cobra scan inspection

Improved Ultrasonic Phased Array Inspection of Small Diameter Pipes

4th International CANDU In-service Inspection Workshop and NDT in Canada 2012 Conference, June 2012, Toronto

Andre Lamarre - OlympusNDT Canada

Presentation Outlines

• Small diameter pipes inspection issues

• Olympus solution description- the COBRA scanner

• Ultrasonic advantages

• ASME code conformities

• Case study

• Conclusions

Scope of the Presentation

• Developed a complete assembly to perform ultrasonic inspection of welds on small diameter pipes with the following characteristics:

– Phased-array inspection from both sides in one pass for fast inspection

– Scanner is manually driven but encoded for repeatability

– Scanner and the probes are designed to be low-profile to fit between tubes

Scope of the Presentation

• The OmniScan MX instrument provides ultrasonic settings and imaging

• Phased-array probes are geometrically focused to improve accuracy

• Applicable to a large range of pipe diameters

Phased Array Systems for Small Diameter

• Users demand for replacement of RT with UT for inspection of welded pipe for small diameter is getting more frequent

• The COBRA kit was specifically designed to meet the needs of ASME B31 Code Cases 179 and 181 (Or similar) and provide a complete solution for the replacement of radiography on small diameter girth welds

Introducing the New Phased-Array Instrument

• New phased-array instrumentation fully compatible with the OmniScan MX2

OmniScan MX2

Issues with Small Diameter Pipe Inspection

• High Volume – Typically large number of welds to inspect

• Many different configurations (diameter, thickness, etc)

• In-situ inspection

• Limited clearance

• Limited accessability (one side only)

• Welds on curved Pipes

• Specifications may or may not require transverse defect inspections

Issues with Manual and Automated Ultrasonics

• Manual ultrasonics

– Slow

– Operator dependent

– No auditable record

• Automated ultrasonics

– Scanners must be small enough to fit

– Beam defocuses in small diameter pipes

– Cost generally high

• Multi-elements probes are pretty large

• Wedges badly adapted to the small diameter pipes

Issues with the use of Ultrasonic Phased-Array

Issues with the use of Radiography• Radiation safety

• Licensing

• Environmental side effects from chemicals

• Film storage

• Poor planar defect detection

• Comparatively slow

• Subjective interpretation

• Production disruption:

– For small diameter pipes in particular

• usually many welds in close proximity.

• ASME Cases allowing Ultrasonics in lieu of radiography

Codes

Ultrasonic Inspection in-lieu of Radiography

?

?

• Becoming more frequently utilized

• Standards are being set to allow it

• Phased-Array inspection assures full coverage of the weld

• Ultrasonic imaging is significant and easy to understand

Complete Solution Components

• OmniScan MX 16:128

• MXU 2.0 software with multigroup option

• COBRA Scanner

• Low-profile focusing phased array probes

• Adapter wedge, which covers all pipe diameters

• Irrigation system

COBRA Scanner Features

• Holds 2 PA probes for complete weld coverage in one pass

• Pipe diameter range 0.84 in. to 4.5 in. OD.

• Requires only 0.5 in. clearance

• Spring-loaded system that can be installed on any material

• Can be configured for pipe-to-component inspection

Cobra Scanner – One Sided Inspection

• The Cobra scanner can be configured for two sided or one sided inspection

• Permitted by ASME code where two sided coverage is not practical.

• High probability of detection cracks

Opposite side (Far side)

detection of lack of fusion from one sided inspection.

• Inspection results consistently outperforms RT even with one side inspection limitation

COBRA Scanner – Requires Low Clearance

• The scanner is adaptable to diameters from .84inches – 4.5 inches (21-114mm)

• When configured with low profile probes the scanner has a clearance of ½ inch (12mm)

• Designed to be utilized in tight access applications

COBRA Phased Array System

• OmniScan is used to adjust the setting, to acquire the data and the perform the analysis

• MultiGroup options allows to use multiple phased-array probe during the same acquisition.

