ML20115J748
| ML20115J748 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 03/26/1996 |
| From: | Battelle Memorial Institute, PACIFIC NORTHWEST NATION |
| To: | |
| Shared Package | |
| ML20006H945 | List: |
| References | |
| PROC-960326, NUDOCS 9607250054 | |
| Download: ML20115J748 (28) | |
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. 1 PROCEDURE FOR ULTRASONIC EXANINATION OF CENTRIFUGALLY CAST ~
STAINLESS STEEL PIPING USING THE LOW FREQUENCY SAFT-UT SYSTEM I
Prepared by Pacific Northwest National Laboratory
- Operated by Battelle Memorial Institute for the l U. S. Nuclear Regulatory Commission
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. e Table of C:ntznts 1.0 SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
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2.0 REFERENCES
. . . . . . . . . . . . . . . . . . . . . . . . . . ... 5 3.0 GLOSSARY
............................. 5 4.0 PERSONNEL QUALIFICATION . . . . . . . . . . . . . . . . . . . . . . 6 5.0 EQUIPMENT AND MATERIALS . . . . . . . . . . . . . . . . . . . . . . 7 6.0 CALIBRATION . . . . . . . . . . . . . . . . . . . . .' . . . . . . . 11 7.0 EXAMINATION PROCESS . . . . . . . . . . . . . . . . . . . . . . . . 13 ,
1 8.0 RECORDING OF INDICATIONS ...................., 15 9.0 INTERPRETATION OF INDICATIONS . . . . . . . . . . . . . . . . . . . 16 10.0 EVALUATION OF INDICATIONS . . . . . . . . . . . . . . . . . . . . . 18 11.0 RECORDS AND REPORTS . . . . . . . . . . . . . . . . . . . . . . . . 19 t
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Figure Captions l Figure 1. Example of Calibration Data Sheet for SAFT-UT Applications . 21 Figure 2. Sketch Showing Examination. Volumes and Scanning Surfaces for
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Pipe . . . . . . . . . . . . . . . . . . . . . . . . . . ... 22 Figure 3. Sketch Showing Scanning Conventions and Nomenclature for Pipe ............................ 23
- Figure 4. Example of a Microsoft Excel Spreadsheet for Recording Flaw Detection Data .......,............... 24 Figure 5. Example of a Microsoft Excel Spreadsheet for Recordin Siz ing Data . . . . . . . . . . . . . . . . . . . . . g Fl aw
.... 25 Figure 6. Example of SAFT-UT Processed Pulse Echo B-Scan View Images of Corner Trap and Tip Time-of-Flight Signals . . . . . . . . 26 Figure 7. Example of SAFT-UT Processed Tandem B-Scan View Images of a 0.3" Deep Sawcut ...................... 27
- Figure 8. Example of Examination Data Sheet for Reporting SAFT-UT Indications . . . . . . . . . . . . . . . . . . . . . . . . . 28 Tables l Table 1. Search Units for Scanning of Pipe Welds Using SAFT-UT ..... 8 l Table 2. Pipe Wall Thickness and Maximum Search Unit Size ........ 9 l
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. , l PROCEDURE FOR ULTRASONIC EXAMINATION OF CAST STAINLESS STEEL PIPING USING A LOW FREQUENCY /SAFT-UT SYSTEM l r 1.0 SCOPE
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1.1 This procedure specifies requirements for ultrasonic (UT) flaw detect' ion i in cast stainless steel piping welds using a low frequency-ultrasonic l synthetic aperture focussing technique (SAFT-UT) system.
1.2 The low-frequency, long-wavelength acoustic inspection technique has demonstrated promising results for coarse grained material inspection under laboratory conditions. In order to " desensitize" our inspection to the effects of the grain structure, we are utilizing 0, 30, 45, and ,
60 degree incident longitudinal waves in a pitch-catch configuration at I 350 kHz. Scattering losses are the predominant factor in ultrasonic l
attenuation, and by plotting the attenuation of ultrasonic energy as a ;
function of frequency, the most significant decrease in attenuation l occurs within the Rayleigh scattering region, where the wavelength is greater than the average grain diameter. Many CCSS components contain l grain diameters on the order of 1/2 inch or greater, therefore, we have chosen a wavelength of 2/3 inch in the material, corresponding to a '
l centar frequency of approximately 350 kHz. Due to the fact that '
compressional wave energy attenuates less than shear wave energy in CCSS, the inspection will focus on the 0, 30, 45 and 60 degree incident i longitudinal waves in the pitch-catch configuration. I 1.3 This procedure is applicable to UT examination of full penetration welds in unclad cast stainless steel piping. Scanning shall be conducted from the outer pipe surface, and the examination shall include the adjacent base metal.
1.4 This procedure is applicable to cast stainless steel piping welds with I nominal diameters of two to thirty-six inches (NPS) inclusive, and nominal wall thicknesses ranging from 0.237 to 3.500 inches, inclusive.
1.5 This procedure describes a multi-inspection angle, low frequency-long wavelength examination process to detect and size discontinuities within i the specified examination volume when scanning is conducted from the l outer surface of the pipe. i 1.6 Where accessible, and when detection of discontinuities that are I oriented both parallel and perpendicular to the weld are required, welds shall be examined with the UT beam aimed in both axial directions (and both circumferential directions, if the transdu:er face has been properly contoured for this orientation).
1.7 Where access to both sides of the weld is not possible, this procedure is applicable for detection and sizing of flaws oriented approximately
, -parallel or perpendicular to the weld when scanning from only one side l of the weld. For such applications, the weld crown shall be ground to ,
l facilitate examination using both angle-beam and straight-beam )
techniques from the accessible pipe surfaces, and/or scanning shall be performed at multiple angles.
