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Industry Information
Factors Affecting the Measurement of Vortex Flowmeters and Problems Needing Attention in Use
2012-3-20 8:48:01

After practice, the following aspects have an impact on the use of the vortex flowmeter, and these problems should be analyzed.
的测量范围较大,一般10∶1,但测量下限受许多因素限制:Re>10000是涡街流量计工作的最基本条件,除此之外,它还受旋涡产生响应信号,旋涡频率f也小,还会使信号处理发生困难。 1. The measurement range of the vortex flowmeter is large, generally 10: 1, but the lower measurement limit is limited by many factors: Re> 10000 is the most basic condition for the vortex flowmeter to work. In addition, it is also responded by the vortex. The signal and vortex frequency f are also small, which also makes signal processing difficult. The upper limit of measurement is the frequency response of the sensor and the frequency limit of the circuit. Therefore, it is necessary to calculate and calculate the flow velocity range during design, and choose according to the flow velocity of the fluid. The environmental conditions at the application site are complex. In addition to paying attention to conditions such as ambient temperature, humidity, and atmosphere, you must also consider electromagnetic interference.
2. Vibration is also a great enemy of this type of instrument. Therefore, when using it, care should be taken to avoid mechanical vibration, especially the lateral vibration of the pipeline (the vibration that is perpendicular to the axis of the pipeline and the axis of the vortex generator). This effect cannot be suppressed or eliminated in the flowmeter structure design. Since the vortex signal is also sensitive to the influence of the flow field, it is not suitable to use it when the length of the straight pipe section cannot guarantee the necessary flow conditions for stabilizing the vortex street. Even the capacitive and ultrasonic types with strong vibration resistance can ensure that the fluid is a fully developed unidirectional flow, which cannot be ignored.
3. The medium temperature also has a great influence on the performance of the vortex flowmeter. For example, the pressure stress type vortex flowmeter cannot be used at 300 ° C for a long time, because its insulation resistance will drop from 10-100MΩ at normal temperature to 1-101Ω, and the output signal will become smaller, resulting in deterioration of measurement characteristics. In the measurement system, the sensor and converter should be installed separately to avoid long-term high temperature affecting the reliability and service life of the instrument. Vortex flowmeter is a relatively new type of flowmeter. It is in the development stage and is not very mature. If it is not selected properly, the performance will not play well. Only after reasonable selection and correct installation, it is necessary to carefully and regularly maintain during use, continuously accumulate experience, improve the predictability of system failures, and the ability to judge and deal with problems, so as to achieve satisfactory results.

在使用过程中应注意一下问题: Vortex flowmeters should pay attention to the following problems during use:
I. Pipeline design and caliber selection
Vortex flowmeters have higher requirements for pipeline design (such as straight pipeline requirements, same diameter requirements, etc.). If the pipeline design cannot meet the installation requirements of the vortex flowmeter, its measurement characteristics will have a large deviation.
The user needs to select the caliber of the vortex flowmeter according to his own gas consumption. The author found during the work that some users' gas consumption increased sharply as the scale grew, but the pipe diameter remained unchanged, which caused the vortex flowmeter to work over-range for a long time, which made the measurement inaccurate. There are also users who use a larger caliber to measure smaller flows, which will cause frequency leakage and lead to a smaller measurement.
Therefore, when selecting the caliber of the vortex flowmeter, it should be determined according to the actual production of the user, and the pipeline design should be strictly in accordance with the installation requirements of the flowmeter.
Environment
The working principle of the vortex flowmeter determines that its seismic performance is poor, and special attention should be paid to the shock absorption of the flowmeter during its use. External shock absorption measures (such as brackets to fix pipes and rubber cushions) can be used for shock absorption. If the vibration is strong, the source of the vibration should be found to solve or change the pipeline. Vortex flowmeters produced by some manufacturers can also be used for damping by adjusting the flowmeter parameters.
中转换器部分属于电子元器件,温湿度对其影响较大。 Because the converter part of the vortex flowmeter is an electronic component, temperature and humidity have a greater impact on it. Electronic components are also easily damaged at excessively high temperatures. Especially the integrated vortex flowmeter should strictly control the temperature. I have been in contact with a steam user, and the steam pipes have not been insulated, resulting in extremely high ambient temperatures and damage to the amplifier's electronic components. Excessive humidity will also cause the failure of electronic components, especially the current output mode. Bypass current will be formed between the positive and negative terminals due to water conduction, which will cause a phenomenon of no flow and signal.
Third, external electromagnetic interference
The influence of the power frequency on the vortex flowmeter is also serious. Most of our country uses 50Hz AC power supply, and 50Hz in the power sometimes enters the output frequency of the vortex flowmeter, resulting in increased measurement, especially large caliber vortex flowmeter. In view of this situation, methods such as grounding are generally adopted.
In addition to the interference from the power supply itself, some electrical equipment will generate high-frequency interference, and these interferences exist in the power supply line, which cannot be solved by adjusting the flow meter, but can only be eliminated from the source. Such as battery chargers, transformers, welding machines and other high-frequency harmonics generated by electrical equipment will make the flow meter no flow signal or flow increase. In the author's area, there have been cases in which the flowmeter does not work properly due to interference caused by the charging of electric bicycles, so do not ignore these influencing factors when there are problems with the flowmeter.
Fourth, other issues to pay attention to
Turbine flowmeter wiring errors often occur during flowmeter use. This problem can be solved by carefully reading the product manual or consulting the manufacturer.
Problems with vortex generators in turbine flow meters are more complicated. The piezoelectric crystal is placed in the vortex generator. First, it is necessary to determine whether the piezoelectric crystal is damaged by capacitance measurement. If both the amplifier and the piezoelectric crystal are intact, it is necessary to check whether the gap between the piezoelectric crystal and the casing is caught by fine particles and whether the generator is entangled with fibrous objects. If these problems exist, if the production process conditions permit, open as large a flow as possible, and use a mallet to strike vertically on the welding table at the bottom of the flow meter, so that the negative pressure generated by the high-speed fluid will remove the fine solid particles. ; Or remove the vortex generator for cleaning.