III-4IO

APPENDIX IIIDIFFRACTION

III-4IO SCOPE

2OO4 SECTION

_ TIME OF FLIGHT(TOFD) TECHNIQUE

rtt-432.1

TABLE III-422REQUIREMENTS OF A TOFD EXAMINATION

P R O C E D U R E

Requirement(As Applicable)

Essential NonessentialVariable VariableThis Mandatory Appendix describes the requirements

to be used for a Time of Flight Diffraction (TOFD) exami-nation of welds.

III-420 GENERAL

The requirements of Article 4 apply unless modifiedby this Appendix.

lll-422 Written Procedure Requirements

Ill-422.1 Requirements. TOFD shall be performedin accordance with a written procedure which shall, as aminimum, contain the requirements listed in Tables T-422andlll-422. The written procedure shall establish a singlevalue, or range of values, for each requirement.

lll-422.2 Procedure Qualification. When procedurequalification is specified, a change of a requirement inTables T-422 or III-422 identified as an essential variableshall require requalification of the written procedure bydemonstration. A change of a requirement identified asa nonessential variable does not require requalificationof the wr i t ten procedure. Al l changes of essent ia l ornonessential variables from those specified within thewritten procedure shall require revision of, or an adden-dum to, the written procedure.

rrr-430 EQUIPMENTIII-431 Instrument Requirements

III-431.1 Instrument. The instrument shall provide alinear "A" scan presentation for both setting up scanparameters and for signal analysis. Instrument linearityshall be such that the accuracy of indicated amplitude ortime is +5Vc of the actual full-scale amplitude or time.The ultrasonic pulser may provide excitation voltage bytone burst, unipolar. or bipolar square wave. Pulse widthshall be tunable to allow optimization of pulse amplitudeand duration. The bandwidth of the ultrasonic receivershall be at least equal to that of the nominal probe fre-quency and such that the -6dB bandwidth of the probedoes not fa l l outs ide of the -6dB bandwidth of thereceiver. Receiver gain control shall be available to adjustsignal amplitude in increments of l dB or less. Pre-ampli-fiers may be included in the system. Analog to digitalconversion of waveforms shall have sampling rates atleast four times that of the nominal frequency of theprobe. When digital signal processing is to be carried out

Instrument manufacturer and model

Instrument sof twareDirect ions and extent of scanningMethod for s iz ing f faw IengthMethod for s iz ing f faw heightData sampl ing spacing ( increase only)

XXX

XXX

on the raw data, this shall be increased to eight times thenominal frequency of the probe.

lll-431.2 Data Display and Recording. The data dis-play shall allow for the viewing of the unrectilied A-scan so as to position the start and length of a gate thatdetermines the extent of the A-scan time-base that isrecorded. Equipment shall permit storage of all gated A-scans to a magnetic or optical storage medium. Equipmentshall provide a sectional view of the weld with a minimumof 64 gray scale or color levels. (Storage ofjust sectionalimages without the underlying A-scan RF waveforms isnot acceptable.) Computer software for TOFD displaysshall include algorithms to linearize cursors or the wave-form time-base to permit depth and vertical extent estima-tions. ln addition to storage of waveform data includingamplitude and time-base details, the equipment shall alsostore positional information indicating the relative posi-tion of the waveform with respect to the adjacent wave-form(s), i.e., encoded position.

Ill-432 Search Units

Illrl-432.1 General. Ultrasonic probes shall conform[o the fo l lowing min imum requirements:

(a) Two probes shall be used in a pitch-catch arrange-ment (TOFD pair).

(b) Each probe in the TOFD pair shall have the samenominal frequency.

(c) The TOFD pair shall have the same element dimen-sions.

(d) The pulse duration of the probe shall not exceed2 cycles as measured to the 20dB level below the peakresponse.

(e) Probes may be focused or unfocused. Unfocusedprobes are recommended for detection and focused probesare recommended for improved resolution for sizing.

