In simple terms, gamma rays are projected as a single beam from a gamma ray source through a pipe or vessel. A detector situated on the opposite side then measures the gamma ray emissions. This enables the absorption of the gamma ray by the vessel and its contents to be calculated electronically, giving a visual read-out. By moving the source and detection devices in a controlled manner along the vessel, engineers trained in the technique and skilled in its application can interpret the printout to analyse a wide range of process problems.

For example, it is possible to detect where erosion or corrosion has occurred in a pipe or where deposits have built up in flare stacks, heavy bottom lines or transfer lines. When applied to fractionation towers, gammetry can lead to accurate diagnosis of possible process problems such as an overflowing distributor, liquid maldistribution, fouling or foaming or mechanical problems such as collapsed trays. This is invaluable for trouble shooting, de-bottlenecking, process studies and preventive maintenance. Similar benefits can be derived for reactors, separators and mixer-settlers.

A similar technique measures the back scattering of neutrons within a vessel, which indicates the presence of hydrogen atoms behind the vessel walls. In this way it is possible to locate the interfaces between gases, liquids and solids. Therefore an accurate picture of the depth of sludge, water, organics and vapour within the vessel can be given.

Application of these new techniques enables Sulzer Chemtech to offer appropriate proposals for correction, process improvement and maintenance.