As the primary detection element for small flow measurement, the metal rotor flowmeter has been applied in the argon gas metering system of special steel plant, oxygen metering system of medium-sized plant and oxygen metering system of machinery plant. Among them, the oxygen metering system of medium-sized plant has achieved good results. Measurement effect. The following is a brief description of the characteristics and selection and use of metal rotor flowmeters.1. Measuring principle and characteristics of metal rotor flowmeterThe measurement part of the metal rotor flowmeter consists of an orifice plate and a cone-shaped float. When the fluid flows upward through the pipe, the cone-shaped float moves upward and reaches a balance at a certain position. At this time, the annular gap between the float and the orifice remains constant. The area of the annulus is directly proportional to the rising height of the float, and a certain height of the float represents the flow rate. When the float moves up and down, it is transmitted to the external indicator in the form of magnetic coupling, so that the pointer of the indicator follows the displacement of the float. And with the help of the cam plate, the pointer linearly indicates the size of the flow. Features: The metal rotor flowmeter has simple structure, reliable operation, wide application range, and high range ratio, generally 10B1.Second, the selection of metal rotor flowmeterWhen measuring liquid, the metal rotor flowmeter is generally marked with water in the standard state (20e); when measuring gas, it is marked with air in the standard state (20e, absolute pressure 011013MPa). Therefore, when selecting a meter for a measuring fluid, the flow range should be converted to water or air flow in a standard state, and then the converted flow range should be compared with the standard scale of the metal rotor flowmeter for selection. The following is an example of the oxygen consumption in the riveting and welding workshop in the oxygen metering system of the machinery factory.The original data are as follows: pipe diameter: Ф70@5; maximum oxygen consumption: 110m3/h; minimum 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 actual use of the metal rotor flowmeter: Where: ZS (ZSN) is the compression coefficient of the measured gas in the standard state (working state) (generally ZSUZSN ); QS is the actual flow of oxygen under working conditions; QN is the actual flow of air under standard conditions; QN is the density of air under standard conditions (11293kg/m3); pN is standard atmospheric pressure; TN is standard temperature 293115K; QSN is standard In this case, the density of oxygen (ie Q20); pS is the actual operating pressure of oxygen (ie p1); TS is the actual operating temperature of oxygen (ie T1). According to the selection manual of the metal rotor flowmeter, LZDH-25 (315～35) is the most suitable.Third, the setting of the upper limit of the flow rate of the secondary meterTaking the oxygen consumption in the riveting workshop as an example, the secondary meter selected is the compensating intelligent flow totalizer produced by Jinan Zhonghuan Automation Research Institute. The parameters that need to be set in the middle ring meter are: FH, PH, Ph, Ps, CH, Ch, Cs The upper limit of flow FH should be the oxygen flow in the standard state corresponding to the upper limit of the scale of the metal rotor flowmeter, because the metal rotor flowmeter has The scale is marked for air in the standard state, so it must be converted to the oxygen flow rate in the standard state. QN upper (QN lower): that is, the upper (lower) limit of the flow rate of the metal rotor flowmeter according to the air calibration in the standard state. According to the selected model LZDH-25 (315～35) metal rotor flowmeter, the measuring range of oxygen is 121711m3/h～127111m3/h. Basically meet the proposed measurement requirements of 11m3 ~ 110m3.4. Matters needing attention during installation and use of metal rotor flowmeter(1) The flowmeter must be installed vertically. The measured fluid passes through the flowmeter from bottom to top. The inlet and outlet are guaranteed to have a straight pipe section of 5 times the diameter of the meter. For the newly installed pipeline, the pipeline should be flushed before the flowmeter is installed. (2) In order to facilitate the maintenance and replacement of the flowmeter, the bypass pipeline should be connected when the instrument is installed. (3) A valve should be installed upstream of the flowmeter, and a flow regulating valve should be installed downstream of 5-10 times the diameter of the meter. For small-caliber instruments, a filter should be installed upstream. If the measured medium contains magnetic substances, a 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 rotor flowmeter is generally 215. When the measurement accuracy is required to be high, it is not suitable to choose the metal rotor flowmeter.5. Concluding remarks The use of metal rotor flowmeters solves the problem of inaccurate measurement of small flows, makes energy measurement more perfect, and provides more reliable settlement data for the cost accounting of secondary factories and mines
Post time: 21-09-21