Improvements in PA Inspection of LNG Tanks Presentation Objectives: - Overview of the equipment and hardware that make up an LNG phased array inspection system - Overview of the unique considerations for inspection of 9% Ni to I-625 dissimilar metal welds typical of LNG tank shell fabrication - Overview of API 620 and ASME V code requirements and references relative to LNG tank shell inspection - Overview of the LNG quad-probe phased array inspection strategy - Overview of personnel requirements and production expectations Learn more at: https://www.olympus-ims.com/en/phasedarray/

1. Advances in Phased Array Inspection
of API 620 LNG Tanks
0081_0122_000246

2. Improvements in PA Inspection of LNG Tanks
• Overview of the equipment and hardware that make up an LNG phased
array inspection system
• Overview of the unique considerations for inspection of 9% Ni to I-625
dissimilar metal welds typical of LNG tank shell fabrication
• Overview of API 620 and ASME V code requirements and references
relative to LNG tank shell inspection
• Overview of the LNG quad-probe phased array inspection strategy
• Overview of personnel requirements and production expectations
Objectives

3. Improvements in PA Inspection of LNG Tanks
• LNG tank requires low-temperature cryogenic storage conditions
• 9% Ni inner tank shell to remain ductile at low temperature. (−160 °C)
• Concrete outer shell and thermal insulation layer
• LNG tank shell wall thickness 7 mm (top rings) to 45 mm (bottom rings)
• Typical shell dimensions up to 12 m × 3 m with thickness variation of
approx. 3 mm for successive rings
• Large LNG tanks can exceed 5000 m (16,000 ft) of total linear welds
LNG Tank Construction Overview — Shell Sections

4. Improvements in PA Inspection of LNG Tanks
• LNG shell welds are made with high-alloy consumables, typically I-625
• I-625 welds have an anisotropic, coarse-grained structure that results in
the high attenuation of ultrasound typical of other austenitic welds
• I-625 requires highly skilled welders (more expensive, higher rejection
rate)
• I-625 welding is slower due to the size of passes and WP
LNG Tank Construction Overview — Weld Bevels
9% Ni I-625

5. Improvements in PA Inspection of LNG Tanks
• LNG shell welds include vertical, horizontal, and annular at tank bottom
• Vertical welds are symmetrical and often start out as a V weld, are back-
gouged on the outside, and rewelded to form an X-weld bevel
LNG Tank Construction Overview — Weld Bevels
Horizonal Girth Weld
Vertical Seam Weld

6. Improvements in PA Inspection of LNG Tanks
• The inspection system software includes an integrated module for creation
of the LNG tank shell weld bevels
• All weld bevels for the entire LNG tank are configured in the inspection
software before starting and are typically part of the new system training
• Weld bevels can be imported quickly and easily for the current production
LNG Tank Construction Overview — Weld Bevels

7. Improvements in PA Inspection of LNG Tanks
• Phased array instrumentation
• Phased array probes and wedges (LNG quad probe)
• Phased array acquisition and analysis software
• Mechanical encoded scanner (manual or mechanized)
• Water supply (probe coupling)
• Inspection personnel
Phased Array LNG System Overview

8. Improvements in PA Inspection of LNG Tanks
• Phased array instrument pulser configuration of 32:128 minimum
• 30 MBsec 12-bit digitizing capability
• AC power or battery operated for up to 5 hours of continuous scan time
• IP rating, industrial casing with bumper protection, no cooling fan inputs
Phased Array System Overview — Instrumentation

9. Improvements in PA Inspection of LNG Tanks
• >50 mmsecond acquisition speed
• Typical file size of an LNG shell weld is 1–3 GB
• Compact job site for fast setup time and mobilization
Phased Array System Overview — Instrumentation