(/) Probes may be single element or phased array.(g.) The nominal fiequency shall be from 2 MHz to

l5MHz unless variables, such as production material

59. I

ttt-432.1

U p t o I ( 2 5 )

0ver I (25) th ru 2 (50)

Over 2 (50) th ru 4 (100)

Over 4 (100)

grain structure, require the use of other frequencies toassure adequate penetration or better resolution.

lll-432.2 Cladding - Search Units for TechniqueOne. The requirements of T-432.2 are not applicable tothe TOFD technique.

lll-434 Calibration Blocks

lll-434.1.1 Reflectors. Side drilled holes shall beused to confinn adequate sensitivity settings.

lll-434.2.1 Basic Calibration Block. The basiccalibration block configuration and reflectors shall be asshown in Fig.III-434.2.1(a). A minimum of two holesper zone, if the weld is broken up into multiple zones,is required. See Fig. III-434.2.1(b) for a two zone exam-ple. The block size and reflector location shall be adequateto confirm adequate sensitivity settings for the beamangles used.

lll-434.2.2 Block Thickness. The block thicknessshall be at +10Vo of the nominal thickness of the pieceto be examined for thicknesses up to 4 in. (100 mm) or+0.4 in. (10 mm) for thicknesses over 4 in. (100 mm).Alternatively, a thicker block may be utilized providedthe reference reflector size is based on the thickness to

ITT-434

3/r , t2.4)t / , {3.2)3/ru {4.8)

lo tol

be examined and an adequate number of holes exist tocomply with III-434.2.1 requirements.

lll-434.2.3 Block Range of Use. The requirementsof T-434.2.3 are not applicable to the TOFD technique.

lll-434.2.4 Alternate Block. The requirements ofT-434.2.4 are not applicable to the TOFD technique.

III-434.3 Piping Calibration Block. The require-ments of T-434.3 are not applicable to the TOFD tech-nique.

III-434.4 Cladding Calibration Blocks. The require-ments of T-434.4 are not applicable to the TOFD tech-nique.

Ill-434 Mechanics

Mechanical holders shall be used to ensure that probespacing is maintained at a fixed distance. The mechanicalholders shall also ensure that alignment to the intendedscan axis on the examination piece is maintained. Probemotion may be achieved using motorized or manualmeans and the mechanical holder for the probes shall beequipped with a positional encoder that is synchronizedwith the sampling of A-scans.

ARTICLE 4 - ULTRASONIC EXAMINATION METHODS FOR WELDS

Weld Th i ckness , i n . (mm) Ho le D iame te r , i n . (mm)

-f-I

T

IY

G E N E R A L N O T E S :(a ) Ho les sha l l be d r i l l ed and reamed 2 i n . ( 50 mm) deep m in imum, essen t i a l l y pa ra l l e l t o t he exam ina t i on su r f ace .(h) Hole Tolerance. The to lerance on diameter shal l be + l t r in. {x 0.8 mm). The to lerance on Iocat ion through the block th ickness shal l be

t l" in. tx 3.2 mm).( c ) A l l ho l es sha l l be l oca ted on t he same face ( s i de ) o f t he b l ock and a l i gned a t t he app rox ima te cen te r o f t he f ace ( s i de ) .(d) When the weld is broken up into mul t ip le zones, each zone shal l have a T, /4 and Tr3/4 s ide dr i l led hole, where I , is the zone th ickness.

FIG. III-434.2.Ih) TOFD REFERENCE BLOCI(

59.2

III.46O 2OO4 SECTION V trr-47t.1

t-I

T

II

_l-G E N E R A L N O T E S :(a) 11 equals the thickness of the upper zone.(b) 12 equals the thickness of the lower zone.

III-460 CALIBRATION

III-463 Calibration for Nonpiping

III-463.1 Calibration Block. Calibration shall be per-formed ut i l iz ing the cal ibrat ion b lock shown in F ig.434.2.1(a) or on the material to be examined.

lll-463.2 Calibration. Set the TOFD probes on thesurface to be utilized for calibration and set the gaincontrol so that the lateral wave amplitude is from 407oto 90Vo of the full screen height (FSH) and the noise(grass) level is less than 5-10Vo FSH. This is the referencesensitivity setting. For multiple zone examinations whenthe lateral wave is not displayed, or barely discernible,set the gain control based solely on the noise (grass) level.

