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.
Precautions
The correct selection of ultrasonic flowmeters can ensure better use of ultrasonic flowmeters. The type of ultrasonic flowmeter to be selected should be determined according to the physical properties and chemical properties of the fluid medium to be tested, so that the diameter, flow range, lining material, electrode material and output current of the ultrasonic flowmeter can be adapted to the properties of the fluid to be measured. And flow measurement requirements.
1, precision function check
Accuracy levels and functions are based on measurement requirements and usage scenarios to select instrument accuracy levels for cost-effectiveness. For example, in the case of trade settlement, product handover and energy measurement, the accuracy level should be higher, such as 1.0, 0.5, or higher; for process control, select different accuracy levels according to control requirements; It is to detect the process flow, no need to do precise control and measurement, you can choose a lower accuracy level, such as 1.5, 2.5, or even 4.0, then you can use a low-cost plug-in ultrasonic flowmeter.
2, measurable medium
Measuring medium flow rate, meter range and caliber When measuring a general medium, the full flow rate of the ultrasonic flow meter can be selected within the range of 0.5-12 m/s of the measured medium flow rate, and the range is relatively wide. The selection of the meter specification (caliber) is not necessarily the same as the process piping. It should be determined according to whether the measured flow range is within the flow rate range. That is, when the pipeline flow rate is too low to meet the requirements of the flow meter or the measurement accuracy is not guaranteed at this flow rate. It is necessary to reduce the gauge diameter, thereby increasing the flow rate inside the tube and obtaining satisfactory measurement results.
Turbine Flowmeter Product Introduction
A flow meter that uses a turbine for measurement. It first converts the flow rate to the speed of the turbine and then converts the speed into an electrical signal proportional to the flow. This flow meter is used to detect instantaneous flow and total integrated flow, and its output signal is frequency, which is easy to digitize. In the figure, the induction coil and the permanent magnet are fixed together on the casing. When the ferromagnetic turbine blade passes the magnet, the magnetic resistance of the magnetic circuit changes to generate an induced signal. The signal is amplified and shaped by an amplifier and sent to a counter or frequency meter to display the total integrated flow. At the same time, the pulse frequency is frequency-voltage converted to indicate the instantaneous flow rate. The speed of the impeller is proportional to the flow rate, and the number of revolutions of the impeller is proportional to the total amount flowing. The output of the turbine flow meter is a frequency modulated signal that not only improves the immunity of the detection circuit, but also simplifies the flow detection system. It has a turndown ratio of 10:1 and an accuracy of ±0.2%. Turbine flowmeters with small inertia and small size have a time constant of 0.01 seconds.
Turbine flowmeter is the main type of velocity flowmeter. When the fluid to be measured flows through the turbine flowmeter sensor, under the action of the fluid, the impeller is forced to rotate, and its rotational speed is proportional to the average flow velocity of the pipeline. At the same time, the blade periodicity The magnetic flux generated by the electromagnet is cut and the magnetic flux of the coil is changed. According to the principle of electromagnetic induction, a pulsating potential signal, that is, an electric pulse signal, is generated in the coil, and the frequency of the electric pulsation signal is proportional to the flow rate of the fluid to be measured.