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Electromagnetic flowmeter flow output does not match the actual zero point shaking, unstable introduction

A plurality of electromagnetic flowmeters are used in the gasification device, and the failures encountered during the gasification operation of the gasification device are as follows:

1. The flow signal suddenly drops or no indication

The process operator reported that the flow rate of the gray water flow meter from the circulating grey water cooler suddenly dropped. According to the experience of instrument maintenance for many years, the main reason for the occurrence of such a situation is that the insulation between the electrodes is deteriorated or short-circuited, resulting in signal transmission. stay home. After careful inspection, it was found that the signal socket was corroded, so it was cleaned and dried with water, and it was normal after loading. Of course, in addition to the above reasons, it is also possible to measure the dirt deposit on the inner wall of the catheter and measure the damage of the catheter lining.

2, the output signal shakes

When the instrument personnel inspected, it was found that the output signal of the electromagnetic flowmeter was shaken badly. Check that the fluid to be measured was not fluctuating or pulsating, and that the pipe was full of liquid. After careful inspection, the electromagnetic flowmeter itself was not faulty and found not far away. A device maintenance personnel is welding a joint, which is determined to be caused by electromagnetic interference when the welding machine is working. The flow meter indicates normal after leaving the electromagnetic interference.

3, zero instability

When the process is stopped, the zero point of the thick mortar flow meter is unstable. It is found that there is dirt deposit in the pipe measured by the watch, and it is attached to the inner wall of the measuring tube, which causes the zero point of the flow meter to change, and removes the dirt on the electrode and near the electrode. After the dirt, it was found that the zero point still changed somewhat. After re-calibration with bt200, the watch showed normal. Of course, the reasons for zero instability may be due to the following four reasons:

The pipe is not filled with liquid or there are bubbles in the liquid;

Whether there is a leak in the pipeline;

Whether there is external electromagnetic interference;

4. The measured value does not match the actual value.

After ensuring that the liquid in the tested pipeline is filled with the sensor and is stationary, after using the bt200 to re-adjust the zero point of the meter, there is still an error between the measured value and the actual value. After careful inspection, it is found that the range setting of the converter is incorrect. After setting the correct range according to the table, the indication is normal. The reason for the discrepancy may also be as follows: the sensor is not installed properly, the tube is not full or the liquid in the test contains bubbles. The fault is mainly the pipe network engineering design. Poor, and related equipment is not perfect; the insulation capacity of the signal cable is reduced.

Firstly, the on-site and main control room joint school confirms that the cable connection is correct, and then checks whether the connection at the terminal or the cable is damp, resulting in a decrease in the insulation capacity of the cable; the upstream flow condition of the sensor does not meet the requirements. The upstream flow condition of the sensor is often limited by the installation space and does not meet the specified requirements. For example, the flow block that is close to the spoiler but does not have a long straight pipe section, which will introduce factors affecting the measurement accuracy. The inner wall of the measuring tube has a silt layer or a pipe wall. Being worn, thereby changing the flow area, affecting the measured value; the resistance between the electrodes of the sensor changes or the insulation of the electrode drops. This fault is often caused by the intrusion of rainwater from the terminal to make it wet. Insulation can be restored by eliminating moisture.

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