Control Valve Thermal Compensation for Precise Positioning
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Solution Overview
Problem
Control valves in process plants experience significant positioning and control errors due to thermal expansion, especially in extreme temperature conditions, leading to shifts in valve positions and deteriorated control quality, with existing solutions being difficult to implement and limited in effectiveness.
Innovation Solution
A system that includes a position control system with a pneumatic actuator and a position controller, which determines a travel correction based on the temperature difference between the process fluid temperature and ambient temperature, using expansion coefficients to adjust the control valve position and correct for dimensional changes caused by thermal stress, thereby maintaining and improving control quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If control valves are used in extreme temperature conditions, then the control valve can operate in cryogenic or high temperature applications, but positioning and control errors increase due to thermal expansion
Solution Approach 1:
The patent applies thermal expansion principles by introducing a compensation rod made of material with different thermal expansion characteristics than the control valve body. The compensation rod is designed to expand or contract in response to temperature changes, thereby compensating for the dimensional changes in the control valve components and maintaining positioning accuracy across extreme temperature ranges.
Solution Approach 2:
The patent changes the material parameter (thermal expansion coefficient) by using a compensation rod made of a different material than the control valve body. This parameter change allows the system to adapt to temperature variations, as the compensation rod's dimensional changes counterbalance the dimensional changes in the control valve components, thus resolving the positioning accuracy issue.
2Manufacturing precision
If thermal compensation elements are added to control valves, then positioning accuracy improves, but device complexity increases
Solution Approach 1:
The patent uses thermal expansion of a compensation rod to automatically compensate for dimensional changes in the control valve. This passive compensation mechanism improves positioning accuracy without requiring complex active control systems, sensors, or actuators, thereby limiting the increase in device complexity.
Solution Approach 2:
The compensation rod acts as an intermediary element between the temperature environment and the control valve positioning mechanism. It mediates the thermal effects by absorbing dimensional changes and translating them into compensatory movements, thereby improving positioning accuracy while adding only a single mechanical component rather than a complex control system.
3Reliability
If different materials are selected for control valve components, then thermal expansion differences can be managed, but material selection becomes more difficult and costly
Solution Approach 1:
The patent deliberately selects materials with different thermal expansion coefficients for the compensation rod and control valve body. This material selection exploits thermal expansion differences to achieve automatic compensation, improving thermal stability and positioning reliability while maintaining a relatively simple manufacturing process.
Solution Approach 2:
The patent employs a composite material approach by combining the control valve body material with a compensation rod made of a different material. This composite construction allows the system to leverage the thermal expansion characteristics of both materials, achieving thermal stability and positioning accuracy while keeping the manufacturing process manageable through the use of standard engineering materials.
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 effectively corrects control valve positions and maintains control quality by compensating for thermal expansion, ensuring precise control and preventing shifts in valve positions, especially under extreme temperature conditions, with a simple and easy-to-implement method.
Implementation Method 1
Adjusting fittings, which influence, in particular control and/or regulate, a process medium flow of a process engineering system, can experience changes in length due to their thermal expansion coefficients, in particular due to the thermal expansion coefficients of the components of the adjusting fittings.
Implementation Method 2
The actuating rod of the actuating fitting, which is connected to the actuating drive and the actuator, can therefore transfer heat or cold along the actuating rod between the actuating drive and the actuating element.
Data Source
Figure 1
AI summary
The present invention relates to a system for compensating for a dimensional change of a control fitting, which dimensional change accompanies thermal loading, for setting a process fluid stream of a process plant, such as a chemical plant, a food processing plant, a power plant or the like, wherein the control fitting has a control valve and an actuating drive which drives the control valve, in particular pneumatically, wherein the system determines an actuating travel correction for the actuating drive on the basis of a temperature difference between a process temperature, such as the process fluid temperature, and an ambient temperature, such as an actuating drive temperature.