Omniscan MXU 16:128

Cobra Phased Array System

• New CCEV curved arrays for improved focusing, resolution and length sizing

• Low profile custom housing allows to maintain ½ inch (12mm) clearance

• 16 and 32 options available for specific needs and budgets

• Different frequencies: 2.25, 3.5, 5, 7.5 and 10 MHz

CCEV PA Probes

Radius Wedge kit for Different Diameters

• A kit of wedges is provided to cover a large range of diameter pipes

• A reference table helps to select the right wedge

• Flat wedges also included

• Irrigation holes

• Low-profile to work with a 0.5 in clearance

• Small footprint on the pipe

• Natural refracted angles: 60 SW

Longitudinal Wave Wedges Available

Note: the clearance using the LW-wedges is 25 mm

• Nominal angle: 60LW

• Compatible with the existing COBRA probes

• Same diameter curved wedges

Flat Array Beam Profile Curved Array Beam Profile

CCEV PA Probes – What is the Advantage

• The CCEV probes combine mechanical focusing in the passive plane with electronic focusing in the active (Phased array)

• The result is improved resolution and accuracy in length sizing

Flat Array

Measured notch length = 4.2mm

Curved Array


CCEV PA Probes – What is the Advantage?

Lenght sizing accuracy of the flaw is largely improved with the curved array

• 2.75 inch (70mm) diameter pipe inspection with 1mm through wall hole

• Data below visualizes detection of the outside end of 1mm through wall hole after 1 skip using -6dB drop sizing technique

Example 1

Flat Array


Curved Array


CCEV PA Probes – What is the Advantage?

Lenght sizing accuracy of the flaw is largely improved with the curved array

• 2.75 inch (70mm) diameter pipe with ASME B31.3 CC181 with OD notch of 6.9mm X .5mm and through wall hole.

• Data below visualizes detection and sizing of the notch using -6dB drop

Example 2


Coupling Requirements

• Coupling for the system is provided by water and manual pump sprayer– Standard ultrasonic gel is not recommended

and will result in degraded results

• Manual water pump comes in 4 or 8 liter capacity

• System required approx 10-100ml of water per weld (2 probes) depending on surface condition

• System comes with all required adapters, valves and tubing for two probe inspection

Conformity with the ASME code

• Recent edition of ASME, Article 4, Mandatory Appendix- V calls for PAUT and the requirements are mentioned as per this table

• We will see in the next slides that the COBRA kit meets all these requirements

Cobra Phased Array System

Due to the nature of the small diameter thin wall girth weld inspection, there

are far fewer considerations and decisions to make when engineering the

inspection strategy.

• Scan plans typically include two symmetrical sector scan groups that are exact mirrors with respect to the index position, range, gate, UT parameters, PA parameters, etc.

• The two phased array probes are positioned at skew 90 and skew 270 and are equal distance from the weld centerline.

• Where the entire volume of the weld cannot be inspected from one index position, a second acquisition from another position is required.

Scan Plan Design


• Add the Sectorial Beamset. Linear Beamsets are not compatible with the Cobra probes due to insufficient elements (16-32)

Scan Plan Design


• The Index Offset is the position of the probe relative to the weld centerline. Negative -15mm for probe pictured below (Skew 90), and positive for the opposite side probe (skew 270).

• The maximum spacing between the two probes is 55mm

• All parameters of the phased array sector scan are then manipulated to determine minimum and maximum required angles, beam deviation (resolution), etc.

Scan Plan Design


• Information you will need from the scan plan to populate the Omniscan Group Wizard

– Probe Model = 7.5CCEV35-A15

– Wedge Model = SA15N55S

– Index Offset Probe Position = -15mm (Skew 90) and +15mm (Skew 270)

– Sector Scan Aperture Elements = 16

– Min Angle = 45 degrees

– Max Angle = 75 degrees

– Beam Deviation = .5 (45, 45.5, 46, 46.5, etc)

Scan Plan Design – Essential Parameters

Inspection Setup

• The Omniscan MXU is capable of acquiring data for up to 8 groups simultaneously but is limited in how many can be displayed at one time during the inspection or on analysis of saved data files

• The A-S-[C] display is the primary inspection layout and is capable of displaying the A-scan, S-scan, and C-scans simultaneously for both probes (2 groups) during the inspection and analysis.

Configure Displays and Readings

OmniScan/COBRA Set up

• It is essential to have a complete understanding of how the Omniscan MXU Readings work and how they relate to the phased array sector scan displays and individual focal laws or A-scans.

• Phased array inspection techniques require analysis of many individual focal laws (A-scans) and groups of focal laws and the use of tools and views in the software to quickly and efficiently evaluate and record welds and weld flaws.

