内衬材质说明 Material description of electromagnetic flowmeter lining
The liquid contains uniformly distributed small air bubbles, which usually does not affect the normal measurement. However, when the measured volume flow is the sum of both liquid and gas, the output signal will fluctuate due to the increase of air bubbles. The electrode signal loop is momentarily disconnected, and the output signal will produce greater fluctuations. When two or more liquids are used in the pipeline mixing process, if the conductivity of the two liquids (or their respective potentials with the electrode chapters) is different, they will enter the flow sensor for flow measurement before the mixing is not uniform, and the output signal will also fluctuate. Low frequency (50/16 ～ 50 / 6Hz) rectangular excitation electromagnetic flowmeter will measure slurry noise when the solid content in the liquid exceeds a certain content, and the output signal will fluctuate to some extent. Improper selection of the electrode material and the measured medium will cause chemical effects such as passivation or oxidation, the formation of insulating films on the electrode surface, and electrochemical and polarization phenomena, which will prevent normal measurement. Piping system and installation
传感器安装位置不正确引起的故障，常见的有将流量传感器安装在易积聚潴留气体的管网高点；流量传感器后背压，液体径直排入大气，形成其测量管内非满管；装在自上向下的垂直管道上，可能出现排空等原因。 It is usually caused by the incorrect installation of the electromagnetic flowmeter sensor. It is common to install the flow sensor at the high point of the pipe network where it is easy to accumulate retained gas; the back pressure of the flow sensor, and the liquid is directly discharged into the atmosphere, forming a non-full inside of the measuring tube. Pipe; installed on the vertical pipe from top to bottom, may cause emptying and other reasons. In terms of environment, it is mainly stray current interference of pipelines, electromagnetic interference in space, and magnetic field interference of large motors. Pipeline stray current interference can usually be achieved by taking a good separate grounding protection. However, if the pipeline has a strong stray current (such as the electrolytic workshop pipe), it may not be overcome, and measures must be taken to isolate the flow sensor from the pipe. Space electromagnetic wave interference is generally introduced through signal cables, and is usually protected by single-layer shielding, but it has also been encountered that shielding protection cannot be overcome.
The electromagnetic flowmeter cannot be used to measure the cause of gas. This is mainly due to the inherent shortcomings of the electromagnetic flowmeter, that is, the shortcomings. The following is a detailed analysis of the reasons. The main disadvantage of electromagnetic flowmeters is that they cannot be used to measure gases, vapors, and liquids containing large amounts of gas. It cannot be used to measure liquids with very low conductivity, such as petroleum products or organic solvents. At present, electromagnetic flowmeters are powerless. The electromagnetic flowmeter is made according to Faraday's law of electromagnetic induction, and is used to measure the volume flow of conductive liquids. Due to its unique advantages, it has been widely used in industrial flow measurement of various conductive liquids, such as various acids, alkalis, salts and other corrosive media; various slurry flow measurements have formed unique application fields. Structurally, the electromagnetic flowmeter is composed of an electromagnetic flow sensor and a converter. The sensor is installed on the industrial process pipeline, and its role is to linearly convert the volumetric flow value of the liquid flowing into the pipeline into the induced potential signal, and send this signal to the converter through the transmission line. The converter is installed not too far from the sensor. It amplifies the flow signal sent by the sensor and converts it into a standard electrical signal output that is proportional to the flow signal for display, accumulation and adjustment control.
The electromagnetic flowmeter is a volume flow measuring instrument. During the measurement process, it is not affected by the temperature, viscosity, and density of the measured medium and its conductivity (within a certain range). Therefore, the electromagnetic flowmeter can be used to measure the flow of other conductive liquids only after it has been calibrated with water. The output of the electromagnetic flowmeter is only proportional to the average flow velocity of the measured medium, and has nothing to do with the flow state (laminar or turbulent) in a symmetrical distribution. Therefore, the range of the electromagnetic flowmeter is extremely wide, and its measurement range can reach 100: 1, and some even reach the operational flow range of 1000: 1.
的传感器结构简单，测量管内没有可动部件，也没有任何阻碍流体流动的节流部件。 1) The structure of the sensor of the electromagnetic flowmeter is simple, there are no moving parts in the measuring tube, and there are no throttling parts that hinder fluid flow. Therefore, it will not cause any additional pressure loss when the fluid passes through the flow meter, and it is one of the flow meters with the lowest energy consumption in the flow meter. It can measure the flow rate of dirty media, corrosive media and suspended liquid-solid two-phase flow. This is because there are no obstructing flow parts inside the measuring tube of the instrument, and only the lining and electrodes of the measuring tube are in contact with the measured fluid, and the material can be selected according to the properties of the measured fluid. For example, using polytrifluoroethylene or polytetrafluoroethylene as the inner lining can measure various corrosive media such as acids, alkalis, and salts; the use of wear-resistant rubber as the inner lining is particularly suitable for measuring the wear of solid particles. Large liquid-solid two-phase flows such as mineral slurry and cement slurry, and various suspended liquids such as fiber-containing liquids and pulp. 2) The electromagnetic flowmeter has no mechanical inertia and is sensitive in response. It can measure the instantaneous pulsating flow, and it can also measure the flow in both directions. The diameter range of industrial electromagnetic flowmeters is extremely wide, from a few millimeters to several meters, and there are already actual flow calibration equipment with a caliber of 3m in China, which has laid the foundation for the application and development of electromagnetic flowmeters.