Separating different products
Distillation products are often mixed with other substances of varying density and consistency. In the separating tank, for example, water is separated from the hydrocarbons and collected at the bottom of the tank. To determine the exact proportion of each substance, a so-called interface measurement is necessary. Previously used displacer systems have several disadvantages: they can only detect the interface if the densities of the products remain constant, and they cannot measure the total level, i.e. the top surface of the upper medium.
New measurement technology for interface detection – VEGAFLEX 67
Because microwaves radiate freely through non-conductive substances, such as for example hydrocarbons, interface measurement is also possible in addition to pure level measurement. The two measured substances must simply have a diferent dielectric fgure. The classic interface appli-cation – water and oil product – yields a strong refection at the interface due to the very large diference in the dielectric figure. Interestingly, the total level can also be measured at the same time with one sensor. The signals from the two measured value outputs are then transmitted either digitally via HART or as 4 … 20 mA signal via the signal conditioning instrument.
