Main problems of vortex flowmeters and their solutions

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The main problems include: ① Inaccurate indications over the long term； ②No indication at all③; indications show large fluctuations, making them unreadable ； ④Indicate not to return to zero ； ⑤No indication at low flow rates③ The indication is acceptable at high flow rates, but not at low flow rates ； ⑦The indication fails to keep up when the flow rate changes ； ③The K coefficient for the instrument cannot be determined, as there are inconsistencies in various sources. Summary of analysis and solutions for vortex flowmeters: The main causes of these problems relate to the following aspects: 1. Issues related to selection. Some vortex flow meter sensors, either during the selection of the diameter or after the design phase due to changes in manufacturing conditions, end up with a larger specification than necessary; in such cases, it is advisable to choose the smallest possible diameter in order to improve measurement accuracy. The reasons for this are mainly related to issues ①, ③, and ⑥. For example, in the design of a vortex street pipeline intended for use by several devices, since some of the equipment in the process system is not used at times, the actual flow rate in use is reduced. This results in the originally selected pipe diameter being too large, which in effect raises the lower limit of the flow rate that can be measured; the gauge cannot provide accurate readings when the flow rate is low, but it still functions properly when the flow rate is high. After all, it can be difficult to carry out modifications, and changes in process conditions are usually only temporary. The indication accuracy can be improved by adjusting the parameters. 2. Issues with installation. Mainly, the length of the straight section in front of the sensor is insufficient, which affects the measurement accuracy; this issue is primarily related to problem #1. For example, there is clearly a insufficient straight section in front of the sensor; since FIC203 is not used for measurement but only for control, the current accuracy can be considered as equivalent to a reduced-grade version. 3. Reasons for the parameter tuning direction. Due to incorrect parameters, the instrument readings are inaccurate. These parameter errors result in an incorrect calculation of the full-scale frequency of the secondary instrument; the reasons for this are mainly related to issues #1 and #3. A difference in full-scale frequency that is not significant enough causes the indication to be inaccurate over time; whereas a full-scale frequency that is much higher than the calculated value leads to large fluctuations in the indication, making it impossible to obtain a readable reading. The inconsistency in the parameters listed in the documentation further hinders the final determination of these parameters. This issue was resolved by re-calibrating and comparing the values accordingly. 4. Secondary instrument failure. There are many faults in this area, including broken wires in the circuit boards of the primary instruments, faulty display of individual bits related to range setting, and faulty display of individual bits related to the K coefficient setting, which makes it impossible to determine the range setting and the K coefficient value. These issues are mainly related to problems ① and ②. The problem was resolved by fixing the corresponding fault. 5. Issues with the connection of four circuits. On the surface, the wiring in some circuits appears to be properly connected; however, upon closer inspection, it is found that some connectors are actually loose, resulting in interruptions in the circuit. In other cases, although the connectors are tightly fitted, issues with the auxiliary wires cause the tightening screws to press against the wire insulation, which also leads to circuit interruptions. These problems are mainly related to issue #2. 6. Issues related to the connection between secondary instruments and subsequent instruments. Due to issues with the subsequent instruments or maintenance work on those instruments, the mA output circuit of the secondary instrument is interrupted. For this type of secondary instrument, such problems are mainly related to issue #2. Especially for subsequent recorders, when the recorder is permanently damaged and cannot be repaired, it is essential to short-circuit the output of the secondary instrument. 7. The circuit shows no indication at all due to a fault in the flat-axis cable of the secondary instrument. Due to long-term operation and the impact of dust, faults occurred in the flat cable; the problem was resolved by cleaning or replacing the flat cable wires. 8. Regarding issue No. 7, it was mainly caused by loose fixing screws of the gauge coil in the secondary instrument, which led to the gauge dropping downward; this resulted in excessive friction between the pointer and the gauge casing, causing poor performance. The problem was resolved by adjusting the gauge and re-fixing it. 9. Environmental issues related to use. Especially the sensor part installed in the well, where high environmental humidity causes the circuit boards to become damp; this issue is primarily related to problems ② and ②. Through appropriate technical modifications, the probes of some sensors that operated in high humidity environments were separated from their conversion units, and separate-type sensors were used as a result; this improved the working conditions, and these instruments are now functioning well. 10. Due to poor on-site calibration, or due to further changes in the actual conditions after calibration. Issues with indications arise due to poor adjustment of the on-site vibration and noise balance as well as sensitivity settings, or because of changes in the on-site conditions after operation for a while following such adjustments; these causes are mainly related to problems ④ and ⑤. Use an oscilloscope, and adjust again in conjunction with the operation status of the process.