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1.8 This procedure is intended to satisfy all applicable requirements of the ASME Code,Section XI, Appendices III and VIII.
2.0 REFERENCES
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2.1 ASME Boiler and Pressure Vessel Code,Section XI (1995 Edition).
2.2 NRC Quality Assurance Manual, Rev.1, November.1989, Nondestructive Examination Independent Measurement Program. .
2.3 Hall, T. E., L. D. Reid, S. R. Doctor. 1988. The SAFT-UT Real-Time Inspectton System - Operational Principles and Implementatfon.
l NUREG/CR-5075, PNL-6413, prepared by Pacific Northwest Laboratory for the U.S Nuclear Regulatory Commission, Washington, D.C.
2.4 Doctor, S. R. , G. J. Schuster, L. D. Reid, T. E. Hall . 1995.
Development and Validation of a Real-Time SAFT-UT System for the Inspection of Light Water Reactor Components. Final Report. NUREG/CR-4583, PNL-5822, prepared by Pacific Northwest Laboratory for the U.S.
Nuclear Regulatory Commission, Washington, D.C.
2.5 Harris, R. V., Jr., L. J. Angel, S. R. Doctor, W. R. Park, G. J.
Schuster, T. T. Tay1or. 1994. Evaluatfan of Computer-Based Ultrasonic In Service Inspection Systems. NUREG/CR-5985, PNL-8919, prepared by Pacific Northwest Laboratory for the U.S. Nuclear Regulatory Commission, Washington, D.C.
3.0 GLOSSARY The following list of key terms and abbreviations are provided along with definitions to clarify their use within the context of this document.
3.1 Centroid (i.e., tip centroid and base centroid) - A point located in the center of the SAFT-UT image (ellipsoidal shape) of discontinuities.
3.2 Corner Trao Sianal - The strong signal reflection obtained from the intersection of a surface connected discontinuity with the pip,e inner (ID) surface.
3.3 . Crack Tio Diffraction Sianal - The low amplitude reflection obtained
~ from the tip of an inner surface connected discontinuity that extends into the wall of the pipe.
3.4 Discontinuity - A lack of continuity or cohesion; an intentional or unintentional interruption in the physical structure or form of a material or component.
3.5 Evaluation - A review, following interpretation of the indications noted, to compare SAFT-UT images with specified criteria. When using this procedure, evaluation is usually limited to those i processes / techniques used to size flaws in either the length or through-t s
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i wall (i.e., depth) dimension. For convenience, the terms length-sizing )
I and depth-sizing are often used within this document.
i 3.6 False Indication - An NDT indication interpreted to be caused by a
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discontinuity at.a location whers no discontinuity exists.
3.7 Flaw - An imperfection or discontinuity that is detectable by l nondestructive testing and is not necessarily rejectable.
3.8 Flaw Characterization - The process of quantifying the size, shape, orientation, location, growth, or other properties of a flaw based on NDT/NDE response.
3.9 Indication - Evidence of a discontinuity that requires interpretation to determine its significance.
3.10 Interoretation - The determination of whether indications are relevant or nonrelevant.
3.11 Nonrelevant Indication - An NDT/NDE indication caused by a condition or type of discontinuity that is not rejectable. False indications are nonrelevant.
3.12 Relevant Indication - An NDT/NDE indication caused by a condition or type of discontinuity that requires evaluation. 3 l
3.13 SAFT-VT - Synth' etic Aperture Focussing Technique for Ultrasonic Testing l 3.14 SAFT-VT Imaae - The two dimensional images (B-scan or C-scan) produced with SAFT processed data using the SAFT-UT imaging software called "APLOT."
3.15 Time of Flioht Shace (Image) - The two dimensional images produced from !
a specular reflector or a corner trap reflector in the appropriate B- !
scan view that contains the UT beam insonification angle. This image is at a ~right angle to the insonification direction. See Figure 6 for an example.
4.0 PERSONNEL QUALIFICATION 4.1 Personnel that do scanning, data acquisition, data manipulation, and data analysis activities shall be technically competent and equivalent to certified NDT Leve' II or III Examiners as defined in Section XI of '
the ASME Code.
4.2 Personnel that mount scanners, tracks, search units, etc. shall be proficient in the performance of these duties as required by the NDE supervisor or cognizant Level III.
, 4.3 Trainees and other junior personnel may help in conducting examinations; I however, interpretation and analysis of data shall be done only by personnel that are technically equivalent to certified Level II or III '
Examiners.
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. O 5.0 EQUIPMENT AND MATERIALS i 5.1 Low Frequency /Long Wavelength SAFT-UT System
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The low frequency /long wavelength' data acquisition electronics are coupled to the SAFT-UT system. The low frequency data acquisition system consists of the following components.
5.1.1 Preamplifier - Amplifies the received UT signal response, producing high gain output under low noise constraints for low amplitude signals under 2 MHz.
5.1.2 Filter - Conditions the preamplified UT signal i response by applying a high pass and low pass filter i (bandpass filter) to the rf waveform.
5.1.3 Receiver - Further conditions and amplifies the filtered UT signal response by applying a high pass filter and amplifying the rf waveform.
5.1.4 Digital Oscilloscope - Displays amplified single-cycle tone burst for excitation of the transmitter and displays real-time UT signal response as data is being acquired. -
5.1.5 Arbitrary Waveform Generator - Produces a low frequency tone burst from a custom designed single cycle driving function for excitation of the transducer.
- 5.1.6 Rf Amplifier - Amplifies output of arbitrary waveform l
generator, providing a high amplitude excitation pulse I to the transducer.
