Advanced Ultrasonic Inspection

OlympusNdtNick Bublitz

What is Phased Array?Advanced Ultrasonic technique used for flaw detection, sizing, and imaging.Allows for electrical manipulation of probe characteristics by introducing time shifts to sent and received signalsUtilizes multi-element (array) probes for increased capabilities over conventional ultrasonics.

Industrial PA Medical PA

Advantages of Phased ArrayElectronic scanning (raster) possible without moving probe.Increased control of beam characteristics.Simultaneous inspection with multitude of angles using one probe.Can better inspect complex geometries or limited access areas.Can replace costly and hazardous radiography applications.

Phased Array

Phased Array Probe ConfigurationIt is like having many small conventional UT probes integrated inside a single probe.128 elements !

How Does Phased Array Work?Elements are pulsed in groups with precalculated time delays for each element (i.e., phasing).

Modern software allows an operator to input test parameters-Material, wave type, desired angles etc and all calculations are done by the software. Probe recognition and Wedge databases further simplify setup.

How Phased Arrays Work - Beam Steering

Electronic Scanning modesSectorial scan

Linear/ Electronic scan

35-70 degrees45 degree

CombinationsAdvanced software options (i.e.: Multi group) allow for many different combinations to be performed to increase detection, speed up inspections, or fulfill code requirements.

Sectorial ScanThe ability to scan a complete sector of volume without any probe movement.Useful for inspection of complex geometries, or geometries with space restrictions.Combines the advantages of a wide beam and/or multiple focused probes in a single phased array probe.

Sectorial ScanAllows for a swept range of anglesAllows for full volume inspection without probe movement.

Electronic/Linear ScanningAllows movement of beam along probe array without physical movement of probe by multiplexing.

Each beam will be at the same angle from its respective exit point.

This can mimic conventional UT rastering towards and away from a weld, but does it electronically, allowing for movement of the probe in only one direction (ex. Line scan down the length of the weld), simplifying automation and encoding.Also used to cover large areas more rapidly.

Linear Electronic ScanThe movement of the acoustic beam is along the axis of the array, without any mechanical movement.

The beam movement is performed by time multiplexing of the active elements. Arrays are multiplexed using the same focal law.

Conventional raster vs. 1 Line Linear

Large Area ScansVSPA 128 elementSingle crystal

Key ConceptPhased arrays do not change the physics of ultrasoundPAs are merely a method of generating and receiving a signal

ImagingAn important part of a phased array system is imaging. Usually imaging is created from the rawA-scan Amplitude or TOF data.

Imaging Linear Electronic ScanBy using the electronic scanning capability of the phased array technology, imaging becomes possible without mechanical movement.Arrays are multiplexed using the same focal law and the resulting A-scan of each beam is color-encoded and displayed in a linear S-scan.Beams12345678910111213Beams12345678910111213dd

Imaging Linear Electronic ScanA linear electronic scan can also be performed with a steering angle (15 in the image below).Linear Angle S-scan

Imaging Sectorial ScanUsing a small angle step value, the sectorial scan resolution is very precise.

Each beam goes back to a single conventional A-Scan

Imaging On Omniscan

Phased Array Instruments1000i Tomoscan Focus LT Omniscan Quickscan PA

Manual Applications

Manual Inspections

Root CrackRadiographyPhased Array technique

PorosityRadiographyPhased Array technique

Double V Images Tomoview

Semi-automated InspectionsAddition of scanners and encoders to record dataProvides digital data of weld inspections that is repeatable and auditable using the Omniscan or computer based software -TomoviewAllows advanced software features including weld overlays, sizing algorithms, custom displays, advanced measurement tools, etc.Low cost portable systems now allow NDT service companies and fabrication shops to offer advanced AUT solutions that are have historically been cost prohibitive and required an enormous amount of expertiseUse of phased array technology allows low cost magnetic one-line scanners to replace fully automated raster scanning motorized equipment by using S-scans and E-scans for coverage

Imaging with EncodersTop view of weld-CscanA scanSide view of weld-S scan

Small wheel encoders

Multi-Probe Capable Scanners

Fully AutomaticFully automated phased ArraysBenefits includeBest quality dataMost repeatable results

Driven by Focus LT or OmniScan

Pipe Wizard- Zonal Technique

What about Codes?ASMECase 2235 Use of Ultrasonic Examination in Lieu of RT for ASME Sec VIII Pressure Vessels Case 2600 Use of Linear PA S-scan per Art. 4 Sec VCase 2557 Use of Manual PA S-scan per Art. 4 Sec VCase 2599 Use of Linear PA E-scan per Art. 4 Sec VCase 2541 Use of Manual PA per Art. 4 Sec VCase 2558 Use of Manual PA E-scan per Art. 4 Sec VCase 181 Use of Alternative UT Examination Accept Criteria for ASME B31.3Case 179 Use UT in Lieu of RT for B31.1 Applications < inch in Thickness

Code\Procedure Compliance (continued)ASME Code Case 2235 allows for the use of UT (Phased Array) in lieu of RT if the inspection can be demonstrated on a representative calibration or manufactured defect specimen.The short version of this is that from one or more probe positions or scans, if the calibration targets of flaws can be detected and sized, the technique is allowed to be used in lieu of RT.