III-463.3 Confirmation of Sensitivity. Scan the cali-bration block's SDHs with them centered between theprobes, at the reference sensitivity level set inIII-463.2.The SDH with the weakest response shall display anindication of 80Vo of FSH minimum.

ll l-463.4 Multiple Zone Examinations. When aweld is broken up into multiple zones, repeat lll-463.2and III-463.3 for each TOFD probe pair. In addition, thenearest SDH in the adjoining zone(s) shall be detected.

III-463.5 Width of Coverage Confirmation. Twoadditional scans per III-463.3 shall be made with theprobes offset to either side of the applicable zone's weldedge +'f in. (13 mm). If all the required holes are notdetected, two additional offset scans are required with

F IG I I I - 434 .2 .1 (b ) TWO-ZONE REFERENCE BLOCI ( EXAMPLE

the probes offset by the distance(s) identified above. SeeFig. III-463.5 for an example.

III-463.6 Encoder. Encoders shall be calibrated perthe manufacturer's recommendations and confirmed bymoving a minimum distance of 20 in. (500 mm) andthe displayed distance being +lqo of the actual distancemoved.

lll-464 Calibration for Piping

The requirements of T-464 are not applicable to theTOFD technique.

III-465 Calibration for Cladding

The requirements of T-465 are not applicable to theTOFD technique.

Ill-467 Encoder Confirmation

A calibration check shall be performed at intervals notto exceed one month or prior to first use thereafter, madeby moving the encoder along a minimum distance of 20in. (500 mm) and the displayed distance being +l7o s1the acutal distance moved.

III-470 EXAMINATION

Ill-471.1 Examination Coverage. The volume to bescanned shall be examined with the TOFD probe pair

Upper zone

Lower zone

59.3

Ut-471.1

centered on and transverse to the weld axis and thenmoving the probe pair parallel to and along the weld axis.If offset scans are required due to the width of the weld,repeat the initial scan with the probes offset to one sideof the weld axis and again with the offset to the oppositeside of the first offset scan.

lll-471.4 Overlap. The minimum overlap betweenadjacent scans shall be I in. (25 mm).

III-471.5 Multiple Zone Examination. When a weldis broken down into multiple zones, repeat III-411.1 foreach weld zone.

III-471.6 Recording Data (Gated Region). Theunrect i f ied (RF waveform) A-scan s ignal shal l berecorded. The A-scan gated region shall be set to startjust prior to the lateral wave and, as a minimum, not enduntil all of the first back-wall signal with allowance forthickness and mismatch variations, is recorded. Usefuldata can be obtained from mode-converted signals; there-fore, the interval from the first back-wall to the mode-convefied back-wall signal shall also be included in thedata collected when required by the referencing Code.

III-471.8 Transverse Examination. When requiredby the referencing Code Section, position each TOFDprobe pair essentially parallel to the weld axis and move

ITI-473

the probe pair along and down the weld axis. If the weldreinforcement is not ground smooth, position the probeson the adjacent plate material as parallel to the weld axisas possible.

lll-471.9 Supplemental Shear Wave Examination.Due to the presence of the lateral wave and back-wallindication signals, flaws occurring in these zones maynot be detected. Therefore, the weld's near surfaces (i.e.,both top and bottom faces) shall be angle beam examinedper Article 4 requirements with the angles chosen thatare closest to being perpendicular to the fusion lines. Thisexamination may be performed manually or mechanized;if mechanized, the data shall be collected in coniunctionwith the TOFD examination.

ttt-472 Weld Joint Distance AmplitudeTechnique

The requirements of T-412 are not applicable to theTOFD technique.

III-473 Cladding Technique

The requirements of T-473 are not applicable to theTOFD technique.

