Main problems of vortex flowmeters and their solutions

Thread Content

Main problems of vortex flowmeters and their solutions The main problems include: ① Inaccurate readings over time； ②No instructions at all ； ③Indicates large fluctuations; no reading possible ； ④Indicate not to return to zero ； ⑤No indication at low flow rates ； ⑧The indication is okay at high flow rates, but inaccurate at low flow rates ； ⑦The indication fails to keep up when the flow rate changes ； ⑧The K coefficient for the instrument cannot be determined, as there are inconsistencies in various sources. Analysis and Solutions for Vortex Flow Meters The main causes of these problems can be summarized as follows: 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 having a diameter that is one size too large. In practice, it is necessary to choose the smallest possible diameter in order to improve measurement accuracy; this is mainly related to issues ①, ③, and ⑥. For example, a vortex flow meter pipeline is designed to serve 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 turn raises the lower limit of the flow rate that can be measured. The meter cannot provide accurate readings when the flow rate is low, but it still functions properly when the flow rate is high, as redesigning it can be very difficult in such cases. Changes in process conditions are usually 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. Incorrect instrument readings are caused by parameter errors. These errors lead to mistakes in the calculation of the full-scale frequency of the secondary instruments, and 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 performing re-calibration and making comparisons between different values. 　　4. Secondary instrument failure. There are many faults in this area, including broken wires in the primary instrument circuit boards, faulty display of individual bits related to range setting, and faulty display of individual bits related to K-factor setting, which makes it impossible to determine the range setting and the K-factor 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 a disruption of 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 a disruption of the circuit. 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, this issue is mainly related to problem No. 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 abnormal operation. The problem was resolved by adjusting the gauge and re-fixing it. 　　9. Environmental usage issues. Especially the sensor part installed in the ground well suffers from moisture on the circuit boards due to high environmental humidity; this issue is primarily related to problems ② and ②. Through appropriate technical improvements, 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. Due to improper adjustment of the on-site vibration and noise balance as well as sensitivity settings, or due to further changes in the on-site conditions after operation for a period of time following such adjustments, indication problems occur; these reasons are mainly related to issues④ and⑤. Use an oscilloscope, and adjust again by taking into account the operation conditions of the process.