What factors should be considered when selecting a vortex flowmeter?

When selecting a vortex flowmeter for measurement, many aspects need to be considered, such as performance, fluid characteristics, installation specifications, environmental impact, etc. Let us analyze and discuss the measurement methods and selection considerations in detail below.

1. Considerations of performance requirements and instrument specifications

After the vortex flowmeter determines the measurement method, the following performance requirements need to be considered for the selected flow meter: First, measure flow rate or total amount; the measurement of flow rate and the measurement of total amount are the two main purposes of measuring the object; for example, for continuous proportioning production or process control in pipelines, the main measurement place is instantaneous flow, while for commercial accounting and storage and transportation distribution, the main measurement place is total amount; second, accuracy; usually the accuracy level locked by the flow meter specification can be applied to a relatively wide flow range; third, repeatability; an important indicator in process control applications is repeatability, which is specifically determined by the manufacturing quality and principle of the instrument itself; fourth, linearity; related to linearity and square root nonlinearity, these are the two main outputs of flow meters. For most flow meters, nonlinear error is regarded as a component of basic error, and is not listed as a separate indicator; fifth, upper limit flow and flow range; the so-called upper limit flow rate and flow range. The limited flow is usually referred to as the full-scale flow. The selection of the flow meter diameter cannot be simply matched according to the diameter of the pipeline. It should be selected according to the upper and lower flow limits and flow range of the selected instrument used; Sixth, range; The ratio of the upper and lower flow limits is the range, and its value is positively correlated with the flow range. Usually, the linear instrument has a larger range, while the non-linear instrument has a smaller range; Seventh, pressure loss; For most flow sensors, when the flow direction changes or the static setting is set in its flow channel, there will be a pressure loss that changes with the flow and cannot be restored; Eighth, output signal characteristics; The factor of output signal plays a decisive role in the selection of instruments; Ninth, response time; If the flow meter is used in a pulsating flow place, the response time of the flow step change should be tested; Tenth, maintainability; Because the installed flow meter, if it encounters a fault and then disassembles it for maintenance, it is troublesome and time-consuming, so the factor of maintainability must be carefully considered.

2. Considerations of fluid properties

After the vortex flowmeter has determined several preliminary plans such as the preliminary measurement method according to the fluid type, in order to make the obtained fluid characteristics (parameters and properties) as detailed as possible, it is also necessary to investigate and visit the relevant process flow department so that the adaptability of the selected plan can be further verified; for the fluid category, there are many fluid characteristics that need to be considered, which can be summarized as follows: 1) temperature; 2) pressure; 3) density; 4) viscosity; 5) lubricity; 6) corrosiveness; 7) abrasiveness, etc.; in addition, for individual places, relevant hygiene requirements must also be taken into consideration; for individual measurement methods, special parameters related to fluid characteristics must also be considered, such as using an electromagnetic flowmeter, the conductivity of the relevant liquid must be understood. Various parameters related to fluid properties will have different effects on various flow meters. Therefore, the selection of the flow meter to be selected is largely dominated by the fluid properties. Therefore, the selected flow meter or measurement method must not only adapt to the properties of the measured fluid, but also be able to adapt to the impact caused by the change of a certain parameter of the fluid property during the measurement process. The various parameters of the fluid under the use conditions and the technical specifications and adaptability of the selected instrument can usually be found in the evaluation manual; for those who are not very familiar with the exact composition of the fluid, the relevant users must take the initiative to consult the manufacturer to clarify whether the selected instrument can be used normally.

3. Installation considerations

The vortex flowmeter has different measurement principles and therefore has very different installation requirements. For example, turbine and differential pressure instruments must use a longer upstream main pipe section to ensure sufficient flow at the inlet of the instrument, while float and volumetric instruments do not have this requirement during installation. The instruction manuals of some flow meters do not provide detailed descriptions of the installation location, flow maintenance space, flow direction, etc. of the relevant instruments, but many practices and studies have shown that the installation status of the relevant flow meters will have a great impact on the measurement performance of the instrument. It can be seen that a large part of the errors caused by flow meters are caused by improper installation, errors caused during installation, and factors that should be considered in installation.

4. Environmental considerations

During the molding process of the vortex flowmeter, the expected changes in the instrument and the surrounding conditions must be fully considered. The specific analysis is as follows: 1) Ambient temperature: Changes in the ambient temperature will have a greater impact on the electronic components of the instrument and some flow detection parts of the instrument; if the flow characteristics are affected by changes in ambient temperature, some pipes need to be wrapped with a thermal layer; 2) Ambient humidity: If the ambient humidity increases, the electrical insulation will be reduced and atmospheric corrosion and electrolytic corrosion will be accelerated; if the ambient humidity decreases, static electricity will be easily generated; therefore, for problems caused by humidity, the user should anticipate the possible range of changes and verify whether unnecessary problems will occur in the operation of the selected instrument; 3) Safety: When selecting and installing instruments, safety rules must be considered, such as whether the installation environment poses an explosive threat; 4) Electrical interference: Electrical electromagnetic interference is usually generated in power cables, electrical switches and motors, which is also a source of measurement errors.