Because all kinds of ultrasonic flowmeters can be installed outside the pipe, non-contact flow measurement, the cost of the instrument is basically independent of the size of the pipe to be tested, while other types of flowmeters increase with the increase in caliber, so the cost is increased. The flowmeter is superior to the other functions of the same type of flowmeter. It is considered to be a good large-diameter flow measuring instrument. The Doppler ultrasonic flowmeter can measure the flow of two-phase medium, so it can be used for the measurement of dirty sewage such as sewers and sewage. In power plants, the use of portable ultrasonic flowmeters to measure large pipe diameters such as turbine water inflow and turbine circulating water is much more convenient than in the past. Ultrasonic flow juice can also be used for gas measurement. Pipe diameters range from 2cm to 5m, from a few meters wide open channels, culverts to 500m wide rivers.
In addition, the accuracy of the flow measurement of the ultrasonic measuring instrument is almost independent of the temperature, pressure, viscosity, density and other parameters of the measured fluid, and can be made into non-contact and portable measuring instruments, so it can solve the problem that other types of instruments are difficult to measure. Flow measurement problems for corrosive, non-conductive, radioactive, and flammable and explosive media. In addition, in view of the non-contact measurement characteristics, coupled with reasonable electronic circuits, one instrument can adapt to a variety of pipe diameter measurements and a variety of flow range measurements. The adaptability of ultrasonic flowmeters is also unmatched by other instruments. Ultrasonic flowmeters have some of the above advantages, so it has received more and more attention and has been developed into a series of products and generalization. It has been made into standard, high-temperature, explosion-proof and wet instruments of different channels to adapt to different media. Flow measurement for occasions and different pipeline conditions.
Ultrasonic flowmeter classification
●Insert ultrasonic flowmeter: can be installed and maintained without stopping production. Ceramic sensors are used for non-stop production installation using dedicated drilling equipment. Generally for mono measurement, in order to improve measurement accuracy, three channels can be selected.
● Pipe-type ultrasonic flowmeter: It is necessary to cut the pipeline installation, but the subsequent maintenance can be stopped. Mono or 3-channel sensors are available.
● External clip-on ultrasonic flowmeter: capable of performing fixed and mobile measurements. It is installed with a special coupling agent (silicone rubber cured at room temperature or high-temperature long-chain polymer grease) and does not damage the pipeline during installation.
● Portable ultrasonic flowmeter: portable, built-in rechargeable lithium battery, suitable for mobile measurement, with magnetic sensor.
1, non-contact measurement method, small size, easy to carry
2, suitable for on-site measurement of various sizes of pipe sound guiding media
3, built-in nickel-metal hydride rechargeable battery working time of more than 20 hours
4, user interface is flexible, easy to use
5, intelligent on-site printing function to ensure the integrity of the flow data
6, equipped with an integrated aluminum alloy protective box, can be used in harsh outdoor environments
● Hand-held ultrasonic flowmeter: small size, light weight, built-in rechargeable lithium battery, hand-held, with magnetic sensor.
● Explosion-proof ultrasonic flowmeter: used for explosive liquid flow measurement, it is explosion-proof and intrinsically safe. That is, the converter is explosion-proof and the sensor is intrinsically safe.
How the turbine flow meter works
The working principle of the turbine flowmeter: the fluid flows through the sensor housing. Since the blade of the impeller has a certain angle with the flow direction, the momentum of the fluid causes the blade to have a rotational moment. After the friction torque and the fluid resistance are overcome, the blade rotates, and the rotational speed is stabilized after the torque balance. Under certain conditions, the rotational speed is proportional to the flow rate. Due to the magnetic permeability of the blade, it is in the magnetic field of the signal detector (composed of permanent magnet and coil). The rotating blade cuts the magnetic field lines and periodically changes the coil. Magnetic flux, so that the two ends of the coil induce electricity
Pulse signal, which is amplified and shaped by the amplifier to form a continuous rectangular pulse wave with a certain amplitude, which can be transmitted to the display instrument to display the instantaneous flow rate and cumulative amount of the fluid. Within a certain flow range, the pulse frequency f is proportional to the instantaneous flow rate Q of the fluid flowing through the sensor. The flow equation is: Q = 3600 × f / k
In the formula:
F——pulse frequency [Hz];
K——the meter factor of the sensor [1/m], given by the checklist. If [1/L] is used, Q=3.6×f/k
Q——the instantaneous flow rate of the fluid (under working condition) [m3/h];
3600 - conversion factor.
The meter factor of each sensor is filled in the verification certificate by the manufacturer, and the k value is set in the matching display meter to display the instantaneous flow rate and the cumulative total amount.