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A vortex flow meter is a flow measurement device best suited for flow measurements where the introduction of moving parts presents problems. They are available in industrial grade, brass or all plastic construction. Sensitivity to variations in the process conditions are low and with no moving parts have relatively low wear compared to other types of flow meters.
Vortex flow meters operate under the vortex shedding principle, where an oscillating vortexes occur when a fluid such as water flow past a bluff (as opposed to streamlined) body. The frequency that the vortexes are shed depend on the size and shape of the body. It is ideal for applications where low maintenance costs are important. Industrial size vortex meters are custom built and require appropriate sizing for specific applications.
KEY ELEMENTS TO CONSIDER BEFORE CHOOSING A VORTEX FLOW METER
1. What is the fluid being measured?
2. Pressure Maximum and Minimum
3. Flowrate Ranges
4. Fluid Temperature
5. Fluid Density Range
6. Viscosity Range
7. Pipe Size
8. Maximum Acceptable Pressure Drop
9. Pipe Schedule or Wall Thickness
10. Pipe Material
11. Nearest Upstream Obstruction
Vortex Flow Meter Styles
Smart vortex meters provide a digital output signal containing more information than just flow rate. The microprocessor in the flowmeter can automatically correct for insufficient straight pipe conditions, for differences between the bore diameter and that of the mating pipe, for thermal expansion of the bluff body, and for K-factor changes when the Reynolds number drops below 10,000.
Intelligent transmitters are also provided with diagnostic subroutines to signal component or other failures. Smart transmitters can initiate testing routines to identify problems with both the meter and with the application. These on-demand tests can also assist in ISO 9000 verification.
Some vortex flowmeters can detect mass flow. One such design measures both the vortex frequency and the vortex pulse strength simultaneously. From these readings, the density of the process fluid can be determined and the mass flow calculated to within 2% of span.
Another design is provided with multiple sensors to detect not only the vortex frequency, but also the temperature and pressure of the process fluid. Based on that data, it determines both the density and the mass flow rate. This meter offers a 1.25% of rate accuracy when measuring the mass flow of liquids and a 2% of rate accuracy for gases and steam. If knowledge of process pressure and temperature is of value for other reasons, this meter provides a convenient, less costly alternative to installing separate transmitters.