I A 486 cunputer containing an A/D converter will be used to digitize ;
incoming data and initialize a trigger output signal to the arbitrary waveform generator. This trigger signal will be used to sync all instruments. The arbitrary waveform generator is used for programming i and implementing custom designed waveforms for driving the transmitter.
The optimal excitation pulse is a single cycle sine wave tone burst.
The driving pulse is amplified by a low frequency 200 watt RF power amplifier and sent to the transmitter. The received signal (echo) is then sent to a Panametrics low-noise, preamplifier. Bandpass filtering is implemented using a Krohn-Hite filter in order to allow suitable amplification while minimizing extraneous low frequency. noise components under 150 kHz and higher frequency noise components over 600 kHz. This preamplified and conditioned signal echo is then amplified by a wideband Panametrics amplifier and further conditioned using a high pass filtering option. All outgoing (to-the transmitter) and incoming (received echoes) signals are monitered using a digital oscilloscope.
This signal is received by the A/D converter where a linear averaging.
scheme is implemented and the' received A-scans are averaged up to 128 times per repetition for purposes of increasing signal-to-noise and minimizing the effects of motor noise and random electronic noise from
, the motors and other environmental factors. The instrumentation system t
used for ultrasonic data acquisition has also been optimized with regard to signal processing and scanning mechanics. This system is capable of acquiring ultrasonic data within a region of 40 dB to 120 dB.
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The Low frequency /SAFT-UT system is an automated, computerized UT imaging system designed and developed by the Battelle-Pacific Northwest National Laboratory. A general description of computerized UT imaging systems is provided in Appendix A, and a functional description of the
( SAFT-UT imaging system is provided in Appendix B.
1 The SAFT-UT system consists of the following subsystems and components. I 5.1.7 Pulser - Produces high voltage pulses that excite the transducer. This pulser is not used with the low frequency system.
5.1.8 {
Receiver - Conditions and amplifies the received UT !
response signals. May apply a time varied i amplification factor (i.e., electronically generated DAC). This receiver is not used with the low frequency system.
5.1.9 Data Acquisition and Storage Subsystem - Contains the )
l analog-to-digital converter and a magneto-optical disk drive to store digital data.
5.1.10 Data Processing Subsystem - Performs SAFT processing ,
of raw (unprocessed) UT data using a. Sun computer. -
l 5.1.11 Data Display and Analysis Subsystem - Displays 'the !
SAFT-UT processed data (A-scans, B-scans, and C-scans) l during analysis of UT indications using the graphics !
workstation features of the Sun computer.
5.2 Search Units and Wedges
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The search units and wedge forms to be used for examining pipe welds are listed in Table 1.
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Table 1. Search Units for Scanning of Pipe Welds Using SAFT-UT Loncitudinal Wave Search Units - Mecasonics l Model CSS-45L 1.0 MHZ Z .50" x 1.0" F = 1.5" Model CGD-45L 1.5 MHZ Z = .38" x .75" F = 1.0" Lonaitudinal Wave Search Units - RTD j Model 85-737 2.0 MHZ 2(10x18), 60 TRL-Aust. SA 16 , FS 20 Loncitudinal Wave Search Udts - SwRI Model 45RL 2.25 MHZ 1/4"x1/2" 1.0" T Lonoitudinal Wave Search Un#ts - Aerotech (Krautkramer Branson)
Model 2910387 1.0 MHZ 1.0" DIA. Alpha l Lonaitudinal Wave Search Units - Vincotte Model V 45L 1.0 MHZ SE 85F S-PMS-1-D, N* 02-03 Lonoitudinal Wave Search Units - Siama Transducers Model SVADA.35 350 KHZ 2PC(2"x1") F2 Variable Angle 0 -70 RL l 8 l
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- Plastic Wedaes Longitudinal wave search units manufactured by Megasonics, SwRI, and Aerotech (K-B) have detachable wedges for 45* and/or 60* RL in steel.
The RTD unit and the Vincotte transducer are integrated units consisting of non-detachable 45* tiedges con'tained within the transducer hous.ings.
The Sigma Transducers variable angle unit is an integrated unit with a non-detachable ultem wedge providing 0 - 70* RL in steel by the turn of 1 a dial. !
l 5.2.1 Search units with ' nominal center frequencies equal to or greater than 1.5 MHZ shall be used for pipirg with wall thicknesses less I than 0.500" (NPS). Search units with nominal center frequencies I of 1.0 MHZ and under shall be used for piping with wall I thicknesses greater than 0.500" (NPS).
5.2.2 For cast stainless steel piping, search units with a nominal 2
center frequency in the range from 350 KHZ to 1.5 MHZ shall be used for examinations conducted to detect intergranular stress corrosion cracking (IGSCC). Search unit bandwidth shall be 1 greater than 30% and nominally 50% to 60%. The search unit characteristics shall be sufficient to provide a minimum signal-to-noise ratio of 10 to 1 on the inner surface notch in the calibration block. Search unit size shall comply with Table 2.
1 5.2.3 The performance of the Sigma Transducers, dual element search unit i
and has been optimized with regard to bandwidth, materials (crystal type) used for transmit and received elements, beam
- characteristics, and pulser-receiver instrumentation characteristics.
Table 2. Pipe Wall Thickness and Maximum Search Unit Size Pipe Wall Thickness Maximum Search Unit Size (Nominal) (Nominal)
Less than 0.5" 0.25" 0.5" through 2.0" 0.5" .
