Kline MFL Limitations

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    Magnetic Flux Leakage (MFL) Inspection Limitations

    API 2006 Storage Tank ConferencePresentation

    Morris KlineGeneral Manager of Domestic Sales

    HMT Inc.

    All Limitations

    • Technology

    • Human (Training and experience)

    • Physical

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    Let’s Talk about the Physical Limitations

    • Tank Bottom inspection preparation• Bottom Plate Lap Welds seams• Bottom Plate Shapes and Sizes (sketch plates)• Shell (corner weld) radius• Patch Pla tes• Tank Bottom Obstructions (columns / re-pads, internal

    piping, etc.)• Edge Settlement• Uneven Bottom Plates – peaks and valleys• Thick Reinforced Coating• Thick Annular Plates• “Edge effect” of Magnetic field extends the non-scanned

    areas• Magnet and Sensor location

    Typical Full Sized MFL Scanner

    Overall scanner width = 14”Bridge Width = 12”

    OverallLength = 36”

    Front to basesensor = 10”

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    Bottom Plate Lap Weld Seams

    Limitation Zone

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    Sketch Plate Example

    Another Sketch Plate Example

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    Typical Patch Plate

    Patch Plate near lap seam - hole

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    Typical Column with repad

    Floating Roof Leg Striker Pad

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    Tank Bottom Obstructions

    Potential Multiple Patch Plates

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    Manual/Mini Scanner for Near Corner Weld

    Solutions/Options

    • Following an informed “risk assessment” – what are yourbest options:

    – Do Nothing!!– Extensive Visual Exam (should already be standard)– Vacuum Box Testing (leak detection only)– ACFM Crack Detection / Magnet Particle Examination

    (surface breaking crack-like indications only)– Helium Testing (leak detection only)– Manual Ultrasonic Scrubs (corrosion locator)

    – Hand/ Mini MFL Scanner (corrosion locator)

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    Vacuum Box Testing

    ACFM Crack Detection Equipment

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    Helium Testing - Equipment

    Helium Testing – Weld Seam Scanning

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    In Summary

    • Be aware of Limitations• Make an informed risk assessment• Revise or develop a work scope for your inspection vendor

    that addresses either:– All tanksor– Specific to particular tanks based upon tank

    characteristics, risk analysis or tank condition