ARTICLE 4 - ULTRASONIC EXAMINATION METHODS FOR WELDS

. SCAN #3PCS offset +1/z of applicable zone

SCAN #1PCS centered on weld

axts

SCAN #2PCS offset -1lz of appl icable zone

wid th +r /z in . (13 mm)

FIG, I I I -463.5 OFFSET SCANS

59.4

III-475

ilt-475

2OO4 SECTION V tv-492

Data Sampling Spacing

A maximum sample spacing of 0.040 in. (l mm) shallbe used between A-scans collected fbr thicknesses under2 in. (50 mm) and a sample spacing of up to 0.080 in.(2 mm) may be used for thicknesses greater than 2 in.(50 mm).

III-485 Missing Data Lines

Missing lines in the display shall not exceed 5Vc ofthe scan lines to be collected. and no adiacent lines shallbe missed.

III-486 Flaw Sizing and Interpretation

When height of flaw sizing is required, after the systemis calibrated per III-643, a free run on the calibrationblock shall be performed and the depth of the back-wallreflection calculated by the system shall be +0.4 in. (lmm) of the actual thickness. For multiple zone examina-tions where the back wall is not displayed or barelydiscernible. a side drilled hole in the calibration blockshall be used. See Nonmandatory Appendix N of thisArticle for additional information on flaw sizins and inter-pretation.

III-490 DOCUMENTATION

III-492 Examination Record

For each examination. the required information inT-492 and the following information shall be recorded:

(a) probe center spacing (PCS)(b l dan sampl ing spacing(c) flaw height. if specified

III-493 Report

A report of the examination shall be made. The reportshall include those records indicated in T-491, T-492,and III-492. The report shall be filed and maintained inaccordance with the referencins Code Section.

APPENDIX IV - PHASED ARRAY.SINGLE FIXED ANGLE WITHMANUAL RASTER SCANNING

IV-410 SCOPE

This Mandatory Appendix describes the requirementsto be used for a manual phased array ultrasonic examina-tion utilizing a single fixed angle with manual rasterscanning.

TABLE IV-422R E Q U I R E M E N T S O F A P H A S E D A R R A Y , S I N G L E

FIXED ANGLE WITH MANUAL RASTER SCANNINGEXAMINATION PROCEDURE

Requirements(As App l icab le )

Essential NonessentialVariable Variable

Search uni t type, e lement s izeand number, and pi tch andgap d imens ions

Focus range ( ident i fy ing plane,

depth, or sound path, asapp l i cab le )

TV-420 GENERAL

The requirements of Article 4 apply except as modifiedby this Appendix.

lV-422 WrittenProcedureRequirements

lV-422.1 Requirements. Phased array, single fixedangle with manual raster scanning shall be performed inaccordance with a written procedure which shall, as aminimum, contain the requirements listed in TablesT-422andIII-422. The written procedure shall establish a singlevalue or range of values for each requirement.

lY -422.2 Procedure Qualifi cation. When procedurequali{ication is specified, a change of a requirement iden-tified as an essential variable shall require requalificationof the written procedure by demonstration. A change ofa requirement identified as a nonessential variable doesnot require requalification of the written procedure. Allchanges of essential or nonessential variables from thosespecified within the written procedure shall require revi-sion of, or an addendum to, the written procedure.

IV-461 Instrument Linearity CheckslY-461.2 Amplitude Control Linearity. The ultra-

sonic instrument's amplitude control linearity shall beevaluated in accordance with Mandatory Appendix IIIfor each pulser-receiver circuit.

lV-462 GeneralCalibrationRequirements

lV-462.7 Focal Law.r The focal law to be used durinsthe examination shall be used for calibration.

IY-492 Examination Record

For each examination, the required information ofT-492 and the following information shall be recorded:

' Focal law is defined as a phased array operational file that definesthe search unit elements and their time delavs, for both the transmitterand receiver function.

59.5

IY.492 ARTICLE 4 - ULTRASONIC EXAMINATION METHODS FOR WELDS TV-492

(a) search unit type, element size and number, andpitch and gap dimensions

(b) focal law parameters, including angle, focal depth,and elements used

59.6