Phased Array Wedges

OmniScan MX2 Training Program

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OmniScan MX2 Training – Phased Array Wedges Overview 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.

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

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

1D Wedges typically used in OmniScan MX2 applications come in 3 varieties:

1. Shear wave angle beam2. Longitudinal wave angle beam3. Longitudinal wave straight beam

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OmniScan MX2 Training – Phased Array Wedges Overview cont.

Phased array wedges from Olympus are made of high quality Rexolite material that has been tested at the factory for velocity tolerance, and internal flaws prior to machining.

Rexolite is an isotropic material meaning it has a constant velocity in each axis and is ideal for phased array wedge manufacturing.

Rexolite is more brittle than Lucite or typical plastic and more easily damaged. Care should be taken not to over tighten screws or drop.

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OmniScan MX2 Training – Phased Array Wedges Overview Wedges can be optimized for manual hand

inspection, automated scanner inspection, or special applications.

Wedge features available include:– Carbide feet for protection from wear.– Built-in irrigation ports and channels.– Scanner and encoder attachments points.– Inner and outer component radius

curvature.– Water channels on base of wedge.– Stainless steel scanner guides.– Multiple positions for the probe.– ….and more.

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OmniScan MX2 Training – Wedges Material - Rexolite Rexolite is a rigid and transparent plastic produced by cross linking polystyrene with

divinylbenzene. Rexolite is an isotropic material that has a constant velocity in each axis of 2330

meters/sec and impedance similar to water. Rexolite has an outstanding dielectric constant of 2.5 to up to 500 GHz with an

extremely low dissipation factor making it well suited for advanced NDT, sonar lenses, sonic medical systems, missile guidance systems, microwave circuitry and many other ultrasonic and optical applications. (Does not filter the bandwidth)

Rexolite exhibits no permanent deformation under loads up to 2000 psi and at temperatures between 20-125 degrees Celsius. (257 degrees Fahrenheit)

Rexolite can be machined with tolerances much tighter than Lucite or low grade plastics.

For these reasons Rexolite is an ideal material for phased array wedge manufacturing.

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OmniScan MX2 Training– Olympus Wedge Definition The complete definition for wedges is available in the current Olympus

probe catalog and below. The part number is divided into 4 sections and may or may not contain the

last two.

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OmniScan MX2 Training – Wedge Housing Compatibility Olympus wedges are manufactured to be compatible with a type of

Olympus probe housing. Typical housing numbers are A2, A10, A12, etc. and are printed on the probe and wedge.

Any probe and wedge of the same housing type are compatible. Example: All SA12 wedges in the catalog are compatible with A12 probes

and all the parameters required for the phased array calculator are available in the OmniScan MX2 wedge database.

In the SA12 example below we have options for shear wave angle beam, longitudinal wave angle beam, and longitudinal straight beam.

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OmniScan MX2 Training – Wedge Housing Compatibility cont. Some housing types can accommodate probe models of different pitch size and

frequency, and may not be symmetrical in the housing. Wedges compatible with these types of probes contain separate probe position

options with separate attachment points including reversing the probe. Care should be taken to ensure the correct probe, wedge, AND WEDGE

POSITION are selected from the wedge database.

5L64 Position2.25L64

Position

A2 Housing

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OmniScan MX2 Training– Wedge Carbide Wear Pins Use of carbide wear pins on the wedges is common for auto and semi-auto

inspections where high production or repetitive scanning is required. The wear pins provide both protection from wear on the wedge, and stability for

improved performance and repeatability. Wear pins should be secured in place with “Lock-tight” and require a constant

water supply through the water ports. UT couplant gel is not recommended. Use of carbide wear pins directly affects wedge delay and sensitivity calibration.

Failure to complete the calibration process with the same couplant technique and pin position as the inspection will result in a reduction of precision measurement and repeatability.

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OmniScan MX2 Training– Wedge Refracted Angle Included in the wedge label after the housing family (SA10, SA12,

etc) is the nominal refracted angle (N60S) in steel with no beam steering.

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)

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

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OmniScan MX2 Training – 0L Straight Beam Wedge 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.

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

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

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OmniScan MX2 Training – Wedge Curvature Definition Overview 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.

