What kind of compensation should be used for saturated steam

Abstract: What kind of compensation information should be used for saturated steam is provided by excellent flowmeter and flowmeter manufacturers and quotation manufacturers. (1) Look-up table method to obtain the consistency of density Saturated steam adopts temperature compensation and pressure compensation, which are essentially the same. The reason is that the steam in the saturated state has a single-valued function relationship between its pressure and temperature, and the density detected from the steam temperature is the same. More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following is the details of the compensation article for saturated steam. (1) Look-up table method to obtain the consistency of density Saturated steam adopts temperature compensation and pressure compensation, which are essentially the same. The reason is that the steam in the saturated state has a single-valued function relationship between its pressure and temperature, and the density detected from the steam temperature is consistent with the density detected from the pressure corresponding to this temperature. Therefore, both temperature compensation and pressure compensation are feasible in principle. (2) The difference in investment is considered from the perspective of saving investment and reducing installation workload. Because the price of a platinum thermal resistance is only a few tenths to a fraction of that of a pressure transmitter, it is more economical to use temperature compensation. (3) The difference in compensation accuracy is not only related to the accuracy of the temperature sensor and pressure transmitter, but also to the type of flowmeter, the working conditions and The range selection of the pressure transmitter is related. Generally speaking, the temperature measurement compensation accuracy has a great influence, and the specific analysis is as follows. The influence of temperature measurement error on the flow measurement results. The relationship between the temperature measurement error and the flow measurement result has little effect on superheated steam. For example, for superheated steam with a temperature of 250 °C, if the temperature measurement error is 1 °C, the uncertainty of the flow measurement result will be caused by the temperature compensation. From 0.096%R (differential pressure flowmeter) to 0.19%R (steam flowmeter). The most influential thing is that the temperature signal is used for the compensation of the saturated steam flow measurement. For example, the saturated steam with a pressure of 0.7MPa has an equilibrium stability of 170.5°C and a corresponding density of 4.132kg/m3. If the temperature measurement error is -1°C , and check the saturated steam density table accordingly, the density is 4.038kg/m3, resulting in a flow measurement error of about -1.14%R (differential pressure flowmeter) to -2.27%R (vortex flowmeter). Considerations for temperature sensor accuracy classes. The temperature measurement error is related to the accuracy of the temperature sensor and the measured temperature value. For example, the saturated steam with a pressure of 0.7MPa is used to measure the temperature with a grade A platinum thermal resistance. The error limit is±0.49°C [13], if this measurement result is used to check the steam density table for compensation, the flow compensation uncertainty is about±0.56%R (differential pressure flowmeter) to±1.11%R (steam flowmeter). If the B-grade platinum heat mass temperature is used, the error limit is increased to±1.150°C, the flow compensation uncertainty increases to±1.31%R (differential pressure flowmeter) to±2.61%R (steam flow meter). Obviously, the error that may be caused by the use of B-grade platinum thermal resistance for such purposes is considerable, so it is generally not suitable for use. Here only a relative comparison of side temperature components with different accuracy levels is made. Of course, the error mentioned here is only the part of the temperature measuring element. As for the uncertainty of the flow measurement system, the influence of the flow secondary meter, flow sensor, flow transmitter, etc. must be taken into account. Pressure transmitter accuracy classes, pressure measurement errors and their effects. The pressure measurement error is related to the accuracy level and range of the pressure charge. For example, if a pressure transmitter with an accuracy of 0.2 and a measurement range of 0-1MPa is used to measure the saturated steam pressure of 0.7MPa, the error limit is ±2kPa. If this result is used Check the steam density table for compensation, the flow compensation uncertainty caused by this error limit is about±0.13%R (differential pressure flowmeter) to±0.25%R (steam flow meter). Obviously, pressure compensation can achieve higher compensation accuracy than temperature compensation. Difficulties in Specific Implementation The viewpoint that the above two compensation methods are feasible is only a discussion in principle, and other problems will arise in specific implementation. Installation is difficult. For differential pressure flowmeters used to measure the mass flow of saturated steam, if temperature compensation is selected, the scheme is often modified because the temperature measuring sleeve is too close to the throttling piece, which interferes with the flow state or is installed at an ideal position. Into an overheated state due to a phase transition. For dry saturated steam, when flowing through the steam flow meter at a higher flow rate, the adiabatic expansion caused by pressure loss often makes the steam enter a superheated state. At this time, it is still regarded as saturated steam, and the saturated steam density is checked according to the steam temperature. Table, the obtained value is obviously on the high side. Due to the above reasons, when measuring the mass flow of saturated steam, only the temperature is measured, and the density table is checked accordingly to calculate the mass flow, which is not widely used in practice. This article comes from: The compressed air flowmeter reprint needs to indicate the above is the entire content of this article, you are welcome to inquire about the flowmeter selection and quotation of our manufacturer. 'What kind of compensation should be used for saturated steam'

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