Over 2.0" 1.0" 5.2.4 Angle beam wedges that produce longitudinal waves between 0 and 70* shall be used. The 45 longitudinal wave shall be used as the primary examination angle. When a geometric configuration precludes 100% coverage using a 45* search unit, a 30 , 60" or 70 search unit shall be used. Actual search unit angles shall be within 3* of the nominal angle. Additional search units may be used provided they comply with the essential variable tolerances listed in ASME Section XI, Appendix VIII, Paragraph VIII-4110.
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4 3 5.2.5 Search unit wedges shall be contoured to achieve adequate surface contact and signal-to-noise ratio.
I 5.2.6 Tandem search units used for flaw depth sizing shall be of the same nominal frequency and ' size.
5.3 Cables The cables used to connect the SAFT-UT system to the scanne~r mechanism i shall be Type RG-58 or equivalent with a length not to exceed 60 m (200 !
ft.) using no more than two intermediate connectors. The cables used to i connect the scanner mechanism / receiver preamp to the search unit shall be Type RG-174 or equivalent with a length not to exceed 60 cm (24 in.)
without intermediate connectors.
l 5.4 Calibration and Reference Blocks l
Time-based settings and refracted angles shall be established using CSS !
reference blocks that have similar metallurgical structure and acoustic- I properties to the component that will be examined. Due to the anisotropic and inhomogeneous nature of cast stainless steels, the unfinished ends of piping may also be used to establish refracted angles <
and time-based settings. Calibration blocks shall be used to establish the reference sensitivity level (s) at which subsequent examinations will be done. Calibration block designs shall be as follows:
l 5.4.1 The basic calibration block described in ASME Section XI, Appendix III-3400 or paragraph 5.4.2 below. Alternative calibration block designs may be used to assure that the required examinatica volume is insonified.
5.4.2 Alternative calibration blocks provided by the utility, that are representative of the material to be inspected with appropriate UT reflectors such as side-drilled holes, saw cuts, EDM notches or end-milled notches may also be used.
5.5 Couplant Materials l The couplant material shall be Ultragel, water, heavy mineral oil, or other materials that comply with site-specific requirements.
l 5.6 Scanner and Controller The scanner and controller equipment shall utilize a two search unit scanner assembly (Brockman Scanner) with special track (Virginia Corp.
style). A Compumotor multi-axis model S or LN motor control unit with joystick and appropriate interface cables between.the controller (PC)
- and the scanner shall be used.
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6.0 CALIBRATION 6.1 Initial and final calibration shall include the complete SAFT-UT system.
During an examination, any change in search units, wedges, cables, instruments, personnel, or any other parts of the system shall require that a calibration check be performed.
6.2 The temperature of the. calibration block and the surface to be examined l shall be within 25 F. The temperature of the component being examined ,
' shall not exceed 125 F. These temperatures shall be recorded on the l
calibration data sheet (similar to Figure 1). -
6.3 Prior to calibration, the actual UT beam angle and exit point shall be verified using the appropriate reference block.
6.4 All initial calibration and subsequent calibration check data shall be documented on a calibration data sheet (similar to Figure 1) as !
described in Section 11.3.
6.5 Calibration checks, or a complete system calibration, shall be. performed at periodic intervals not to exceed 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Calibration checks shall.
be performed using CSS reference calibration blocks and shall include both the time base (sampling window) and amplitude calibration points.
6.6 Signal response during calibration checks, and post-examination calibration verifications, must be within 10% of the initial time base and signal strength values. In the case.of SAFT-UT, the time base is
' checked by processing the data and producing an image to verify that the calibration reflectors are properly displayed (within 10%) and are within 2dB of the initial amplitude response. If any calibration point exceeds these limits, all examinations conducted since the last acceptable calibration or calibration check shall be voided and the affected components shall be reexamined.
6.7 Angle Beam (Longitudinal Wave) Calibration 6.7.1 Weld profile data shall be available and reviewed prior to conducting angle beam calibration.
6.7.2 Establish a metal path that will provide sufficient coverage of the required examination volume (i.e. 4,1, or 1-1/2 Vee-path).
NOTE: When using the b Vee-path technique from two sides, the weld surface contour or crown width may preclude full examination coverage.
6.7.3 When using Section XI, Appendix III blocks, select an appropriate block (material, diameter, and thickness). Manipulate the search unit to maximize the response from an inner surface notch. Using the digitized A-scan display set this response amplitude between 80% and 100% of the digitizer full dynamic range. This is done by setting the SAFT-UT system parameters which are then stored as 11
information in a header file on the computer. This is the reference sensitivity.
6.7.4 When using an alternative calibration block, select a thickness that equals or exceeds the thickness of the component to be, examined. Manipulate the search unit to maximize the notch response in that section of the block. Using the digitized A-scan display set this response amplitude between 80% and 100% of the digitizer full dynamic range. This is done by setting the system
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parameters which are then stored as information in the header file on the computer. This is the reference sensitivity.
Note: The term "digitizer full dynamic range" is equivalent to the term " full screen height" when referring to the calibration of manual UT instruments.
6.7.5 For 1-1/2 Vee-path examinations, the system parameters shall be adjusted to produce the desired response amplitude from other notches or the same notch at different Vee path positions to cover the examination range. Using the digitized A-scan display', set this response amplitude between 80% and 100% of the digitizer full dynamic range. This is done by setting the system parameters which are then stored as information in a header file on the computer.
6.8 The SAFT-UT system parameters from the calibration shall be stored to disk with an identifying file name. Either a hard copy of this file shall be attached to the calibration data sheet; or this file shall be retained with the examination data in electronic form.
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7.0 EXAMINATION PROCESS
- l 7.1 Scanning Plan
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A mandatory first step when apply'ing this procedure to the examination of any component shall be the preparation of a written scanning plan.
