Pipe flowmeter measurement method
Ultrasonic waves carry information about the fluid flow rate as they propagate through the flowing fluid. Therefore, the flow rate of the fluid can be detected by the received ultrasonic wave, and converted into a flow rate. According to the detection method, it can be divided into different types of ultrasonic flowmeters such as propagation velocity difference method, Doppler method, beam offset method, noise method and correlation method. Ultrasonic flowmeter is a kind of application that has been applied since the rapid development of integrated circuit technology in the past decade.
Non-contact instrument for measuring fluids that are difficult to access and observe, as well as large pipe runoff. It is linked to a water level gauge for flow measurement of open water flow. The use of ultrasonic flow rate does not change the flow state of the fluid without installing the measuring element in the fluid, and does not generate additional resistance. The installation and maintenance of the instrument can not affect the operation of the production pipeline and is an ideal energy-saving flowmeter.
As we all know, industrial flow measurement generally has the problem of large diameter and large flow measurement difficulty. This is because the general flowmeter will bring difficulties in manufacturing and transportation with the increase of the measuring pipe diameter, and the cost will increase and the energy loss will increase. Installation is not only a disadvantage, but ultrasonic flowmeters can be avoided.
Vortex flowmeter selection
(1) Selection of vortex flow transmitter
In the measurement of saturated steam, VA type piezoelectric vortex flow transmitter is adopted. Because of the wide range of vortex flowmeter, in practical applications, it is generally considered that the flow of measuring saturated steam should not be lower than that of vortex flowmeter. The lower limit, that is to say, the fluid flow rate must not be less than 5 m/s. According to the size of the steam, the vortex flow transmitters with different calibers are selected, and the caliber of the transmitter cannot be selected by the existing process pipe diameter.
(2) Selection of pressure compensation pressure transmitter
Since the saturated steam line is long and the pressure fluctuates greatly, pressure compensation must be adopted. Considering the corresponding relationship of pressure, temperature and density, only pressure compensation can be used in the measurement, because the saturated steam pressure of Mingtong Company is 0.3-0.7MPa. Range, the range of pressure transmitter can be selected 1MPa.
(3) Display instrument selection
Display instrument intelligent flow display instrument with voltage regulation compensation, instantaneous flow display and cumulative flow accumulation function.
Vortex flowmeter verification detection method
Standard table method
The vortex flowmeter is used as a standard device in series with the flowmeter to be inspected, and can be verified by static method or dynamic method. By comparing the readings of the two flow meters, the error of the vortex flowmeter to be tested is obtained.
Standard table flow meter standard device features:
1. Standard table method is suitable for measuring various fluids (including liquids and gases), and also for liquids of various viscosities.
2. The indication value is checked. The flow meter used as the standard meter is installed in series with the flowmeter to be tested in the same closed pipeline system. Generally, there is no time measurement error.
3. As a standard table, the vortex flowmeter can be the same as or different from the flowmeter to be tested.
4. When the flow meter is verified by the standard meter method, the airflow or liquid flow can be not cut off, so it is suitable for online verification, and is also suitable for the measurement standard for the closed pipeline. 5, the standard table method is easy to achieve automation, sealed and safe, does not pollute the environment.
6. Small size, light weight, simple device structure, convenient operation, easy transportation and installation, and low cost.
7. Standard meter flowmeters have low accuracy and poor stability, and often need to be compared regularly or irregularly to monitor their metering performance. The standard table has a shorter verification period.