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)

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OmniScan MX2 Training – Wedge Curvature Definition Overview Other custom wedge configurations are available on request as well as wedges

machined to a particular component like a dove tail joint.

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MX2 Wedge Curvature Definition – AOD Wedges AOD wedges are contoured for the pipe diameter for typical girth weld inspections in

the axial axis. Depending on the footprint of the probe\wedge combination and pipe diameter, a flat

probe may be sufficient for the inspection eliminating the need for a contour. The phased array calculator need not differentiate between flat and AOD wedges

because the probe element position (Height) is the same for both. For this reason, separate entries for AOD wedges do not appear in the OmniScan

MX2 database. Both are calculated as flat. In the Olympus probe catalog you will find a reference for the curvature limits for

common wedges based on housing type and nominal pipe diameter.

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MX2 Wedge Curvature Definition – COD Wedges Inspection in the circumferential axis or “Long seam” type inspection requires a COD

wedge and special hardware and software considerations. 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. 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.

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MX2 Training Program – Integrated Wedges Wedges can be integrated directly into the probe or custom built for specialized

scanners and mechanics. Integrated wedges are used for angle beam and straight beam inspection. The phased array calculator requires the same independent information for the

wedge parameters in relationship to the probe.

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OmniScan MX2 Special Application Wedges - Rexoform The Olympus Rexoform system uses a specialized 0 degree longitudinal

wedge for corrosion mapping applications. The Rexoform wedge has an integrated mechanical support that is designed

to adapt to different pipe diameters eliminating the rocking effect and minimize the need for a contoured wedge.

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OmniScan MX2 Special Application Wedges - Hydroform The Hydroform corrosion mapper is a form of a specialized phased array probe and

wedge using water as the coupling medium. It uses a stable water column with an adjustable probe height to transmit sound into

the component for corrosion inspection and C-scan generation. 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. The benefits of using water as the wedge include improved component coupling and

improved near surface defect resolution.

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OmniScan MX2 Special Application Wedges - Radii Solution The Olympus Radii solution is a immersion corner

wedge for curved linear array probes. Allows for internal and external radius inspection and

adjustment of different wedge height and radius size. Wedge parameters are entered into the calculator for

correct beam formation.

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OmniScan MX2 Special Application Wedges - Custom Contours In this example the phased array wedge was manufactured to the same taper as

the component for a perfect fit. 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.

The inspection below is for cracks using an amplitude C-scan and metal loss using a position or “Time of flight” C-scan.

Position C-scan

Amplitude C-scan

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OmniScan MX2 Special Application Wedges - Aqualene Wedges Aqualene is an elastomer designed specifically

for ultrasonic inspection applications. Acoustic impedance is nearly the same as

water and its attenuation coefficient is lower than many documented plastics.

Aqualene couplant reduces the drawbacks of wet coupling when used on porous refractory surfaces and acts as a thermal insulator.

Aqualene couplant products are available in many sizes and thicknesses including custom design specifications.

Benefit for customer phased array applications include: Flexible couplant pads and minimal water addition. Low velocity delay lines. Water box coupling system membranes.

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OmniScan MX2 Training – Wedge Selection in MX2 Software In the OmniScan MX2 software the wedge selection and management can

be accessed from two locations:1. Setup wizard.2. Probe and wedge sub menu.

Wedges are selected from the database. New or custom wedges can be created and stored.

One wedge may have many entries based on probe position, orientation, and different probe model within the same type of housing. (SA1, SA2, etc)

Care should be taken when selecting the wedge model in the software. It is a common source of problems including angle error, wedge delay error, and improper beam formation.

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OmniScan MX2 Training – Wedge Specification Data Sheet 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.

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OmniScan MX2 Training –Wedge Database Update on the Web New wedges are added to the database periodically at different intervals

than the software updates. At any time the current wedge database can be directly updated on the OmniScan MX2 memory card by downloading a utility from the software support section of the Olympus web page at www.olympus-ims.com

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OmniScan MX2 Training – Phased Array Wedge Parameters Overview

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).

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OmniScan MX2 Training – Phased Array Wedge Parameters - AngleQuestion: What is the affect on the UT data if the wedge angle is different than the

calculator (Wizard) input?Answer: Beam formation is incorrect resulting in angle, focusing, and delay errors that

cannot be overcome in the calibration process. Minor angle errors due to machining tolerances are the same as conventional UT wedges and typically need not be corrected with precision measurement on specific wedge serial number.