Courtesy of AIT

Other CodesAPI- Many API inspections possible including zone discrimination (1104) with the right equipmentAWS- was codified in 2006 (Manual) but requires engineers approval each case- encoded annex submitted- we are working with AWS now on other code workASTM- E-2491- published recommended practice for setting up PA

CalibrationsTo fulfill codes- must have full sensitivity/wedge delay/ TCG/DAC across all anglesMust be realistically accomplished-quick/easy (OmniScan Wizards)

Sensitivity Calibration ExampleBefore After

Code ComplianceWhen used by certified personnel, Olympus Phased Array Systems are cable of meeting the basic requirements of any code with respect to all the following parameters.

Vertical and Horizontal Linearity Time of Flight Calibration Sensitivity CalibrationACG (Angle Corrected Gain as defined by the ASME)TCG Calibration DAC CalibrationVelocity Calibration

Scan PlansIn order for advanced inspections to be successful setup must be quick and easy and documented

What is Tofd- TOFD Basics

Tofd is a wide beam longitudinal wave technique using TOF Information for sizing. It utilizes diffraction versus reflection

TOFD Basics ContinuedFLAWDiffractedwavesDiffractedwavesIncidentwaveReflectedwaveAll directions

Low energy

Independent of incidence angle

Why use TOFD in a Phased Array Inspection?Where weld bevel design does not allow a pulse echo A-scan to intersect the weld bevel at near perpendicular angles, the probability of detection and over all inspection quality is severely reduced on the fusion line. TOFD uses diffracted rather than reflected signals and is not dependent on flaw orientation.Setting up a TOFD channel on the Omniscan MXU takes less than 5 minutes and calibration is typically performed in analysis mode after the inspection.Of the 256 available focal laws (A-scans) in the Omniscan, the TOFD channel uses only one. Low overhead on the acquisition rate and file size.TOFD is an industry accepted technology that has been in use for decades.The ASME, AWS, and API codes have either specific rules for TOFD or alternative rules for computer based inspection techniques that allow flexibility in inspection strategy if a qualification is performed. TOFD is an excellent tool for fulfilling these requirements.For thick welds that are difficult to cover on one line scans, TOFD can provide a large coverage area reducing acquisitions and probe changes.For some codes such as ASME CC2235, the technology used for detection can be different than that of sizing. This is a great combination for PA and TOFD!TOFD - BIG VALUE - LOW COST - EASY!

In most instances, particularly on thin welds, TOFD is not necessary and the phased array is sufficient. However on thicker welds whether it is required or not, it is extremely useful for the following reasons:

Why use TOFD in a Phased Array Inspection?The 30 degree V weld can easily be inspected using standard PE techniques from the phased array without the use of TOFD. A 60 degree linear scan would intersect the weld bevel perpendicular providing a very high probability of detection throughout the entire weld volume when inspected from both sides.

For weld bevels that have a vertical plane, PE scan plans without the use of TOFD would have a low probability of detection on the vertical fusion lines.

Tofd and Phased Array

Phased Array Offline Analysis- TomoviewTomoview Full- Includes capability to acquire data through an Omniscan MXU or Focus LT and all analysis Features.Tomoview Analysis- Includes all analysis features without the ability to acquire data.Tomoview Weld LT- Limited version specifically designed for analysis of Omniscan data files with most common analysis tools and limited customization.Tomoview Viewer- Free version that can be provided to customers or inspectors for basic data file screening without advanced tools.

Phased Array Offline Analysis- TomoviewAn essential tool used in the offline analysis of phased array data files is the volumetric data merge. The C-scan below is the sum of all focal laws used in the scan plan. In this example over 200 focal laws on 6 linear scan channels from 2 probes. The ability to merge all focal laws into one C-scan allows all focal laws on all channels to be analyzed in seconds in one display.

Phased Array Offline Analysis- TomoviewFrom the Merged C-scan, individual flaws are analyzed on the relevant channels using B-scans, D-scans and S-scans. Additionally, every A-scan from every focal law is available on customized views designed for the particular application.The typical WeldROVER application would use 2 or 4 phased array channels from probes on both sides of the weld combined with 1 or 2 TOFD channels.

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