The scanning plan shall specify the area and volume of the component to be examined and shall identify the flaw types and orientations that are to be detected. Figure 2 illustrates the weld and adjacent base metal that must be examined to satisfy ASME Section XI requirements (see Fig.
IWB-2500-8 in SC-XI). The scanning plan shall also specify the type of ~
scan (pulse-echo, tandem, etc.), the beam direction (s) with respect to the weld and flow dircction, beam angle (s), search unit types, sizes, frequencies, and the signal recording requirements. Figure 3 is an examination reference sketch that shows the scanning conventions and nomenclature. This information shall be recorded as notes in the header on the computer with hard copy diagrams, if applicable. The written scanning plan shall be approved by personnel that are technically equivalent to certified Level III Examiners.
7.2 Examination Surfaces '
The surface from which the examination will be performed shall be free of irregularities (i.e. excess roughness), loose foreign materials, or coatings that interfere with effective transmission of UT energy.
7.3 Contours, Thicknesses, and Coverage Plots
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7.3.1 Surface contours and UT thickness measurements shall be used, as necessary, to obtain inner and outer surface profiles to assist the signal interpretation / evaluation process. If satisfactory thickness and contour information is on file (e.g. previous PSI /ISI information), these measurements need not be repeated unless wall thickness changes due to erosion etc. may have occurred.
7.3.2 The UT examiner should establish, where possible, the location of the weld root and counterbore, as applicable. The relationship of the root, counterbore, and search unit should be established and identified on the thickness and contour sketches, and in the i
1 scanning plan (see Section 7.1).
7.3.3 Coverage plots shall be used to specify the area of examination and to map areas / regions of inaccessibility.
1 i 7.4 Examination Sensitivity Examination sensitivity shall be established on the base metal adjacent to each weld being examined. This sensitivity shall be adjusted by increasing the inner surface response roll signal (noise) to a minimum of 5% of the digitizer dynamic range at the Vee-path chosen for 13 i
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l performing the examination. The examination sensitivity shall not be less than the reference sensitivity. Record the examination sensitivity setting used during each examination on the calibration data sheet and
, in the header notes for each examination.
7.5 Scan Pattern '
7.5.1 When examining for reflectors parallel to the weld, the examination shall be performed from both sides of the weld, where possible. If access is limited to one side, alternate angles, frequencies and modes to improve coverage should be used. A scan pattern shall be established depending on UT wavelength and the required examination. The size of the scanning increment shall not be greater than IA for detection and 1/2A for sizing.
7.5.2 When examining for reflectors perpendi.cular to the weld, the examination shall be performed from both sides of the weld, if accedible, with the beam sufficiently skewed (parallel to the weld) to examine the root and b inch of adjacent base metal on either side of the weld. A scan pattern shall be established depending on wavelength and examination requirements. The size of the scanning increment shall not be greater than 1A for detection and 1/2A for sizing. When examining small diameter, thin-walled piping, it may be necessary to perform the examination from the weld-crown.
7.5.3 When access is possible from only one side, the weld shall be g ground flush or flat-topped. The weld on the far side shall be examined using refracted longitudinal wave search units by scanning across the accessible base metal and weld metal.
7.6 Limitations Limitations due to joint configuration or permanent attachments that preclude examination of the required volume shall be fully documented.
l The examiner shall. attempt to achieve full coverage by reducing the distance between the exit point and the front of the wedge, changing angles, using a smaller search unit, or requiring additional weld surface preparation. Any changes in equipment shall be within the limits specified in this procedure.
- 7.7 Testing Protocol
l l The objective is to acquire low frequency ultrasonic data on various CSS piping components. This data will be post processed using the Synthetic Aperture Focusing Technique (SAFT).
Initially, the inspection team will perforn the following scans:
- 1. O degree L-wave at 350 kHz
- 2. 30 degree L-wave at 350 kHz
, 3. 45 degree L-wave at 350 kHz l
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- 4. 60 degree L-wave at 350 kHz j After configuring the workspace, instrumentation, scanning track, l cabling and grounding, transducer fixturing, etc., and evaluat4g a i practice specimen and a CCSS calibration block using scans 1, 2, 3, and I 4, the test-plan will be optimized. After performing a preliminary l analysis of these scans, we will then evaluate our needs for acquiring l
more ultrasonic data of a different mode based on the time remaining to j complete our objective and meet our milestones.
i 7.8 Inspection Procedures:
- 1. Adjust and control scanning track to alluw for access to the top 140" of the pipe circumference. Utilize proper lift screws 1 to accommodate required distance between scanning track and transducer making sure the coupling is appropriate for the component under test.
- 2. Configure the designated transducer attachment, and connect coaxial cables to transducer.
- 3. Attach transducer fixture to scanning track, and configure coordinate axes by taking photographs and making drawings of the component orientation and transducer orientation. These steps include:
A] Lining up the central axis of the transducer perpendicular with the weld center line. .
B] Measure the Y-path length (circumferential width of scan area) from center to center of the transducer.
C] Measure the X-path length (axial width of scan area) from !
center to center of the transducer
- 4. Configure the instrumentation for the specified scan, (i.e.,
pitch-catch or pulse-echo), and make the repriate cable connections. Adjust instrument settings n as filter bandwidths, driving frequency and functica, etc..
- 5. Invoke digitizer and view an A-scan response from the test 1 material . Adjust system gain, making sure not to saturate the '
amplitude.
- 6. Initiate data acquisition. Simultaneously view incoming data (A-scan representations) as the scan is being performed.
- 7. When scan is completed, invoke SAFT algorithm for processing of raw data file, utilizing beam processing angles of 6*, 12*, 20*
and 25*.
