Advanced NDT
MFL tank floor scanning
Tank floors corrode from the soil side where nobody can see them, and a leak from the floor is the failure mode that drives most out-of-service tank inspections. Magnetic flux leakage floor scanning covers the floor plate area quickly and finds both product-side and soil-side corrosion, so the inspector can prove up the worst areas with ultrasonic thickness readings and calculate the next inspection interval with real data.
How MFL floor scanning works
A scanner carrying strong magnets saturates the floor plate as it is pushed across the floor. Where the plate is thinned, magnetic flux leaks out of the steel and sensors between the magnet poles record the signal. Indications above the reporting threshold are marked on the floor and then measured with ultrasonic thickness testing to establish remaining thickness, because MFL signals estimate rather than measure depth.
Areas the scanner cannot reach, such as the critical zone next to the shell, lap welds and around sumps and supports, are covered by hand-held scanners or UT so that coverage gaps are recorded rather than ignored.
Qualified procedures and examiners
API 653 requires tank bottom examination procedures and examiners to be qualified (Annex G), so the owner knows the probability of detection the floor scan achieves. The floor-scan report states the procedure, the qualification basis, the coverage achieved and the reporting threshold used.
What the tank needs before scanning
- Tank out of service, gas-free and certified for entry.
- Floor cleaned of sludge and loose scale; heavy coatings and deposits reduce sensitivity.
- Floor layout drawing for plate numbering and the inspection map.
How we deliver it
MFL tank floor scanning is carried out to a written procedure approved for the scope, naming the code and edition, the equipment and calibration, the coverage and the acceptance criteria. The procedure and each technician’s certification are submitted for the client’s review before mobilisation.
Work is planned and supervised by ASNT Level III personnel; our founder holds ASNT NDT Level III in UT, RT, MT, PT and VT. Reports state the coverage achieved and any limitations, so the engineer reading them knows what was examined and what was not, and any reportable finding is raised the same day.
Governing codes and standards
- API 653 (tank inspection, repair, alteration and reconstruction)
- API 653 Annex G (qualification of tank bottom examination procedures and examiners)
- API 575 (inspection practices for atmospheric and low-pressure tanks)
- EEMUA 159 (users’ guide to above-ground storage tanks)
What you receive
- Floor plate map showing all indications and coverage
- UT prove-up thickness of each reported area
- Remaining-thickness and corrosion-rate input for the next inspection interval
- Repair recommendations in API 653 terms
Industries served
- Refining and petrochemical tank farms
- Terminals and storage
- Power generation (fuel and water tanks)
- Chemical and fertiliser plants
Frequently asked questions
Does MFL measure the remaining floor thickness?
MFL estimates the depth of metal loss. Reported indications are proved up with ultrasonic thickness readings, which give the measured remaining thickness used in the API 653 calculation.
Talk to an inspection engineer
Send the equipment list or drawings, the inspection you need and your timing. Quotes are prepared for each scope and region.
Request a QuoteRequest an inspection quote (RFQ)
Tell us the asset, the method, where it is, the governing code, your dates, the size of the job and the report you need. We reply with questions or a quote. Affordable, accessible, fully customizable — no published pricing.
Or email the same details to info@atlantisndt.com. Mobilisation: North America; confirm your location in your RFQ.
Speak to an ASNT NDT Level III
Atlantis NDT provides ASNT Level III consulting, NDT training to ASNT SNT-TC-1A, inspection management software and independent report validation. Request a free consultation and we will return a tailored quote — affordable, accessible and fully customizable to your programme.