Gamma-ray scanning for troubleshooting, optimisation and predictive maintenance of distillation columns

D istillation columns are considered as one of the most critical components in petroleum refineries, gas processing installations and chemical plants. Plant performance depends to a large extent on the ability of these columns to function as intended. Defective columns may lead to serious consequences to the plant operation and hence the quality of the product. Thus, when a distillation column experiences irregularities, it is urgently necessary to find out exactly what is happening inside the column. Any kind of problem can result in a large financial loss especially when it involves off-spec product, lost of production or unexpected shut down of the plant. The earlier the problem is identified and corrected, the lesser will be the loss and the cost to rectify it. In most cases, troubleshooting to pinpoint the cause of the problem in columns is conducted on-line. It seems that this is the only way column performances can be observed. Inspection while the column is in operation also enables continuous monitoring and assessment of the component. Gamma-ray scanning, often referred to as “column scanning”, is a convenient, cost-effective, fast, efficient and non-intrusive technique to examine inner details of a distillation column, while it is in operation. Column scanning allows an engineer to study tray or packing hydraulics inside a column at any set of online condition. It provides essential data to optimise the performance of columns, extend column run times, track the performance-deteriorating effects of fouling and solids deposition, and identify maintenance requirements well in advance of scheduled turnarounds. This on-line knowledge can reduce repair downtime significantly. By analysing the scanning results, a number of common malfunctions in trayed or packed columns can readily be determined, some of which are summarised in the following table. In Malaysia and the surrounding region, the examination of process vessels (columns, separators, reactors,