Electromagnetic flowmeter structural parts damage caused by the failure

Case introduction

Troubleshooting methods for faults caused by damage to the structural parts of the electromagnetic flowmeter:

There are two types of faults caused by the electromagnetic flowmeter during operation: First, the fault of the meter itself, that is, damage to the structural parts or components of the meter The second is the failure caused by external reasons, such as improper installation, flow distortion, deposition and scaling, etc. This article discusses these two types of failures.

1. The instrument has no flow signal output

1. Cause analysis This type of fault is more common during use, and the reasons generally include:

(1) Instrument The power supply is abnormal;

(2) The cable connection is abnormal;

(3) The liquid flow condition does not meet the installation requirements;

(4) Sensor parts Damaged or there is an adhesion layer on the inner wall of the measurement;

(5) The converter components are damaged.

2. Electromagnetic flowmeter solution

(1) Confirm that the power supply is connected, check whether the output voltage of each channel of the power circuit board is normal, or try to replace the entire power circuit board to determine Its good and bad. (2) Check whether the cable is intact and the connection is correct.

(3) Check the direction of liquid flow and whether the liquid in the tube is full. For electromagnetic flowmeters that can measure forward and reverse, if the directions are inconsistent, they can be measured, but the set display flow direction does not match the forward and reverse directions and must be corrected. If the workload of dismantling the sensor is heavy, you can also change the direction of the arrow on the sensor and reset the displayed instrument symbol. The pipe is not full of liquid, which is mainly caused by the improper installation position of the sensor. Measures should be taken during installation to avoid causing the liquid in the pipe to be full of liquid. (4) Check whether the inner wall of the transmitter is covered with a layer of liquid scarring. Measurement liquids that are prone to scarring must be cleaned regularly.

(5) If it is determined that the fault is caused by damage to the converter components, just replace the damaged components.

2. Output value fluctuations

1. Cause analysis: Most of these faults are caused by the influence of the measurement medium or the external environment. The faults can be eliminated by themselves after external interference is eliminated. To ensure measurement accuracy, such failures cannot be ignored. In some production environments, due to the large vibration of the measuring pipe or liquid, the circuit board of the flow meter may become loose, which may also cause fluctuations in the output value.

2. Solution

(1) Confirm whether it is due to process operation. The fluid does indeed pulsate. At this time, the flow meter only reflects the flow conditions truthfully. After the pulsation ends, the fault can be eliminated by itself.

(2) Electromagnetic interference caused by external stray currents, etc. Check whether there are any large electrical appliances or welding machines operating in the operating environment of the instrument. Make sure the instrument is well grounded and the operating environment is good.

(3) When the pipeline is not filled with liquid or the liquid contains bubbles, both are caused by process reasons. At this time, you can ask the process personnel to confirm that the output value can return to normal after the liquid tube is full or the bubbles subside.

(4) The transmitter circuit board is a plug-in structure. Due to the large vibration of the on-site measurement pipe or liquid, the power supply of the flow meter will often be damaged.The board is loose. If it is loose, disassemble the flow meter and re-fix the circuit board.

3. The flow measurement value does not match the actual value

1. Cause analysis

(1) Whether the transmitter circuit board is intact;

contains tiny bubbles. The bubbles rise and gradually gather above the pipe, and the liquid flow area changes. When there is a lot of gas, interference signals will be generated. Affecting the measurement accuracy;

(3) The signal cable is not well connected or the cable performance is degraded during use, causing inaccurate measurement; (4) The parameter setting value of the converter is inaccurate.

2. Solution

(1) Check whether the transmitter circuit board is intact. If water enters the junction box or is corroded by corrosive test liquids, the performance of the electrical appliance may be reduced or damaged. The circuit board should be replaced at this time.

(2) Ensure that the flow rate of the liquid being measured in the pipeline is above the lowest flow limit value so that the transmitter can work normally.

(3) Check whether the signal cable connection and cable insulation are intact. If the signal cable is loose, just reconnect it; if it is found that the cable insulation does not meet the insulation requirements, you need to Replace the cable with a new one.

(4) Reset the converter setting value and verify the zero point and full scale values ​​of the converter.

IV. The output signal exceeds the full scale

1. Cause analysis The causes of this type of failure are roughly as follows:

(1) Error in signal cable wiring Or the cable connection is disconnected;

(2) The parameter settings of the converter are incorrect;

(3) The converter and sensor models do not match.

2. Solution

(1) Check whether the signal loop connection is normal. If the signal loop is disconnected, the output signal will exceed the full scale value. At this time, the signal needs to be reconnected correctly. cable. At the same time, it is necessary to check whether the insulation performance of the cable is intact. If it no longer meets the requirements, the cable needs to be replaced with a new one.

(2) Check in detail whether the parameter settings of the converter and the zero point and full scale meet the requirements.

(3) If it is found that the model of the converter and sensor do not match, it needs to be replaced with the manufacturer.

5. Zero point instability

1. Cause analysis

(1) The pipe is not filled with liquid or the liquid contains bubbles.

(2) Subjectively, there is no flow of liquid in the tube pump, but in fact there is a slight flow.

(3) Liquid reasons (such as poor uniformity of liquid conductivity, electrical pollution, etc.).

(4) The signal loop edge drops.

2. Solution

(1) The pipeline is not filled with liquid or the liquid contains bubbles, which are caused by the process. At this time, the process personnel should be asked to confirm. After the process is normal, the output value can be Back to normal.

(2) There is a trace amount of flow in the pipeline. This is not caused by the electromagnetic flowmeter.barrier.

(3) If impurities are deposited on the inner wall of the measuring tube or scale is formed on the inner wall of the measuring tube, or the electricity is contaminated, the zero point may change, and it must be cleaned at this time; if the zero point changes not much, you can also try Re-zero.

(4) Due to the influence of environmental conditions, dust, oil, etc. may enter the watch case. Therefore, it is necessary to check whether the edge of the electric part has dropped or been damaged. If it does not meet the edge requirements, it must be cleaned.