Tank Floor MFL scanning is a non-destructive examination method which uses a magnetic field to detect corrosion and pitting in carbon steel. A powerful magnet is scanned close to the surface to ‘saturate’ the steel with the magnetic field.
The magnetic field “leaks” from the steel where there is corrosion and this is detected by the scanner. Between the scanner bridge magnetic poles, a near-saturation magnetic flux is induced in the material examined. The scanner sensor detects flux leakage changes when the plate thickness changes. This may indicate the presence of discontinuities, such as pitting and corrosion, on the process and/or soil side. The scanner is moved over the entire tank bottom surface to provide the required inspection coverage. Technicians interpret the scanner display to identify damaged areas and in some cases, estimate the amount of metal loss. Thickness losses detected by ultrasound are reported and mapped in a CAD rendering of the floor.
KAOTHEEM PERFORMS MFL SCANS
- On storage tank bottoms for all industries: upstream, mid-stream, petrochemical, refineries
- To identify soil and product side metal losses, pitting and general corrosion
ADVANTAGES
- Fast method for inspecting large areas
- Minimal set-up time
- Yields reliable and economic qualitative tank floor assessments. High sensitivity: acceptable sensitivity can be obtained through up to 0.500” of combined steel and coating thickness
- Requires access to only one side of the material
LIMITATIONS
- Not a quantitative technique for identifying remaining wall thickness
- Requires ultrasonic follow up where indications of wall loss are found
- Cannot differentiate between soil side and product side indications
- Poor surface conditions (scale, debris, roughness, and certain coatings) may limit the integrity of the inspection
- Internal tank components close to the floor limit the access to particular areas
