Precautions for the use of gas flow meters

Abstract: The information on the precautions for the use of gas flow meters is provided by excellent flowmeter and flowmeter manufacturers. Precautions for the use of gas flow meters 1. When the working conditions of the instrument change (such as changing the medium, the ambient temperature changes greatly, etc.), the zero position of the instrument should be re-adjusted. At the same time, the conduit of the instrument must be installed horizontally and calibrated with a spirit level. Otherwise will. More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following are the details of the article on the precautions for the use of gas flowmeters. Precautions for the use of gas flowmeters 1. When the working conditions of the instrument change (such as changing the medium, the ambient temperature changes greatly, etc.), the zero position of the instrument should be re-adjusted. At the same time, the conduit of the instrument must be installed horizontally and calibrated with a spirit level. Otherwise, it will increase the influence of working condition changes on zero drift. The rack should not be vibrated or swayed, so it is not suitable for use on ships. 2. Pair is equivalent to 0—A large number of test data in the range of 100kg/cm2 pressure and 0-7 standard liters/hour flow (air) are correlated and calculated, and the linear regression equation is obtained by the principle of least squares, and its correlation coefficientλThe values ​​are all in the range of 0.999 to 0.9999, which proves that the instrument has good linearity. However, the linearity and range size have the larger the flow, the more serious the nonlinearity, so the range is generally limited to within 0 ~ 4 standard liters/hour (air) to ensure good linearity. In order to measure large flow and ensure linearity, the shunt principle can be used to expand the range of the instrument. If the bypass tube, venturi tube, orifice plate, etc. are used together, the range can be expanded to tens, hundreds, thousands of standard liters per hour, up to tens of thousands of standard cubic meters. 3. Although the specific heat of the real gas varies with the pressure, and even some gases vary greatly, the measurement accuracy of the instrument can still be maintained within a certain range. 4. In the selection of conduit materials, in addition to considering corrosion resistance, it is better to choose materials with better thermal conductivity. Taking the measurement of nitrogen as an example, also at 0—100kg/cm2 pressure and 0 to 7 standard liters/hour flow rate, the measurement accuracy of nickel tube is 2 to 2.5% and that of stainless steel is 3 to 4% (the thermal conductivity of nickel is about three times that of stainless steel. ). 5. Since the gas flowmeter can work normally only when the specific heat of the gas is relatively stable, the specific heat value is very unstable in the case of unstable gas composition, fog in the center of the gas, and working conditions approaching the liquefaction critical area of ​​the gas. , should not use this instrument. For example, the critical point of ethylene liquefaction is 50 kg/cm2 and 9.9 °C. When the pressure exceeds 30 kg/cm2 during the test, the meter reading begins to become unstable. 6. If a gas medium is changed, re-calibrate. In the manual of the instrument, it is often introduced not to recalibrate, but to convert the uncalibrated gas flow only according to the specific heat of the two gases. Although it is simple and convenient, it will cause large errors, especially when working under high pressure. It is found that the sensitivity of the instrument is not completely proportional to the specific heat, and it is better to re-calibrate the meter. 7. The instrument must be turned on to preheat before use. Before it is fully preheated, the instrument will be unstable. Better models, the boot warm-up time is less than two hours. 8. During use, when the gas flow changes suddenly, the temperature in the tube must be redistributed through the transfer of heat, so the re-stabilization of the output signal takes a certain amount of time. In order to reduce this hysteresis, the manufacturer often adds a differential network to the electrical circuit of the instrument to make the output signal respond quickly. This is especially necessary when cooperating with other instruments for automatic flow control. The above is the whole content of this article. You are welcome to inquire about the flowmeter selection and quotation of our factory. 'Precautions for the use of gas flow meters'

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