Electromagnetic flowmeter common maintenance and maintenance methods

Case introduction

A brief analysis of the common maintenance methods of domestic electromagnetic flowmeters:

However, as a flow meter, if the quality is qualified and other conditions, some failures will also occur due to some factors. The vortex flowmeter What are the common faults? 1. The reasons for signal output when there is no flow are analyzed as interference signals introduced by instrument lead shielding or poor grounding; there are strong electrical equipment or power line interference around the instrument; and the pipeline is strongly vibrating. The solution is to strengthen the lead shielding to ensure good grounding of the line; keep the instrument away from interference sources; jump to a higher trigger level or reduce shock. 2. The reasons for the excessive deviation of the indication error and the excessive repeatability are analyzed as the vortex generator of the primary element is damaged; the length of the upstream and downstream straight pipe sections is not enough; the instrument constant K is only set incorrectly; the probe is seriously contaminated; the fluid disturbance in the pipeline is too large . The solution is to replace the vortex generator; change the installation location; re-measure and calibrate to obtain the correct instrument constant K; clean the probe; change the installation location and increase the inlet pressure. 3. There is no display on the secondary instrument after power on. The reasons are analyzed as incorrect power wiring or power open circuit; wiring voltage is greater than 220V, the electric furnace is burned out; power supply voltage does not match the power supply voltage required by the instrument; sensor failure or amplifier board failure; The flow rate is too small or there is no flow in the pipe. The solution is to check the circuit and connect it correctly; if it is burned, find the damaged parts and replace the original parts; provide power supply as required; replace the faulty parts of the secondary instrument; and adjust the pipeline flow. 4. The flow lower limit expansion is limited. Use a flow display calculator that can set the flow compensation correction coefficient, and realize the expansion of the flow lower limit through software programming. Taking the triangular cylindrical vortex generator as an example, the Reynolds number range is 2×104 ~ 7×106. In order to achieve the lower limit of flow rate extending to 5×103, it should be corrected when measuring small flow rates. According to the theoretical compensation correction coefficient in the range of Reynolds number 5×103 ~ 2×104, the flow lower limit is expanded and the flow measurement error is compensated. 5. The reason for abnormal remote signal output is analyzed as follows: if it is a frequency or pulse signal output, the receiving circuit is compatible with the output circuit; if it is a (4~20) mA current output, the flow setting range does not correspond to the output current one by one. The solution is to connect external electrical components (such as resistors with a certain resistance in series) to make the output and input circuits well compatible; when setting parameters, the upper and lower flow limit values ​​correspond to 4mA and 20mA. 6. The flow rate is inaccurate and differs greatly from the process parameters.

The reason is that the process parameters are entered incorrectly; the instrument range does not meet the actual flow requirements. The solution is: correctly enter the instrument parameters; adjust the process or select an instrument suitable for the actual flow range. 7. The instrument constant K changes with the change of the medium used. When the vortex flow sensor is used to measure liquid flow, water should be used to calibrate the instrument constant K value. When measuring gas and steam, the instrument constant K value should be calibrated with gas. Although in principle, the instrument constant K value has nothing to do with the properties of the measured medium, due to the processing technology of the sensor, there are differences between manufacturers, and the K value corresponding to different fluidsThere will be some differences. Therefore, when using different media, the same medium should be used for calibration to obtain the instrument constant K value. At the same time, when the medium temperature is higher than 150°C, the instrument constant K value should also be corrected. 8. After the instrument has been used for a period of time, the error deviates from the normal range. Since industrial fluid media often contain some impurities, the sensor should be cleaned within the specified time according to the specific situation.