Advantages and disadvantages of German Krohne electromagnetic flowmeter

What are the advantages and disadvantages of the German Krohne electromagnetic flowmeter:

The details are as follows: 1. Advantages (1) The electromagnetic flowmeter can be used to measure industrial conductive liquids or slurries. (2) No pressure loss. (3) The measurement range is large, and the diameter of the electromagnetic flow transmitter ranges from 2.5mm to 2.6m. (4) The electromagnetic flowmeter measures the volumetric flow rate of the fluid under test. The measurement principle does not involve the influence of the temperature, pressure, density and viscosity of the fluid. 2. Disadvantages (1) The application of electromagnetic flowmeter has certain limitations. It can only measure the liquid flow of conductive media, but cannot measure the flow of non-conductive media, such as gas and heating water with better water treatment. In addition, its lining needs to be considered under high temperature conditions. (2) The electromagnetic flowmeter determines the volume flow rate under working conditions by measuring the speed of conductive liquid. According to the measurement requirements, for liquid media, the mass flow rate should be measured, and measuring the medium flow rate should involve the density of the fluid. Different fluid media have different densities, and they change with temperature. If the electromagnetic flowmeter converter does not consider the fluid density, it is inappropriate to only give the volume flow rate at room temperature. (3) The installation and debugging of electromagnetic flowmeters are more complicated than other flowmeters, and the requirements are more stringent. The transmitter and converter must be used together, and two different types of instruments cannot be used together. When installing the transmitter, from the selection of the installation location to the specific installation and debugging, the product instructions must be strictly followed. There should be no vibration or strong magnetic field in the installation location. During installation, the transmitter and pipeline must have good contact and good grounding. The potential of the transmitter is the same as that of the fluid being measured. During use, the gas remaining in the measuring tube must be exhausted, otherwise it will cause large measurement errors. (4) When the electromagnetic flowmeter is used to measure viscous liquids with dirt, the sticky matter or sediment adheres to the inner wall of the measuring tube or the electrode, causing the output potential of the transmitter to change, causing measurement errors. The dirt on the electrode reaches a certain level. Thickness may cause the meter to be unable to measure. (5) Scale or wear of the water supply pipeline changes the inner diameter, which will affect the original flow value and cause measurement errors. For example, a 1mm change in the inner diameter of a 100mm diameter instrument will bring about an additional error of approximately 2%. (6) The measurement signal of the transmitter is a very small millivolt level potential signal. In addition to the flow signal, it also contains some signals that have nothing to do with the flow, such as phase voltage, quadrature voltage and common mode voltage. In order to accurately measure flow, it is necessary to eliminate various interference signals and effectively amplify the flow signal. The performance of the flow converter should be improved by using a microprocessor-type converter. Use it to control the excitation voltage. Select the excitation mode and frequency according to the properties of the fluid being measured, which can eliminate in-phase interference and orthogonal interference. However, the improved instrument structure is complex and the cost is high. (7) Higher price

2. Disadvantages

(1) The volume flow rate of the vortex flowmeter under working conditions is not affected by thermal parameters such as temperature, pressure, and density of the fluid being measured, but liquid or steam The final measurement result should be the mass flow rate, and for gases, the final measurement result should be the standard volume flow rate. Either mass flow or standard volume flow must be determined by fluid densityFor conversion, the change in fluid density caused by changes in fluid operating conditions must be considered.

(2) The main factors causing flow measurement errors are: measurement errors caused by uneven flow rates in pipelines; inability to accurately determine the medium density when fluid conditions change; assuming wet saturated steam to be dry saturated steam. Measurement. If these errors are not limited or eliminated, the total measurement error of the vortex flowmeter will be very large.

(3) Poor anti-vibration performance. External vibration will cause the vortex flowmeter to produce measurement errors and even fail to work properly. The impact of high flow velocity of channel fluid will cause additional vibration on the cantilever of the vortex generator, which will reduce the measurement accuracy. The influence of large pipe diameter is more obvious.

(4) Poor adaptability to measuring dirty media. The generator body of the vortex flowmeter is easily contaminated by the medium or entangled with dirt, which changes the geometric size and greatly affects the measurement accuracy.

(5) The straight pipe section has high requirements. Experts pointed out that the straight pipe section of the vortex flowmeter must ensure 40D in the front and 20D in the back to meet the measurement requirements.

(6) Poor temperature resistance. Vortex flowmeters generally can only measure fluid flow in media below 300°C.