V cone flowmeter can be widely used to measure high temperature and complicated industrial control media, which is very suitable for gas and liquid such as steam, gas, nitrogen, sewage and other dirty and corrosive special media.
I. Measuring principle:
是一种差压型的流量仪表。 V cone flowmeter is a differential pressure type flow meter. Flow meters designed based on the differential pressure principle have been used for more than 100 years. Differential pressure flow meters are based on the principle of energy conversion in sealed pipes, that is to say
For stable fluids, the pressure of the pipeline is inversely proportional to the square root of the velocity of the medium in the pipeline: the pressure will decrease when the velocity increases. When the medium approaches the cone, its pressure is P1. Will fall
Low is P2, P1 and P2 are both led to the differential pressure transmitter through the pressure tap of the cone flowmeter. When the flow rate changes, the differential pressure between the two pressure taps of the cone flow meter Will increase or decrease. When the flow velocity is the same, if the throttle surface
The larger the product, the larger the differential pressure. The β value is equal to the throttle area of the cone divided by the cross-sectional area of the inner diameter of the pipe (convertible to the diameter ratio between the two).
The characteristics of traditional differential pressure instruments are based on ideal flow conditions; in fact, this situation does not exist in real applications. Any changes in pipeline layout, such as elbows, valves, reducers, expanders, pumps, tee joints, etc.
Destroy the full development flow. It is difficult for general flow meters to obtain correct measurements in disturbed flows. V-cone flow meters overcome these shortcomings. Under extremely harsh installation conditions, such as two elbows that are not on the same plane upstream, and
Close to the cone, the V-shaped cone also makes the velocity distribution flat and symmetrical, thereby ensuring measurement accuracy. Because the throttle edge of the V-cone flowmeter is an obtuse angle, a boundary layer is formed when flowing, which makes the fluid leave the throttle edge. Boundary layer effect
Dirty fluids must not wear away the throttling edges and their values will not change for a long time. Therefore, it is not necessary to repeat the calibration and has long-term stability.
Features: Significantly improves the limitations of the traditional differential pressure flowmeter, improves accuracy and repeatability, almost no straight pipe requirements during installation, self-cleaning function, suitable for two measurements of easily soiled media, gas and liquid Is a connection
Throttle device near ideal.
1. The front and rear straight pipe sections are short. Generally, the upstream only needs 0 to 3D, and the downstream only needs 0 to 1D.
2. High accuracy, differential pressure output value can achieve repeatability of ± 0.1%.
3. The pressure loss is small, only 1 / 2-1 / 3 of the orifice plate.
4. The vortex generated at the trailing edge of the V cone is small, the differential pressure output is stable, and the fluctuation is small.
5. The V-cone is flushed by the fluid, and no debris remains.
6. It can measure high temperature medium 600 ℃ and medium with complicated working conditions.
Product classification and structure:
V-cone flowmeters can be divided into 3 categories according to the scope of product supply and the output signal:
1.V cone flow sensor
Only the forming part of the differential pressure signal (throttling parts and pipelines) is provided. The differential pressure transmitter and flow display part are not provided. The output signal is differential pressure. Other configurations are performed by the user.
2.V cone flow transmitter
Composed of V-shaped cone flow sensor and differential pressure transmitter. There are two types of structure: split installation and integral installation.
Split V-cone flow transmitter consists of independent V-cone flow sensor and differential pressure transmitter. The connection of the impulse tube between the V-cone flow sensor and the differential pressure transmitter is done by the user.
The integrated installation is that the differential pressure transmitter and the V-cone flow sensor are connected as a whole when the product leaves the factory. After the user purchases the integrated V-cone flow transmitter, there is no need to connect the pressure tube when using it. But must be matched with the corresponding flow accumulation
Meters, pressure transmitters and temperature transmitters.
3.V cone flowmeter
There are two types of structure: split installation and integrated installation:
Split installation is composed of independent V-shaped cone, differential pressure, pressure, temperature transmitter, flow calculator, shut-off valve and other parts. The combination of connections between the parts is done by the user himself. There are two types of explosion-proof and ordinary.
