Flowmeter Proving Error Correction Using Statistical Sampling
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Solution Overview
Problem
Transit time ultrasonic flowmeters face challenges in achieving accurate meter factor determination using small volume provers due to short proving durations and turbulent fluid flow, leading to high uncertainty and potential biases from flow rate changes during the proving process.
Innovation Solution
A computer program that corrects errors in meter factors by processing signals from upstream and downstream prover detection switches and flow instruments, employing algorithms to account for flow rate changes and filter time constants, thereby reducing the number of proving runs required for accurate calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If small volume provers are used for proving ultrasonic flowmeters, then the proving process can be performed with compact equipment, but the proving duration becomes very short (typically between 0.5 and 1 second) leading to high uncertainty in meter factor determination
Solution Approach 1:
The system performs preliminary actions by collecting and storing multiple flow rate samples (typically 25-100 samples) during the short proving duration before calculating the meter factor. This preliminary data accumulation allows the system to compute a statistically reliable mean flow rate even though the individual proving run is short, thereby resolving the contradiction between small prover volume and measurement precision.
2Adaptability or versatility
If the flow rate changes during the proving run, then the prover can accommodate variable flow conditions, but transient flow errors are introduced that bias the meter factor determination
Solution Approach 1:
The system applies feedback by using the measured flow rate samples to detect changes in flow conditions during the proving run. By comparing the mean flow rate to the flow rate at the midpoint of the proving duration, the system identifies transient flow errors and applies corrections to the meter factor calculation. This feedback mechanism allows the system to maintain measurement precision even when flow conditions vary, resolving the contradiction between adaptability and precision.
3Measurement precision
If multiple proving runs are performed to reduce uncertainty, then the meter factor accuracy improves, but the time and resources required for calibration increase
Solution Approach 1:
The system changes the parameter of data processing by applying statistical analysis (calculating mean and standard deviation of multiple samples) and correction algorithms to the flow rate data collected during each proving run. This transformation of raw data into corrected meter factor values allows the system to achieve the required accuracy (standard deviation of mean meter factor less than 0.05%) in fewer proving runs, typically 3-5 runs instead of the 200+ runs that would be required without these parameter transformations.
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 solution significantly reduces errors in meter factor determination, achieving the required accuracy of ±0.027% with fewer proving runs, even with small volume provers, by effectively accounting for flow rate changes and turbulence, thus enhancing the precision of flow measurement.
Implementation Method 1
Transit time ultrasonic meters determine fluid velocity by measuring the transit times of pulses of ultrasonic energy traveling along clearly defined paths, with and against the direction of the flow.
Data Source
AI summary
An apparatus for increasing the accuracy of meter factors of a flow instrument in conjunction with a prover having upstream and downstream prover detection switches and a flow computer including a computer program embodied on a computer readable medium for correcting errors in a meter factor of the flow instrument measured in a proving run and correcting effects of flow rate changes during proving. A computer program embodied on a computer readable medium whose contents causes a processor to increase the accuracy of meter factors of a flow instrument in conjunction with a prover having upstream and downstream prover detection switches and a flow computer. A method for increasing the accuracy of the meter factors of a flow instrument in conjunction with a prover having upstream and downstream prover detection switches and a flow computer.