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Phased Array UT in Lieu
of RadiographyNDTMA Las Vegas 2018
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January 23,2018
Curtiss-Wright History
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BackgroundCode Case N-831, “Ultrasonic Examination in Lieu of Radiography for Welds in Ferritic Pipe” has been developed to allow the use of UT for weld acceptance
– ASME Board Approved October 20, 2016 and published in the
2017 Edition of Code Cases
Major Benefits over performing RT
– Eliminates exclusion zone and allows work to continue in
adjacent areas
– Eliminates radiation safety concerns of using a source to perform
RT
– Eliminates the unnecessary repair of insignificant fabrication
flaws
– Better detection capabilities for planar flawsProprietary3
Developed PAUT in lieu of RT techniques with clients for B31.1 and ASME Code applications
− ASME Section XI, Repair replacement welds for ferritic piping.− ASME B31.1 piping welds 2004 through 2014 edition with or
without use of B31 Case 189. Examination Acceptance Criteria, Approval date: January 3, 2013
− ASME Section VIII pressure Vessel final closure welds where access does not permit interpretable radiographs, in accordance with UW-11(a)(7) or UT examinations in accordance with UW-51
− Qualified procedures, equipment and personnel to perform PAUT in lieu of RT for ASME Code activities
Overview
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ASME Code Case N-831
Highlights of N-831 Requirements − Applicable to carbon steel welds
− All flaws are considered planar
− Acceptance Standard of Section XI IWB-3000, IWC-3000 or IWD-3000
shall be utilized
− Examination shall be performed utilizing encoded UT system and
recorded to provide that produces an electronic record of the combined
UT data
− The examination procedure, equipment and personnel shall be qualified
by performance demonstration
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The examination volume shall include 100% of the weld volume and the weld-to-base-metal interface
− Angle beam examination of the complete examination volume for fabrication flaws oriented parallel to the weld joint shall be performed
− Angle beam examination for fabrication flaws oriented transverse to the weld joint shall be performed to the extent practical
Encoded ultrasonic examination shall be performed− Where component configuration does not allow for effective
examination for transverse flaws (e.g., pipe-to-valve, tapered weld transition, weld shrinkage), non- encoded ultrasonic examination technology may be used for transverse flaws
Development of N-831 Program
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Procedure and personnel performance demonstrations are based on:
− Type of fabrication flaw (Planar and volumetric)− Flaw location (near/far side and upper, middle, inner− Flaw size (both acceptable and unacceptable)− Min and max diameter and thickness− Surface condition (as demonstrated)− Welding processes
Development of N-831 Program
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UT in lieu of Radiography is now included in the following ASME Codes:
− ASME Section I, Power Boilers− ASME Section VIII, Pressure Vessels− ASME B31.1, Power Piping− ASME B31.3, Process Piping
Applications in Additional ASME Codes
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The examination shall be conducted using encoded techniques
− Examination are shall include the volume of the weld plus the lesser of 1.0” or t adjacent base metal
− Procedure and personnel qualified in accordance with Section V Mandatory Appendices
B31.1 Code
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Qualifications performed in accordance with N-831 exceeds these requirements
The alternative acceptance criteria is similar to N-831 − Uses total flaw height (h) instead of a or 2a of section XI− Flaw length shall not exceed 4t − Most benefits are for t>1.0”− No longer reject/repair for small planar flaws
Procedure and personnel qualified in accordance with Section V Mandatory Appendices
− Qualifications performed in accordance with N-831 exceeds these requirements
B31.1 Code Case 189 (continued)
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Field Experience
The following slides illustrate PAUT field results:
− Sidewall Lack of Fusion detected in a 16” SCH 100 Carbon Steel field weld
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Field Experience
Sidewall Lack of Fusion - 16” SCH 100 Carbon Steel Field Weld
Flaw
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Field Experience
Dye Penetrant examination results after weld removal
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Flaw Specimen: Lack of Fusion (LOF)
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Flaw Specimen: Lack of Fusion (LOF)
Future State
Code Case N-831 is limited to ferritic piping welds made as part of a repair/replacement activity
− Most repair/replacement welds are ferritic materials of various sizes
− To prepare for unplanned weld R/R activities demonstrating a procedure for the full range of possible weld sizes is desirable
− Austenitic weld R/R activities are less common and may be limited in sizes
− It would be advantageous to have the ability to use UT in lieu of RT
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EPRI Research
EPRI performed research to assess the effectiveness of UT to detect
fabrication related flaws for austenitic piping welds
− 3002010297, “Technical Basis for Substituting Ultrasonic Testing
for Radiographic Testing for New, Repaired, and Replacement
Welds for ASME Section XI, Division 1, Stainless Steel
Piping”(publicly available)
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Summary of EPRI Research
− Fabricated stainless steel mockups in accordance with N-831 requirements
− Mockups examined as single side access
− All flaws were detected and sized within N-831 criteria
− Demonstrated PAUT as effective for stainless steel fabrication flaw detection and sizing
This report provides the technical basis for revising N-831 to include austenitic piping
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On-going ASME Code Activity
CC N-831 is being revised to include austenitic materials using EPRI report as the technical basis
Revision to include addition of material through a procedure expansion demonstration
− Through the personnel demonstration process− Specimens must include diameter and thickness range of new
material− Must use same techniques already qualified− All flaws must be detected
If expansion process is unsuccessful, a full demonstration must be performed
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On-going ASME Code Activity
− EPRI research completed and report published -June 2017
− Discussed concept of procedure expansion for austenitic piping at the August 2017 Code meeting
− Draft Code Case revision presented at the November 2017 Code meeting
− Feedback provided by Task Group− Comments incorporated into N-831-1 (draft) and will be presented at
the February 2018 Code meeting− Expect endorsement through NDE Subgroup
− Updated the supporting white paper for the Code Case revision
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Conclusion
Phased Array UT provides a reliable alternative to radiography
− Established and Regulatory accepted protocol for performing PAUT in lieu of RT
− Significant savings have been realized for near critical path activities by utilizing PAUT ILO RT
− PAUT has provided collateral benefit of more realistic acceptance criteria for R/R welds
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