How to deal with electromagnetic flowmeter encountered faults?

Case introduction

　　Electromagnetic flowmeters are flowmeters that measure flow according to Faraday's law of electromagnetic induction. Electromagnetic flowmeter has the advantage of very small pressure loss, measurable flow range. The ratio of maximum flow rate and minimum flow rate is generally 20:1 or more, applicable to a wide range of industrial pipe diameter, up to 3m, the output signal and the measured flow rate into a linear, high accuracy, can measure the conductivity ≥ 5μs/cm of acid, alkali, salt solutions, water, sewage, corrosive liquids and mud, slurry, pulp, pulp and other fluid flow. But it can not measure the flow of gas, steam and pure water.

　　Electromagnetic flowmeter in the use of faults in the process of how to solve the problem

　　1 instrument flow without signal output?

　　Cause analysis:

　　The instrument power supply is not normal;

　　Cable connection is not normal;

　　Liquid flow conditions do not meet the installation requirements;

　　Damaged transducer components or adherent layer on the measuring inner wall;

　　Damaged transducer components.

　　Solution:

　　Confirm that the power supply has been connected, check whether the output voltage of each circuit of the power supply circuit board is normal, or try to replace the whole power supply circuit board to judge whether it is good or bad.

　　Check whether the cable is intact and connected correctly.

　　Check the direction of liquid flow and whether the liquid in the tube is full. For the electromagnetic flowmeter can be measured in the positive and negative direction, if the direction is inconsistent although it can be measured, but set the display flow rate of positive and negative does not match, it must be corrected, if the workload of removing the sensor is large, you can also change the direction of the arrows on the sensor and reset the display instrument symbols. Pipeline is not full of liquid is also caused by the sensor installation position is not proper, should be installed to take measures to avoid causing the liquid in the pipeline is not full of pipe.

　　Check whether the electrodes on the inner wall of the variable speed transmitter are covered with a liquid scarring layer, and for the measurement of liquids that are prone to scarring, they should be cleaned regularly.

　　If the judgement is that the converter components are damaged caused by the fault, replace the damaged components can be.

　　2 Output value fluctuation?

　　Cause analysis:

　　Caused by such failures are mostly caused by the measurement medium or the influence of the external environment, the fault can be eliminated by itself after the elimination of external interference. In order to ensure the accuracy of the measurement, such failures should not be ignored. In some environments, due to the measurement of pipeline or liquid vibration, can cause the measurement of the meter's circuit board loose, can also cause fluctuations in the output value.

　　Solution:

　　Confirm whether the process operation reasons, the fluid does occur pulsation, this time the flowmeter only truthfully reflect the flow conditions, pulsation after the end of the fault can be eliminated by itself.

　　External stray current and other electromagnetic interference. Check whether there are large electrical appliances or welding machine working in the instrument operating environment, to confirm the instrument grounding and good operating environment.

　　When the pipeline is not filled with liquid or the liquid contains air bubbles, both are caused by process reasons. At this time, you can ask the technician to confirm that the output value can be restored to normal after the pipe is filled with liquid or the air bubbles are calmed down.

　　Transmitter circuit board for the plug-in structure, due to the field measurement of pipeline or liquid vibration, often caused by the flowmeter power board loose. If loose, the flowmeter can be disassembled, re-fixed circuit board.

　　3 no flow after power on when there is a signal output?

　　Cause analysis:

　　Input shielding or poor grounding, the introduction of electromagnetic interference;

　　The meter is close to strong electrical equipment or high-frequency pulse interference source;

　　Strong vibration of the pipeline;

　　The agility of the converter is too high;

　　Treatment.

　　Improve shielding and grounding to exclude electromagnetic interference;

　　Installation away from the source of interference, take isolation measures to strengthen power filtering;

　　Take vibration damping measures, strengthen signal filtering to reduce the agility of the amplifier;

　　Reduce the agility, improve the trigger level.

　　4 DD error?

　　Cause analysis:

　　Tube pressure is too high

　　Engineering pressure selection error;

　　Damaged seals;

　　Sensor erosion;

　　Treatment:

　　Adjust high pressure and change mounting position;

　　Selection of a higher engineering pressure sensor;

　　Replacement of seals;

　　Taking anti-corrosion and protective measures.