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technical article
Metal tube float flowmeter is a variable area flow measurement instrument commonly used in control
2012-3-6 11:26:28

浮子在测量管中,随着流量的变化,将浮子向上移动,在某一位置浮子所受的浮力与浮子重力达到平衡。 The metal tube float flowmeter floats in the measuring tube. With the change of the flow rate, the float is moved upward, and the buoyancy received by the float at a certain position reaches a balance with the gravity of the float. At this time, the area of the circulating annulus between the float and the orifice plate (or cone tube) remains constant. The area of the ring gap is proportional to the rising height of the float, that is, the position of the float rising in the measuring tube represents the magnitude of the flow. The position of the float is transmitted by the internal magnet to the external indicator, so that the indicator correctly indicates the value of the flow . This makes the indicator housing not in direct contact with the measuring tube, so even if a limit switch or transmitter is installed, the instrument can be used under high temperature and high pressure working conditions.

是工业自动化过程控制中常用的一种变面积流量测量仪表。 Metal tube float flowmeter is a variable area flow measurement instrument commonly used in industrial automation process control. It has the characteristics of small size, large detection range and convenient use. It can be used to measure the flow of liquid, gas and steam, especially suitable for medium flow measurement with low flow rate and small flow. Features of measurement part: 1. Robust all-metal structure design type float flow meter 2. Measuring tube indicator with independent concept design 3. Stainless steel, Hastelloy, titanium, PTFE material measurement system can be selected 4. Low pressure loss design 5. Short stroke, small structure design, total height of the instrument 250 6. Magnetic coupling structure to ensure data transmission and more stable signals 7. Insulation or heat tracing jacket 8. Vertical, horizontal and various installation methods are more suitable for different occasions 9. Suitable for small-caliber and low-velocity medium flow measurement10. Reliable work, small maintenance, long life11, low requirements for straight pipe sections 12, wide flow ratio 10: 1 13, double-line large LCD display, optional field Instantaneous / cumulative flow display, with backlight 14, single-axis sensitive indication 15, non-contact magnetic coupling drive 16, all-metal structure, suitable for high temperature, high pressure and strong corrosive media 17, can be used in flammable and explosive hazardous places 18 、 Choose two-wire system, battery, AC power supply mode 19, multi-parameter calibration function 20, with data recovery, data backup and power failure protection functions
检测部分是由一个自下向上扩张的垂直锥形管和一个沿着锥形管轴可以上下自由移动的浮子组成。 The detection part of the metal tube float flowmeter is composed of a vertically conical tube that expands from the bottom up and a float that can move freely up and down along the axis of the conical tube. The working principle is shown in Figure 1. When the measured fluid passes from the bottom to the ring gap formed by the cone tube and the float, a differential pressure is generated at the upper and lower ends of the float to form the rising force of the float. When the floating force is greater than the float immersed in the fluid When the weight rises, the float rises, and the area of the annulus increases. The flow velocity of the fluid at the annulus decreases immediately, and the differential pressure at the upper and lower ends of the float decreases. The weight stabilizes the float at a certain height. The height of the float in the cone has a corresponding relationship with the flow rate. The basic equation of volume flow Q is: where the flow coefficient of the α instrument varies with the shape of the float; ε the gas expansion coefficient when the measured fluid is a gas, which is usually ignored due to the small correction amount of this coefficient, and has been verified by verification. Include it in the flow coefficient. If it is a liquid, ε = 1 △ F Circulation annular area, m2; g Local gravity acceleration, m / s2; Vf float volume, if it is an extension, it should also include, m3; ρf float material density , Kg / m3; ρ The density of the measured fluid, such as the density of the gas at the upstream cross section of the float, kg / m3; Ff cross section at the working diameter (maximum diameter) of the float, m2; Gf float weight, kg. The relationship between the circulation ring area and the height of the float is shown in equation (3). When the structural design has been determined, d and β are constant. There is a quadratic term of h in the formula. Generally, this nonlinear relationship cannot be ignored. Only when the cone angle is very small can it be regarded as approximately linear. Where d is the maximum diameter of the float (that is, working diameter), m; h the float's inner diameter from the cone is equal to the height of the rise from the maximum diameter of the float, m; β cone angle of the cone; a, b are constants from (1), (2 ), (3) The formula shows that under certain conditions, the height of the float in the cone tube has a certain proportional relationship with the volume flow. After reading the height of the float, you can know the corresponding volume flow rate, and then convert the height of the float to the corresponding volume flow rate through the converter. This is the detection principle of the metal tube float flowmeter. The conversion indicator converter is actually a scale that converts the height of the float in the cone into the corresponding volume flow. Divided from the output signal: with local display and remote signal output: Local display: The following magnetic steel in the local indicator is coupled with the magnetic steel in the float to rotate, while the electric pointer passes the scale The disk indicates the intelligent remote transmission of the flow at this time. The following magnetic steel in the intelligent indicator is coupled with the magnetic steel in the float to rotate. At the same time, the magnetic steel and pointer are driven, and the magnetic field is transformed by a magnetic sensor. The electric signal is processed by A / D conversion, digital filtering, microprocessor processing, D / A output, LCD liquid crystal display to display the instantaneous flow rate and accumulated flow rate. In the formula, the flow coefficient of the α meter varies depending on the shape of the float; ε The gas expansion coefficient when the measured fluid is a gas, which is usually ignored due to the small correction amount of this coefficient, and it has been included in the flow coefficient through verification. For liquid, ε = 1 △ F circulating annular area, m2; g local gravitational acceleration, m / s2; Vf float volume, if extended, should also include, m3; ρf float material density, kg / m3; ρ measured Fluid density, if gas is the density on the upstream cross section of the float, kg / m3; Ff cross section at the working diameter (maximum diameter) of the float, m2; Gf float weight, kg. The relationship between the circulation ring area and the height of the float is shown in equation (3). When the structural design has been determined, d and β are constant. There is a quadratic term of h in the formula. Generally, this nonlinear relationship cannot be ignored. Only when the cone angle is very small can it be regarded as approximately linear. Where d is the maximum diameter of the float (that is, working diameter), m; h the float's inner diameter from the cone is equal to the height of the rise from the maximum diameter of the float, m; β cone angle of the cone; a, b are constants from (1), (2 ), (3) The formula shows that under certain conditions, the height of the float in the cone tube has a certain proportional relationship with the volume flow. After reading the height of the float, you can know the corresponding volume flow rate, and then convert the height of the float to the corresponding volume flow rate through the converter. This is the detection principle of the metal tube float flowmeter. The conversion indicator converter is actually a scale that converts the height of the float in the cone into the corresponding volume flow. Divided from the output signal: with local display and remote signal output: Local display: The following magnetic steel in the local indicator is coupled with the magnetic steel in the float to rotate, while the electric pointer passes the scale The disk indicates the intelligent remote transmission of the flow at this time. The following magnetic steel in the intelligent indicator is coupled with the magnetic steel in the float to rotate. At the same time, the magnetic steel and pointer are driven, and the magnetic field is transformed by a magnetic sensor. The electric signal is processed by A / D conversion, digital filtering, microprocessor processing, D / A output, LCD liquid crystal display to display the instantaneous flow rate and accumulated flow rate.