- 8. Repeat steps 1-7.
L 8.0 RECORDING OF' INDICATIONS 15 1
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s 1 8.1 Weld profile data and thickness readings should be recorded in those t
areas where angle beam indications are detected. The number of thickness readings should provide adequate information for constructing
, a cross-sectional view of the weld and adjacent base metal.
8.2 All digitized data from the gated region shall be saved on permanent storage media (tape drive, hard disk, optical drive, etc.).
8.3 The coordinate system used to record and report SAFT-UT indications shall be consistent with the nomenclature shown in Figure 3; where X corresponds to W, Y corresponds to L, and Z corresponds to through-wall distance from the scanning surface.
8.4 Ultrasonic reflectors (SAFT-UT images), regardless of amplitude, shall be investigated to the extent necessary to characterize the shape, identity, and location of the reflector. Coordinates of indications shall be recorded on a form such as the example shown in Figure 4. The'
" Filename" shall contain information to uniquely identify the component, scan starting position and direction, UT beam mode, dates, and times.
8.5 All indications of suspected flaws shall be recorded rega'rdless of -
signal amplitude.
8.6 Any other indications that are interpreted to not be caused by geometrical or metallurgical conditions (i.e. non-geometrical and non-metallurgical indications) shall be recorded if they are -12dB of reference or greater. For non-geometrical and non-metallurgical 7
indications, record the signal amplitudes and the volumetric location coordinates at the point of maximum indication response (maximum image amplitude).
8.7 Indications from geometrical or metallurgical origin with amplitudes equal to or exceeding -6dB at the reference sensitivity shall be recorded. Record the peak amplitude, background noise value, and volumetric location of the SAFT-UT image. Coordinates of indications shall be recorded on a form such as the example shown in Figure 5. '
i 8.8 When length-sizing reflectors using longitudinal waves that do not travel through cast stainless steel weld metal, the end points shall be determined by measuring the AX or AY to complete loss of signal and i record these data using a form such as Figure 5. If it is determined that the indication is due to IGSCC, the end points shall be determined by tracking the indication until the signal is lost in the baseline noise. There are currently no qualified techniques for length sizing reflectors using ultrasound that travels through cast stainless steel l weld metal. However, it may be useful to record the points at which the !
signals are lost in the baseline noise. I i
9.0 INTERPRETATION OF INDICATIONS l 9.1 Flaw Verification l
l
. l 16
( j
i i
> 1 Whenever possible, flaw existence and location shall be verified by
. recording the response from two apposite directions for each indication.
The weld crown should be properly prepared (i.e. flat topped) to I( accommodate this verification.
' 9. 2 Plotting Recordable indications, as defined in Section 8.0, shall be plotted on a cross-sectional drawing of the weld. The indication coordinates taken
. from SAFT-UT processed images assume flat, smooth surfaces and must be l combined with cross-sectional drawings to facilitate accurate determination of flaw location. Flaw location plots must identify the geometric origin of the reflector image. . Additional scanning to the extent necessary to accurately characterize the reflector image is permissible, provided the equipment used meets the requirements of this procedure. Suspected geometric indications may be verified using manual UT, radiographs, as-built drawings, or any other means available to l reliably characterize the reflector.
9.3 Geometric Indications .
An indication should be classified as geometric if one or more of the following conditions are observed:
l l
9.3.1 The indication image ends at the counterbore and a scan in the opposite direction yields no response.
)
9.3.2 The indication image ends at the counterbore and another scan I( using a higher angle yields a much lower response or no response.
l 9.3.3 The indication image ends at the far side of the weld root and l supplemental scans at additional angles produce no response or a l very low response. ,
9.4 Non-Geometric Indications An indication should be classified as a relevant indication if two or ;
more of the following conditions are observed: '
9.4.1 The indication image ends at the counterbore and a scan in the I l opposite direction also shows an indication image at the same l location.
9.4.2 The iridication can be imaged while the search unit is aimed away from the weld.
9.4.3 The indication can be imaged using a different beam angle aimed in the same direction and the indication plots in the same location.
9.4.4 The indication can be imaged using the same beam angle from the opposite direction and it plots in the same location.. ;
i 9.4.5 The indication can be imaged with a different beam angle from the l
! opposite direction and it plots in the same location. '
i 9.4.6 The indication can be imaged with a different beam angle (30', 60'
- or 70') and it plots in the same location but exhibits a j substantially greater amplitude. l 3
. 9.4.7 The indication image plots on the near side of the root and either V of the following two conditions is observed:
1 l 17 i
9.4.7.1 Two images are observed closely together when using a higher frequency search unit.
9.4.7.2 The image eventually disappears on either side of the peak signal along the weld root.
9.4.8 Confirmation is achieved using an inner surface (ID)' ' !
creeping wave search unit (see Section 9.5).
9.4.9 A review of the weld radiographs show no obvious geometric reflectors.
9.4.10 A circumf'erential scan reveals that the main indication contains an axial component. -
Note: The presence of multiple low-level indications (similar to " clad roll") suggests the existence of thermal fatigue cracks.
9.5 Crack Confirmation Using Inner Surface (ID) Creeping Waves !
Ultrasonic examinatiie, using inner surface (ID) creeping waves can be helpful in interpreting crack-like indications in areas that are thought to be free of significant counterbores and other reflectors. This ,
technique may not be particularly useful in very coarse grained materials.
9.5.1 Since root geometry does not usually produce an ID creeping wave, the presence of this type of signal suggests a ;
relevant indication.
