How to make good use of a turbine flowmeter has always been a problem of great concern to many users. It is necessary for users to understand the working principle, structural form, advantages, and disadvantages of turbine flowmeter, as well as correct and reasonable installation and use in industrial production.
Operating principle of turbine flowmeter
The basic structure of a turbine flowmeter consists of an impeller, bearing, preamplifier, flow totalizer, etc. An impeller is placed in the fluid pipe, and both ends are fixed with bearings. When the turbine flowmeter measures the flow of fluid, due to the rotating movement of the impeller, the speed and velocity are in direct proportion to determine the flow speed of the fluid and obtain the flow data of the measured medium.
The speed of the impeller is detected by the sensing coil in the flowmeter. When the blade of the impeller rotates at a high speed, cuts the magnetic line of force, generates induced current in the magnetic induction coil, and forms a pulse electrical signal. The sensing coil sends the electrical pulse signal to the preamplifier, amplifies and reshapes the signal, and forms a continuous rectangular pulse wave with a certain amplitude. Then, send the pulse wave to the integrator for calculation and output, and obtain the values of instantaneous flow and cumulative flow.
Structure of turbine flowmeter
A turbine flowmeter is mainly composed of an instrument housing, deflector, impeller, bearing, signal detection amplifier, and other components.
The instrument shell is generally made of non-magnetic stainless steel, which is directly connected to the pipeline, and the fluid flows through it. The casing is the casing of the turbine flowmeter to ensure the airtightness of the flowmeter. The casing must bear a certain pressure to connect the components of the entire flowmeter to form an integral structure.
The deflector is usually made of non-magnetic stainless steel or duralumin material and installed at the inlet and outlet of the sensor to guide and rectify the fluid, ensure the normal rotation of the impeller, make the measured fluid relatively stable, and accurately reflect the fluid flow.
The impeller is a rotating part with blades installed on it. It is generally made of magnetic conductive stainless steel. The impeller rotates under the impact of the measured fluid in the pipeline and has good magnetic conductivity. The running state of the impeller directly affects the measured results.
Shaft and bearing
The shaft and bearing play a supporting role in the turbine flowmeter. They can support the rotating parts and are made of high-quality materials, so that they have a certain strength, avoid bending and deformation of the shaft, ensure the lubrication of the bearing, better support the shaft of the flowmeter, enable the rotating parts to rotate normally, and achieve the purpose of flow measurement. The shaft and bearing have good wear resistance.
Signal detection amplifier
The signal detection amplifier is generally of variable reluctance type, which is composed of permanent magnetic steel magnetic conductor coil, etc. Its function is to convert the rotation of the impeller into an electrical signal for printing. Since the rotation of the impeller is in direct proportion to the liquid flow, the signal detection amplifier will rectify and filter the input electrical signal and output it to the display system to obtain the flow value of the measured medium.
Advantages and disadvantages of turbine flowmeter
Turbine flowmeter has many advantages in industrial production and uses, generally including the following:
Simple structure and wide application scope
Vortex flowmeter has simple structure, convenient installation and maintenance, smooth fluid flow, and can be used for flow measurement of various media, such as gas, liquid, steam, etc.
The turbine flowmeter has outstanding repeatability and high measurement accuracy. The eddy current flowmeter is the best choice for trade settlement.
High accuracy of measurement
When measuring with a turbine flowmeter, it can reach a higher accuracy level, reduce measurement error and ensure accurate measurement effect.
(1) Output pulse frequency signal, which can obtain a high-frequency signal with strong signal resolution; No zero drift, strong anti-interference ability, and the total quantity measurement can be connected with the computer.
(2) The turbine flowmeter can measure the high pressure. Under the condition of high pressure, it can measure the flow normally and obtain accurate flow data.
(3) Vortex flow meters can be used to prepare various sensors, such as cryogenic sensors, downhole equipment sensors, and special sensors for sand mixing.
Similarly, the turbine flowmeter also has certain shortcomings and deficiencies. To sum up, there are the following: (1) Turbine flowmeter must be calibrated for correct use in order to achieve accuracy after long-term use.
(2) It can not be used to measure the pulsating fluid. The measurement effect of mixed-phase liquid flow is poor, and the accuracy of measurement results is poor.
(3) Gas flowmeters are highly sensitive to density, while liquid flowmeters have a great influence on viscosity changes.
(4) During the measurement of the turbine flowmeter, the change in flow velocity will affect the measurement results, and the rotating flow state will also lead to inaccurate measurement results.
(5) If the measured medium is not clean, the measurement results will be affected. By installing a filter to remove impurities and then measuring, the input of equipment will be increased, resulting in an increase in the cost of flow measurement.
(6) The flow of small diameter flow measuring instruments is greatly affected by the measured physical properties.
Installation requirements and use of turbine flowmeter
The installation requirements of the turbine flowmeter are relatively high, and the installation environment is relatively harsh. In order to ensure the safe and effective operation of the turbine flowmeter and the accuracy of measurement, the installation position, and form of the turbine flowmeter must be correctly selected, so as to avoid and reduce errors and failures. It mainly includes the following aspects.
1) Turbine flowmeter cannot be installed in a strong magnetic field, strong electric field, and thermal radiation environment, which will cause great interference and affect its measurement accuracy.
2) The turbine flowmeter shall be installed horizontally rather than vertically. The front and rear pipe flanges shall be horizontal during installation. The flowmeter axis shall be concentric with the pipe axis and the flow direction shall be consistent. It is necessary to ensure that there are certain straight pipe sections in front of and behind it. Generally, the upstream straight pipe section is 10 times the nominal diameter and the downstream straight pipe section is 5 times the nominal diameter. At the same time, the inner diameter of the upstream and downstream piping of the flowmeter installation point shall be consistent with the inner diameter of the flowmeter.
3) Before the installation of the turbine flowmeter, the fluid pipeline shall be cleaned. When the measured fluid medium is not clean, the pipeline shall be equipped with a filter to reduce the wear of the bearing and prevent the impeller from being stuck. It is not allowed to directly connect the filter and flowmeter to prevent damage to the flowmeter.
4) During the maintenance of the turbine flowmeter, it is only necessary to switch the process, export the fluid through the bypass pipeline, and reasonably control the upstream and downstream processes of the turbine flowmeter. Therefore, during the maintenance of the flowmeter, there is no impact on the fluid and it can pass normally.
5) The power line of the turbine flowmeter shall be metal shielded wire, and the grounding shall be good and reliable, and shall not be shared with the strong current system ground wire.
6) During the installation and removal of the turbine flowmeter, the magnetic induction components of the flowmeter shall be protected without any collision.
With the continuous progress of automation technology, more and more attention has been paid to intelligent instruments, and more and more intelligent instruments are used in industrial production. The self-diagnosis function of the turbine flowmeter is introduced into the flowmeter, which makes the flowmeter not only a simple measuring instrument but also more for the purpose of system maintenance. At the same time, advanced field bus communication technology is added to the turbine flowmeter, so that the production personnel can obtain the flow data and historical data of the production site remotely and in real time. In a word, a turbine flowmeter has the advantages of small pressure loss, wide measuring range, simple structure, convenient maintenance, low purchase price, small maintenance cost, wide measuring flow range, etc., so it has a wide use value in petroleum, chemical industry, metallurgy, urban gas pipe network, and other industries.