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Introduction to the importance of installation and use of electromagnetic flowmeters

The correct installation of the electromagnetic flowmeter is extremely important for the normal operation of the electromagnetic flowmeter. Here we mainly introduce the problems that should be paid attention to when installing and using the electromagnetic flowmeter sensor and converter.

(1) Installation location. The common electromagnetic flow juice sensor has an enclosure rating of IP65.

1) When measuring the mixed phase fluid, choose a place that will not cause phase separation.

2) Select a place where there is no negative pressure in the measuring catheter.

3) It should be installed in an environment without strong electric field. There should be no large electrical equipment nearby. The requirements for the installation site are such as electric motors and transformers. To avoid interference with electricity.

4) Avoid installation in places where the week is inherently corrosive.

5) The ambient temperature should generally be in the range of -25-60 °C, and avoid direct sunlight as much as possible.

6) Installed in a place with no vibration or vibration. If the vibration is too large, the pipe should be fixed before and after the sensor.

7) The relative humidity of the environment should generally be in the range of lo%.-90%.

8) Avoid installation in places where it can be drenched by rain or immersed in water. If the sensor is protected by IP67 or IP68 (dust and water proof). Then the last two items can be left unrequested.

(2) The length of the straight pipe section. The electromagnetic flowmeter has relatively low requirements on the length of the straight pipe section in front of the watch. Generally, it is a flow resistance member such as a 90" elbow, a T-shaped three-way, a reducer, and a full-opening door. It is away from the sensor shaft axis center line (not the sensor inlet end face). There should be a straight pipe length of 3 - 5D; for valves with different opening degrees, the length of the straight pipe section of the IOD is required; after the sensor, there should be a length of the straight arm section of 2D. When the valve is fully open, if the valve is closed The orientation is 450 mounted on the sensor electrode shaft, which greatly reduces additional errors.

(3) Installation position and flow direction. The electromagnetic flowmeter can be installed in water, vertical or tilted. When mounted horizontally, the sensor electrode shaft must be placed horizontally.

This not only prevents short-time insulation of the electrodes due to bubbles entrained by the fluid; it also prevents the electrodes from being covered by deposits in the fluid. The flowmeter should not be installed at the highest point to avoid gas volume. The electromagnetic flowmeter used in b in Figure 4-43 is installed at the highest point in the pipeline, which is a bad installation position and should be avoided. When installed vertically, the fluid should flow through the electromagnetic flowmeter from bottom to top, as shown by e in Figure 4-43. This allows no flow or flow to be small, the heavier solid particles entrained in the fluid sink, and the lighter fatty material rises away from the sensor electrode area. When measuring liquid-solid two-phase flow such as mud and slurry, vertical installation can avoid solid phase precipitation and uneven wear of the sensor insulation lining.

The installation of the electromagnetic flow juice should have a certain back pressure at the position shown in a in the 4.43 of the figure. The direct discharge of the flowmeter outlet may cause the liquid to be non-full-filled in the measuring conduit, which is a bad installation position and should be avoided. In order to prevent negative pressure in the electromagnetic flow juice, the electromagnetic flowmeter should be installed behind the pump, as shown by d in Figure 4.43; it should not be installed in front of the pump, as shown by c in Figure 4-43.

(4) Install the bypass pipe. The measurement accuracy of the electromagnetic flow juice is affected by the inner wall of the measuring pipe, especially the fouling near the electrode. The maintenance and cleaning should be paid attention to during use. In order to facilitate the inspection and adjustment of the zero point, the small and medium diameter pipe should be installed as much as possible to make the electromagnetic flowmeter full of the non-flowing liquid to be tested.

(5) Correct grounding, the electromagnetic flow juice signal is weak, only a few millivolts at full scale, when the flow is very small, only a few microvolts, the external interference will affect the measurement accuracy. Therefore, the electromagnetic flow sensor must be grounded separately. And connect its "ground" with the measured ground and the "ground" of the converter with a wire, and then deeply buried it with a grounding wire; the grounding resistance should be small, the grounding point should not have ground current, to ensure Do not connect the motor or the well to the fluid, the casing, the good grounding between the pipes and the good point contact. On the upstream and downstream pipelines.

(6) The signal wire should be penetrated into the grounding steel pipe alone, and never be allowed to be worn in a steel pipe. The signal line must be shielded. The length must not exceed 30m. If it is required to lengthen the signal line, certain measures must be taken, such as double-layer shielded cable and shielded drive. ,

(7) The flow direction of the liquid to be tested should be the direction specified by the transmitter. Otherwise, the flow signal will be phase-shifted by 180°. The phase sensitive detection cannot detect the flow signal, and the meter will have no output.

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