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2 Composition and function Vortex flowmeter instrument consists of the following six parts: Transmitter housing: Vortex generator: Signal detector: Output amplifier: Pulse shaper: Input amplifier.
The transmitter housing is a part of the fluid pipeline. The suitable diameter, the shape and size ratio of the vortex generator are selected by the dry. When the fluid flows in the housing, a stable vortex signal can be generated over a wide Reynolds number range. . The vortex street generates a vortex when the fluid flows through it, and the signal detector detects the vortex train and converts it into a pulse signal. The input amplifier amplifies the weak electrical signal and filters out the interfering signal. The pulse shaper converts irregular electrical pulses into a square wave signal of constant amplitude and width. The output amplifier amplifies the square wave signal into a 4-20 mA DC current signal output, and outputs a square wave pulse signal (as a supply flow integral).
3 Working principle The vortex flowmeter is a flowmeter made from the fluid vibration phenomenon of the Karman vortex street when a fluid flows around a non-streamlined object. This type of flow meter gives a pulse frequency signal that is only proportional to the flow rate and is independent of fluid temperature, pressure, composition, viscosity, and density.
That is F=S,_I-4d/(D)ld
"1 - 4 bin r å…€ DJ_, d type jF is the vortex frequency jv is the average flow rate in the pipe jd is the width of the column inflow surface iD is the pipe diameter jS, for the Strouhal number. When the vortex is generated on both sides of the column, the column is subjected to the alternating lifting force perpendicular to the flow direction, and the frequency of the lift variation is the vortex frequency. The piezoelectric element embedded in the cylinder detects the change in the lift force, converts it into a frequency signal and sends it to an amplifier. The amplifier amplifies and shapes it to obtain a square wave signal whose frequency is proportional to the flow rate. The circuit block diagram is shown in Figure 1. Show. As can be seen from the above equation, the flow rate u can be calculated by measuring the vortex street frequency, and then the flow rate can be obtained from the pipe diameter and flow velocity. Figure 2 shows the vortex occurrence map.
4 Flow meter debugging When there is no liquid flow in the pipeline, the noise caused by the vibration of the pipeline causes the receiver to abnormally count. At this time, the sensitivity of the instrument should be adjusted.
41 Amplifier Gain Adjustment Generally, there is no need to adjust the gain of the amplifier unless the amplifier gain is adjusted by the AMP potentiometer on the amplifier board A after the sensor is replaced.
42 Zero adjustment Correct wiring, input signal with zero amplitude to vortex flowmeter through low frequency signal generator, adjust zero adjustment potentiometer. Display value of digital multimeter should be 4mA.
43 Full-Scale Adjustment If you do not know the meter's full-scale frequency, you can calculate the full-scale frequency of five through the maximum flow. , to adjust the instrument. The relationship is five. . = KQmax, 惋 永 永 永 冲 l l l l. Correct wiring, using the signal generator output signal to the charge amplifier, increase the input signal amplitude, convert the output square wave, change the output frequency of the signal generator, until the value displayed on the frequency meter is calculated according to the above formula full scale Frequency. At this time, the fixed frequency does not change and the potentiometer is adjusted. The digital multimeter's indication is 20mA.
5 Practical applications 5.1 Installation In order to ensure the measurement accuracy, there must be a long straight pipe section before and after the installation position of the vortex flowmeter. If there is a narrowing resistance on the upstream side, a 15D long straight section i should have a 20D long straight section j on the downstream side and the straight section on the downstream side should be 5D or longer. Vortex flowmeters can be installed horizontally, vertically or in other positions. However, if the liquid is to be mounted vertically, the liquid should flow from bottom to top to ensure that the piping is always full of liquid.
5.2 Failure phenomenon and processing method 5.2.1 No indication after power on, no output signal failure Cause:
1) Flow totalizer does not have 24VDC output:
2) Wrong wiring or disconnection:
3) Break in the sensor or damage the amplifier:
4) There is no flow or too little flow in the pipe.
Treatment measures:
1) Check if the integrator output is normal:
2) Rewiring:
3) Repair or Replacement:
4) Reduce the inner diameter of the pipe where the instrument is installed.
5.22 Signal output failure when there is no traffic Cause:
1) Instrument lead shielding or bad grounding introduces 50Hz interference:
2) There are strong electrical equipment or power lines around:
3) The pipeline has a strong vibration.
Treatment measures:
1) Strengthen shielding or grounding to eliminate 50Hz interference;
2) Keep the meter or signal line away from interference sources:
3) Take vibration reduction, strengthen filtering or reduce sensitivity.
5.23 Large fluctuations in flow indicator value Cause:
1) Influence of pipeline vibration:
2) The sensitivity is adjusted too high:
3) There are attachments on the sensor body:
4) Piezoelectric chip damage:
5) The process is fluctuating.
Treatment measures:
1) Strengthen filter or shake:
2) Reduce the sensitivity:
3) Clean sensor body:
4) Replace 5) Install the meter on the process piping with small flow fluctuations.
5.24 Indication Error Major Cause:
1) The length of the upstream straight pipe is not enough:
2) The meter constant is set incorrectly:
3) The power supply voltage and load resistance do not meet the requirements;
4) Severe body fouling:
5) The amplifier parameters change:
6) There is cavitation.
Treatment measures:
1) change the installation site, add rectifier or reduce the use of precision, the upstream straight pipe is greater than 15D;
2) Reset the parameters:
3) Provide the power supply voltage according to the instrument requirements:
4) Cleaning the body:
5) Re-adjustment:
6) Change the installation site and increase the inlet pressure.
6 Application effects The SINIER series vortex flowmeter has the advantages of small size, light weight, etc. It can output 3-wire voltage pulses, and can also output analog signals. It can be used with PLC systems and can be widely used in the detection of water cooling systems in the metallurgical industry. Instantaneous water flow and cumulative water flow.
Application of Vortex Flowmeter in Water Cooling System
1 Introduction The Walking Beam Furnace of High Line Plant adopts four static beams and five moving beam structures. The beam is cooled and cooled by circulating water cooling. Therefore, the normal flow of cooling water is one of the key elements to ensure that nine beams do not collapse. Water pressure does not necessarily have water flow. This is the author's personal experience in a company's inspection and study. The company's bar factory walking beam heating furnace water cooling system is mainly used to detect the pressure indicator, because of the pipe plug, the secondary instrument pressure indicator, the actual lack of flow, leading to the serious consequences of the furnace collapse. For this purpose, the high-line plant adopted a detection method based on detecting the flow of water in the water-cooled circulation system. A SINIER vortex flowmeter was installed on the cooling water main and nine beams, respectively. SINIER vortex flowmeter has the advantages of stable meter constant, easy to ensure accuracy in harsh environments, large range, wide range of measured medium (gas, liquid, steam), small pressure loss, high precision, and small maintenance. It is common to use in various production devices. In addition, when measuring volume flow, it is almost unaffected by parameters such as flow rate, density, pressure, temperature, and viscosity. Below, the author gives a description of the series of problems that occur during the operation of this type of instrument in daily work and the methods for handling the problems.