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technical article
Questions to pay attention to when installing the electromagnetic flowmeter
2012-2-16 10:31:02

的安装电磁流量度的正确安装对电磁流量计的正常运行极为重要,这里主要介绍电磁流量传感器和转换器的安装。 Installation of electromagnetic flowmeter The correct installation of the electromagnetic flow rate is extremely important for the normal operation of the electromagnetic flowmeter. Here we mainly introduce the installation of the electromagnetic flow sensor and converter.
The installation of electromagnetic flowmeter sensors should pay attention to the following issues:
I. Installation site The protection level of the ordinary electromagnetic flow sensor is IP65 (dust-proof and splash-proof level specified in GB4208). The requirements for the installation site are: 1) When measuring mixed-phase fluids, choose a place that will not cause phase separation. 2) Choose a place where no negative pressure will appear in the measuring tube; 3) Avoid installing near electric equipment such as motors and transformers to avoid electromagnetic field interference; 4) Avoid installing in places with strong corrosive gas; 5) Environment The temperature should generally be in the range of -25 ~ 60 ℃, avoid direct sunlight as much as possible; 6) Install in a place without vibration or small vibration. If the vibration is too large, fixed support should be added to the pipe before and after the sensor. 7) The relative humidity of the environment should generally be in the range of 10% ~ 90%; 8) Avoid installation in a place where it can be directly exposed to rain or submerged by water. If the sensor's enclosure protection level is IP67 (dust-proof and water-proof) or IP68 (dust-proof and diving-proof), the last two items may not be required.
对表前直管段长度的要求比较低。 Second, the length of the straight pipe section The electromagnetic flowmeter has a lower requirement for the length of the straight pipe section before the meter . Generally, for 90 ° elbow, T-shaped tee, reducer, fully open valve and other flow resistance parts, it should have a straight pipe length of 3-5D from the center line of the sensor electrode axis (not the sensor inlet end face); for different openings 10-degree valve requires a straight pipe length of 10D; generally 2D straight pipe length behind the sensor. When the valve cannot be fully opened, if the valve's interception direction is installed at 45 ° with the sensor electrode axis, the additional error can be greatly reduced.
3. Installation position and flow direction The electromagnetic flow sensor can be installed horizontally, vertically or obliquely. For horizontal installation, the sensor electrode shaft must be placed horizontally. This can prevent the electrodes from being insulated for a short time due to the air bubbles entrained in the fluid; it can also prevent the electrodes from being covered by the deposits in the fluid. The sensor should not be installed at the highest point to avoid accumulation of air. It is installed at the highest point of the piping system. It is a bad installation position and should be avoided. When installed vertically, the flow direction should be upward, so that no flow or very low flow, the heavy solid particles entrained in the fluid will sink, and the lighter fatty substances will rise away from the sensor electrode area. When measuring liquid-solid two-phase flows such as mud and ore slurry, vertical installation can avoid solid phase sensation precipitation and uneven wear of the sensor lining. At the exit of a downward pipe, a bad installation position should be avoided. There should be a certain back pressure at the installation place of the sensor. The direct exhaustion of the sensor outlet may easily cause the liquid in the measuring tube to be not full. This is a bad installation position and should be avoided. To prevent negative pressure in the sensor, the sensor should be installed behind the pump and not in front of the pump.
Fourth, install the bypass pipe In order to facilitate the inspection and adjustment of zero point when the liquid flow is stationary, small and medium pipe diameter should be installed as much as possible. When measuring fluids containing deposits, consider mounting methods that facilitate cleaning of the sensor.
V. Grounding In order to make the measurement accurate and the electrode will not be corroded by current, the electromagnetic flowmeter sensor must be grounded separately, and the sensor and the fluid should be at about the same potential. In principle, the separation type electromagnetic flowmeter should be grounded on the sensor side, and the converter should be grounded on the same ground point. In most cases, the built-in reference electrode or metal tube of the sensor can ensure the potential balance. Therefore, the fluid in the tube can be grounded through the built-in reference electrode and metal tube, and the ground piece of the sensor can be connected to the ground wire. If the sensor is installed on a pipeline with cathodic corrosion protection, in addition to grounding the sensor and the grounding ring together, a thick copper wire should also be used to bypass the sensor across the two flanges of the pipeline to make the cathodic protection current between the sensor and the sensor.


是根据法拉弟电磁感应定律制成的一种测量导电性液体的仪表。 The electromagnetic flowmeter is a meter for measuring conductive liquids made according to the law of Faraday's electromagnetic induction. The electromagnetic flowmeter has a series of excellent characteristics, which can solve the problems that other flowmeters are not easy to apply, such as the measurement of dirty and corrosive flows. In the 1970s and 1980s, electromagnetic flow made major breakthroughs in technology, making it a widely used type of flowmeter, and its percentage of use in flow meters has continued to rise.
Advantages: (1) The measuring channel is a smooth straight tube, which will not block, suitable for measuring liquid-solid two-phase fluids containing solid particles, such as pulp, mud, sewage, etc .; (2) No pressure loss caused by flow detection. The energy saving effect is good; (3) The measured volume flow is not significantly affected by changes in fluid density, viscosity, temperature, pressure, and conductivity; (4) a large flow range and a wide caliber range; (5) corrosion can be applied Sexual fluid.
Disadvantages: (1) Cannot measure liquids with very low electrical conductivity, such as petroleum products; (2) Cannot measure gases, vapors and liquids with large bubbles;
(3) Cannot be used at higher temperatures.
Application overview: Electromagnetic flowmeters have a wide range of applications, and large-caliber meters are mostly used in water supply and drainage projects; small- and medium-caliber are often used in high-demand or difficult-to-measure applications, such as cooling water control in the blast furnace tuyere of the iron and steel industry, and pulp and black liquor in the paper industry The strong corrosive liquid of chemical industry, the non-ferrous metallurgy industry's ore slurry; small caliber and micro caliber are often used in places with sanitary requirements such as pharmaceutical industry, food industry, biochemistry.