Process Control Valve Stroke-End Calibration During Operation
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Solution Overview
Problem
The adjustment of stroke end positions for process control valves in plants often requires downtime for replacement or re-adjustment, as existing methods cannot be performed during ongoing operation, leading to increased downtime and potential disruption of plant operations.
Innovation Solution
A method and system for adjusting stroke end positions of a process control valve during plant operation using a valve control mechanism with a travel-measurement system, which recognizes and stores actual stroke end positions when the valve is fully open or closed, allowing for continuous operation without interruption, by modifying position set-point values to account for mechanical tolerances and using a differentiating filter for recognition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the valve is proactively opened and closed for adjustment, then the stroke end positions can be calibrated, but the normal plant processes are disturbed and operation is interrupted
Solution Approach 1:
The system performs preliminary calibration actions during naturally occurring valve operations. Instead of forcing additional open/close cycles, the system prepares calibration routines that execute during normal process operations when the valve naturally reaches end positions, thus calibrating without interrupting productivity
Solution Approach 2:
The valve control mechanism performs self-calibration during normal operation by monitoring its own travel measurements and automatically adjusting stroke end position values when end positions are naturally reached, eliminating the need for external intervention and maintaining continuous plant operation
2Productivity
If the valve control mechanism waits for natural end positions, then plant operation is not disturbed, but adjustment time is extended indefinitely
Solution Approach 1:
The system implements periodic calibration attempts at predetermined intervals during normal operation. The control mechanism tries to recognize end positions periodically without forcing valve movement, and if successful, completes calibration quickly; if not, it waits for the next periodic opportunity, thus balancing non-interruption with eventual completion
Solution Approach 2:
The system continuously monitors travel measurement system values and provides feedback to determine when natural end positions are reached. This feedback mechanism allows the system to recognize calibration opportunities in real-time and execute calibration routines immediately when conditions are met, reducing overall adjustment time without disturbing operation
3Loss of time
If the valve is adjusted during operation, then downtime is reduced, but the complexity of the control system increases
Solution Approach 1:
The valve control mechanism performs multiple functions: normal position control, travel measurement monitoring, end position recognition, and calibration execution. By making the control system universal and multi-functional, it can handle calibration during operation without requiring separate dedicated calibration hardware, thus reducing downtime while limiting complexity increase
Solution Approach 2:
The travel measurement system acts as an intermediary between the valve actuator and the control mechanism. It provides continuous position data that enables the control mechanism to detect end positions and execute calibration routines during normal operation, reducing downtime while keeping the added complexity minimal through a single intermediary component
Data Source
AI summary
A method of adjusting stroke end positions of a process control valve is provided. A valve control mechanism is set up to continuously determine an actual position value from a travel-measurement system value acquired by a travel-measurement system, taking a first travel-measurement system final value and a second travel-measurement system final value into account. The method comprises the recognition of a first stroke end position when the process control valve is fully closed, and the recognition of a second stroke end position when the process control valve is fully open. The method further comprises the storage of the travel-measurement system value corresponding to the first stroke end position as the first travel-measurement system final value, and the storage of the travel-measurement system value corresponding to the second stroke end position as the second travel-measurement system final value. The process control valve is a component of a process plant, and the steps of an associated process are carried out during operation of the process plant. The disclosure further relates to a corresponding program code, to a valve control mechanism, and to a process control valve.