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Electromagnetic flowmeter operation and maintenance introduction

Electromagnetic flowmeter operation and maintenance
(1) Zero check and adjustment
Before the meter is put into operation, the zero point must be adjusted after the sensor is fully charged with liquid. After putting into operation, it is also necessary to stop the flow at regular intervals according to the liquid use conditions; especially for sedimentation and contamination of the electrode, the non-cleaning liquid containing the solid phase should be inspected at the initial stage to obtain the experience to determine the normal inspection cycle. The EMF of the AC excitation method is more prone to zero drift than the rectangular wave excitation, so it is necessary to pay attention to inspection and adjustment.
An example of an application error that causes two layers to fail. In the oil drilling and cementing project, the flow rate and total amount of cement slurry are important process parameters, often using high pressure EMF. The meter is used intermittently. After use, rinse the sensor measuring tube with clean water, and the rest of the time is empty. Due to incomplete cleaning, the residual cement slurry on the inner wall of the measuring tube is solidified into a thin layer, which accumulates in the past two months to form an insulating layer, covering the entire surface of the electrode, resulting in abnormal operation and eventually failure to work. The other is the electrolytic cutting process experimental device. The flow rate of saturated brine is controlled by EMF. After a period of use, the flow signal is gradually weakened, and the signal is zero after 2 months. The reason is that iron oxide is deposited on the wall of the tube during electrolytic cutting, resulting in a short circuit. The clear stratification layer immediately returns to normal.
(2) Regularly check the electrical performance of the sensor
1) Roughly measure the resistance between the electrodes and disconnect the signal between the sensor and the converter. The sensor is filled with liquid. Use a multimeter to measure the resistance between the two electrodes and the ground. Is it within the specified range of the manufacturer? And the two values are measured in a large phase. Record the resistance value measured for the first time. This value is useful for determining the cause of the sensor failure (such as whether the deposited layer is conductive or insulated).
2) Check the electrode insulation resistance sensor to empt the liquid, wipe the inner wall, and after completely drying, measure the resistance between the two electrodes and the ground terminal with a megaohm meter.
3) Check the insulation resistance of the excitation coil to remove the connection between the excitation coil terminal and the converter. The insulation resistance of the coil is measured in a megohmmeter.

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