Silverwing is now part of Eddyfi Technologies
Tank Bottom Mapping

The Floormap tank bottom scanner combines two distinct technologies MFL and STARS.

These two technologies are used to detect and understand corrosion. The emergence of STARS (Surface topology air-gap reluctance sensors) enables the surface origin of corrosion to be determined even under thick coating.

How does MFL - Magnetic FLux Leakage work?

MFL is chiefly concerned with interpreting a leaking magnetic field.

The Floormap’s rare earth permanent magnets create a localised magnetic field that fills or “Saturates” the inspection surface.

Then, as the Floormap is driven over a region of corrosion, the magnetic field will leak from the inspection plate.

It is this leaking field that is detected by suitably placed sensors and ultimately, via signal processing, provides an estimated percentage loss (EPL)

A major contributing factor to the amount of leaking field is the amount or volume of material missing from the inspection plate. The larger the corrosion or indication, the greater the leaking field, and thus the greater the outputted MFL signal.

MFL is an excellent means for locating and sizing corrosion but a major limitation of MFL is that it cannot discriminate the surface origin of corrosion.

Imagine the scenario where you have an identical defect on the top surface and the bottom surface of an inspection plate. Let’s assume this defect has a 50% wall loss and is 5mm long.

When scanning both samples the difference is only 7% in the peak to peak measurement making it difficult to accurately and reliably determine which side the defect is on. This may not be a big problem when you can clearly see the tank surface or if there little corrosion, but if the tank bottom is coated which a high percentage are these days it can drastically increase the overall inspection and reporting time.

So the question remains, how do we reliably determine surface origin? The solution, STARS.

Floormap3Di-R - MFL Tank Inspection API 653

MFL signal comparison between top and bottom side defects.

How does STARS work?

STARS is an acronym for “Surface Topology Air-gap Reluctance Sensors”.

STARS developed and patented by Silverwing introduces another set of Hall Effect sensors situated below the rear pole piece. These sensors measure the rate of change of the magnetic field under the pole.

The rate of change is dependent on the field disturbance caused by changes to the surface.

Bottom side corrosion or indications have no effect on the STARS sensors as the magnetic field under the pole does not change.

Top side indications cause a disturbance in the magnetic field, this rate of change in the field is measured by STARS sensors.

STARS Bottom Side Corrosion

Bottom side defect has no effect on the magnetic field.

STARS Top Side Corrosion

Top side defect changes the magnetic field.

The result

By combining the two technologies the Floormap provides the operator with 6 software views which they can easily switch between during analysis.

All view are specifically designed to make the data analysis easier and more reliable. Visually, seeing an image of the top surface dramatically reduces errors as no signal interpretation is required.

STARS Bottom Side Corrosion

STARS high resolution view.

25thOct 2017
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29thNov 2017