Vortex street flowmeter

One, the introduction:
LUGB series vortex street flowmeter is mainly used for various industry industrial pipeline gas, liquid and steam medium fluid flow measurement.Is characterized by low pressure loss, wide range, high precision, working condition of the measurement volume flow is almost not affected by the fluid density, the influence of the parameters such as pressure, temperature, viscosity.No moving mechanical parts, thus high reliability, small amount of maintenance and instrument parameters can long-term stability.
Second, the measuring principle:
LUGB series vortex street flowmeter is by the design in the flow field in the vortex, detecting sensor and the corresponding electronic circuit, etc.When the fluid flows through the spiral body occurs, it is formed on both sides of the two rows of vortex variations, this vortex is known as the karman vortex street.On the basis of the theory of karman vortex street and proposed the karman vortex street frequency is proportional to the velocity of the fluid, the relation between the frequency and velocity are presented:
F = St * V/d type:
F vortex frequency (Hz)
V vortex occurred body on both sides of the average flow velocity (m/s)
St, luo hall coefficient (constant)
These variations of vortex is formed a series of variations of negative pressure, the pressure on detecting probe, and produce a series of alternating electric signals, after dealing with the preamplifier conversion, plastic, amplification, the output is proportional to the vortex synchronous pulse frequency signal (or standard).
Third, the use of vortex street flowmeter selection and application:
1, in order to use convenient, battery type USES the micro power consumption of new and high technology, using lithium batteries don't run around more than a year, saving the purchase cost of installation, cable and display instrument to local display instantaneous flow and cumulative flow, etc.
2, temperature compensation, a shape vortex flowmeter with temperature sensor, can directly measure the temperature of saturated steam and calculate the stress, which shows that the mass flow of saturated steam.
3 size, temperature, pressure compensation with temperature and pressure sensors, used for gas flow measurement can directly measure the temperature and pressure of gas medium, showing the state of the volume of the gas flow.
4, widely used in petroleum, chemical industry, metallurgy, machinery, paper, and the city pipe heating, water supply, gas and other industries of all kinds of low viscosity liquid, gas, steam, etc of single-phase fluid process measurement and energy saving management.
Four, the characteristics of vortex street flowmeter:
1, can accurately measure within wide flow range of gas, liquid and steam flow and not affected by fluid physical properties;
2, not affected by temperature, pressure, not easy to plug at the same time, not easy card, not easy to scale, high temperature resistant, high voltage;
3, safety explosion-proof, suitable for bad environment;
4, have no moving parts, no hole aperture design, product without any abrasion, corrosion resistance, dirt without mechanical maintenance, long service life;
5, using micro power consumption of new and high technology, a battery-powered scene shows type flowmeter, power is not running for more than two years;
6, temperature, pressure compensation integrated design;
7, current output are electrical isolation, good common-mode interference suppression ability;
8, also showed flow values and cumulative flow value, don't have to take turns to switch;
9, using vibration probe, the effective elimination of the influence of external vibration;
10, using split type signal converters, cable up to 100 meters;
11, than a wide range of those days;
12, instrument structure design is reasonable, wide dynamic range, small pressure loss;
13, table body is made of stainless steel material, can be applied to measurements of corrosive medium;
14, the liquid crystal display, pulse, 4 ~ 20 ma output 485 newsletter, or can be connected to the industrial automation system.
Five, the vortex street flowmeter technology parameters:
1, the nominal diameter (mm) : 15,25,40,50,65,80,100,125,150,200,250,300, insert type (200 ~ 2000) can be customized according to user requirements of special non-standard products.
2, nominal pressure (MPa) : DN15 - DN200 (> 4.0 supply agreement), 4.0 DN250 12-1.6 (> 1.6 supply agreement).
3, medium temperature (℃) : piezoelectric: - 40 ~ 260-40 ~ 320;Capacitive: - 40 ~ 300-40 ~ 400-40 ~ 450 order (agreement).
Ingredients: 4, ontology instrument shell adopts aluminium alloy, 1 cr18ni9ti, (other material supply agreement).
5, and allows the vibration acceleration: piezoelectric: 0.2 g;Capacitance: 1.0 ~ 2.0 g.
6, accuracy: + / - 1% R, plus or minus 1.5% R, plus or minus 1 fs.Insert: plus or minus 2.5% R, plus or minus 2.5% FS.
7, scope: 1:6 ~ 1:30.
8, the power supply voltage: sensors: DC + 12 v, + 24 v DC;Transmitter: + 12 v DC, + 24 v DC;Battery type: 3.6 V battery.
9, output signal, square wave pulse type (not including batteries) : a high level 5 v, or low level 1 v or less;Current: 4 ~ 20 ma.
10, the pressure loss coefficient, conform to the standard JB/T9249 Cd 2.4 or less.
11, protection grade: ordinary IP65;Diving IP68.
12, the environmental conditions: temperature - 20 ℃ ~ 55 ℃, relative humidity 5% ~ 90%, atmospheric pressure 86 ~ 106 kpa.
13, suitable medium: gas, liquid and steam.
14, the transmission distance: three-wire system pulse output type: 300 m or less, two wire system standard current output type (4 ~ 20 ma) : load resistance Ω 750 or less.
15, signal interface: female M20 x 1.5.
16, the LCD double line displays (temperature compensation type) : recycled display, such as temperature, pressure, the instantaneous flow and cumulative flow parameters.
Six, installation requirements:
1, the vortex street flowmeter can only one-way measurement, pay attention to when installation to ensure medium flow direction and flow arrow shown in the same direction.
2, the best way to install for vertical vortex flowmeter installation, medium from bottom to top through the flow meter.The flow meter installed in vertical pipe runs, from bottom to top direction of flow.
When mounted horizontally, and 3 meter must be installed in the high of the whole system, and to ensure that the outlet pressure corresponding;Do not install the very top of the line, often because of high gas accumulation, the pipe is not full, export direct vent.
4, when measuring high temperature fluid, used in a vertical installations as far as possible;If have to horizontal installation, please send the flow transmitter partial vertical downward, or horizontal lateral loading, avoid high temperature;Pay attention to the installation location of air flow or well ventilated.
5, straight pipe requirements: at least ensure before 15 times the pipe diameter, flow meter after 5 times the pipe diameter.Before such as flowmeter bend, indentation, expand the interference sources, such as need to ensure before 30 to 40 times the pipe diameter, flow meter after six times the pipe diameter.Flow meter should be installed in regulating valve, pressure or temperature sensors upstream.
6, when installation, pay attention to the pipe size should be slightly bigger than or equal to the inner diameter of the instrument.
7, the use of seals, pay attention to the sealing ring inside diameter should be slightly greater than or equal to the inner diameter of the instrument, sealing ring center located in the heart of the pipeline.
8, cable entry seal instrument electric connection, must pay attention to in line hole sealing.Must choose according to meter cable entry model corresponding sealing interface (M20 Χ 1.5; 1/2 "NPT; G1/2), and properly, closely installation.No seal joint, or careless, can not meet the sealing effect.
Seven, requirement for straight pipe:
In order to ensure that the instrument, accurate to run normally, sensor must have a certain straight pipe upstream and downstream of the installation points, to adjust the flow field, as shown.

