Introduction to Phased Array Using the OmniScan MX2 - Part One

OmniScan MX2 Training Program Introduction to Phased Array Using the OmniScan MX2

Part 1

Please send questions and comments to: [email protected]

Introduction to Phased Array Using the OmniScan MX2 Part 1 - Overview Ø  Supporting documentation for the training program comes primarily from the MX2

software manuals and the Olympus reference manuals below. Ø  Modern phased array systems like the MX2 do not require an advanced knowledge

of mathematics or acoustic theory and the training program focuses on practical explanations and real world application examples for the working inspector.

Ø  Supporting theory, mathematical formulas, and more advanced PA concepts can be found in the books below available from the ONDT web site.

Ø  These manuals can be downloaded at http://www.olympus-ims.com

3

Introduction to Phased Array Using the OmniScan MX2 Part 1 - Overview

Ø  Phased array calculators differ in functionality and complexity as a result of supporting different types of probes, wedges, and applications.

Ø  The most simple or complex phased array calculators can generally be divided into 4 specific sets of parameters: §  Probe parameters. §  Wedge parameters. §  Material parameters. (Velocity) §  Focal law beam formation.

Ø  3 parts hardware and 1 part software to generate the focal laws. Ø  For proper formation of the focal laws, all hardware parameters must be configured

correctly, and the beam formation requested must be within the limits of physics, the hardware, and the instrumentation.

4

Introduction to Phased Array Using the OmniScan MX2 Part 1 - Probes

Ø  1D Linear array probes are the most widely used for industrial inspection and the only type that is supported directly in the OmniScan MX2 software wizards.

Ø  Phased array probes other than 1D linear must use focal laws generated from an external calculator for import into MX2.

5


Ø  1D linear array probes are defined by the following parameters. §  Size or “Pitch” of the elements. (.25-2mm) §  Number of elements. (8, 16, 32, 64, 128, 256) §  Frequency. (1-17 MHz) §  Radius focused or flat. §  Reference point. (Only required for use without wedge and does not affect PA

calculator)

6

OmniScan MX2 Training - Group Setup Wizard - Probe Selection

Ø  The MX2 will read the following information from the chip in the connector of Olympus probes when the probe auto detect is on: §  Probe Model. §  Probe Frequency. §  Probe Element Quantity. §  Probe Element Pitch. §  Reference Point. §  Serial Number (Not displayed).

Ø  With auto detect off, custom and probes from manufacturers other than Olympus can be entered and saved in the MX2 database.

7


Ø  Complex probes and wedges such as 2D or TRL type arrays or complex techniques such as pitch-catch require more input parameters and must be generated with a computer based phased array calculator and imported into the OmniScan MX2 on the memory card.

8


Ø  The dimensional parameters of a 1D linear phased array probe are defined as follows:

A = Aperture. Total length of all elements in active plane. (Pitch X element count)

H = Element height in the passive plane. Also called element elevation. P = Pitch. Center to center distance between two adjacent elements. E = Size. The width of an individual element. G = Gap. The spacing between two adjacent elements.

9


Ø  Olympus probes are sold with common housings to minimize the amount of wedges and accessories.

Ø  Below is pictured a standard 5L64-A2 probe that uses the same housing as the 2.25L64-A2. All A2 probes are compatible with A2 wedges and are listed in the OmniScan MX2 database independently to account for different pitch and position.

10


Ø  Universal probes such as A10, A11, A12, And A14 are designed for hand scanning or automated inspections for a wide range of applications including weld inspection and corrosion monitoring.

Ø  Pitch and frequency makes these probes ideal for thicknesses in carbon steel up to 100mm* for new construction and in-service inspection.

Ø  Specific scanner adapters for automated inspections and low profile wedges to reduce the need for diameter contouring and improve stability.

*Depending on acquisition module i.e. 32:128

11

OmniScan MX2 Training –– Pipeline Weld Probes for use with MX2

Ø  Pipe Wizard probes such as the PWZ series are the workhorse of the Olympus pipeline phased array systems.

Ø  Typical applications include high speed precision inspection using zone discrimination and amplitude techniques on pipeline girth welds.

Ø  Suitable for manual and automated inspections.

Ø  Specialized wedges used with the PWZ include carbide wear pins and sophisticated irrigation channels.

Ø  Internal radius focusing for improved length sizing of pipeline flaws. (Sharp C-scan and B-scan)

Ø  Short cable and front cable exit available for scanner accommodation.

5L32-PWZ3 probe used for piping inspection.

12


Ø  Deep penetration probes such as the A3, A4, and A5 are designed for heavy wall inspections and coarse grain materials.

Ø  Typical applications include the inspection of large plates, castings, and forgings where maximum penetration and power is needed.

Ø  Large element pitch and elevation with low frequency options make the deep penetration probes ideal for stainless steel and course grain material inspection over long sound paths.

13


Ø  Probes for the Olympus Cobra scanner and other tight clearance scanners are optimized for the small piping diameter inspection.

Ø  The Olympus CCEV probes have an internal radius of 35mm and are suitable for thickness range of approximately 4-25mm.

