1.1 Failure during debugging

This failure occurs during the installation and commissioning phase. Once it is eliminated, it will not appear again and again under the same conditions. Such failures are mainly caused by improper installation, environmental disturbances, and fluid properties.

1.2 Installation

It is usually caused by an incorrect installation location, such as at the highest point of a pipe that is liable to collect gas or a vertical pipe section that is installed from top to bottom. Either emptying may occur or there may be no back pressure behind the sensor and the fluid directly enters the atmosphere forming a non-full tube within the measuring tube. The sensor is installed vertically as far as possible so that the measured medium flows through the instrument from the bottom up; when it is installed horizontally, the axis of the electrode should be parallel to the ground. Avoid the highest position of the sensor in the pipeline to prevent air bubbles from accumulating at the electrodes. Both types of installations should have bypass and valves at both ends of the sensor to facilitate instrument maintenance. In addition, the sensor should be concentric with the pipe during installation, especially for the small-diameter flowmeter concentricity deviation will produce measurement error. The installation must meet the straight section L1≥5DN, the straight section L2≥2DN, and the DN is the diameter of the pipe. Avoid installing the regulating valve upstream of the meter and the pump source cannot be installed downstream to ensure the measuring accuracy of the meter. When using the connecting cable correctly, when measuring the low-conductivity medium and using the long-range split electromagnetic flowmeter, the corresponding chart must be calibrated to determine the signal cable and the excitation line with the appropriate cross-sectional area.

1.3 Environment

Such failures are caused by stray currents in the pipeline, strong electromagnetic wave interference in space, and magnetic field disturbances in large motors. Normally, a good individual grounding protection is used. Do not ground it together with other power supplies. The grounding resistance should be less than 10 ? 6 ? 8 to improve the anti-interference performance of the instrument. However, in the event of strong stray currents, other measures must be taken to insulate the flow sensor and the pipe. Space electromagnetic interference is generally introduced via signal cables. Single- or multi-layer shielding should be used. Therefore, strong vibration and strong AC-DC magnetic fields should be avoided in the installation site. If necessary, add support on the left and right sides of the measuring tube. The allowable vibration level should be less than 2.2g and within the range of 20Hz to 50Hz. Do not expose the instrument to direct sunlight. If necessary, add a protective cover.

1.4 Fluid properties

The measured liquid contains evenly distributed microbubbles, which usually do not affect the normal operation of the electromagnetic flowmeter. However, as the air bubbles increase, the output of the instrument fluctuates. If the air bubbles are large enough to cover the entire surface of the electrode, the flow of the air bubbles follows. The short-circuit across the electrode loop causes the output signal to fluctuate more. When a low-frequency square-wave excitation electromagnetic flowmeter measures a slurry with an excessive solid content, slurry noise will also be generated, causing the output signal to fluctuate. When measuring mixed media, if the flow sensor enters the measurement before the mixing is not uniform, it will also fluctuate. Improper matching of electrode material and measured medium will also affect normal measurement due to chemical action or polarization. Therefore, electrode materials should be correctly selected according to the instrument or relevant manual. It is necessary to consider that the electrode material meets the corrosive requirements of the measured medium, and that no chemical reaction occurs on the surface of the electrode, such as no passivation, oxidation, polarization, bubbles, and fouling layer. The measuring medium should be adapted to the measuring tube gasket material so that the gasket can achieve anti-corrosion and necessary wear resistance to increase the service life of the sensor.

2.1 Runtime failure

This type of fault is caused by factors such as the attachment of the inner layer of the flow sensor, lightning strikes, and environmental changes. The following analysis focuses on the failure of the instrument itself.

2.2 inner wall adhesion layer

Since the electromagnetic flowmeter is commonly used to measure the dirty fluid, after a period of operation, the accumulating adhesion layer on the inner wall may cause failure due to too much or too little conductivity of the adhesion layer. If the adherent is an insulating layer, the electrode circuit will be open circuit and the instrument will not work properly. If the conductivity is significantly higher than the conductivity of the fluid, a short circuit in the electrode circuit will occur and the meter will not work, so the adhesion layer should be removed.

2.3 Lightning Strike

Lightning strikes induce high voltage and surge currents to damage the meter. This is mainly introduced through the power line or the excitation coil or the flow signal line between the sensor and the converter. In particular, most of the power is introduced from the control room power line.

2.4 Changes in environmental conditions

If you encounter a strong magnetic field, stray current, etc. should take appropriate measures.

2.5 Judgment and Analysis by Fault Occurrence

General faults are displayed on the output signal meter of the flowmeter converter. The symptoms, causes and exclusion methods are as follows:

(1) When there is no flow signal, there may be: power failure, connection cable failure, medium flow conditions, bad sensor components, and bad converter components.

Remedy: Check the fuse and power supply, cable, flow direction and sensor direction are consistent, replace the sensor and sensor components.

(2) When the output liquid and zero point drift, the fluid may fluctuate or pulsate, the pipeline is not filled with liquid, the external power, magnetic interference, the physical characteristics of the medium and the signal circuit insulation decline, the electrode material and the medium do not match, etc. .

Remedy: Actually reflect the working conditions, make the media full of pipelines, install grounding rings at both ends of the sensor to remove interference, use conductive rubber, increase time and frequency constants, improve insulation performance, and replace electrode materials.

(3) When the flow measurement value does not match the actual value, it may be that: the converter setting parameters are not correct, the pipe is not full, the signal cable is not processed, the resistance between the sensor electrodes changes, and the branch pipe flow rate is not evaluated.

Remedy: Correctly set the instrument parameters, change to a completely filled position, select the signal cables and connect them firmly according to the regulations, remove the conductive deposits, seal the leakage valve of the branch pipe, and cut off the flow of the unassessed branch pipe.

(4) Signal over-range may be caused by sensors, cables, converters, display instruments, etc.
Remedy: Short-circuit the converter signal terminals, determine which part is faulty, correct the wiring, set the instrument parameters correctly, and take isolation measures.

Electrolyte Additives

Electrolyte Additive,Iodine Crystal Granule Crystal,Iodine Crystal,Cas 7553-56-2

Henan Tianfu Chemical Co.,Ltd , https://www.tianfuchem.com