Magnetic Flux Leakage Inspection

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Advanced MFL inspection services for tank floors, pipelines, and large steel structures

Steel assets often corrode in ways that are not visible until significant damage has already occurred. Conventional inspection methods, such as manual thickness measurements, visual checks, and spot ultrasonic testing (UT), are effective for targeted evaluation. However, they struggle to provide the comprehensive coverage required by large steel structures within the time and access constraints of a planned outage.

MISTRAS deploys MFL inspection services across aboveground storage tank floors, pipelines, and large steel structures. These solutions provide rapid, high-coverage screening to identify integrity threats across the full asset surface. MISTRAS MFL services are backed by advanced scanning technology, real-time data analysis, and comprehensive reporting. They provide operators with a complete view of asset condition, enabling confident repair planning and precise maintenance prioritization. 

Core benefits of Magnetic Flux Leakage inspection

MFL applies powerful magnets to saturate steel with a magnetic field. Where the material is sound, flux flows uniformly through it. Where corrosion, pitting, or wall loss is present, the flux leaks out of the material. Sensors in the scanner detect this leakage, indicating the presence, position, and relative severity of defects.

MFL scanning covers large surface areas significantly faster than manual spot inspection. This makes full-floor and large-structure coverage achievable within standard outage windows. 

3D MFL technology identifies whether anomalies originate on the product side or the soil side of floor plates. This level of specificity is required for accurate repair planning. 

MFL scans through non-magnetic coatings up to 6mm, including FRP, GRP, and stainless steel, without requiring coating removal.

All inspection data is recorded above and below the repair threshold. Thresholds can be adjusted after scanning is complete. This allows repair plans to be revised as conditions change without additional scanning. 

Where MFL identifies anomalies requiring confirmation, UT can be deployed to verify defect sizing and strengthen data confidence before repair decisions are finalized.

High-accuracy positioning data enables comparison of inspection results across inspection cycles, supporting trend analysis and remaining life assessment.

MISTRAS MFL inspection services

Tank floor MFL inspection
Aboveground storage tank (AST) floors are among the most difficult assets to inspect comprehensively. Soil-side corrosion develops unseen beneath floor plates, while product-side pitting accumulates from above. The large surface area makes manual UT coverage impractical within a typical outage window.

MISTRAS uses high-resolution 3D MFL scanning to inspect AST floors, with top and bottom defect discrimination.  This identifies whether anomalies originate on the product side or the soil side of the floor plate. This distinction drives more accurate repair planning, as each mechanism requires a different remediation approach. Inspection is performed through coatings up to 6mm, including FRP, GRP, and stainless steel, across material thicknesses up to 0.500 inch. Scan performance is not impacted by pitting or soil-side corrosion. Where indications require further evaluation, UT qualification can confirm defect sizing before repair decisions are made.

Pipeline MFL inspection
For pipelines, MFL is deployed as part of inline inspection (ILI) programs and as an external scanning method for accessible above-ground sections. It provides corrosion screening and metal loss assessment across pipeline systems. MISTRAS MFL services integrate with our broader pipeline integrity program capabilities, including data analysis, GIS services, and risk-based assessment, to support a more complete view of pipeline condition.

General steel structure screening
MFL can be applied as a rapid screening tool across a range of ferromagnetic steel components and structures where large-area corrosion assessment is required. This enables targeted follow-up inspection and maintenance activities rather than blanket replacement or time-consuming manual survey.

Reporting and data

Quality reporting is an essential aspect of MFL Inspection. MISTRAS delivers comprehensive post-inspection reports that give operators the information they need to make documented, defensible repair decisions. Standard reporting outputs include accurate X and Y coordinates for all identified anomalies, colour-coded severity indicators, individual plate diagrams showing defect locations, patch plate sizing recommendations, integrated A-Scan and C-Scan displays, and full floor mapping drawings.

For tank floor inspections, clients receive a read-only version of the analysis software with the ability to adjust repair thresholds after inspection is complete. This allows operators to respond to changed circumstances without requiring a new scan.
Additional data from visual, ultrasonic, vacuum box, and magnetic particle inspections can be integrated into the MFL report, providing a consolidated record of tank condition from a single inspection event.

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