Urgent: We have installed several plug-in vortex flowmeters on-site; do we need the calculation formulas for temperature and pressure compensation? ?
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This post was last edited by zlky2005 on 2018-8-4 at 16:59. We installed several insert-type vortex flowmeters on-site to measure superheated steam and saturated steam. We are currently working on the DCS program and need the temperature and pressure compensation formulas for these vortex flowmeters. If anyone has experience with this, please share them with me. Thank you! I searched on Baidu for a long time but couldn’t find anything suitable; most of the information available dealt with differential pressure types, which didn’t seem appropriate.
Just compensate the existing traffic directly, isn’t that enough? Do not take the flow signal to the square root
The vortex flow meter measures the volumetric flow rate of steam, whereas we need to convert it into a mass flow rate. We know that the density of superheated steam varies at different pressures and temperatures. The thermodynamic properties of steam are complex. Although superheated steam is a single-phase fluid and its density is a function of temperature and pressure, it does not obey the ideal gas law (because a gas remains a gas at all times, whereas steam can turn into water when its temperature and pressure are reduced). Currently, the density of superheated steam is mostly determined using lookup tables, and these density tables are calculated based on formulas published by the IFC (International Formulation Committee) in 1967. The formulas provided by IFC are very complex, and it is impossible for ordinary users to apply them directly in field instruments. It is the steam density table prepared based on the results of this formula, and its content is quite extensive; it is impossible to store all of it in on-site instruments. A more feasible approach is to use a steam density table as a basis, and based on the limited operating range of the instruments, derive a functional relationship between density and pressure and temperature in the form of calculation formulas to meet the needs of on-site flow measurement. The details are as follows; the following content is taken from an unknown paper, and its source has not been verified. But it has been tested by me personally, and I guarantee it works. Upon closer inspection, Equation 4 is the most suitable for the operating conditions in our facility, as it covers a wide pressure range and an even wider temperature range. The only drawback is its lower precision, which is not as good as that of the first two equations. If the pressure and temperature values meet the requirements, it is advisable to use Equations 1, 2, or 3 along with a density interpolation table; this will allow for accurate verification of the density values, to within three decimal places
The steam/gas compensation formulas are already built into DCS systems; there’s no need to write them manually.
For the density formula, simply replace the vortex flow meter with one that measures volumetric flow rate, and incorporate a DCS system to carry out the calculations
Some DCS systems do not have modules for calculating the specific heat capacity and density of steam; for example, the Yokogawa CS3000 requires that formulas be written manually
How is it that people keep asking about such a crappy thing every day?
There is a difference in when one learns something, and there are specialized areas of expertise. Some people have not been exposed to it before and do not understand it.
That person will act tough, do you get it or not?