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technical article
Selection and installation of metal tube float flowmeter
2012-3-12 11:10:19

First, selection points
1 Application Overview
作为直观流动指示或测量精确度要求不高的现场指示仪表,占浮子流量计应用的90%以上,被广泛地用在电力、石化、化工、冶金、医药等流程工业和污水处理等公用事业。 Metal tube float flow meter, as an intuitive flow indication or on-site indicating instrument with low measurement accuracy requirements, accounts for more than 90% of the application of the float flow meter. It is widely used in power industry, petrochemical, chemical, metallurgical, pharmaceutical and other process industries and sewage. Processing and other utilities. Some application sites only need to monitor the flow rate not exceeding or not lower than a certain value. For example, the increase of the cable inert protective gas flow indicates that a new leak point has occurred. The environmental protection atmospheric sampling and process industry online monitoring and analysis instruments continuously sample, and the sampling flow monitoring is also the bulk service object of the float flowmeter. As the measurement of liquid level, density and other parameters in the process industry, constant flow measurement and control auxiliary instruments are widely used and also occupy a considerable share. Remote transmission metal float flow meters with signal output are commonly used in process industries for flow control detection instruments or pipeline mixing ratios, such as controlling the ratio of raw water and chemical solution in the water treatment process. 2 Type and structure selection The main measurement object of the float meter is a single-phase liquid or gas. Particles in the liquid or droplets in the gas are usually not applicable. Because the float adheres to particles or tiny bubbles in the liquid flow, it will affect the measured value. If you need to transmit the signal far away for total accumulation or flow control, generally use a metal tube float flowmeter with electrical signal output. If the ambient atmosphere has explosion-proof requirements and there is a gas source for control instruments on the site, remote transmission metal float flow meters are given priority. If electric remote transmission instruments are selected, they must be explosion-proof. When measuring opaque liquids, a metal tube float meter is more common. For measuring high-viscosity liquids with a temperature higher than the ambient temperature and liquids that easily precipitate crystals or solidify when the temperature drops, a jacketed metal tube float flow meter should be used.

安装使用注意事项 Installation precautions for metal tube float flowmeter
1 Instrument installation direction. Most of the float flowmeters must be installed vertically on non-vibration pipelines. There should be no obvious tilt. The fluid flows through the meter from bottom to top. 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. 4 Installation of extended range. If the measurement requires a wide range of flow, 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 small flow. After the float reaches the top, Taking heavy float readings, the range can be expanded to 50-100. 5 To exhaust the gas in the instrument, the angle type metal float flowmeter with the inlet and outlet not in a straight line, when the liquid is used to pay attention to whether there is residual air in the extension sleeve of the externally transmitted float, it must be exhausted; It is easy to accumulate in the casing and 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 should be converted if necessary. If the meter is not customized to the manufacturer according to the medium parameters such as the density and viscosity, the liquid meter is usually calibrated with water and the gas meter is calibrated with air. The 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. 的校验和标定液体常用标准表法、容积法和称量法;气体常用钟罩法,小流量用皂膜法。 7 Calibration and calibration of float flowmeters, calibration and calibration of metal tube float flowmeters . Standard gauge method, volumetric method and weighing method are commonly used for liquids; bell jar method is commonly used for gas, and soap film method is used for small flow. 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.