Advancements in Phased Array Scan Planning

Phased Array Scan PlanningConsiderations for Weld Inspection

University of Ultrasonics

Olympus Scientific Solutions Americas Webinar

February 4th, 2014

• Scan Planning Introduction

• Basic Scan Plan Requirements

• Basic Methodology

• Hands-on Demonstration

Short Course Outline

Scan Plan History• Scan planning is deeply rooted in day-to-day conventional

UT routines:

– Evaluating Transducer Characteristics

– Determining proper “pullback”/skip distance for Angle Beam

– Beam overlap for C-Scan coverage

– Focal Spot Size Calculations

Scan Plans???• Before ANY Phased Array Inspection is

performed a SCAN PLAN should be in place.– Scan Plans – A documented inspection strategy (plan

of attack) to provide repeatability for inspections. These will aide in evaluating the material and provide insight to individuals reviewing data.

Scan Plan Importance• Variability of Phased Array inspections can create issues in

consistency, repeatability, and personnel training

• The above scan plan includes several scan plan variables, can you find them???

Phased Array Variability• Sectorial Scanning

• E-Scanning

• Encoded vs. Manual

• Aperture Determination

• Multi-Channel/Grouping

• Focusing effects

• Transducer Selection– Frequency & Beam

Spread Considerations

• Angle Selection

Scan Planning

Code Perspective

Scan Plan Variables

• Phased Array Scan plans should provide at minimum:– Part Details (Weld Design,

Curvatures, Connections)

– Probe and Wedge to be Used

– Focal Law Configuration to be Used (Including initial instrument settings)

– Index Offset Info

– Number of Scans

– Direction of Scans

ASME Example Requirements

• Section V

Article 4

• Requirements

of Scan

Planning in

Appendix V

AWS Example Requirements

D1.1

Info Related to Scan Planning under Part G

Testing Procedure under Annex S

API Example Requirements

1104

Info Related to Scan Planning

Procedure specific

Specialized Calibration Requirements

Phased Array

Scan Plan Equipment

• Forming a scan plan involves 3 essential variables:

– Part Configuration

– Probe & Wedge Selection

– Focal Law Selection

• Information may be hand-drawn or plotted via software

Scan Plan Essentials

• Pros:

– Accounts for errors in Equipment

– Plots actual beam index point

– Focal Law adjustments visualized

• Cons:

– Time Consuming

– Visual Measurements

– Requires Equipment

– Actual Inspection piece may vary

Hand-Drawn

• Pros:– Fast and efficient

– Easier Part Drawing/Dimensioning

– Traceable & Transferable

– Flexibility on Custom Parts

• Cons:– Equipment Variations

– Part Variations

– Estimation of Focal Laws

– Manual Prove up required

Software

• Choosing the proper equipment is as much scan

planning as choosing the proper angles or focal laws.

• Transducers should be proper for material properties

• Wedges should allow for good contact and transmission

• Instruments should be capable of handling both

Equipment Selection

• Differences in array patterns will provide unique beam

characteristics

• 4 Primary Variables:

– Element Qty. - A

– Element Size - E

– Pitch - P

– Elevation - H

Element Configuration

p g

e

H

A

• Focusing in Phased Array is

dependent upon the Aperture used

and Pitch of those elements

• Larger Pitch Transducers and Higher

Aperture sizes will provide better

focusing

• Sometime necessary when Height

Sizing is important

“VPA” Considerations - Focusing

16 element aperture

32 element aperture

• Steering in Phased Array is dependent upon the amount of beam spread from individual elements

• Over steering a transducer can lead to grating lobes, resolution losses, and increased errors in refracted angle

• Smaller Element Sizes and Reduced Pitches aid in steering

“VPA” Considerations - Steering

• Caution should be taken in using Phased Array in Axial

or Long Seam weld inspections

• Smaller equipment is easier to use as the compensation

through focal laws may not be necessary

• Larger wedges create non-linear focal law calculations

that sometimes require the addition of special software

Curvature Considerations

Phased Array

Scan Plan Creation

• From the perspective of the technician, a scan plan provides instruction for probe placement and focal law creation