Ø  Have a low profile element design and when used with the Olympus Cobra scanner system need only 12mm pipe to pipe clearance.

Ø  Are available in a range of frequencies for carbon steel and austenitic material inspection.

14


Ø  Olympus immersion probes are designed to be used with a water wedge or in an immersion tank.

Ø  Typical application include thin plate or tubing inspection, composite inspection, inline thickness testing, and any immersion application.

Ø  They are longitudinal wave probes that can be set up for refracted angle shear wave inspections using a wedge or water.

Ø  Acoustic impedance matches water. Ø  Linear scanning allow coverage of

30-90mm in one line. Ø  Corrosion resistant steel casing and

waterproof up to 1meter under water.

15


Ø  Designed to be used with the OmniScan MX2, Olympus offers 4 different housing types with compatible wedges for shear and longitudinal wave inspection of stainless and carbon steel power piping.

Ø  1.5 - 5 MHz Frequency and a range of pitch and apertures for manual crack detection and sizing.

Ø  Small footprint wedges and ergonomic probe casings for hand scanning and access in small spaces and on small diameters for precision measurement.

SS304 2mm SDH depth of 38mm SS304 2mm SDH depth of 6mm SS304 ID notch - 68mm X 33 inch diameter.

16

Ø  Typical applications include inspection of carbon fiber reinforced polymers (CFRP) corners for composite delamination.

Ø  Acoustic impedance of water. Ø  Corrosive resistant stainless steel casings

waterproof up to 1 meter. Ø  Full line of adjustable immersion wedges.


17

Introduction to Phased Array Using the OmniScan MX2 Part 1 - Wedges

Ø  Phased array wedges perform the same function as conventional UT wedges by coupling sound energy from the probe to the material at the desired refracted angle and wave type.

Ø  Phased array wedges come in all shapes and sizes for various applications and are an essential part of the inspection process.

Ø  Phased array wedges are used to assist the probe in beam formation for shear wave and longitudinal wave inspections, just like UT.

Ø  1D probe wedges typically used in OmniScan MX2 applications come in 3 varieties: §  Shear wave angle beam. §  Longitudinal wave angle beam. §  Longitudinal wave straight beam.

18


Ø  Some housing types can accommodate probe models of different pitch size and frequency, and may not be symmetrical in the housing.

Ø  Wedges compatible with these types of probes contain separate probe position options with separate attachment points including reversing the probe.

Ø  Care should be taken to ensure the correct probe, wedge, and wedge position are selected from the wedge database.

5L64 Position 2.25L64

Position

A2 Housing

19


Ø  Included in the wedge label after the housing family (SA10, SA12, etc.) is the nominal refracted angle (N60S) in steel with no beam steering.

Ø  To achieve a shear wave refracted angle of 60 degrees (N60S) in steel the wedge is cut with an incident angle of 39 degrees in Rexolite. (Snell’s law)

Ø  N55 and N60 are common wedge designs because this angle allows good beam steering from approximately 30-70 degrees for most probes\wedge combinations.

39 degrees in Rexolite

60 degrees in carbon steel

20


Ø  A zero degree wedge is designed for both straight beam and angle beam longitudinal wave inspection as is typically used in corrosion mapping or composite lamination type inspections.

Ø  This type of wedge acts as a stand off delay and provides improved near surface resolution compared to using a probe with no wedge.

Ø  The 0L wedge also protects the probe as scanning with no wedge exposes the probe membrane to wear and damage.

21


Ø  Wedge coupling is essential for a good inspection and where the wedge is too large to properly mate against the material, sound is impeded and the wedge must be contoured.

Ø  The 3 most common types of wedge curvature for optimization of a particular component, pipe or vessel inspection are:

1.  Flat 2.  AOD## (Axial Outside Diameter Curvature + Diameter) 3.  COD## (Circumferential Outside Curvature + Diameter)

22


Ø  Inspection in the circumferential axis or “Long seam” type inspection requires a COD wedge and special hardware and software considerations.

Ø  COD wedges are calibrated at the factory for precise incident angle to be used in the focal law calculator. Each wedge is treated independently for precision.

Ø  The COD inspection for the OmniScan MX2 requires that the focal laws be built externally with a computer based calculator like Tomoview and imported into the OmniScan MX2 for use.

23


Ø  The Hydroform corrosion mapper is a form of a specialized phased array probe and wedge using water as the coupling medium.

Ø  It uses a stable water column with an adjustable probe height to transmit sound into the component for corrosion inspection and C-scan generation.

Ø  The Hydroform wedge parameters for the phased array calculator are selected directly from the database in the MX2 software and use the velocity of water.

Ø  The benefits of using water as the wedge include improved component coupling and improved near surface defect resolution.

24


Ø  In this example the phased array wedge was manufactured to the same taper as the component for a perfect fit.

Ø  Custom wedges than cannot easily be defined by the phased array calculator have inherent limitations. The ability to calibrate wedge delay and sensitivity requires a custom calibration block and precision beam steering and focusing is reduced.

Ø  The inspection below is for cracks using an amplitude C-scan and metal loss using a position C-scan.

