Coriolis Flow Meter Balance Member Design
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Solution Overview
Problem
Single tube Coriolis flow meters face challenges in maintaining balance over a wide range of fluid densities, leading to adverse effects on performance and reliability, and existing solutions either increase manufacturing costs or are prone to errors due to thermal expansion differences between materials.
Innovation Solution
A flow meter design featuring a curved flow tube with a balance member positioned on its centerline, coupled with driver and pick-off components, and counter weights to maintain balance, allowing for the use of materials with different thermal coefficients of expansion without significant axial stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single tube Coriolis flow meter is used, then pressure drop and plugging issues are reduced, but the meter becomes unbalanced with changing fluid densities, affecting performance and reliability
Solution Approach 1:
The patent introduces a balance member with counter weights that can be adjusted to compensate for changes in fluid density. The balance member includes adjustable counter weights positioned at specific locations along the flow tube to maintain rotational balance. This allows the single tube design to remain balanced across varying fluid densities, preventing the adverse effects of unbalance while maintaining the benefits of single tube configuration.
2Reliability
If counter weights are added to maintain balance, then meter balance across varying densities is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent implements adjustable counter weights on the balance member that can be modified during operation to adapt to changing fluid densities. The counter weights are positioned on a rotating balance member and can be adjusted without disassembling the entire flow meter. This dynamic adjustment capability maintains balance stability while simplifying manufacturing compared to fixed complex balancing mechanisms.
3Ease of manufacture
If materials with different thermal coefficients of expansion are used, then manufacturing cost is reduced, but thermal expansion differences cause axial stresses and measurement errors
Solution Approach 1:
The patent applies different materials to different components of the flow meter based on their specific functional requirements. The flow tube can be made from one material while the balance member uses a different material with appropriate thermal expansion characteristics. By localizing material selection to match thermal stress requirements in specific areas, the design achieves cost reduction without compromising measurement precision through excessive thermal expansion differences.
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 design ensures the flow meter remains balanced across varying fluid densities, reduces the risk of erroneous measurements, and lowers manufacturing costs by using cheaper materials for the balance member with higher thermal expansion coefficients.
Implementation Method 1
The driver may comprise one of many well known arrangements; however, a magnet and an opposing drive coil has received great success in the flow meter industry. 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
However, while the driver receives a current which induces a motion, the pick-off sensors can use the motion provided by the driver to induce a voltage.
Implementation Method 3
When there is no flow through the flow meter, a driving force applied to the conduit(s) causes all points along the conduit(s) to oscillate with identical phase or small initial fixed phase offset, which can be corrected. As material begins to flow through the flow meter, Coriolis forces cause each point along the conduit(s) to have a different phase.
Data Source
AI summary
A flow meter (200) is provided that comprises a curved flow tube (203) and a balance member (250). The balance member (250) is positioned such that a centerline (341) of the balance member (250) lies on a plane of a centerline (340) of the curved flow tube (203). The flow meter (200) also includes a driver (104) including a first driver component (104a) and a second driver component (104b). The first driver component (104a) is coupled to the curved flow tube (203) while the second driver component (104b) is coupled to the balance member (250) proximate the first driver component (104a). The flow meter (200) also includes at least a first pick-off sensor (105). The first pick-off sensor (105) includes a first pick-off component (105a) and a second pick-off component (105b). The first pick-off component (105a) is coupled to the curved flow tube (203) while the second pick-off component (105b) is coupled to the balance member (250) proximate the first pick-off component (105a).