• With no direct code instruction and high variance on Phased Array use, this leaves more room for interpretation and how to provide these instructions

• 2 Extremes of Scan Plan Creation– Minimalistic

– Flood Method

Scan Plan Thoughts

• From a Code standpoint, coverage is the only requirement and the minimalist approach fulfills only that basic necessity

• Pros: High-Speed, minimal setup time, ease of analysis

• Cons: May require manual follow up, risk of undercalling, difficulties in flaw characterization

Minimalist Scan Plans

• From a Detection standpoint, flaw orientation is always variable and is best detected by multiple beam positions

• Pros: High Resolution, Increased Probability of detection, Improved Sizing

• Cons: Slow Scan speeds, Longer Analysis/Setup times

Flood Scan Plans

• First need a plan of attack….– How am I to approach the inspection? (Single side

access…duel side access..etc.)

– What types of flaw mechanisms are potentially present?

– What incident angles will best reveal the potential flaw mechanisms?

– FLAWS ARE ANGULAR DEPENDANT

• Most codes simply state full volumetric coverage including the Heat Affected Zone is required….. This is too vague.

• Breaking that required coverage into specific areas and specific angles will provide consistency and reliability.

Scan Plan Focal Law Methodology

• More than just coverage!!!!

• Must interrogate specific parts of the joint with specific angles which will provide optimum responses to suspected flaw mechanisms.

• General coverage principles for Weld Inspection– Root Coverage

– Fusion Zone Coverage

– Heat affected zone coverage

– Volumetric

• This does NOT indicate that 4 scans on each side must be configured.…The number of scans is determined by your proof of coverage.

Scan Plan Methodology Welds

• 1. Weld Root Interrogation – First objective is to index close to the weld toe with the intent of weld root interrogation– Primary Flaw Types: Lack of penetration, Root or ID Cracks,

Centerline Cracking in Double Vee Weld

– This is the most critical part of a weld joint and the first objective to cover in scan planning.

– First have to consider the joint type and the potential flaws.

– This also assures maximum 1st leg inspection coverage.

Scan Plan Methodology continued

• 2. Fusion Zone Coverage – second objective is to ensure the fusion zone is covered WITH SPECIFIC ANGLES.

• Primary Flaw Types: Lack of side wall fusion, Sidewall Cracking

• With conventional ultrasonics, the optimum bevel incident angle (BIA) is considered between 5 and 7 degrees of normal incidence with some dependency on the frequency of the sound wave.

• Studies have found that with Phased Array, the optimum BIA with • Sectorial Scans = +/-10 degrees of normal incidence

• E-Scans = +/-5 degrees of normal incidence.

Scan Plan Methodology continued

• Example:– With a 30 degree bevel – perfect bevel incidence would result

from a 60 degree refracted shear wave.

– Fusion Zone to be covered with refracted waves between 50 and 70 degrees (+/- 10 of 60 degrees.)

50

70

Scan Plan Methodology continued

• 3. Heat Affected Zone (HAZ) Coverage – The total code specified area of interest must be covered. ASME specifies the weld zone plus 1” or “t” whichever is less for materials less than 3” thick.

– Primary Flaw Types: CRACKING

– Studies have identified that optimum responses from a notch corner result from shear waves between approximately 35 and 58 degrees.

– Plan for these angles to interrogate the HAZ zone.

– Occasionally, HAZ coverage may be specified as being achieved on the probe side for a given index position.

Scan Plan Methodology continued

• 4. Volumetric Coverage – If the previous three steps

are complete, this will be sufficiently covered without

addition considerations.

– This is for slag and porosity detection which are typically omni-

directional type reflectors (similar to a Side-drilled hole, omni-

directional reflectors tend to reflect sound regardless of the angle

of attack).

Scan Plan Methodology continued

Thank You!

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