The mediums that need to be measured in the site are different. Now, a brief introduction is made on the selection of flow meters for different media.
The selection of large water flow meter: suitable for electromagnetic flowmeter, ultrasonic flowmeter. Other applications such as vortex flowmeters, orifice flowmeters, etc. have faded out of this application, and these two types of flow meters are the most important in the industry. In particular, it should be mentioned that the application of Kaifeng Shengda's plug-in flowmeter and electromagnetic flowmeter are better.
Sewage, pulp and other turbid liquid meter selection: electromagnetic flowmeter can be used. However, when choosing an electromagnetic flowmeter, consider that the liquid does not contain more air or bubbles.
The meter with more bubbles of liquid selection: Doppler ultrasonic flowmeter can be selected, using this type of flowmeter to measure the fluid with bubbles, the effect is very good.
Flow meter selection with low conductivity such as pure water and demineralized water: Turbine flow meter is very suitable for measuring such fluids.
Flow meter selection for strong corrosive media such as acid and lye: 1. Electromagnetic flowmeter with acid and alkali lining. 2. clamp type ultrasonic flowmeter.
Selection of flowmeters for mediums with large concentration and large solid particle content such as mortar and electric powder slurry: electromagnetic flowmeter.
Flow meter selection for oil media such as oil and diesel: turbine flow meter and ultrasonic flow meter.
Gas flow meter selection: vortex flowmeter.
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.
The working principle of the impeller type flowmeter is that the impeller is placed in the fluid to be measured, and is rotated by the impact of the fluid flow, and the flow rate is reflected by the speed of the impeller rotation. Typical impeller flow meters are water meters and turbine flow meters, which may be of mechanical transmission output or electrical pulse output. Generally, the water meter output of the mechanical transmission has low accuracy and the error is about ±2%, but the structure is simple and the cost is low. The domestic production has been mass-produced, standardized, generalized and serialized. The accuracy of the turbine flowmeter for electrical pulse signal output is high, with a typical error of ±0.2% to 0.5%.
Differential pressure flowmeter (variable pressure drop flowmeter)
The differential pressure flowmeter consists of a primary device and a secondary device. The primary device is called a flow measuring element and is installed in the pipe of the fluid to be measured, generating a pressure difference proportional to the flow rate (flow rate) for the secondary device to display the flow rate. The secondary device is called a display instrument. It receives the differential pressure signal generated by the measuring component and converts it to the corresponding flow for display. The primary device of the differential pressure flow meter is often a throttling device or a dynamic pressure measuring device (piteron, constant velocity tube, etc.). The secondary device is equipped with various mechanical, electronic and combined differential pressure gauges with flow display instruments. The differential pressure sensitive components of the differential pressure gauge are mostly elastic components. Since the differential pressure and the flow rate are in a square root relationship, the flow display instrument is equipped with an open square device to linearize the flow scale. Most meters also have a flow accumulator to display cumulative flow for economic accounting. This method of measuring flow using differential pressure has a long history and is relatively mature. Generally, countries all over the world use it in more important occasions, accounting for about 70% of various flow measurement methods. The flow measurement of the main steam, feed water, condensate, etc. of the power plant is based on this meter.