IN-LINE INSPECTION OF 42”
GAS PIPELINE USING AN
ADVANCED TOOL COMBINING
THREE TECHNIQUES –
3TM
Speaker: Dr. Michael Haas
Date: June 2014
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3TM PRINCIPLE: EMAT + COMPLEMENTARY SENSORS
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With the EMAT sensor we measure the local remaining wall thickness in
gas pipelines the same way classical UT ILI tools do in liquid pipelines! Depth
sizing accuracy is ± 0.5mm, compared to ± 10% for MFL!
DISTINGUISHING EXTERNAL AND INTERNAL DEFECTS BY USING EMAT, EC, MFL.
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External Internal
3TM: MEASURING THE LOCAL WALL THICKNESS
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Seamless pipe with varying local wall thickness
MFL: 40% depth
Nominal wall thickness used by MFL: 20mm -> remaining wall thickness 12mm
Local wall thickness 22mm -> remaining wall thickness 13.2mm
Local wall thickness 18mm -> remaining wall thickness 10.8mm
Nominal WT local WT
With the EMAT sensor we measure the local remaining wall thickness in
gas pipelines the same way classical UT ILI tools do in liquid pipelines! Depth
sizing accuracy is ± 0.5mm, compared to ± 10% for MFL!
IN-LINE INSPECTION OF 42’’ GAS PIPELINE
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Inspection Targets & Summary of 3TM ILI Findings
Inspection necessary to identify significant laminations and inclusions,
and internal and external corrosion in the pipeline. Coating: Coal Tar
Enamel, cathodic protection used.
3TM ILI findings:
External and internal corrosion, laminations, inclusions and dents were
found on the line
•25 laminations and 35 inclusions
•Laminations and inclusions are parallel to the wall
•Depth of external corrosion ranges from 8% to 17%
•Depth of internal corrosion ranges from 8% to 16%
•17 dents were found
3TM ILI FINDINGS
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External and internal corrosion
EMAT C-Scan
EC C-Scan
EMAT B-Scan
EC C-Scan
MFL C-Scan
MFL & EC Profile
Deepest internal corrosion, depth 2.0 mm
Deepest external corrosion, depth 2.1mm
0.3m
0.15m
3TM ILI FINDINGS
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Laminations and a dent
Laminations running parallel to the surface
EMAT C-Scan
EMAT B-Scan
EMAT C-Scan
EC C-Scan
Dent next to a girth weld
0.2m
1m
VERIFICATION OF 3TM ILI FINDINGS
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Feature Type Field Depth (mm) 3TM Depth (mm) Field Length (mm) 3TM Length (mm)
external metal
loss 1.7 2.1 15 10
internal metal loss 1.4 2.0 80 69
Field Width (mm) 3TM Width (mm)
lamination 25 17 80 69
laminations
& inclusions 150 120 460 420
intermittent
laminar inclusions 160 n.a. 650 n.a.
laminar inclusions 170/ 159 830 722
intermittent
lamination 115 101 365 346
intermittent
lamination 100 101 300 275
laminations &
inclusion 155 142 880 848
lamination 17 20 55 60
laminations &
inclusion 65 59 360 352
lamination 25 17 80 69
SUMMARY OF IN-LINE INSPECTION OF 42” GAS PIPELINE
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•The pipeline had laminations which needed to be confirmed for any
growth.
•UT-ILI is the only technique that can be used.
•However traditional UT-ILI requires water batch and pipeline
shutdown, which was not possible.
•3TM tool found to be the most suitable option.
•The verification using phased-array proved that the 3TM tool detected
the anomalies including laminations as per specification.
•This inspection activity was successful not only for the use of newly
developed inspection technique but also for the operation of pipeline.
PULL TEST RESULTS
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River Bottom Profile 3TM EMAT vs. Laser
Data: Box ID:229
Length [mm] 1116
Width [mm] 1021
Depth [mm] 1.5 +/- 0.5
RWT [mm] 8.0 +/- 0.5
RSTRENG (effective area)
Failure
pressure
[kPa]
RPR
(Eff.Area,
1.25MAOP)
eff. depth
[mm]
eff. length
[mm]
start eff.
length
[mm]
8510 1.056 0.95 475 275
B31G
Failure
pressure
[kPa]
RPR
(B31G,
1.25MAOP)
7470 0.927
mod. B31G
Failure
pressure
[kPa]
RPR
(mod.B31G,
1.25MAOP)
8210 1.018
Failure pressure calculation: Grade X65 (SMYS 448 MPa); MAOP = 6450 kPa; WT = 9.5 mm
PULL TEST RESULTS
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Integrity Assessment 3TM EMAT vs. Laser Scan
Mean relative difference is 3.1% only!
Failure Pressure 3TM always ≤ Failure Pressure Laser Scan
FURTHER VERIFIED 3TM ILI FINDINGS
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External corrosion: maximum depth from 3TM: 2.6mm, field verification: 2.5mm;
local WT: 14.3mm
0.5m
UNITY PLOT: COMPARING 3TM DEPTH MEASUREMENTS WITH LASER SCANS AND FIELD VERIFICATIONS
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19 out of 22 3TM depth measurements are within ± 0.5 mm of the verification
depths, i.e. within specs. According to API 1163 this corresponds to a confidence of
more than 90%.