技术特点： V cone flowmeter technical characteristics:
1. Low installation requirements: straight 0 ~ 3D straight pipes, and rear 0 ~ 1D straight pipe sections;
2. Wide range ratio: usually 10: 1, choosing the right parameter can achieve a maximum of 50: 1;
3. Small pressure loss: the same β value, the pressure loss is 1/3 ～ 1/5 of the orifice plate;
4. Abrasion resistance: After the streamlined cone is throttled, a vacuum layer effect is generated on the surface of the cone, making the cone difficult to wear;
5. Non-clogging and non-adhesion: The cone-shaped thorough purging design avoids the retention of residues, condensates or particles in the fluid;
6, long-term stability is good: β value can be unchanged for a long time, and ensure long-term accurate measurement;
7, high precision: 0.5 level;
8. Good repeatability: better than 0.1%;
9. Signal stability: "Signal fluctuation" is 1/10 of the orifice flowmeter;
10. Wide β value range: The unique geometry of the V-cone flow sensor allows a wide range of β values;
11. Wide caliber range: DN25 ～ DN2000;
12. Measurable high-temperature and high-pressure media: working temperature up to 850 ℃, maximum pressure 40MPa;
13. Measurable dirty media (coke oven gas, blast furnace gas, raw oil, residue oil, etc.);
14. Measurable gas-liquid two-phase medium (moisture, condensate, etc.);
When the v-cone flowmeter does not match the inner diameter of the pipeline, first find a suitable pipeline and make a reasonable transformation of the original pipeline. If the transformation is more troublesome, you can install a suitable size connector on the site as a transition section and ensure that
There are enough straight pipe sections, so that the flow velocity distribution can be restored to a sufficient normal state. When we usually produce V-cone flow meters, we must know the specific specifications of the on-site pipeline or the specific specifications of the straight pipe sections so that we can
Minimize unnecessary trouble caused by these external factors during production. .
Technical requirements of V-cone flowmeter
的测量准确,必须正确地选择安装位置和方法 In order to ensure accurate measurement of V-cone flowmeter , the installation position and method must be selected correctly
1. Requirements for straight pipe sections:
The flowmeter must be installed horizontally on the pipeline (the pipeline is inclined within 50), and the axis of the flowmeter should be concentric with the pipeline axis during installation, and the flow direction should be the same.
The length of the upstream pipe of the flowmeter should be equal to or greater than 2D. The straight pipe section is recommended to be 5D upstream and 3D downstream if the installation site permits.
2. Requirements for piping:
The inside diameter of the upstream and downstream piping of the flowmeter installation point is the same as the inside diameter of the flowmeter.
3. Requirements for the bypass pipe:
In order to ensure that the normal use of the medium is not affected during the maintenance of the flowmeter, cut-off valves (cutoff valves) should be installed on the front and rear pipelines of the flowmeter, and bypass pipelines should be set at the same time. The flow control valve should be installed downstream of the flow meter.
When used, the shut-off valve installed upstream must be fully opened to avoid the unstable flow of the upstream fluid.
4. Requirements for the external environment:
Turbine flowmeters are best installed indoors. When they must be installed outdoors, they must be protected from sun, rain and lightning to avoid affecting their service life.
5. Requirements for impurities contained in the medium:
To ensure the service life of the flowmeter, a filter should be installed before the straight section of the flowmeter.
The flowmeter should be installed in a place where it is easy to maintain, without strong electromagnetic interference and heat radiation
6. Requirements for installation welding:
The user has another pair of standard flanges welded on the front and rear pipes. Welding with a flow meter is not allowed!
Before installing the flowmeter, it is necessary to strictly remove the dirt such as welding slag in the pipeline. It is best to use an equal-diameter pipe (or bypass pipe) instead of the flowmeter to purge the pipeline. To ensure that the flowmeter is not damaged during use.
The above hopes that it can be helpful to everyone. More consultation about the options of orifice flowmeter, turbine flowmeter and electromagnetic flowmeter.