Stiffness-Correlated FTC for Coriolis Flowmeter Calibration
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Solution Overview
Problem
Coriolis flowmeters are sensitive to temperature changes, which affect the stiffness of the flow tube, leading to variations in temperature correction terms and requiring unique correction factors for each meter, making calibration time-consuming and expensive.
Innovation Solution
A method and apparatus to determine and apply a stiffness-correlated temperature flow coefficient (FTC) by measuring tube periods and using a predetermined relationship between tube period ratio and FTC values for a plurality of flowmeters, allowing for efficient calibration and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If unique temperature correction factors are determined for each flowmeter, then measurement precision is improved, but calibration time and cost increase
Solution Approach 1:
The patent changes the parameter approach by using tube period (a dynamic vibration parameter) as the basis for determining temperature correction factors, rather than using static meter-specific parameters. This allows the correction factors to be derived from easily measurable vibration characteristics that naturally vary with temperature, enabling accurate temperature compensation without time-consuming individual calibrations.
Solution Approach 2:
The patent creates a universal tube period ratio relationship that can be applied across multiple flowmeters of the same model. By establishing a general relationship between tube period ratio and temperature correction factor that works for all meters in a series, the system achieves both individualized correction accuracy and efficient calibration applicable to multiple devices.
2Measurement precision
If traditional calibration methods are used for each flowmeter, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent uses tube period ratio as a changeable parameter that correlates with temperature effects. This parameter can be measured during routine operation without specialized calibration equipment, eliminating the need for expensive individual calibrations while maintaining accurate temperature compensation through the established relationship between tube period ratio and correction factors.
Solution Approach 2:
The patent creates a model or template relationship between tube period ratio and temperature correction factors that can be copied and applied to multiple flowmeters. Instead of performing unique calibration on each meter, the established relationship serves as a template that provides accurate correction factors for all meters in the series, significantly reducing manufacturing and calibration costs.
3Reliability
If temperature correction is applied, then measurement reliability under varying temperature conditions is improved, but device complexity increases
Solution Approach 1:
The patent uses natural changes in tube period with temperature as the basis for correction. Rather than adding complex temperature sensors and correction mechanisms, the system exploits the inherent parameter change (tube period variation) that occurs with temperature, converting a physical effect into a useful measurement signal that automatically provides temperature compensation information.
Solution Approach 2:
The flowmeter system uses its own vibration characteristics (tube period) to provide temperature compensation information. The tube period naturally varies with temperature, and this self-generated signal is used to determine the appropriate correction factor, eliminating the need for separate temperature sensing systems or external correction mechanisms.
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 stiffness-correlated FTC effectively corrects for temperature-induced errors in flow measurements, reducing measurement errors and making calibration more efficient and cost-effective compared to using global or custom correction factors.
Implementation Method 1
An alternating current is passed to the drive coil for vibrating the conduit(s) at a desired flow tube amplitude and frequency
Implementation Method 2
the pickoffs can use the motion provided by the driver to induce a voltage
Implementation Method 3
As material begins to flow through the flowmeter, Coriolis forces cause each point along the conduit(s) to have a different phase
Data Source
AI summary
A method for calibrating a flowmeter is provided that comprises determining a relationship between tube period ratio and a flow tube temperature compensation (FTC) value for a plurality of flowmeters. Tube periods of the flowmeter under test are measured. A stiffness-correlated FTC is calculated using the determined relationship between the tube period ratio and the FTC value for the plurality of flowmeters and the measured tube periods of the flowmeter under test. The stiffness-correlated FTC is applied to an operating routine (314) of the flowmeter under test.