magnetic flux leakage mfl inspection limitations
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Trabalho técnicoTRANSCRIPT
Magnetic Flux Leakage (MFL) Inspection Limitations
API 2009 Storage Tank Conference
Presentation
Aaron Lund
Regional Sales Manager of Gulf Coast
HMT Inc.
Don’t Discard the Technology and go backwards
MFL is the “Best”
method to
evaluate a
tank bottom
condition
quickly and
cost effectively
All Limitations
• Technology
• Human (Training and experience)
• Physical
Information on Technology Limitations
• A lot of information has been available and presented on in regards to technology limitations. However, the information is not common to all brands and types of scanners, so it is not without some controversy.
• API has been trying to quantify these technology limitations through a task group performing the re-write of non-mandatory Appendix G in API Standard 653 which call for operator qualification testing and certification. This effort is on-going but still has not happened thus far.
• This presentation will identify most of the physical limitations and offer some solutions to overcome those physical limitations
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 Plates
• Tank Bottom Obstructions (columns / re-pads, internal piping, etc.)
• Edge Settlement
• Uneven Bottom Plates – peaks and valleys
• Thick Reinforced Coating
• Thick Annular Plates
• Magnet and Sensor location
Bottom Plate Lap Weld Seams
Typical Full Sized MFL Scanner
Overall scanner width = 14”
Bridge Width = 12”
Overall
Length = 36”
Front to base
sensor = 10”
Limitation Zone
Corner Weld – No Scan Zone
Sketch Plate Example
Typical Patch Plate
Typical Column with repad
Floating Roof Leg Striker Pad
Tank Bottom Obstructions
Solutions/Options
• Following an informed “risk assessment” on limitations– what are your best options:
– Do Nothing!!
– Extensive Visual Exam (should already be standard in any scope of work)
– Vacuum Box Testing (leak detection only)
– Helium Testing (leak detection only)
– Manual Ultrasonic Scrubs (corrosion locator)
– Hand/ Mini MFL Scanner (corrosion locator)
– ACFM Crack Detection / Magnet Particle Examination (surface breaking crack-like indications on welds only)
Patch Plate near lap seam – hole/extensive visual exam
Vacuum Box Testing
Helium Testing - Equipment
Helium Testing – Weld Seam Scanning
Manual/Mini Scanner Solution
Hand scanner width = 6”
Overall Scanner
length = 9 ½’
Scanner width = 6”
Front to back of
sensor bar = 6”
Manual/Mini Scanner for Near Corner Weld
ACFM Crack Detection Equipment
HISTORY
• This Technology was introduced in 1991.
• The method was initially developed for offshore structures
• Since then it has been applied to:
– Theme Park Rides
– Bridges
– Ships
– Petrochemical/Refinery Equipment
– Tanks
APPLICATIONS
• Weld inspection
• Detection of Crack-like indications
• Depth Sizing
• Monitoring Dimensional Propagation
SURFACE PREPARATION
• With the Magnetic Particle (MT) and Dye Penetrant Testing (PT) Methods, the quality of the surface preparation is critical to the ability of the method to detect discontinuities.
• This level of preparation is not required for electromagnetic techniques as the method of detection is not based on the migration of inspection media to the site of discontinuities.
SURFACE PREPARATION-Cont’d
• Reduced surface preparation does not imply no preparation
• The presence of ferromagnetic scale will impair the ability of the method to identify discontinuities
• However, the presence of surface rust will not significantly impair the sensitivity of the test
• Coatings-less than .200 does not need to be removed
ADVANTAGES
• No set up Calibration required
• Single direction deployment unlike MT
• Inspection time is reduced
• Data can be recorded for later comparison, review, or audit
CONCLUSION
ACFM has proven effective for:
• Coated Components
• Internal/External Shell-to-Bottom Welds
• Internal Lap Welds
• Sump Welds
• After tank bottom replacement
• When Stress Corrosion Cracking is suspected
This techniques provides consistent results - at a lower cost
In Summary
• Be aware of real world Limitations that exist everyday
• Make an informed risk assessment
• Revise or develop a work scope for your inspection vendor that addresses either:
– All tanks
or
– Specific to particular tanks based upon tank characteristics, risk analysis or tank condition
– Be informed of the technology/tools that can help
QUESTIONS?