The electromagnetic flowmeter has a large measuring range, usually 20:1~50:1, and the optional flow range is wide; the diameter of the electromagnetic flowmeter is wider than other types of flowmeters, from a few millimeters to 3 meters; the positive and negative two-way flow can be measured. The pulsating flow rate can also be measured as long as the pulsation frequency is much lower than the excitation frequency; the meter output is linear in nature; it is easy to select the material type of the fluid contact member, and can be applied to corrosive fluids and the like. Since the electromagnetic flowmeter measures much more with suspended solids or dirt than other flow meters, the probability of failure of the inner wall adhesion layer is relatively high. If the electrical conductivity of the adhesion layer is close to the liquid conductivity, the instrument can output the signal normally, but only change the flow area to form a hidden fault of the measurement error; if it is a high conductivity adhesion layer, the electromotive force between the electrodes will be short-circuited; if it is an insulating adhesion layer The surface of the electrode is insulated to disconnect the measuring circuit. The latter two phenomena will make the meter inoperable.
Vortex flowmeter analysis and solution
Summarizing the main causes of these problems, mainly related to the following aspects:
1. Problems with selection. Some vortex sensors are selected on the caliber selection or after the design selection, due to the change of process conditions, so that the selection is larger, the actual selection should be as small as possible to improve the measurement accuracy. The main reason for this is the same. Questions 1, 3, and 6 are related. For example, a vortex pipeline is designed for use by several equipment. Because some of the equipment is not used, the actual actual flow is reduced. The actual design results in too large an original design, which is equivalent to an increase in measurable flow. The lower limit, when the process pipe has a small flow rate, the indication cannot be guaranteed. When the flow rate is large, it can be used, because it is sometimes too difficult to re-engineer. Changes in process conditions are only temporary. The re-tuning of the parameters can be combined to improve the indication accuracy.
2. Installation problems. The main reason is that the length of the straight pipe in front of the sensor is not enough, which affects the measurement accuracy. The reason for this is mainly related to the problem 1. For example, the straight pipe section in front of the sensor is obviously insufficient. Since the FIC203 is not used for measurement, it is only used for control, so the current accuracy can be used equivalent to the downgrade.
Mass flow meter
Since the volume of the fluid is affected by parameters such as temperature and pressure, it is necessary to give the parameters of the medium when the flow rate is expressed by the volume flow. In the case of changing media parameters, it is often difficult to achieve this requirement, resulting in distortion of the meter display value. Therefore, mass flow meters have been widely used and valued. Mass flow meters are available in both direct and indirect versions. Direct mass flow meters are measured using principles directly related to mass flow. Currently used mass flow meters such as calorimetric, angular momentum, vibratory gyro, Magnus effect and Coriolis force. The indirect mass flow meter is obtained by directly multiplying the density meter by the volumetric flow rate to obtain the mass flow rate.
In modern industrial production, the operating parameters such as temperature and pressure of the flowing working fluid are continuously improved. In the case of high temperature and high pressure, due to the material and structure, the application of the direct mass flowmeter is difficult, and the indirect quality is encountered. Flowmeters are often not suitable for practical applications because they are limited by the range of humidity and pressure. Therefore, a temperature-pressure-compensated mass flowmeter is widely used in industrial production. It can be regarded as an indirect mass flow meter. Instead of using a density meter, it uses the relationship between temperature, pressure and density. It uses a temperature and pressure signal to calculate the density signal by function, and multiplies it by the volume flow. Mass Flow. At present, temperature and pressure-compensated mass flowmeters have been put into practical use. However, when the measured medium parameters vary widely or rapidly, it will be difficult or impossible to correctly compensate, so further study the mass flow rate applicable in actual production. Meters and densitometers are still a topic.
Chen's above-mentioned common structural principle of flowmeters is much better than various types of flowmeters, such as various helium flowmeters and trough flowmeters for open channel flow measurement; flowmeters suitable for large-caliber flow measurement; measuring laminar flow Laminar flowmeter; related flowmeter for two-phase flow measurement; and laser method, nuclear magnetic resonance flowmeter and various tracer methods, dilution method flow measurement, etc. With the development of technology and practical application needs, the new flowmeter will continue to emerge more types of flowmeters.