Small Line Size Vortex Flowmeter Diaphragm Sensor Design
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Solution Overview
Problem
Sanitary vortex flowmeters face challenges in measuring vortex shedding in small line size conduits due to the need for a large shedder and sensor, which blocks a significant portion of the conduit cross-sectional area, and existing solutions fail to meet clean-in-place requirements effectively.
Innovation Solution
The use of two diaphragms on opposite inner wall portions of the conduit, connected to a single sensor via fill tubes, enhances detection of vortex shedding by improving signal-to-noise ratio and allowing for remote sensor placement, eliminating crevices and facilitating cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor is embedded within the shedder to detect vortex pressure variations, then the flowmeter can meet sanitary standards by eliminating crevices, but the shedder must be large enough to accommodate the sensor, which blocks a significant portion of the conduit cross-sectional area in small line size conduits
Solution Approach 1:
The flowmeter is divided into separate functional components: the shedder (obstruction) and the sensor are separated into different locations. The shedder remains in the conduit to generate vortices, while the sensor is moved to the outer surface of the conduit where it can detect pressure variations without being embedded within the flow path. This segmentation allows the sensor to be positioned optimally for detection while minimizing obstruction of the conduit cross-section.
Solution Approach 2:
The sensor placement transitions from a two-dimensional embedded position within the shedder to a three-dimensional position on the outer surface of the conduit. By moving the sensor to the external surface and connecting it via fill tubes to diaphragms inside the conduit, the system achieves sanitary compliance without compromising the internal flow area.
2Measurement precision
If the sensor is placed on the shedder to efficiently detect pressure variations, then vortex shedding frequency can be accurately measured, but the sensor placement creates crevices or pockets that trap food particles and inhibit thorough cleaning
Solution Approach 1:
The sensor is extracted from its traditional position on or within the shedder and relocated to the outer surface of the conduit. This extraction eliminates the crevices and pockets that would otherwise trap food particles, while the sensor continues to detect vortex shedding through pressure variations transmitted via fill tubes to diaphragms positioned near the shedder.
Solution Approach 2:
Fill tubes act as intermediaries connecting the diaphragms (positioned inside the conduit near the shedder) to the sensor (positioned on the outer surface). This intermediary system allows pressure variations from vortex shedding to be transmitted to the sensor without requiring direct placement of the sensor in locations that would compromise cleanability.
3Device complexity
If the shedder and sensor are integrated in a single device, then the configuration simplifies the flowmeter structure, but the integral sensor requires a tail large enough to accommodate it, which is not feasible in conduits smaller than 2 inches in diameter
Solution Approach 1:
The integrated shedder-sensor configuration is segmented into separate components: the shedder remains as a simple obstruction in the conduit, while the sensor system (comprising diaphragms, fill tubes, and the sensor itself) is separated and positioned on the outer surface. This segmentation eliminates the need for a large shedder tail while maintaining the simplified structure benefit through modular design.
Solution Approach 2:
The design proactively prevents the problem of insufficient shedder tail length in small conduits by separating the sensor from the shedder before the size constraint becomes an issue. This preliminary separation allows the shedder to maintain its precise geometry relative to the meter bore without needing to accommodate a sensor, while the sensor is positioned externally where size constraints do not apply.
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
Enables accurate measurement of vortex shedding in small line sizes without blocking the conduit, while meeting sanitary standards by reducing noise and facilitating easy cleaning and maintenance.
Implementation Method 1
detect the pressure variations generated by the vortex shedding
Implementation Method 2
communicably coupled to the sensor with a fill tube
Implementation Method 3
A bluff body in the fluid flow generates eddies, or vortices, downstream of the bluff body, on alternating sides of the bluff body. This trail of vortices is known as the Karman vortex street.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A vortex flowmeter and method includes a conduit for process fluid flow and a shedder disposed within the central bore of the conduit. First and second diaphragms are mounted in inner wall portions of the conduit, on opposite sides of the shedder. A sensor is disposed externally to the conduit, and is coupled to each diaphragm with fill tubes. The diaphragms respond to pressure variations generated by vortex shedding, and transmit pulse trains through the fill tubes to a sensor. The pulse trains, which are substantially out of phase with one another, are effectively synchronized with one another by reversing phase of one pulse train.