10. Improvements in PA Inspection of LNG Tanks
• 4 MHz quad probe designed for austenitic (I-625) dissimilar welds
• Combines two shear-wave PA probes and two dual linear array PA probes
into a single connector; 6 probe housings, 4 S-scans, 128 total elements
• No splitter box required, significantly reducing the probe costs
• Optimized wedges with wear plates, water ports, and minimized echoes
• 5 m umbilical that includes the probe cables, encoder, and water supply
Phased Array System Overview — LNG Quad Probe Set

11. Improvements in PA Inspection of LNG Tanks
• DLA probes at 4 MHz optimized for the I-625 dissimilar metal weld
• Phased array equivalent of conventional UT TRL probes
• Combines the surface “creeper” inspection with volumetric RL
Phased Array System Overview — LNG Quad Probe Set

12. Improvements in PA Inspection of LNG Tanks
• LNG 9% Ni shells are ferrous and compatible with magnetic scanners
• Encoder mounted on scanner for encoding position in data
• Integrated water manifold for supply to all four probes
• Cable management accessories, offset scales, and push handles
Phased Array System Overview — Mechanical Encoded Scanner

13. Improvements in PA Inspection of LNG Tanks
Phased Array System Overview — Play Movie Demo

14. Improvements in PA Inspection of LNG Tanks
• API 620 and ASME V allow use of manual encoded push scanners;
however, some LNG fabricators insist on a fully mechanized AUT scanner
for acquisition
• Steerable in two axes
• Small, easy-to-use handheld LED controller
• More expensive than manual-push encoded scanner
Phased Array System Overview — Mechanized Encoded Scanner

15. Improvements in PA Inspection of LNG Tanks
• Water is required to couple the ultrasound from the wedges to the shells
• On most LNG job sites, water flow from the PA is not an issue
• Most crews prewet the welds before and during the inspection with a
manual pump (bug sprayer) water supply using <1 liter per 12 m weld
• Scanner and probes are compatible with an electric water pump
• Water supply tank or hose somewhere near the job site required
Phased Array System Overview — Water Supply

16. Improvements in PA Inspection of LNG Tanks
• DLA 30–89 degree S-scan
• DLA uses a pitch-catch technique with an acoustically insulated receiver
• Only refracted longitudinal beams can penetrate the I-625 weld
• Typical flaws are incomplete penetration in weld root, lack of fusion in
weld volume, and centerline vertical cracking
• Shear-wave beams cannot penetrate the weld, and successful qualification
of LNG shell welds without use of conventional or PA refracted longitudinal
(RL) is not possible
PA Setup and Configuration — DLA (Dual Linear Array)

17. Improvements in PA Inspection of LNG Tanks
• Expert use of DLA includes understanding
mode converted beam dynamics related to
conventional UT TRL techniques:
– Direct L-wave
– RTT (round trip tandem)
– Primary and secondary surface creeping wave
– TLL and 30-70-70
• Phased array DLA or dual matrix array
(DMA) probes combine all these techniques
into a single S-scan beam set
PA Setup and Configuration — DLA (Dual Linear Array)
1
4
3

18. Improvements in PA Inspection of LNG Tanks
• In this example, embedded lack of fusion is detected, and the length is
sized from the 270° skew of the DLA probe, using RTT detection.
• Inspection below is at reference sensitivity IAW API 620 (3 mm SDH)
• Flaw length is sized on the C-scan or B-scan
PA Setup and Configuration — DLA (Dual Linear Array)
4
S-scan
C-scan
A-scan

19. Improvements in PA Inspection of LNG Tanks
• Reference gain is increased 6 dB and the direct L is visible in the weld
• A precision depth and height measurement is made for the API 620
acceptance decision and excavation for repair
PA Setup and Configuration — DLA (Dual Linear Array)
4
1

20. Improvements in PA Inspection of LNG Tanks
• In the fusion flaw example below, an upper and lower tip diffracted signal
is visible for a precision depth and height measurement
• The flaw is at a depth of 10 mm to 13 mm for a through-wall dimension of
3 mm for the acceptance decision
• Direct correlation between size of weld pass and maximum size of flaw
PA Setup and Configuration — DLA (Dual Linear Array)
3.0mm

