Analysis of LDCK Magnetic flowmeter failure during commissioning and operation

LDCK Magnetic flowmeter consists of two parts: sensor and converter. It works based on Faraday's law of electromagnetic induction and is used to measure the volume flow of conductive liquids with a conductivity greater than 5μS/cm. It is an inductive instrument for measuring the volume flow of conductive media. In addition to measuring the volume flow of general conductive liquids, it can also be used to measure the volume flow of strong corrosive liquids such as strong acid and alkali, and uniform liquid-solid two-phase suspension liquids such as mud, ore pulp, and paper pulp. Widely used in petroleum, chemical, metallurgy, textile, paper, environmental protection, food and other industrial sectors and municipal management, water conservancy construction, river dredging and other fields of flow measurement.

1. Product overview: As a flow measuring instrument used more and more in industrial production, the electromagnetic flowmeter is not affected by the temperature, viscosity, density and conductivity (within a certain range) of the measured medium due to its measurement results. influence. Electromagnetic flowmeters can directly measure the flow of other conductive liquids only after water calibration. There are no throttling components to obstruct fluid flow. Therefore, when the fluid passes through the flow meter, it will not cause any additional pressure loss, which is a low energy consumption flow meter. Shanghai Automation Instrument Co., Ltd. is a company specializing in electromagnetic flowmeters and has accumulated rich experience in the installation, operation and maintenance of electromagnetic flowmeters over the years. We summarize the common faults of electromagnetic flowmeters, which can be generally divided into two categories: faults during installation and debugging (faults during debugging) and faults during normal operation (faults during operation). Some failures are caused by damaged components of the instrument itself, and some are caused by improper selection, improper installation, environmental conditions, fluid characteristics, etc., such as display fluctuations, decreased accuracy, or even instrument damage.

2. Failure analysis during product debugging

Debugging Anticipated failures usually occur during instrument installation and commissioning. Once eliminated, they cannot happen again in the future under the same conditions. Common commissioning failures are usually caused by improper installation, environmental disturbances, and fluid characteristics.

1) Installation

The failure is usually caused by the incorrect installation of the electromagnetic flow sensor, such as installing the sensor at a high point in the piping system, where gas tends to accumulate; or installing it from top to bottom on a vertical pipe, where evacuation may occur; or the sensor There is no back pressure behind and the fluid is vented directly to the atmosphere, creating a partial tube in the measuring tube.

2) Environmental aspects

Usually it is mainly pipeline stray current interference, space strong electromagnetic wave interference, large motor magnetic field interference, etc. Stray current disturbances to pipes can usually be achieved satisfactorily by employing a good single earth protection. However, in the case of strong stray currents (such as pipes in electrolysis plants, sometimes the peak Vpp of the AC potential induced on both electrodes can reach 1 V), additional measures and insulation of the flow sensor from the pipes are required. Space electromagnetic interference is usually introduced through signal cables, which are usually protected by single or multiple layers of shielding.

3) Fluid

The measured liquid contains evenly distributed tiny air bubbles, which usually do not affect the normal operation of the electromagnetic flowmeter. However, as air bubbles increase, the output signal of the flowmeter fluctuates. If the bubbles are large enough to cover the entire electrode surface, the electrode circuit will be cut off immediately as the bubbles flow through the electrodes, resulting in greater fluctuations in the output signal.

When the electromagnetic flowmeter excited by the low frequency square wave measures the mud with too high solid content, it will also produce mud noise and the output signal will fluctuate.

When measuring mixed media, if the flow sensor is used to measure unevenly before mixing, the output signal will also fluctuate. Improper selection of electrode material and measured medium will also affect normal measurement due to chemical action or polarization. Electrode materials should be correctly selected according to the instrument selection or related manuals. three. Failure analysis during instrument operation

The failure during operation is the failure of the electromagnetic flowmeter after a period of debugging and normal operation. Common run-time failures are usually caused by factors such as adhesion layers on the inner wall of the flow sensor, lightning strikes, and changes in environmental conditions.