Viking Inspection offer both the very latest MFL and SLOFEC floor scanners for tank inspections and have the sole UK licence to offer SLOFEC in the UK – so which technology is right for your tank floor?

The question is not really which is better, but which may be most appropriate for a given inspection.

MFL scanners have in general served the industry well for most standard bare or thinly coated tank floors. Floormaps are some of the fastest motor-driven scanners on the market. It is capable of variable speeds up to 1 m/s (3.2 ft/s), improving inspection efficiency and reducing the time spent in tanks.

Viking inspects using the latest Floormap3Di-R Floormap. This combines two distinct technologies: MFL and STARS.

MFL sensors are used to detect corrosion in the tank bottom, while STARS is a patented technology that helps determine whether corrosion is top side or bottom side. STARS can also be used to see the top surface, under a coating – although to a very limited thickness normally no more than 6mm.

SLOFEC (Saturation Low Frequency Eddy Current) is more sensitive to small flaws and has a high detection capacity for small defects and local top and bottom-side corrosion can be detected in the early stages. The latest v6 builds on this with software that allows for clear corrosion mapping reporting.

This technology performs well through thicker plates up to 25mm and is proving to give more accurate inspection results through lined tanks. Non-conductive and non-magnetic coatings such as rubber and paint up to 10mm are also testable.

As the Eddy Current signal window has a wider spread, even the signals of surface debris (such as rust), inclusions and laminations can be distinguished from defects. As a result, SLOFEC inspections often requires less surface cleaning and preparation than the MFL Floormap.

SLOFEC, with its greater level of sensitivity, requires a high degree of operator skill and experience to translate the screen data and Viking have a dedicated SLOFEC team with many years of experience.

The design of the SLOFEC floor scanner also means testing closer to the welds and tank wall considerably reducing dead zone areas down to 20mm. Testing can be done under installations and heating pipes down to 130mm.

The picture shows the shell tracks to the tank wall. A SLOFEC inspection of a tank with a lined floor is therefore likely to detect more defects than a standard MFL inspection.

Because of the more complex nature of the inspection a SLOFEC inspection will cost slightly more per m2 to inspect than a standard MFL inspection – approx. 20% more.

However, that is often more than considerably offset by the savings of not having to remove the floor linings of the tanks and in some cases by reducing the need to blast clean – so for operators SLOFEC has to be factored into their overall tank planning.

If you have a tank that requires an out of service inspection or a tank floor scan, then we recommend talking to an accredited inspection company to discuss the options.

As Viking are the only licenced operator of SLOFEC in the UK, to discuss the benefits of using SLOFEC then you can contact our operations team on for more information, a no obligation site visit or demonstration of these two technologies.