Process Valve Leakage Diagnosis Using Stable Pressure States
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Solution Overview
Problem
Existing methods for diagnosing process valve assembly units often lead to incorrect results due to temporary changes in measured variables, such as pressure drops, which can be misinterpreted as leaks, reducing the reliability of the diagnosis.
Innovation Solution
A method that determines a diagnosis system state after the completion of actuation, where the measured variable remains constant, and uses this state to acquire and analyze the temporal course of the variable to prevent incorrect diagnosis, ensuring a reliable leakage recognition by distinguishing between temporary changes and actual leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If diagnosis is performed immediately after actuation completion, then diagnosis speed is improved, but diagnosis accuracy deteriorates due to temporary change processes falsifying measured variables
Solution Approach 1:
The system performs preliminary action by waiting for the temporary change process to complete before initiating diagnosis. The control device determines that a diagnosis system state suitable for diagnosis is present only after the temporary change process has ended, ensuring that measured variables have stabilized and are not being falsified by transient effects.
Solution Approach 2:
The system dynamically adjusts the timing of diagnosis based on the state of the system. Instead of using a fixed timing approach, the control device continuously monitors whether the diagnosis system state is suitable, allowing the diagnosis to proceed as soon as conditions are favorable while preventing premature diagnosis that would yield inaccurate results.
2Loss of information
If measured variable monitoring continues during temporary change process, then complete temporal course data is obtained, but diagnosis reliability deteriorates due to incorrect interpretation of temporary changes as leaks
Solution Approach 1:
The system segments the temporal course of the measured variable into distinct phases: the temporary change process phase and the diagnosis system state phase. By identifying and separating these phases, the system can analyze the complete temporal course while ensuring that diagnosis is performed only on data from the stable phase, preventing misinterpretation of temporary changes.
Solution Approach 2:
The control device acts as an intermediary that filters and selects which portions of the temporal course data to use for diagnosis. It determines the suitable diagnosis system state and uses only the measured variable data from this state, effectively filtering out the problematic temporary change process data while retaining complete information for comprehensive analysis.
Data Source
AI summary
A method for the diagnosis, in particular for the leakage recognition, of a process valve assembly unit, said process valve assembly unit including a control device (4), a valve drive (3) which is pneumatically controlled by the control device (4) and a process valve (1) which is driven by the valve drive (4), wherein the method includes the following steps which are carried out by a diagnosis device (50): determining that a diagnosis system state which is suitable for the diagnosis is present after the completion of an actuation of the process valve assembly unit (20), acquiring a temporal course of a measured variable, in particular a pressure, during the diagnosis system state, and on the basis of the acquired temporal course, determining diagnosis information which indicates a diagnosis result, in particular a presence of a leakage, of the process valve assembly unit (20).