Figure 1: concentric contraction tube;
Figure 2: the concentric expansion tube;
Figure 3: a 90 - degree Angle;
Figure 4: the same plane of two 90 - degree Angle;
Figure 5: different plane of two 90 - degree Angle;
Figure 6: regulating valve should be installed downstream of the sensor in 5 d to the distance, if the sensor must be installed in the upstream, the sensors should be not less than 50 d upstream, straight pipe section downstream straight pipe section should be not less than 5 d.
Eight, the requirement of pipe:
1, upstream and downstream piping diameter D, and the same as the sensor inner diameter DN, its difference satisfy the following conditions: 0.95 DN D 1.1 or less or less DN.
In 2, piping should be one of the sensor, the coaxial degree should be less than 0.05 DN.
3, gasket not protruding into the pipe, the inner diameter slightly larger than sensors.
4, if you want to stop inspection and cleaning the sensor, the by-pass pipe should be set up, as shown in the figure below.
Nine, the requirement of pipe vibration:
Sensors to avoid installed on the strong pipeline vibration, if necessary to install, shock absorption measures must be taken, respectively at the upstream and downstream of sensor 2 d piping fastening device, and vibration-proof pad.
Special note: in the air compressor exit strong vibration, cannot install the sensors, shall be installed after the gas storage.
The technical performance of the vortex flowmeter, :
The case flow range profile: unit (m3 / h)

Eleven, vortex street flowmeter selection table:

Twelve, order selection selection guidelines:
1, as far as possible not to use in the selection of flowmeter work flow in the lower limit value, so the meter diameter should be as small as possible, in order to obtain larger flow velocity and flow range.
2, the flowmeter should be used in the technical parameters of medium pressure and temperature range.Don't deliberately choose the high pressure level and ultra-high temperature instrument, should be selected according to the actual work pressure and temperature instruments, which had higher prices.
3, in the explosive dangerous location, should choose explosion-proof type flowmeter.
The lower limit of 4, LUGB vortex street flowmeter flow depends on the operation condition of the medium density and kinematic viscosity, the maximum flow is generally not affected by medium pressure and temperature, so to determine the flow range as long as you determine the actual minimum flow can be available.Calculate the minimum flow rate, flow range check table to determine the appropriate diameter.