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Common problems and solutions in the use of vortex flowmeters. Vortex flowmeters are primarily used for measuring the flow rate of fluids in industrial pipelines, including various media such as gases, liquids, and vapors. It is characterized by low pressure loss, a wide measurement range, and high precision; when measuring volumetric flow rate under operating conditions, it is hardly affected by parameters such as fluid density, pressure, temperature, and viscosity. There are no moving mechanical parts, thus it offers high reliability and requires minimal maintenance. The instrument parameters can remain stable over the long term. This instrument uses piezoelectric stress sensors, offering high reliability, and can operate within a working temperature range of -20°C to +250°C. It provides both analog standard signals and digital pulse signals for output, making it easy to integrate with digital systems such as computers; it is a relatively advanced and ideal flow meter. I. Main existing problems mainly include: ① Inaccurate indications over the long term ； 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 acceptable 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 resolution of key issues The analysis and resolution of these issues took nearly half a year from all the members of the technical department at Jiangsu Sukede Instrument Co., Ltd. Due to the complexity of these problems, there were issues of varying degrees in design and installation, parameter setting, daily maintenance, and the operating environment; many of these problems were interrelated, and furthermore, resolving some of them required waiting for certain conditions to be met during the operation process, which posed significant difficulties in addressing them. Some of these problems were caused by multiple factors, with each factor being related to several different issues. Summarizing the main reasons for these problems, they mainly relate to the following aspects: 1. Issues with product selection. Some vortex flowmeter sensors, either during the selection of the diameter or after the design phase due to changes in manufacturing conditions, end up having a larger specification chosen than necessary; in fact, the smallest possible diameter should be selected to improve measurement accuracy. The reasons for this are 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 decreases. As a result, the diameter selected in the original design is too large, which 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 degraded level of performance. 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 causes of this are mainly related to issues ① and ③. A significant difference in the full-scale frequency leads to inaccurate readings over time; when the actual full-scale frequency is much higher than the calculated value, the readings fluctuate greatly and become unreadable. Moreover, inconsistencies in the parameters listed in the documentation affect 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 interruptions in the circuit. In other cases, although the connectors are tightly fastened, issues with the auxiliary wires cause the fastening screws to tighten against the wire insulation, which also leads to circuit interruptions. These problems are mainly related to issue #2. The corresponding wiring issues have been resolved, and the existing problems have also been fixed. 6. Issues with the connection between secondary instruments and subsequent instruments. Due to issues with 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 exposure to dust, the flat cable developed faults; 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 sinking; 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 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 improvements, the probes of some sensors that operate 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 causes are mainly related to issues ④ and ⑤. Use an oscilloscope, and adjust again by taking into account the operation conditions of the process. 11. Question ⑧ was raised separately because it has had a significant impact on the analysis and resolution of the issue for a long time. Since Dongfang Chemical Plant does not have the conditions necessary to determine the K coefficient, this coefficient can only be obtained from the data provided by the manufacturer. However, due to certain changes within the manufacturer itself, the K coefficients indicated in the various pieces of data provided are inconsistent, which hinders the resolution of the issue. By seeking conditions for re-calibration, or through repeated modifications and comparisons, unified instrument parameters were finally determined. II. Solutions: Through careful analysis and summarization over a period of time, the problems associated with vortex flow meters have been largely resolved. At present, these instruments are operating properly and meet the requirements of the factory’s production processes. 1. Since the determination of the K coefficient is extremely important in the entire vortex flowmeter process, its accuracy directly affects the precision of the measurement system. Factors such as the replacement of components in the instrument and wear and tear on the process pipelines can all influence the K coefficient. Moreover, Dongfang Chemical Plant lacks the means and capabilities for calibration; it can only send the flowmeters for calibration. Due to the demands of the production process, it takes 5 to 6 days to remove the vortex flowmeters from the pipelines for calibration, which is difficult to accommodate from a process perspective, thus preventing the determination of the K coefficient. This year, through modifications to the flow meters, the conditions for calibrating vortex flowmeters of smaller diameters have been established; however, such methods are still ineffective for vortex flowmeters of larger diameters. In the future, it is necessary to employ on-site calibration techniques for vortex flowmeters, using standard frequencies and portable ultrasonic flowmeters to measure the instantaneous flow rate in the pipeline as well as the pulse output frequency of the sensor, so as to calculate the K coefficient on-site. 2. The probes of vortex flow meters should be cleaned regularly. During inspections, it was found that the detection holes of some probes were blocked by dirt or even covered with plastic sheets, which affected accurate measurement. 3. Regularly check the grounding and shielding to eliminate external interference. Sometimes, indication problems are caused by interference. 4. Probes installed in humid environments should be dried regularly or treated to prevent moisture absorption. Since the probe itself is not treated to prevent moisture, it suffers from impaired performance when exposed to moisture. 5. Sufficient attention should be paid to the management of instrument data to facilitate future work.