engineering ndt advanced nde pressure equipment integrity management lab analysis development of ndt...
TRANSCRIPT
Engineering
NDT
AdvancedNDE Pressure
Equipment Integrity
Management
Lab Analysi
s
Development of NDT Inspection Development of NDT Inspection Techniques For Heavy Wall Stainless Techniques For Heavy Wall Stainless
Steel PipingSteel Piping
Presented by:
Larry Bartley - Canspec Group Inc. Plant Services Coordinator
Presented to
National Pressure Equipment ConferenceNational Pressure Equipment ConferenceFebruary 9 – 11, 2005
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Acknowledgements
• Brian BeresfordCanspec Group Inc.
• David MackintoshCanspec Group Inc.
• Wayne SmithOxy Vinyls, Canada
• Hang ZhengCanspec Group Inc.
• Gary Kroner Carbon Steel Inspection
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Overview
• Introduction• Detection method• Probe development• Test standard • Inspection of the test pipes• Analysis technique• Conclusions
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Introduction• Canspec developed a nondestructive
examination method for SA-312 TP 316L SS pipes:– NPS 3 in. diameter (0.121 in. wall thickness) and– NPS 6 in. diameter (0.146 in. wall thickness).
• Examine pipes while in operation• Pipes in horizontal position• Pipes had been used to carry liquid vinyl
chloride monomer (VCM) at 150 psig and approximately 17C since 1996.
• Pipes were known to have corrosion pits on the internal surface.
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Corrosion mechanism• Water condensates containing chlorides tended
to gather at the bottom of the pipe, causing pitting on the internal surface.
• Inside the pits, water and high concentrations of chloride ions collected.
• Corrosion rate inside pits increased, eventually caused a large cavity inside the pipe wall.
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Sample
NPS 3 in. diameter test piece
Engineering
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Equipment Integrity
Management
Lab Analysis
Choice of NDE Method• Factors in decision: material, size of pipes, type
of defects• Eddy current was considered to be the best
choice.• Eddy current has good sensitivity to corrosion
pits on the pipe internal surface while scanning from the outside.
• Eddy current allows a fast and efficient inspection of the pipes while the plant is in operation.
Engineering
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Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Probe Development• Probe consisted of a differential coil embedded
in a hand-held housing.• Two stainless steel bars maintained constant
clearance between the coils and the pipe surface and provided wear resistance
• Probe is hand-held for easy scanning along the pipe surface.
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Test Standard • A section of the test pipe (NPS 3 in.) was
longitudinally split in half and one half was made to be a test standard piece.
• Defects: four 3/64 in. (0.047 in.) diameter drilled
holes of depths 100%, 75%, 50% and 20% wall.• Natural corrosion pit about 0.05 in. diameter, 0.032
in. deep (26% wall loss)• Tests indicated good sensitivity to the shallowest
hole (20% wall loss).• The calibrated test system could detect and size
the natural pit.
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
View of Test Standard
Engineering
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Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Permeability variation• A simulated permeability variation was also added
to the test standard piece.• Objective: to set the system to differentiate
irrelevant indications due to permeability variations.
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Inspection Results —Flaws detected:
1) Through-wall pinhole
2) Inside diameter indication, 90% wall-loss pit.
3) Inside diameter indication, 20% wall-loss pit.
(All above defects located at the bottom of the pipe.)
Engineering
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Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Eddy Current Data from the 90% pit
Engineering
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Equipment Integrity
Management
Lab Analysis
Visual Verification
• Pipe was longitudinally split in half, and internal surface was cleaned by wire brush.
• Small diameter pits could be seen at locations predicted by eddy current examination.
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Results from the Pit Called at 90%
• Metallographic examination revealed a 1 mm diameter opening on the pipe internal surface.
• Inside the pipe wall, the pit broadened to an area of 3.5 × 5 mm.
• Wall loss was physically measured to be 90%.
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
View of the 90% pit from the internal surface
Engineering
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Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Scanning electron microscope (SEM) image of the cross section of the 90% pit.
Engineering
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Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Scanning electron microscope (SEM) image of the 90% pit.Scanning electron microscope (SEM) image of the 90% pit.
Engineering
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Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
• Diameter 0.04 in., depth 0.020 in. (17% wall loss).
• Results verified that the system met the required sensitivity to 25% wall loss.
Results from the Shallow Pit
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Advanced NDE Pressure
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Lab Analysis
Inspection of the Test Pipes (cont’d)
• The second indication was a 0.04 in. diameter, 0.020 in. deep pit which accounted for a 17% wall loss. More importantly, the system could detect a pit where the wall loss was as small as 17%, which met the required 25% wall loss criteria.
View of the 20% pit from the internal surface
Engineering
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Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Analysis Technique
• An inspection and analysis procedure was developed specifically for the pipes to be inspected.
• The procedure detailed the equipment required, the calibration standard, the operation parameters and procedure.
• Methods of identifying irrelevant indications were specifically addressed.
Data Analysis
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Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Analysis Technique (Cont’d)
• ASME standard
100%
60%
20%
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Equipment Integrity
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Lab Analysis
Analysis Technique (Cont’d)
• Permeability Mix
100%Standard Perm
Test Pipe
Engineering
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Management
Lab Analysis
Analysis Technique (Cont’d)
• Defect in test pipe 17% wall loss
Engineering
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Equipment Integrity
Management
Lab Analysis
Continued NDE• Inspection of another NPS 3 in.-diameter pipe in
the plant showed an indication different from pit-like indication.
• Subsequent metallographic examination of this area revealed longitudinally-oriented crack-like defects associated with corrosion.
• The defects were up 0.025 in. deep inside the pipe, which accounted for a 20% wall loss.
Engineering
NDT
Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Analysis Technique (cont’d)
Engineering
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Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Conclusions
Pitting was caused by chloride corrosion as a result of moisture in the liquid VCM in the pipe.
The wall loss measured from the cross section of the pit was 90%, which confirmed the eddy current inspection results.
The inspection system can detect pits larger than 20% wall loss, which meets the 25% wall loss criteria required by the customer.
Engineering
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Advanced NDE Pressure
Equipment Integrity
Management
Lab Analysis
Conclusions
The system can give a reasonably good estimation of the amount of wall loss and the size of a pit within its resolution ranges.
The system can also detect crack-like defects associated with corrosion.
The system has the ability to eliminate false indications caused by permeability variations.
Engineering
NDT
AdvancedNDE Pressure
Equipment Integrity
Management
Lab Analysi
s
Thank You
(www.canspec.com)