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Industry Information
Vortex flowmeter is the most important part to choose and install the correct flowmeter
2012-3-14 10:31:07


主要存在的问题主要有:①指示长期不准;②始终无指示;③指示大范围波动,无法读数;④指示不回零;⑤小流量时无指示;⑧大流量时指示还可以,小流量时指示不准;⑦流量变化时指示变化跟不上;⑧仪表K系数无法确定,多处资料均不一致。 The main problems with vortex flowmeters are: ① long-term inaccurate indication; ② no indication at all times; ③ indication of large-scale fluctuations, unable to read; ④ indication does not return to zero; ⑤ no indication at small flow; 指示 indication at large flow Yes, the indication is inaccurate when the flow rate is small; 指示 the indication change cannot keep up when the flow rate is changed; ⑧ the K factor of the meter cannot be determined, and many data are inconsistent.

Analysis and solution

Summarize the main causes of these problems, mainly related to the following aspects:

1. Selection issues. Some vortex sensors have a larger size in the selection of the caliber or after the design selection due to changes in process conditions. The actual selection should choose the smallest caliber as possible to improve the measurement accuracy. The main reasons for this are the same as Questions ①, ③, ⑥ are related. For example, a vortex street pipeline is designed to be used by several equipments. Because the process equipment is sometimes not used, the current actual flow rate is reduced. The actual use causes the original design to be selected too large, which is equivalent to increasing the measurable flow rate. At the lower limit, the indication cannot be guaranteed when the process flow is small, and it can be used when the flow is large, because it is sometimes too difficult to rebuild. Changes in process conditions are only temporary. Can be combined with parameter re-tuning to improve the indication accuracy. 2. Installation problems. The main reason is that the length of the straight pipe section in front of the sensor is not enough, which affects the measurement accuracy. The reason for this is mainly related to problem ①. For example, the straight pipe section in front of the sensor is obviously insufficient. Since FIC203 is not used for metering, it is only used for control, so the current accuracy can be used equivalent to degraded use. 3. Reason for parameter setting direction. Due to the wrong parameter, the instrument indication is wrong. The parameter error causes the secondary meter full-scale frequency to be calculated incorrectly. The main reason for this is related to problems ① and ③. The full-scale frequency is similar, which makes the indication inaccurate for a long time. The full-scale frequency calculated by the actual full-scale frequency makes the indication fluctuate widely and cannot be read. The inconsistency of the parameters on the data affects the final determination of the parameters. Re-calibration combined with mutual comparison determined the parameters and solved this problem. 4. Secondary instrument failure. This part has many faults, including: once the instrument circuit board is disconnected, the range setting has a single bit display that is bad, the K coefficient setting has a single bit display that is bad, making it impossible to determine the range setting and the K coefficient setting. Part of the reason is mainly related to problems ① and ②. The problem was resolved by fixing the corresponding fault. 5, four-way line connection problems. Some circuits look good on the surface of the circuit. Carefully check that some connectors are actually loose and cause the circuit to be interrupted. Although some connectors are tightly connected, due to the problem of the auxiliary line, the fastening screws are fastened to the wire cover, which also makes the circuit. Interruption, this part of the cause is mainly related to problem ②. 6. The connection between the secondary instrument and the subsequent instrument. The mA output circuit of the secondary meter is interrupted due to a problem with the subsequent meter or the maintenance of the subsequent meter. For this type of secondary meter, this part of the cause is mainly related to problem ②. Especially for subsequent recorders, if the recorder is damaged for a long time and cannot be repaired, it is necessary to pay attention to shorting the output of the secondary instrument. 7. There is no indication on the circuit due to the secondary instrument flat axis cable failure. Due to the long-term operation and the influence of dust, the flat-axis cable is faulty. The problem can be solved by cleaning or replacing the flat-axis wire. 8. For the problem, it is mainly due to the looseness of the screw on the coil of the secondary meter display meter head, which causes the meter head to sink, the pointer to the watch case to have a large friction, and the action not working. By adjusting and refixing the meter head, the problem is solved accordingly. 9, the use of environmental issues. Especially the sensor part installed in the ground well, due to the high ambient humidity, the circuit board gets wet. This part of the reason is mainly related to problems ② and ②. Through corresponding technical reform measures, some sensors with high ambient humidity have been re-separated from the probe part and the conversion part, and a separate sensor has been used instead, which has improved the working environment. This part of the instrument has been running well. 10. Due to poor on-site adjustment, or due to changes in the actual situation after adjustment. Due to poor on-site vibration and noise balance adjustment and sensitivity adjustment. Or due to the change of the on-site situation after a period of operation after the adjustment, the indication problem is caused. This part of the cause is mainly related to problems ④ and ⑤. Use an oscilloscope, coupled with the process running conditions, readjust.

安装对直管段的要求: Vortex flowmeter installation requirements for straight pipe sections:

The correct selection of the installation point and the correct installation of the flow meter are very important links. If the error in the installation link is weak, it will affect the measurement accuracy, and the serious one will affect the service life of the flow meter and even damage the flow meter. Vortex flowmeter installation is very important for straight pipe sections. Its detailed requirements are as follows:

1. The flowmeter has certain requirements on the upstream and downstream straight pipe sections at the installation point, otherwise it will affect the measurement accuracy. 2. If there is a tapered pipe upstream of the installation point of the flowmeter, there shall be an equal-diameter straight pipe section of not less than 15D (D is the pipe diameter) upstream of the flowmeter and an equal-diameter straight pipe section of not less than 5D downstream. 3. If there is a gradually expanding pipe upstream of the installation point of the flowmeter, there shall be an equal-diameter straight pipe section of not less than 18D (D is the pipe diameter) upstream of the flowmeter and an equal-diameter straight pipe section of not less than 5D downstream. 4. If the flowmeter is installed There is a 90 ° elbow or a downward joint upstream of the point. The upstream of the flowmeter should have an equal diameter straight pipe section of not less than 20D, and the downstream should have an equal diameter straight pipe section of not less than 5D. 5. If there is a 90 ° elbow on the same plane upstream of the installation point of the flowmeter, there shall be an equal-diameter straight pipe section not less than 25D upstream and an equal-diameter straight pipe section not less than 5D downstream. The flow regulating valve or pressure regulating valve should be installed as far as 5D downstream of the flow meter. If it must be installed upstream of the flow meter, there should be an equal-diameter straight pipe section of not less than 25D upstream and an equal-diameter straight pipe section of not less than 5D downstream. . If there is a piston or plunger pump, piston or roots fan, compressor upstream of the flowmeter, there shall be an equal diameter straight pipe section of not less than 25D upstream and an equal diameter straight pipe section of not less than 5D downstream.

安装点的上游较近处若装有阀门,不断地开关阀门,对流量计的使用寿命影响极大,非常容易对流量计造成永久性损坏。 Special attention: If a valve is installed near the installation point of the vortex flowmeter , the valve will be continuously opened and closed, which will greatly affect the service life of the flowmeter and easily cause permanent damage to the flowmeter. The flow meter should be avoided to be installed on a very long pipeline as much as possible. After a long time, the seal of the flow meter to the flange is likely to leak due to the sag of the flow meter. If it is necessary to install it, it must be 2D upstream and downstream of the flow meter. Pipe fastening device