1、 Instrument Introduction:
Stainless steel vortex flowmeterIt is a new type of flowmeter developed based on the principle of fluid vibration, using all stainless steel material. Widely used in the measurement of fluids in industries such as petroleum, chemical, metallurgy, and papermaking, this flowmeter has no movable parts, strong reliability, high accuracy, and long service life. It can measure the instantaneous flow rate and cumulative flow rate of liquids over a wide flow range. It is not affected by the temperature, pressure, viscosity, and composition of the medium, and is not blocked, stuck, easy to scale, resistant to high temperature and high pressure, safe and explosion-proof, suitable for harsh environments. Integrated display and remote transmission of flow scoring, and can output pulse signals or current signals to be networked with a microcomputer.
2、 Working principle:
Stainless steel vortex flowmeterWhen a cylindrical object is vertically inserted into the measuring tube, the fluid alternately generates regular vortices on both sides of the object, which are called Karman vortex streets. The release frequency of the Karman vortex street is related to the fluid velocity and the width of the column, and can be expressed by the following equation:
In the formula f=St · v/d, f represents the release frequency of the Karman vortex street
St coefficient (known as Strouhal number)
V - Flow velocity
D - Width of the pillar
The release frequency f of the Karman vortex street is directly proportional to the flow velocity v, so the instantaneous flow rate can be calculated by measuring the release frequency of the Karman vortex street.
Strouhal number is an important coefficient of vortex flowmeter. In the straight part of the curvature with St ≈ 0.17, the release frequency of the vortex is proportional to the flow velocity, so the detection frequency f can be used to obtain the flow velocity v, and the volume flow rate can be calculated from v.
The vortex release frequency of the vortex flow sensor is detected by the alternating action of vortices on the stress on the detection sensor (probe) through piezoelectric elements inside it.
3、 Application scope:
Stainless steel vortex flowmeterIt can be widely used for measuring the flow of water supply and drainage, industrial circulation, sewage treatment, oil and chemical reagents, compressed air, saturated and superheated steam, natural gas, and various media in large, medium, and small pipelines.
4、 Advantages:
1. It can measure the volume flow rate and mass flow rate of steam, gas, and liquid.
2. It can achieve continuous disassembly and assembly of sensors, and can separate amplifiers from sensors (separation distance of 15m).
3. By using anti-interference circuits and anti vibration sensing heads, the instrument has a certain degree of resistance to environmental vibrations.
4. Low pressure loss, wide range, and a range of 10-40 times.
5. No mechanical moving parts, long-term stability, simple structure for easy installation and maintenance.
6. The measurable medium temperature reaches+350 ℃ (+450 ℃).
5、 Performance indicators:
Measurement media: liquid, general gas, natural gas, steam (saturated steam and superheated steam);
Possible measurement range: Reynolds number ranging from 5 × 103 to 7 × 106
Normal measurement range: Reynolds number ranging from 2 × 104 to 7 × 106
Measurement flow rate range: liquid 0.5-7m/s, gas 4-35mm/s, steam 7-70m/s
Temperature of the tested fluid: -40 ℃ to+300 ℃
Tested fluid temperature: 1.6, 4, 25MPa
Accuracy: Level 1, Level 1.5, Level 0.5 (Level 0.5 can only be achieved through non-linear adjustment);
Repeatability: 0.2% of the indicated value;
Table body material: ICr18Ni9Ti;
Pressure loss: △=1.2 × r × V2 × 10-6. In the equation: △ P - pressure loss r - measured fluid density (Kg/m3) v - average flow velocity inside the pipe (m/s) Environmental temperature: -20 ℃~+55 ℃ (special requirements for ordering instructions)
Environmental humidity: ≤ 90% RH
Atmospheric pressure: 86-106KPa
External power supply: 3.6-224VDC
Internal power supply: 3-4.5VVDDC
Working power supply: 80/A
Working voltage: 2.7-3.6V
Working frequency: 0.1-3000H
Distance of signal transmission: 100mm
Signal output: Pulse output (external power supply) Current output 4-20mADC (two-wire external 24VDC power supply) Pulse output and current output can only be selected in one way.
6、 External dimensions:

7、 Requirements for straight pipe sections:
In order to ensure the normal and accurate operation of the instrument, there must be a certain straight pipeline upstream and downstream of the sensor installation point to adjust the flow field,As shown in the figure.

