Safety Valve Partial-Stroke Testing With Adaptive Termination Curves
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Solution Overview
Problem
Existing methods for determining termination criteria in partial stroke tests for fluidically driven safety valves are inflexible and do not account for changes in physical behavior due to factors like downtime, medium pressure, and temperature, leading to unclear maintenance needs and potential operational failures.
Innovation Solution
A method that records and stores a reference curve from a partial stroke test, allowing for dynamic adjustment of termination criteria based on specific valve conditions, including tolerance bands that vary by position and range of movement, to assess the operability of safety valves more accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed termination criteria are used for partial stroke tests, then the test evaluation is simple and consistent, but the criteria cannot account for changes in valve behavior due to downtime, pressure, and temperature variations
Solution Approach 1:
The patent applies dynamics by transitioning from fixed termination criteria to dynamic, adaptive criteria. The system records reference curves during initial operation and uses these as baselines for comparing subsequent partial stroke tests. The termination criteria automatically adjust based on deviations from these reference curves, allowing the evaluation system to adapt to changes in valve behavior caused by downtime, pressure variations, and temperature changes while maintaining systematic and automated assessment.
2Measurement precision
If tolerance bands are made position and range-dependent, then the termination criteria become more accurate for different valve positions, but the complexity of defining and applying these criteria increases
Solution Approach 1:
The patent applies local quality by implementing position-dependent tolerance bands. Instead of using a single uniform tolerance band for the entire stroke range, the system defines different tolerance bands for different positions and ranges of valve movement. This allows the termination criteria to be more precise and appropriate for the specific local conditions at each stage of the partial stroke test, while the system automatically manages the complexity of defining and applying these position-specific bands through automated comparison with reference curves.
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
This approach provides more reliable and situation-specific termination criteria for partial stroke tests, enabling better maintenance optimization and diagnosis of valve impairments, ensuring the safety valve's functionality.
Implementation Method 1
a spring return (200), wherein the spring return (200) is to move the valve member (203) into a safety position in the event of a complete drop in the pressure of the drive fluid (201), the pressure of the drive fluid (201) acting against the spring (200)
Implementation Method 2
the pressure of the drive fluid (201) acting against the spring (200)
Implementation Method 3
If a valve member remains in one position for a long time, the static friction and thus the breakaway force required to move the valve member may be greatly increased
Implementation Method 4
In the range of sliding friction, the actual stroke curve 230 runs approximately linear and parallel to the target stroke curve 210
Data Source
AI summary
A method is proposed for establishing termination criteria for a partial stroke test on a safety valve, including: a) A partial stroke test is carried out when the safety valve is operational. b) Position of the valve member and pressure in the drive fluid are recorded. c) A first relation is derived, which relates position of the valve member, time, pressure of the drive fluid, and/or control deviation to one another. d) This relation is defined as a safety valve reference curve. e) A second relation is defined, which has a predetermined distance from the reference curve. f) Termination criterion include: If the partial stroke test is repeated on the same valve, the same data are recorded and a third relation is derived for the reference curve, the partial stroke test is not passed if the third relation has a greater distance to the reference curve than the second relation.