Which level gauge should be used to determine the oil-water interface in an extraction tower?
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This post was last edited by zjchen on 2015-11-5 at 15:08. There is one extraction tower, and it is necessary to transmit signals regarding the oil-water interface level to the central DCS using a remote-level gauge, so that operators can determine the position of this interface and use that information to guide their operations. The height of the level gauge is only 900 mm; although there is a glass level gauge at the top of the tower that allows the interface to be seen on-site, the tower is too tall, which makes it quite inconvenient. Previously, a double-flange capillary differential pressure level gauge was used; it’s not clear whether the wrong type of level gauge was chosen or if there were errors in the calculation formulas used, but in any case it was impossible to determine the oil-water interface. The measured specific gravity of the oil phase is 0.9068, while the specific gravity at the water phase interface is 0.9920. Some people are suggesting the use of a guided wave radar level gauge; I wonder if such a level gauge would be suitable for this purpose How to set it up in DCS programming. Need help from experts! Thank you! ! !
A guided-wave radar level gauge should work!
For a guided-wave radar level gauge, how should settings be made on both the gauge side and the DCS?
You can try servo level gauges; among the domestic ones, there is one brand that is used for measuring the oil-water interface – Beijing Junyou
You can try servo level gauges; among the domestic ones, there is one brand that is used for measuring the oil-water interface – Beijing Junyou
A float made of a medium with a density between that of oil and water should work
Using a material with a density between those of the two options to make the float ball is indeed a good idea; I wonder if it will work well in practice
First, using guided-wave radar to determine boundaries is not recommended at all; the vast majority of such devices do not work well. There are generally no major issues with using guided-wave radar for level measurement. At the level reached by the poster, the density difference is only 0.0852, which is a very small value; the density of the oil phase is quite high at 0.9068. It’s not clear what kind of oil it is – is it relatively heavy? What about the viscosity? Is the medium temperature not expected to be too high? The entire differential pressure range for this application is only around 0.75 kPa; it is recommended to use a micro-differential pressure transmitter for measurement. If the viscosity of the oil is low and its fluidity is good, a float can be used for measurement.
The differential pressure of the instrument is too low; it’s impossible to obtain accurate readings using double flanges, so installing them is pointless. Electrostatic floats or radio frequency admittance can be considered as alternatives; the manufacturer needs to determine whether they are suitable for use. The costs are relatively high, as the conditions here are quite stringent. The last method, which I use, involves using a camera to point at the glass tube interface gauge; generally, the main control unit has video monitoring capabilities. DCS systems generally accept 4-20mA analog signals, and the configuration follows the same standard procedures.
This post was last edited by lsv on 2018-7-13 08:26. When the density difference of the media is less than 0.1 g/cm3, neither the float nor the differential pressure method works very well. If the dielectric constant difference between oil and water is large, a guided radar can be used; if the difference is small, these methods are not very effective.