• Explanations of all relevant Readings with examples are available in the Omniscan Analysis section of this series.

Configure Displays and Readings

Set up – Calibrate Sensitivity and TCG

• For new construction codes such as ASME B31.3 Code Cases 179 and 181 (and similar) that reference ASME Sec V Art 4 for calibration requirements, every A-scan must meet the basic requirements for horizontal\vertical linearity, sensitivity\TCG, and Wedge Delay\TOF similarly to a single channel conventional flaw detector


• Data files acquired on the OmniScan MXU/COBRA Scanner system are available for analysis offline and reporting directly on the instrument

• The OmniScan MXU software was designed to provide all of the tools for analysis and reporting to comply with codes such as ASME CC179, ASME 181 and similar

• All data files are created on stored on the compact flash card to the User/Data directory

OmniScan MXU Analysis Overview


OmniScan MXU Analysis Overview

• Flaw analysis using the OmniScan MXU for the Cobra system consists of

– Amplitude of the Flaw relative to a calibration standard

– Length of the flaw

– Depth pf the flaw

– Height of the flaw

– Volumetric position of the flaw

– Characterization of the flaw (Slag, Crack, lack of Fusion, etc)

• Depending on the code, work procedure and weld bevel (thickness/diameter/bevel prep), some or all of the above may be required to determine weld acceptability

• ASME code case 179 and 181 are dependent on all of the above

Omniscan MXU Analysis

Flaw Amplitude

• To ensure the maximum amplitude of the flaw is displayed, the data curser must be manipulated on the scan axis and the angle changed while observing the A% reading

• The AdBr Reading will display the difference between the signal in gate A and the reference dB determined from the calibration when the set reference function is enabled


S(r-m)

Flaw Length Sizing

• Length sizing is performed on the C-scan display using the reference, measure and data cursers

• The relevant readings used for length sizing are S(r), S(m), and S(r-m) that were preconfigured in the OmniScan setup and passed to the data file

• In the OmniScan software, the scan axis is colored blue and represents the weld line. All readings based on the scan axis are indicated by S as above

• The scan axis (Blue) is only available in the C-scan and B-scan

• -6 dB drop, -3 dB drop, and rapid amplitude drop are all common UT techniques for determining the length of a flaw

• The ASME codes (And similar) do not specify a technique for length sizing and it should be referenced from the work procedure


DA

U(m-r)

• The height sizing can be completed using the color palette or by manipulating the data curser angle while watching the A% reading for an exact –X dB drop technique where appropriate for the flaw type

• The DA reading is the true depth reading that is corrected for skips based on the part thickness

• The data curser should be placed at the position of maximum amplitude (center of energy) to obtain the DA reading

Flaw Depth/Height Sizing


-3dB

-6dB

100%

• The height sizing can be completed using the color palette or by manipulating the data curser angle while watching the A% reading for an amplitude drop technique where appropriate

Flaw Depth\Height Sizing


+-+-

• The VIA reading is displayed as a negative (-) number or positive (+) number relative to the weld centerline. By default the OmniScan skew 90 probe side is negative

• The OmniScan MXU software displays skip lines as B0, T1, B2, etc. relative to the data for visualization of the volumetric position of the flaw

Volumetric Position


• Recording flaws and generating reports is completed by adding entries into the OmniScan flaw table.

• The report will include the eight readings that were configured in the OmniScan set up and described in the earlier slides

• The flaw table in the OmniScan MXU is activated in the Measurement-Table menu

• Entries are added to the table and include the image of the current display A-S-[C].

Flaw Reporting


Flaw Reporting

• The built-in report contains all of the instrument information, set up parameters, calibration parameters, and statistical information from the flaw

• The report can be printed directly from the OmniScan with a Windows CE compatible printer or saved on the flash card and viewed offline

Historical Archiving – Offline Analysis

• Data files are archived and available for computer analysis using computer based software or the Omniscan instrument.

