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technical article
Flow measurement of metal tube float flowmeter based on constant pressure drop and variable throttle area
2012-4-12 12:55:00

使用注意事项:1仪表安装方向、绝大部分浮子流量计必须垂直安装在无振动的管道上,不应有明显的倾斜,流体自下而上流过仪表。 Installation precautions for metal tube float flowmeters : 1. Instrument installation direction, most of the float flowmeters must be installed vertically on a non-vibrating pipe, there should be no obvious tilt, and the fluid flows from the bottom to the top of the meter. The angle between the center line and the plumb line of the float flowmeter generally does not exceed 5 degrees. If θ = 12 °, there will be 1% additional error. There is no strict requirement for the length of the upstream straight pipe section, but there are also manufacturers that require (2-5) D length, which is actually not necessary. 2 For the installation of dirty fluid, a filter should be installed upstream of the instrument. When a magnetically coupled metal tube float flowmeter is used for fluids that may contain magnetic impurities, a magnetic filter should be installed in front of the meter. To keep the float and cone tube clean, especially for small-caliber instruments, the cleanliness of the float significantly affects the measured value. 3 The installation of pulsating flow, the pulsation of the flow itself, if there is a reciprocating pump or regulating valve upstream of the position where the instrument is to be installed, or there is a large load change downstream, etc., the measurement position should be changed or the pipeline system should be remedied and improved, such as installing a buffer tank ; If the instrument itself oscillates, for example, the gas pressure is too low during measurement, the upstream valve of the instrument is not fully opened, and the regulating valve is not installed downstream of the instrument, etc., it should be improved by targeted measures, or a meter with a damping device should be used instead. 4The installation of the extended range, if the flow range required by the measurement is wide, when the range exceeds 10, two floats of different shapes and weights can be placed in one meter. Take a light float reading at a low flow rate. After the float reaches the top, Take the reading of heavy float, the range can be expanded to 50-100. 5 To exhaust the gas in the instrument, the angle type metal float flow meter with the inlet and outlet not in a straight line, pay attention to whether there is any residue in the extended sleeve of the externally transferred float when used for liquid. The air must be exhausted; if the liquid contains micro-bubbles, it is easy to accumulate in the casing, and it should be vented regularly. This point is more important for small-caliber instruments, otherwise it will significantly affect the flow indication. 6 The flow value needs to be converted. If it is not a custom-made instrument to the manufacturer according to the medium parameters such as density and viscosity, the liquid instrument is usually calibrated with water and the gas instrument is calibrated with air. The fixed value is in the engineering standard state. When the fluid density, gas pressure and temperature of the operating conditions are inconsistent with the calibration, necessary conversion must be done. Conversion formulas and methods are detailed in each manufacturer's instruction manual. 7Float flowmeter calibration and calibration, float flowmeter calibration and calibration liquid commonly used standard table method, volume method and weighing method; gas commonly used bell cover method, small flow using soap film method. The bulk products of some foreign manufacturers have achieved dry calibration, that is, controlling the size of the conical tube and the weight of the float, and indirectly determining the flow value to reduce costs. Only high-precision instruments are calibrated by solid flow. There are also some domestic manufacturers that strictly control the inner diameter and taper of the starting point of the conical tube and the size of the float. The actual flow verification only serves to check the quality of the inner surface of the conical tube. Gauges, tapered tubes and floats from these manufacturers have been interchanged and do not need to be replaced in sets. The float meter is calibrated with a standard meter method, which is a high-efficiency method.


技术参数测量范围:水(20℃)1-200000 l/h 空气(20℃,0.1013MPa)0.03-4000m3/h 参见流量表,特殊流量可订制量程比:标准型10:1 特殊型20:1 Technical parameters of metal tube float flowmeter Measurement range: water (20 ° C) 1-200000 l / h air (20 ° C, 0.113MPa) 0.03-4000m3 / h See flow meter, special flow rate can be customized range ratio: standard Type 10: 1 Special type 20: 1
Accuracy: Standard type 1.5 Special type 1.0 Pressure level: Standard type: DN15-DN50 4.0MPa DN80-DN200 1.6MPa
Special type: DN15-DN50 25MPa? DN80-DN200 16MPa
Jacket pressure rating is 1.6MPa
Special models should be negotiated with the factory before selecting and ordering pressure loss: 7kPa-70kPa
Medium temperature: standard type: -80 ℃-+ 200 ℃: PTFE: 0 ℃ -85 ℃
High temperature type: up to 400 ℃
Medium viscosity: DN15: <5mPa.s (F15.1-F15.3)
<30mPa.s (F15.4-F15.8)
DN25: <250mPFa.s
DN50-DN150: <300mPa.s
Ambient temperature: LCD type -30 ℃ - + 85 ℃
Pointer -40 ℃ - + 120 ℃
Connection form: standard type: DIN2501 standard flange special type: any standard flange or threaded cable interface specified by the user: M20 * 1.5
Power supply: standard 24VDC two-wire system 4-20mA (10.8VDC-36VDC)
AC type: 85-265VAC? 50HZ
Battery type: 3. 6V @ 4AH Ni-MH battery alarm output: upper or lower limit instantaneous flow alarm standard type: open collector output (maximum 100mA @ 30VDC internal impedance 100 ohms)
Special type: relay output (contact capacity up to 5A @ 250VAC )
Pulse output: cumulative pulse output, minimum interval 50 milliseconds LCD display: instantaneous flow rate display value range: 0-50000
Accumulated flow display value range: 0-99999999
Protection level: IP65
Explosion-proof mark: intrinsically safe iaⅡCT6 flameproof dⅡCT6

属于面积式流场计,基于定压降变节流面积测量流量。 The metal tube float flow meter belongs to the area flow field meter, which measures the flow based on the constant pressure drop and the variable throttle area. The flowmeter is installed vertically on the pipeline. When the fluid flows through the cone from bottom to top, a differential pressure is generated before and after the float. The float generates a rising or falling displacement under the action of differential pressure. When the differential pressure that raises the float is equal to the combined forces of gravity, buoyancy, and drilling force, the float is in equilibrium. Therefore, there is a unique correspondence between the displacement of the float and the size of the basin . By detecting the displacement of the float out of the side, you can get the flow value of the side fluid.