Introduction to Phased Array Using the OmniScan MX2 Part 1 - Wedges Ø  A 20mm 0 degree Rexolite wedge is a common design and will put the wedge

interface echo at 50mm of the component when using carbon steel velocity (5980m\sec).

Ø  The primary offset (-56mm) represents the position of probe element #1 in relation to the front face of the wedge in the primary axis.

Ø  The wedge is selected from the data base that includes standard Olympus wedges and ability to create custom entries.

26


Ø  The following parameters are required for the OmniScan MX2 wedge database and phased array calculator: –  Wedge model. –  Wedge angle. –  Wedge orientation. (Normal

or reverse) –  Height of element #1 of the

probe (h1). –  Wedge material velocity. –  Primary and secondary

offsets (x,y).

27


Ø  Every wedge from Olympus is delivered with a wedge specification data sheet that contains all of the parameter values to populate the OmniScan MX2 database or external focal law calculator. These values are relative to the probe and its orientation on the wedge. For that reason one wedge may be listed many times in the database.

28

Introduction to Phased Array Using the OmniScan MX2 Part 1 - Velocity

Ø  The only component material parameter that is required for the phased array calculator is the velocity of sound for shear wave and\or longitudinal wave transmission.

Ø  The OmniScan MX2 software contains a database with common material types and their velocities.

Ø  The material type and shear\longitudinal are normally selected during the wizard group creation as part of the setup process.

Ø  Custom velocities can be entered manually as needed in the UT settings sub menu and can be measured using the velocity calibration wizard.

Ø  The material velocity must be known prior to focal law creation. The velocity cannot be modified in the MX2 without recreating the focal laws.

29

Ø  A focal law is the pattern of time delays applied to pulsing and receiving elements of an array probe in order to steer and focus the resulting sound beam and echo response.

Ø  The speed or PRF, the quantity of A-scans in one or more groups, and the type of beam formations possible is limited by instrument specifications and software capability.

Single pulse echo focal law example Software input Transmitter delays (Pulse) Receiver delays (Echo) Resulting A-scan

Intro to Phased Array Using the OmniScan MX2 Part 1 – Beam Formation

30


Ø  A simpler explanation is that a focal law is an A-scan. When used in pulse echo mode the transmitted and received delays are the same and are using the same group of elements.

Ø  The phasing affect allows multiple focal laws or A-scans that differ in angle and focus to be generated from the same group of elements and summed in a sector scan or linear scan type display.

31


Sector Scan Definition §  Focal laws of different angles

generated using the same elements. §  A-scan density and coverage is

defined by the range of angles (45-70) and angle resolution. (45, 46, 47, etc)

Linear Scan Definition §  Focal laws generated over a series of

elements using the same angle. §  A-scan density and coverage is

defined by the element step resolution.

32

Intro to Phased Array Using the OmniScan MX2 Part 1 – Beam Formation Ø  Sound beams can be focused like light rays with the energy focusing at a given

point and then expanding beyond it. Ø  The depth of focus is changed by varying the applied delays on the elements and is

built into the focal law along with the angle steering. Ø  The maximum depth or sound path that a beam can be focused is defined by the

near field which is a function of element size, frequency, and material velocity. Ø  The effective sensitivity is improved by a smaller beam diameter with more energy

at the focus point. Ø  Increasing the size of the aperture or creating the same aperture using more

smaller elements increases the sharpness of the focused beam and improves results.

33


Ø  Beam focusing is only possible within the near field of the probe. Ø  The near field is different in the active and passive axis of the array and can be

calculated with the formula below. Ø  Most methods for calculating the near field should be considered close

approximations due to simplifying the formula and not taking into account every probe parameter.

34


Depth Sound Path Projection Focal Plane

Ø  Different focusing strategies can provide optimized results for different applications.

Ø  There are five primary types of focusing associated with phased array inspection: 1.  Depth focusing. Defined from the bottom of the wedge in depth and different

for every angle. 2.  Sound path focusing. Defined by the uncorrected sound path and the same for

every angle. 3.  Projection focusing. Defined by the surface distance from the wedge face. 4.  Focal plane focusing. Defined by an X,Y position in the material. 5.  Unfocused. Any value that is beyond the near field of the probe\aperture.

35


Ø  In addition to standard IIW and similar calibration blocks, there are industrial standards such as ASTM E2491 that specify techniques and calibration block designs for verification of the phased array beam profile.

Ø  Beam profile, beam steering limits, beam focusing, element activity, etc can be verified similarly to the requirements of conventional UT with specialized reference standards.

37

OmniScan MX2 Training – Phased Array Calculator Review

Ø  Question: What are the four groups of essential parameters for the phased array calculator?

1.  Probe parameters. 2.  Wedge parameters. 3.  Material Velocity 4.  Beam Formation.

Please send questions and comments to: [email protected]

For more information visit our website: www.olympus-ims.com

Thank You!

Introduction to Phased Array Using the OmniScan MX2 - Part One

Technology

d linear phased array

d linear array probes

probes complex probes

mx2 database

probe parameters

omniscan mx2 software

modern phased array

mx2 software manuals