21. Improvements in PA Inspection of LNG Tanks
• Is the flaw surface connected? No, flaw is subsurface
• What is the length of the flaw? 12 mm using −3 dB drop sizing method
• What is the height of the flaw? 3 mm using tip diffraction sizing method
• Flaw is rejectable: 3 mm subsurface flaw can be up to 8 mm long
PA Analysis — API 620 Acceptance Criteria

22. Improvements in PA Inspection of LNG Tanks
• Production example of a good weld with no rejectable flaws or relevant
detections above amplitude threshold requiring evaluation
PA Analysis — API 620 Acceptance Criteria

23. Improvements in PA Inspection of LNG Tanks
• Shear-wave P/E phased array probes are used for detection and sizing of
the bevel’s fusion flaws and HAZ flaws
• In qualification and production, failure to supplement the DLA S-scans
with shear-wave P/E S-scans results in a higher rejection rate because of
oversizing of bevel defects related to the orientation of the RL beam
PA Setup and Configuration — Shear-Wave P/E PA Probes

24. Improvements in PA Inspection of LNG Tanks
• The 9% Ni material at 4 MHz is unique from carbon steel in that the weld
bevel interface for the dissimilar material is clearly visible in the data
PA Setup and Configuration — Shear-Wave P/E PA Probes

25. Improvements in PA Inspection of LNG Tanks
• Scan reference sensitivity is set on static or dynamic weld sample plates
with a 3 mm SDH referenced from API
• System calibration at shift start or on bevel change takes approx. 15
minutes
• Entire thickness range of LNG tank uses same 3 mm SDH sensitivity
PA Setup and Configuration — Scan Sensitivity Calibration

26. Improvements in PA Inspection of LNG Tanks
• TCG table files for both the shear-wave P/E and DLA probes are created in
advance and imported to expedite daily setup and bevel change time
• Sensitivity check on weld plates of production thickness is done at the
start of each shift or on bevel change
PA Setup and Configuration — Sensitivity Calibration

27. Improvements in PA Inspection of LNG Tanks
• Improved software for more efficient workflow with emphasis on
modularity for fast setup and simplicity for production
• Setup, calibration, acquisition, analysis, and workflow optimization
through the use of module files (weld bevels, probewedge configurations,
scan plans, TCG tables, and LNG inspection display layouts)
PA Setup and Configuration — Acquisition Software

28. Improvements in PA Inspection of LNG Tanks
• Two-man inspection crew can keep pace with the production of 8–10
welders working the same shift
• In some cases, 3 days of inspection for 5 days of welding
• The weld quality and rejection rate are factor #1 in production
• Manual probe-in-hand prove-up for height sizing is eliminated
• PA certified inspectors require 1–2 days training on the unique aspects of
LNG quad probe usage to include DLA training
PA Setup and Configuration — Personnel and Production

29. Improvements in PA Inspection of LNG Tanks
• All weld bevels, inspection scan plans, configuration files, pre-engineered
TCG tables, etc. are created in advance
• Inspectors’ day-to-day business is to load weld bevel, load configuration
file, position probe offsets in scanner, check calibration, and acquire data
• Analysis performed in real time during acquisition, and flaws are marked
and graded when detected; data review and reporting are done offline
• Level III data review and support can be done remotely via the cloud
PA Setup and Configuration — Personnel and Production

30. Improvements in PA Inspection of LNG Tanks
• Availability of off-the-shelf LNG inspection solutions for compliance with
API 620 enables more inspection companies and fabricators to bid with
confidence on these projects
• Improved equipment, software, and procedures enable faster operator
training, confident qualifications, and improved production
• Strong financial incentive to replace RT and AUT zone systems
Conclusions

31. Questions? Thank You!
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