the valve element from the valve seat, then the valve can be opened from stuck position, but the response time increases due to delay
Solution Approach 1:
The actuation process is segmented into two phases: an initial high-force phase to overcome static friction and release the stuck valve element, followed by a low-force fine-tuning phase to complete the opening process. This segmented force application reduces the total time required compared to applying high force throughout the entire movement.
Solution Approach 2:
The system applies a preliminary high-force control signal specifically targeted at overcoming the static friction and releasing the stuck valve element. This preliminary action prepares the system for the subsequent fine-tuning phase, ensuring that the valve is released quickly before transitioning to the slower, more precise positioning phase.
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
Enables quick and precise control of control valves, preventing dangerous operating states and oscillations, ensuring reliable and efficient regulation of process media by using high-pressure signals for rapid displacement and low-pressure signals for fine-tuning.
Implementation Method 1
A current-to-pressure converter coupled to the working chamber for pressurizing the working chamber with a pneumatic pressure
Implementation Method 2
a pneumatic drive chamber and a spring-loaded return chamber can be formed within a drive housing
Data Source
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AI summary
In a pneumatic drive system (1) for actuating a control valve (5), in particular a control valve or a safety valve, of a process engineering plant, comprising a pneumatic working chamber (3) and a current-pressure converter (7) coupled to the working chamber for pressurizing the working chamber with a pneumatic pressure through which the control valve is moved, wherein the current-pressure converter has at least one electrical input (w) for receiving an electrical control signal, it is provided that the current-pressure converter generates at least two pneumatic control signals (S1, S2, S3) with which one working chamber is pressurized.