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The proper operation of an electromagnetic flowmeter depends on the correct installation of the electromagnetic flowmeter
2012-3-12 9:28:21



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.


传感器安装电磁流量计传感器安装要注意以下几个问题: The installation of electromagnetic flowmeter sensors should pay attention to the following issues:
(1) The housing protection level of the ordinary electromagnetic flow sensor at the installation site is IP65 (dust-proof and splash-proof grade specified in GB4208). The requirements for the installation site are: 1) When measuring mixed-phase fluids, choose a one that will not cause phase separation Place 2) Choose a place where there is no negative pressure in the measuring tube; 3) Avoid installing near electric equipment such as electric motors and transformers to avoid electromagnetic field interference; 4) Avoid installing in places with strong corrosive gas around 5) Ambient temperature Generally, it should 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 within the range of 10% to 90%; 8) Avoid installation in a place that 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.
(2) Straight pipe length The electromagnetic flowmeter has lower requirements for the length of the straight pipe 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.
(4) Installation of bypass pipe In order to facilitate the inspection and adjustment of the zero point when the liquid flow is stationary, small and medium pipe diameters should be installed with bypass pipe as much as possible. When measuring fluids containing deposits, consider mounting methods that facilitate cleaning of the sensor.
(5) Grounding In order to make the measurement accurate and the electrode will not be corroded by current, the electromagnetic flow 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.

发生流量无显示,断电后可恢复。 The flow rate of the electromagnetic flowmeter is not displayed, and it can be restored after power failure. There is a large polarization voltage between the two electrodes. It can be determined that the so-called polarization caused by the electrode polarization is due to the excessive positive or negative charge attached to the opposite electrode, which causes a strong capacitance effect and the current cannot pass through normally. That is, the phenomenon that the electrode potential deviates from the equilibrium potential when a current passes.
Electrode polarization of electromagnetic flowmeters is generally not caused by material problems, but caused by excitation. If the electromagnetic flowmeter uses DC excitation, and the medium flow rate is slow, and the medium has a tendency to corrode, then the possibility of polarization will be large. The three-value low-frequency rectangular wave excitation technology (with 1/8 of 50Hz as the period and a sinusoidal excitation current) can eliminate the polarization interference of DC magnetic field. It has better zero point stability and solves the influence of interference potential. .