Analysis of the Data

Porosity cluster

Lack-of-fusion

Toe Crack

• The weld profile overlay display greatly helps the results interpretation

Case Study

• ASME Standards for Thermal Power Plants

– Thermal Power Plants adopts ASME Section VIII, Division 1&2 guide lines for their construction needs for high pressure and high temperature circuits

– Structural integrity parts are subjected to one surface and one volumetric NDT methodology for welded construction

– Visual, liquid penetrant and magnetic particle testings are used for surface anomalies, radiography and ultrasonic testing are used for volumetric approaches

– Smaller dia, less wall thickness pipe weld joints (21.3mm to 114.3mm) are mostly used in water wall tubes, high pressure high temperature steam circuits in thermal power plants

Case Study – Objectives

• Present day NDT methodology utilizes radiography is the main method with a double wall double image technique to check the integrity of these weld joints.

• Semi automated PAUT is attempted to solve the weld inspection for the pipe ranges from pipes of 21.3 mm (0.84" OD) outside diameter to 114.3mm (4" OD) with wall thicknesses as per schedule 40, schedule 80 and schedule XS varieties as specified by pipe manufacturers.

Case Study – Methodology

• Natural weld defects were included in 3 pipes of 44.5 mm of diameter and 5 mm thickness with a single V configuration such as:

– (i) toe crack and lack of incomplete penetration in Pipe-1

– (ii) root crack and lack of side wall fusion in Pipe-2

– (iii) an individual porosity and cluster porosities were introduced in Pipe-3

• The three pipe samples were subjected to radiography and the results were analyzed

• The samples were also inspected utilizing the COBRA Phased Array system

Case Study – Essential Variables

• Scan Plan

• ESBeam tool was used to create the scan plan

• Sector scan from 50 to 70 SW with an angle step of 0.5˚

• Each wedge was located 12 mm from the center of the weld and thescanner was setted accordingly

• Full coverage of the weld is assured with some beam travelling 1.5 skip

Case Study – Results: Pipe 1

Toe Crack

Incomplete

prnetration

• The defects are

– Toe crack

– Incomplete penetration


• These defects are

– Root crack

– Lack of side wall fusion

Root crack

Lack of Side

wall fusion


• The defects are

– isolated porosity

– Cluster of porosities

Cluster

porositiesti

es

Customer comments

Customer has inspected around 25 000 boiler piping welds in coal-fired power stations (3 different sites) with the COBRA scanner kit.

When they first started using the Cobra, they were detecting stop/start lack of sidewall fusion which did not show up with radiography. (RT had been used in the power station for decades).The welders were quickly able to change their technique to avoid this lack of fusion.

Because PAUT can be done just after the welding, not on the next shift, there were only a few welds that needed to be repaired, not hundreds.

The customer had to increase the gain to detect wormholes and porosity that might cause leaks, but once they had the right setup, they could reliably detect better than RT. There has never been a hydraulic leak from a weld passed by PAUT. There have been leaks from welds in which RT did not detect wormholes.

Customer commented that they performed the analysis on the Omniscan. Doing most of the analysis on the Omniscan keeps their productivity rate up. They also do some reviewing on the Omni.

Case Study – Summary

• The COBRA kit meets the specifications of the ASME codes for the inspection of small diameter

• The embedded defects were succesfully found and the results were confirmed by RT

• The COBRA kit has all the tools to guide the user into any standards like ENIQ and others..

Additional Olympus Solution

• 2 phased-array probes combined with a pair of TOFS transducers

• Pipe diameter coverage from 1.5 in to 38 in

• Manual scanner with high-resolution encoder

• Compatible with OmniScan and Focus LT

Chain Scanner


Weld Rover

• Full automated

• Can drive up to 6 transducers

• Adjustable scanner speed form 0.2 to 2 in per second

• Laser guide for weld

• Lightv motion control device


• Compatible with OmniScan

• Detection of corrosion, érosion, pitting, etc.

• Detection of FBH 40 mils with 7.5 MHz probe

• 2 in long array probe for fast acquisition

• Encoder resolution of 40 x 40 mils on Cscan image mapping

• Ascans acquistion

• Use of water box improves couplant efficiency

Corrosion Mapping

Conclusion

• Olympus has developed a complete assembly to perform ultrasonic inspection of welds on small diameter pipes with the following characteristics:

– Phased-array inspection from both sides in one pass for the inspection to be fast

– The Scanner is manually diven but encoded for repeatability

– The scanner and the probes are designed to be low-profile to fit between tubes

– The OmniScan MX instrument provides ultrasonic settings and imaging

– Phased-array probes are geometrically focused to improve accuracy

– Applicable to a large range of pipe diameter

Thank You

cobra scan inspection

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