Common problems in the use of pull-out electromagnetic flowmeters, some are caused by damage to the components of the instrument itself, some are caused by improper selection, improper installation, environmental requirements, fluid characteristics, etc., such as showing shaking, accuracy degradation and even Instrument damage, etc. It can be generally divided into two types: the faults displayed during the commissioning of the device (the fault during the commissioning period) and the faults during the normal operation (running problems):
1. During the commissioning period, the fault diagnosis period is usually displayed in the debugging stage of the instrument device. Once it is removed, it will not be displayed again after the opposite request. The more common debugging problems are caused by improper equipment, environmental disturbances and fluid characteristics.
2, the device is usually caused by the incorrect status of the electromagnetic flow sensor device, such as the sensor device at the highest point of the pipe that is easy to accumulate gas; or the device is displayed on the vertical pipe from top to bottom, can display emptying Or no back pressure after the sensor, the fluid is indirectly discharged into the atmosphere to form a non-full tube inside the measuring tube.
3, the environmental aspects are usually important to the pipeline stray current disturbance, space strong electromagnetic wave disturbance, large motor magnetic field disturbance. Pipe stray current disturbance usually takes good grounding maintenance to achieve satisfactory results, but if you encounter strong stray current (such as electrolysis workshop piping, sometimes the peak potential Vpp induced on the two electrodes can be as high as 1V), still Additional measures and insulation of the flow sensor and piping are required. Space electromagnetic wave disturbances are usually introduced through signal cables and are usually maintained by single or multiple layers of shielding.
4, the fluid aspect of the measured liquid containing the average spread of large bubbles usually does not affect the normal task of the electromagnetic flowmeter, but as the bubble increases, the meter input signal will show shaking, if the bubble is large enough to cover the entire electrode appearance, As the bubble flows through the electrode, the electrode circuit is tripped and the input signal shows a greater shake.
When the low-frequency square-wave excited electromagnetic flowmeter measures the solid content over the slurry, slurry noise will also occur, causing the input signal to shake.
When measuring mixed media, if the flow sensor is measured before the mixing is not averaged, the input signal will also be shaken.
The electrode data and the measured medium are not properly selected, and the normal measurement will also be affected due to chemical action or polarization. The electrode data should be correctly selected according to the instrument selection or related manual.
1. The fault during the running period of the operation period is the fault that the electromagnetic flowmeter has been debugged and operated normally for a period of time. The common operational problems are caused by factors such as the adhesion layer on the inner wall of the flow sensor, lightning strikes and environmental requirements.
2. The adhesion layer on the inner wall of the sensor is commonly used to measure the dirty fluid. After a period of operation, the adhesion layer often accumulates on the inner wall of the sensor. These problems are often caused by the electrical conductivity of the adhesion layer being too large or too small. If the attachment is an insulating layer, the electrode circuit will show an open circuit, and the meter cannot perform the normal task; if the electrical conductivity of the adhesion layer is significantly higher than the fluid conductivity, the electrode circuit will show a short circuit and the instrument will not function properly. Therefore, the fouling layer in the measuring tube of the electromagnetic flowmeter should be cleared in time.
3, lightning strikes lightning strikes easily induce high voltage and surge current in the instrument line, making the instrument damaged. It is important to be introduced through the power line or the excitation coil or the flow signal line between the sensor and the converter, especially from the control room power line.
4. Changes in environmental requirements During the commissioning period, due to environmental requirements (for example, there is no source of disturbance), the flowmeter task is normal, and the device requirements are often easily ignored (for example, the grounding is not good). Under this condition, once the environmental requirements change, the operation period shows a new source of disturbance (such as welding on the left side of the flowmeter, large transformer on the left device, etc.), which will disturb the normal task of the meter, input and input of the flowmeter. The signal will show shaking.