( 9.5.2 The presence of a 30*-70*-70* mode converted signal suggests ;
a flaw whose depth is more than 10% through-wall. i 9.6 Single Side Access When an indication is imaged while examining through weld metal, the existence of a flaw shall be confirmed using one or more of the following techniques:
9.6.1 Use of a different mode of propagation.
9.6.2 Use of a different beam angle to detect the flaw from the weld crown.
l 9.6.3 Use of a higher beam angle from the near or unrestricted side to detect the flaw through weld metal.
9.6.4 Use of a different frequency search unit to detect the flaw.
10.0 EVALUATION OF INDICATIONS i
10.1 Through-wall dimensions (depths) of relevant indications shall be determined in accordance with the following sizing procedure.
10.2 When using SAFT analysis software for image characterization and sizing,
'- normalize the signal image by isolating (boxing) the indication on the 18 l
i 1 distlay screen. Image intensity can be related to the calibration j
reference sensitivity by comparing normalized digital signal values, '
l including any difference between the reference sensitivity (see Section i / 6.0) and the examination sensitivity (see Section 7.4). Ensure that the l signal image is not saturated since image saturation inflates the, sizing l values.
10.2.1 Tip and corner trap signal images are indicative of planar ;
flaws and will appear as time-of-flight shapes stacked above and below each other in the B-Scan Side View when the UT beam is oriented parallel to the X axis (or in the B-Scan End View when the UT beam is oriented parallel to the Y axis). Such signal images are illustrated in Figure 6.
Determine the through-wall depth of planar flaws by using i the cursor to measure M from the tip centroid to the -
centroid of the corner trap where it crosses the back (ID) surface. Record this value of M in the M column on the '
sizing spreadsheet (similar to Figure.5).
10.2.2 Tandem SAFT images that are centered across the computer .
generated back-surface trace are indicative of planar back '
surface connected cracks. See Figures 7 and 8 for examples of Tandem SAFT-UT images. Determine through-wall depth by using the cursor _to measure the distance between the -6dB signal points perpendicular to the back surface and dividing by two (2). Record this value in the M column on the sizing spreadsheet (similar to Figure 5).
l 10.3 Determine flaw length in both pulse echo and tandem by using the cursor !
to measure the distance between loss of signal points using the B-Scan Side View when the UT beam is oriented perpendicular to the X-axis (or the B-Scan End View W the UT beam is oriented perpendicular to the Y axis). Record this va m as AX or AY, as applicable on the sizing spreadsheet (similar to Figure 5).
10.4 Flaw Location I
l Indications recorded on the flaw sizing spreadsheet shall also be recorded on the examination report sheet (similar to Figure 9) as l
described in the scanning plan. All flaw sizing measurements from the sizing spreadsheet shall be adjusted to include the effect of wall thickness variations due to weld profile and counterbore when l
translating values to record on the examination report sheet.
I 11.0 RECORDS AND REPORTS 11.1 All SAFT-UT indications shall be reported in accordance with the applicable plant specific requirements.
11.2 The use of computerized spreadsheets should be used to facilitate the collection of examination results (see Figures 4 and 5).
19
s
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11.3 Calibration data shall be recorded on a calibration data sheet (similar l to Figure 1), and as a minimum, shall include the following: l 1
g 11.3.1 Calibration sh,eet identification and date of. calibration; 11.3.2 Names of examination p' ersonnel; 11.3.3 Examination procedure number and revision; 11.3.4 Basic calibration block identification; 11.3.5 SAFT-UT system identification and serial number; j 11.3.6 Beam angle, couplant, and mode of wave' propagation in the
~
material; 11.3.7 Orientation'of search unit with respect to the pipe (axial or circumferential);
11.3.8 Search unit identification, frequency, size, and manufacturer's serial number; 11.3.9 )
Special search units, wedges, shoe type, or saddle identification, if used; 11.3.10 Search unit cable type and length; 11.3.11 Dates and times of initial calibration and subsequent calibration checks; l 11.3.12 Verification that the calibration reflectors are within the l dynamic range of the data acquisition system (A-D converter) and within the sampling start and stop times; and 11.3.13 Attach a copy of SAFT-UT system parameters that were established during calibration, as appropriate.
11.4 Examination data shall be recorded on an examination data sheet (similar to Figure 9), and as a minimum shall include the following:
(
11.4.1 Data sheet identification and date and time period of the examination; 11.4.2 Names and qualifications of examination personnel; 11.4.3 Examination procedure and revision; 11.4.4 Calibration sheet identification; 11.4.5 Data file names;
- 11.4.6 Identification and location of the weld (s) and volume (s) scanned; 11.4.7 Surface (s) from which the examination was conducted; and 11.4.8 Examination results. -
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20
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NiiniMiMiliumtansiliifilBM Date: _ /_ /_ SAFT-UT system ident.: Page of _
- . Operator Name(s)
Data Sheet # _
,1 Plant / Unit: >
-Tsearch tin i Manufacturer- _ Model: Serial No.:
IS! Org.: Size:_ Shape: Config.: '
Mode:.
No.of Elements: Nom. Angle: Measured Angle:_
Comp / System: Nom. Freq.: Catr. Freq.! ' Bandwidth:
Wedge, shoe, or saddle:
Procedure No.: ww... ' Seed Unit.cabt"~~ --- ^- el Type: RG-58 ] '
Rev/Chng. No.: RG 174 L Number ofintermediate connectors!
Cal. Block No.:
Cat Slock Temp.: Transducer freq (MHz): Full beam angle in metal (deg):_
Spoomen Temp.: StandoN. hgt (in): Transducer velocity (in/sec):
X incident angle in metal (dog): , Beam entry diameter On):
g ea m mmmmmm -
Sch.: Matenal vetooty (in/sec): Pipe Diameter (in) (0= flat):
Thickness: gic Femte Austenitic .. .. Sample Period (ns):
Depth (stors sound path )in mat,erial to: Start sampling:
Ml Aaual _
Stop sampilan Circ. Range (volts p-p):_ Time 0:
Both ..
