Interface measurements in desalters are often regarded as not being very critical, even though every drop of oil, to be refined, passes through the desalter. As refineries try to maximize their margins, so-called opportunity crudes are often used. These crude oils generally contain increased levels of sulphur, oil sands, bitumen, heavy oils and oils with high TAN. This can lead to problems with the proper operation of the desalter. In addition, refineries are increasingly confronted with stricter environmental regulations. The efficient level control of water/emulsions/oil layers in the desalter ensures that salts and minerals are effectively removed and that environmental requirements are met. Therefore, more and more operators are turning to radiometry as a highly reliable and accurate measurement solution for this application.