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Metal rotor flowmeter selection formula and installation and use precautions:
Metal rotor flowmeter is used as a primary measuring component for small flow measurement. It has been applied in argon gas metering system of special steel plant, oxygen metering system of medium-sized plant and oxygen metering system of machinery factory. Among them, metal rotor flowmeter in medium-sized plant oxygen metering system. It has been running stably for several months and has achieved good measurement results. The following is a brief description of the characteristics, selection and use of metal rotameters.
First, the measurement principle and the measurement characteristics of the metal portion of the metal rotor flowmeter rotameter cone and plate by a float composition, when the fluid flows through the tube upward, the float moves upwardly tapered, to achieve equilibrium at a certain position, where The annulus of the float and the orifice plate is kept constant, and the annulus area is proportional to the rise height of the float, and a certain height of the float represents the flow rate of the flow. When the float moves up and down, it is transmitted to the external indicator in the form of magnetic coupling. The pointer of the indicator follows the displacement of the float and the pointer is linearly indicated by the cam plate. Features: Metal rotor flowmeter has simple structure, reliable operation, wide application range and high range ratio, generally 10B1.
Second, the selection of metal rotor flowmeter
When measuring the liquid, the metal rotameter is generally marked with water in the standard state (20e) and water; when measuring the gas, the air is marked in the standard state (20e, absolute pressure 011013MPa). Therefore, when measuring a certain measuring fluid, the flow range should be converted into water or air flow under standard conditions, and then selected according to the standard flow scale of the metal rotameter according to the converted flow range. The following is an example of the oxygen consumption in the riveting workshop in the oxygen metering system of the mechanical plant. The raw data is as follows:
Pipe diameter: Ф70@5; Zui large oxygen consumption: 110m3/h; Zui small oxygen consumption: 10m3/h; Working pressure: 113MPa; Working temperature: 30e; Local average atmospheric pressure: 011MPa.
Calculation:
(1) Oxygen density
(3) The flow correction formula under the condition of the actual use of the metal rotameter:
Where: ZS (ZSN) is the compression coefficient of the measured gas in the standard state (working state) (general condition ZSUZSN); QS is the actual flow rate of oxygen under working conditions; QN is the actual flow rate of air under standard conditions; QN is the standard The density of air (11293kg/m3); pN is the standard atmospheric pressure; TN is the standard temperature 293115K; QSN is the density of oxygen under standard conditions (ie Q20); pS is the actual working pressure of oxygen (ie p1); TS is the actual oxygen Working temperature (ie T1).
According to the selection manual of the metal rotor flowmeter product, LZDH-25 (315~35) is suitable.
Third, the setting of the upper limit of the secondary flow
Taking the oxygen consumption in the riveting workshop as an example, the secondary meter selected is the compensation intelligent flow totalizer produced by Jinan Central Automation Research Institute. The parameters to be set in the Central Table are: FH, PH, Ph, Ps, CH, Ch, Cs
The upper flow limit FH should be the oxygen flow rate in the standard state corresponding to the upper limit of the metal rotor flowmeter. Since the scale of the metal rotameter is marked with air in the standard state, it must be converted to the oxygen flow under the standard state.
On the QN (under QN): the upper (lower) limit of the flow rate of the metal rotor flowmeter according to the standard air.
According to the selected metal rotor flowmeter of model LZDH-25 (315~35), the measurement range of oxygen is 121711m3/h~127111m3/h. It basically meets the measurement requirements of 11m3~110m3.
Fourth, the metal rotor flowmeter in the installation and use of the precautions
(1) The flowmeter must be installed vertically. The measured fluid flows through the flowmeter from bottom to top. The inlet and outlet are guaranteed to have a straight pipe section with 5 times the gauge diameter. For the newly installed pipeline, the pipeline should be flushed before installation.
(2) In order to facilitate the repair and replacement of the flowmeter, it is necessary to connect the bypass pipeline when the instrument is installed.
(3) A valve should be installed upstream of the flowmeter, and a flow regulating valve should be installed at the downstream 5~10 times of the gauge diameter. For small-diameter instruments, filters should be installed upstream. If the measured medium contains magnetic substances, the magnetic filter should be installed in front of the flowmeter.
(4) When the measured medium is dirty, the pipe and float should be cleaned in time.
(5) The measurement accuracy of the metal rotameter is generally 215. When the accuracy of the measurement is required to be high, the metal rotameter should not be selected.
V. Conclusion
The use of the metal rotameter solves the problem that the small flow cannot be accurately measured, makes the energy metering work more perfect, and provides more reliable settlement data for the cost accounting of each secondary mine.
Further reading: Mingyu Instrument Technology
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