Improving process operating margins can be achieved by maximising production of higher value products and/or minimising production costs. It is important for plant engineers to know how much capacity is available in the trays in a distillation tower. Gamma scanning is an established method used by many in the process industries as a qualitative tool to help troubleshoot distillation towers. Gamma scanning can be used to diagnose virtually any operating malfunction that can be identified by an observable change in density. This includes most mechanical, process or rate related problems such as tray damage, foaming, weeping and entrainment. By deploying new measurement detector technology and incorporating innovative analysis of gamma scanning data, plant engineers can now acc ss the all-important quantitative data about the capacity of distillation towers.