[ 4 Slope 0:
Time 1:
Slope 1:
' Offset (volts):
" Ml Parallel _
Video:
Delay-Reps:
Time 2:
Slope 2:
Pem. C Type:
Batch g[ : .. 7.J~
0 0 Date Time initial
_ volts / div. Intermediate intermediate intermediatal
_ micro sec. /div. Final l Figure 1. Example of Calibration Data Sheet for SAFT-UT Applications
- 21
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t Profile of valve body.
vessel norrie, or Enam, surface _, pump connection A-8 4 1/2in. + --.a. '
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1/2 in. + j
/ Weld end buttering A "
8 (where appliedi 1
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1/3r
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,, m m,x t L "
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6 l 1/4 in.-> + -> -*--1/4 in. 1 L Emam,vo. a ! l I C-O-E-F ;
l NPS 4 or Larger SIMILAR AND DISSIMILAR METAL WELDS IN COMPONENTS, N0ZZLES, AND PIPING l Figure 2. Sketch Showing Examination Volumes and Scanning Surfaces for Pipe i
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l l .
i e 22 l
l
I _ . . a..<,
h Xo Downstream Side +X l -X Upstream Side
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I /' /l / / / / ,<' / /
=
Flow I
- . 1 Weld .
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Typical Section of Circumferentiot Weld
@tpt Seom Weld gc ,p y
-' igod' 90' or 270' Skewed
,c Scon Pottern i
YO
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so
, c,co " .
s, po\ ,
p yso . !
Yno -
Standard Circurnerential
o$o ,
Weld Scan Pottern eo\ -
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90 Circ.- (Y) Yo TDO Yo increme TDC Yo Note: See ASME Section XI, Appendix ill, j
Paragraph l11-4330 FI
- which - describes scanning reference systems. Yo Reference ' Point Locations Figure 3. Sketch Showing Scanning Conventions and Nomenclature for Pipe 23
n , o a.
- is
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Edii.,EE 2 I I 3
4 5
6 I 7 i 8 1 9
10 11 i i 12 13 i I J
14 ! I 15 16 I 17 e 18 19 20 21
- l 22
! 23 '
24 j 25 26 8 27
[- 26 29 l l 30 l l -
31 l 32 l 33 34 i 35 l
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Figure 4. Example of a Microsoft Excel Spreadsheet for Recording Flaw Detection Data i
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AtOSJ atO54 46dBf 1
2 3
4 5
6 7
8 9
10 11 12 13 14 15 16 17 18 _
19 20 21 22 23
[ 24 25 26 27 28 29 j 30 , j 31 32 33 34 l
Figure 5. Example of a Microsoft Excel Spreadsheet for Recording Flaw Sizing
. Data
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SOIVE.M Sil5Uisuf@%AMG3M8Rl*W[G6T% M jj:[,3ffgg gpif#jil,i g Este g y g gd g g
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1 l 20 l C .j4 4
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B-Scan End View 3 7 .
g X:-0.204 -> 0.2210-) 10 pts
., t 0.30 -) 1.27(in) 40 pts
_c - - .
0 227 - 0 lun) 44 pts
, 0 i T 7 ., 6 175 f .
er J l 6 3
8-Scan Side View X:-0.204 -> 0.221 Un) 18 pts M 0.30 -> 1.27 On) 40 pts 2: 0.227 -> 0.631 On) 44 pts Scale = 0.10(in) 175 i . _ _ _ _ . . . . -
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Figure 6. Example of SAFT-VT Processed Pulse Echo B-Scan View Images of Corner Trap and Tip Time-of-Flight Signals t
1 26 l
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. - _ . ~ . . - . . . . . - . . . - - - - . - - - . - , _ - - . _ _ . _ _ _ _ _ _ - ___ . - - - _ _ . _ .
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j B-Scan End View 3
-j 6 X:-1325 -> -2.000 (In) 20 pts V. 0A0 -> 2.30 (in) 77 pts
' Z: 0.000 -> 1 A76 (in) 133 pti Scale - 0.20 (in) 0 i "
175
!( 3 B-Scan Side View X:-1.325 -> -2.000 (in) 28 pts j Y. 0.00 -> 2.00 (in) 113 pts 6 Z: 0.000 -> 1 A76 (in) 133 pts
- Scale - 0
- 20 (in) 175 i
l . . . _ .
i d
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. Figure 7. Example of SAFT-UT Processed Tandem B-Scan View Images of a 0.3"
! Deep Sawcut I
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] 27
1 e .
-I SAFT-UT Examination Data Report Sheet ''
Dese Fles:
Planti Urut: CG-:- osas shesilo: Y Locahon; Start (Date and Time): Exammer (Name & NOT Level):
Gipe sus *eall System idenuncanon: X Locahon:
Finish (Date and Time): Examiner (Name & NOT Level);
(uwsean oiream)
Component idenuncauon:
Weld Crown Wictri: Counternore Dimensions: Procedure No. Rev:
Diameter (nom): TNekness (nom): '
Indcahon UT % of Indication Length Max Scan Scan Number Beam Reference (Fw sers. =ces a m) Surface Direction Comments / Results Angle SensitMay Y1 Y Max Y2 X Z (oono) (usucire.)
f R2 viewer (s):
Further Evolustion Required Yes No Figure 8. Example of Examination Data Sheet for Reporting SAFT-UT Indications 4
28
. .. . - _ _ _ - _ _ . _