Figure 1: Concentric contraction tube;
Figure 2: Concentric expansion tube;
Figure 3: A 90 degree elbow;
Figure 4: Two 90 degree elbows on the same plane;
Figure 5: Two 90 degree elbows in different planes;
Figure 6: The regulating valve should be installed 5D downstream of the sensor. If it must be installed upstream of the sensor, there should be an equal diameter straight pipe section of not less than 50D upstream and an equal diameter straight pipe section of not less than 5D downstream.
8、 Requirements for pipelines:
1. The inner diameter D of the upstream and downstream piping is the same as the inner diameter DN of the sensor, and the difference satisfies the following condition: 0.95DN ≤ D ≤ 1.1DN.
2. The piping should be concentric with the sensor, and the coaxiality should be less than 0.05DN.
3. The sealing gasket cannot protrude into the pipeline, and its inner diameter may be slightly larger than that of the sensor.
4. If it is necessary to cut off the flow for inspection and cleaning of sensors, a bypass pipeline should be installed,As shown in the following figure.

9、 Requirements for pipeline vibration:
Sensors should be avoided from being installed on pipelines with strong vibrations as much as possible. If installation is necessary, shock absorption measures must be taken. Pipeline fastening devices should be installed at the 2D positions upstream and downstream of the sensor, and anti vibration pads should be added.
Special attention: The vibration at the outlet of the air compressor is strong, and sensors cannot be installed. They should be installed after the air storage tank.
10、 Key selection points:
1. The selection of flow meters should avoid using flow rates that operate at the lower limit, so the diameter of the flow meter should be as small as possible to obtain a larger flow rate and flow range.
2. The flowmeter should be used within the technical parameters of the working pressure and temperature range of the medium. Do not deliberately choose instruments with high pressure levels and ultra-high temperatures. Choose instruments based on actual working pressure and temperature, as the latter is more expensive.
3. Explosion proof flow meters should be selected in explosive hazardous areas.
4. The lower limit flow rate of a vortex flowmeter depends on the working density and viscosity of the medium, and its upper limit flow rate is generally not affected by the pressure and temperature of the medium. Therefore, determining the flow range only requires determining the actual available lower limit flow rate. After calculating the lower limit flow rate, the corresponding caliber can be determined by checking the flow range table.
11、 Installation conditions:
1. Sensors can be installed indoors or outdoors. The environmental conditions must meet the requirements.
2. Sensors should be installed on pipelines that are horizontal, vertical, or inclined (with fluid flow from bottom to top) and correspond to their nominal diameter.
3. Sensors should be avoided from being installed on pipelines with mechanical vibrations. When vibration is inevitable, it should be considered to add a fixed support bracket on the straight pipe section about 2DN away from the sensor.
4. Sensors should be installed in places with strong electromagnetic field interference, thermal radiation, corrosive gases, small space, and inconvenient maintenance.
5. When the measured medium contains a large amount of impurities, a filter should be installed beyond the required length of the straight pipe section upstream of the sensor.
6. The upstream and downstream of the sensor should be equipped with a certain length of straight pipe section, and the inner wall of the straight pipe section should be clean, smooth, and free of obvious protrusions, dents, scale deposits, and peeling. Its length should meet the requirements of Figure 2. The pipeline near the installation of the liquid sensor should be filled with the measured liquid.
7. The inner diameter of the straight pipe section should be as consistent as possible with the sensor diameter. If it cannot be consistent, a diameter slightly larger than the sensor diameter should be used, with an error of ≤ 3% and no more than 5mm.
12、 On site requirements:
1. Low maintenance volume - Most vortex flowmeters on the market use pressure tapping holes or inserted detection elements to sense vortices. Once impurities in the medium are embedded in the pressure tapping holes or gaps between the sensing element and the meter body, the signal becomes weak or unstable. A good design should have no easily clogged parts, thereby reducing maintenance.
2. Online replacement of sensing elements - Some manufacturers' sensing elements are combined with vortex generators, which may seem simple in design but bring inconvenience to practical use. Because once the sensing part fails, the medium inside the pipeline needs to be emptied and depressurized before replacing the components, which affects production. A perfect design should separate the two, so that the sensing part can be replaced separately without emptying the medium.
3. Vortex flow meters are susceptible to vibration interference, and well-designed vortex flow meters can eliminate interference through hardware and digital signal processing, thereby obtaining stable signals.
4. The installation of a vortex flowmeter requires a long straight pipe section, and some manufacturers can provide a design for reducing the diameter inside the flowmeter, greatly reducing the need for users to equip vortex flowmeters with straight pipe sections.