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OmniScan MX2 Training – Phased Array Wedge Parameters - AngleQuestion: Can the angle of the wedge be measured if it is unknown?Answer: Yes. This can be done mechanically and ultrasonically. If it is different than

the database or more precision is required it can be entered as a new or custom wedge. The procedure for measuring the wedge angle ultrasonically is covered in the wedge delay calibration section.

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OmniScan MX2 Training – Phased Array Wedge Parameters - Orientation Due to the scanner limitation or inspection access it is sometimes necessary

to reverse the orientation of the probe elements to accommodate the probe cable.

This is a function of the wedge orientation and it is defined as either normal or reverse. Selecting reverse will have the affect of reversing the probe element wiring. (1-64 changes to 64-1)

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OmniScan MX2 Training –Wedge Parameters – Height of Element 1Question: What is the affect on the UT data if the height of the first element is different

than the calculator (Wizard) input?Answer: The wedge delay of the A-scan is not calculated correctly resulting in depth

reading errors. The selected focus distance is short or long based on the error. Angle is not affected. Wedge delay can be corrected in the calibration wizard without reforming the focal laws but it will not correct the focus position.

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OmniScan MX2 Training –Wedge Parameters – Height of Element 1Question: Does normal usage result in wedge wear that will change the height of the first

element?Answer: Yes. This can be corrected in the wedge delay calibration wizard or created in

the wedge database as specific serial numbered wedge. This is normal and can be minimized with use of carbide wear pins on the wedge. Unlike probes, wedges in some environments are consumables.

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OmniScan MX2 Training – Phased Array Wedge Parameters - HeightQuestion: Can the height of the first element on the wedge be measured if it is unknown?Answer: Only ultrasonically, not mechanically. This is done by using the fixed velocity of

the wedge as the component. (Inspecting the wedge) This process is covered in a later section. It cannot be measured mechanically because element #1 is hidden behind the membrane in the probe housing and it is impossible to know the exact position to measure.

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OmniScan MX2 Training – Phased Array Wedge Parameters - Velocity The velocity of the wedge must be known prior to formation of the focal

laws. It cannot be measured or corrected during the calibration process. Most wedges from Olympus that are designed to be used with the

OmniScan MX2 are made of Rexolite. Rexolite is an isotropic material that has a constant velocity in each axis of

2330 +\- 20 meters\sec Wedge velocity like component velocity is directly related to the incident and

refracted angles and is an essential variable in the calculator. (Snell’s Law). Temperature affects velocity and similarly to conventional UT the calibration

must be performed near the same wedge and component temperature as the inspection.

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OmniScan MX2 Training – Wedge Parameters - Offsets Offsets are the relationship of probe element #1 to the side and front of the

wedge. As pictured right, X is the primary offset and Y is the secondary offset and is normally 0mm.

The element #1 position is normally referenced from the front of the wedge face and for that reason the number is negative. (-69mm below)

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OmniScan MX2 Training –Wedge Parameters – Offsets cont.Question: What is the affect on the UT data if the primary offset is wrong?Answer: The beam exit point is miscalculated by the software and the surface distance

to the indication is incorrect. The offsets are only for determining position and do not affect focal law calculation. The A-scan is normal and trigonometry and depth readings are normal.

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OmniScan MX2 Training – Phased Array Wedge Parameters - Offsets

Question: Is it possible to know the primary offset of element #1 by measuring it on the

probe and wedge?Answer: No. The probe elements are not visible through the protective membrane and

the position of element #1 cannot be measured with precision. The offset position must come from the drawing of the probe married to the wedge. Close approximations are unacceptable and result in reduced precision.

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OmniScan MX2 Training – Phased Array Calculator Review

What are the essential parameters of 1D linear array wedge that are required by the OmniScan MX2 software?

1. Wedge model number.2. Wedge orientation.3. Height of element #1 on probe.4. Wedge velocity.5. Wedge offsets.

Answer: All of the above

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OmniScan MX2 Training – Phased Array Calculator Review

Question:What are the essential parameters for the phased

array calculator?1. Probe parameters.2. Wedge parameters.3. Material Velocity4. Beam Formation.

Answer: All of the above.