Ultrasonido Por Arreglo de Fases

Q SPACE Engineering Oil & Gas Services

PHASED ARRAY UT PROCEDURE FOR WELDS

PHASED ARRAY

ULTRASONIC INSPECTION

GENERAL PROCEDURE

FOR WELDS

QSE/JV Revision 00, issued: 03-09

P.O. Box 534, Doha, State of Qatar, Office Tel +974 4110939, Fax:+974 4764239, Mobile: 0974-3120085 Email: [email protected]



CONTENTS

DESCRIPTION PAGE

COVER PAGE 1

CONTENTS 2

SECTION

1.0INTRODUCTION 3

2.0 PURPOSE AND SCOPE 3

3.0 REFERENCES 3

4.0 PERSONNEL QUALIFICATION 3

5.0 PREPARATION OF EXAMINATION AREA 4

6.0 EQUIPMENT 4

7.0 CALIBRATION 6

8.0 EXAMINATION AND RECORDING CRITERIA 8

9.0 ACCEPTANCE CRITERIA 12

10.0 REPORTING 12

QSE/JVRevision 00, issued: 03-09-09, page 2 of 2




1.0 INTRODUCTION

This procedure describes the contact ultrasonic method in which the probe makes direct contactwith the material and the ultrasonic instrument is a phased array unit. The probes addressed bythe instrument may be phased array or single element probes.

2.0 PURPOSE AND SCOPE

This procedure defines the requirements of mechanized pulse echo mode contact ultrasonicexamination of welds. This procedure shall apply to the general aspects of ultrasonic inspectionof welds using the phased array techniques and equipment.

These aspects include;

• monitoring the performance of the equipment• configuring the display and data acquisition parameters• calibration of time base and sensitivity• description of the recording criteria• identification and layout of the components to be tested• surface conditions required• details of the equipment used and the volumes covered

Details of scanning shall be found in the associated technique sheets. Scanning for transverseflaws may be done using either manual, fully automatic or mechanised techniques.This procedure is applicable to ultrasonic examination of welded components for new and inservice welds

Provisions are incorporated into this procedure and the special adaptations unique to theirimplementation are described in this procedure and the associated standard practices referencedby this procedure. Since the qualification of this procedure and associated standard practicesand techniques is unique to the TD Handy Scan instrument, this procedure is not valid with anyother instrument.

This procedure is valid for only those techniques that are identified and are recorded in the latestrevision of this procedure.

3.0 REFERENCES

The following documents shall be referenced with this procedure:GSOP5003, Q Space Eng/JV Written Practice for Training, Qualification and Certification of NDTPersonnel to ASNT SNT-TC-1AGSOP5004, Procedure for Training, Qualification and Certification of NDT Personnel to CP-189EN 473, Qualification and Certification of NDT PersonnelBS 7706, Guide to Calibration and Setting-up of the Ultrasonic Time-of-Flight Diffraction (ToFD)technique for Detection, Location and Sizing of FlawsASNT SNT-TC-1A, Recommended Practice for Training, Qualification and Certification of NDTPersonnelASNT CP-189, ASNT Standard for Training, Qualification and Certification of NDT PersonnelASME Section V, Non-destructive Examination



4.0 PERSONNEL QUALIFICATION

4.1 Personnel shall be qualified in accordance with QSPACE/JV Written Practice as referenced initem 3.0 above.

4.2 Personnel evaluating phased array ultrasonic inspection results shall be qualified to a minimum ofLevel II.

4.3 The responsibility for the accuracy and completeness of an examination report is verified byeither Level II or III qualified ultrasonic personnel. Level I operators may perform specific dutiesrequired for the examination if under the direct supervision of a Level II or III certified technician.

5.0 PREPARATION OF EXAMINATION AREA

5.1 Surface PreparationThe scanning area shall be rendered free of dirt, loose scale, weld splatter, machining particles,or corrosion products. Where the surface cannot be made suitable for ultrasonic inspection bylight brushing and wiping, the Client representative and Q Space/JV shall be advised. The basematerial or weld shall be prepared as needed to permit examination.

5.2 Weld Marking and Inspection Area LocationNumbers allocated to welds being examined shall designate inspection areas.

Each weld designated for inspection shall be marked with a reference index and/or positionnumbers marked on the examination surface during initial examination. This shall include amethod for identifying the location of the weld centerline. If welds are to be permanently marked,low stress stamps or vibra-tools may be used such that the marks are not deeper than 1mm.

Unless specifically noted otherwise, all circumferential measurement shall be made clockwisefrom the zero reference position on the weld when looking in the direction of product flow. Whenscans are made from a pipe to a flange or fitting where no scan access is had on the flange orfitting, the circumferential measurement shall be made clockwise when looking at the flange orfitting from the pipe side.

6.0 EQUIPMENT

6.1 Examination Equipment

6.1.1 Ultrasonic Test Instruments

This procedure shall use the TD Handy Scan phased array ultrasonic inspection unit exclusively.The ultrasonic flaw detection instrument shall be used in the pulse echo or pitch-catch mode withan A-Scan presentation used for calibration. The instrument is equipped with a stepped gaincontrol calibrated in units of 1dB or less. The equipment is capable of amplitude control over itsuseful range and Time Corrected Gain (TCG) shall be used in lieu of a simple Distance

Amplitude Correction (DAC) curve.

6.1.2 Search Units

Search units used for weld examinations shall operate at a frequency between 2 MHz and 10MHz. either phased array or single element probes may be used. Phased array linear arrayconfigurations shall have 16 elements or more having element width of 6mm to 15mm. Elementspacing will be search unit design specific and based on the calculations for element pitch to



provide beam steering of +/- 20°. For typical shear wave applications the phased array probe willbe placed on a refracting wedge of suitable material and refracting angle as to be compatiblewith the requirement to provide beam steering of +/- 20°.

In addition to phased array search units, pulse-echo single element probes may be used wheregeometry or resolution or other factors dictate that there is advantage to do so such as forthickness assessments, transverse scanning and TOFD techniques.

6.1.3 Couplant

Couplant used shall contain no ingredients deemed harmful to the test piece. For automated ormechanised scanning, water shall be used. Alternatively, Ultragel or Glycerine may be used anddiluted with water to reduce viscosity so as to facilitate its movement through irrigation lines.Ultragel or Glycerine is also approved for use on the work piece when performing manualtransverse scans.

6.1.4 Calibration Blocks

Weld inspections using the TD Handy Scan shall be calibrated using standard calibration blocksand blocks fabricated from material that is acoustically similar to that being inspected and whichhas been subjected to minimum heat treatment required by the material specification. Thesurface of calibration blocks is finished to approximately 10 micron Ra. At no time shall thecalibration block surface be inferior to the test piece surface.

Calibration blocks are of 2 types i.e. range setting calibration blocks and sensitivity settingcalibration blocks.

6.1.4.1 Range Setting Calibration Blocks

Blocks used to set instrument range include:

a) International Institute of Welding (IIW) (BS A2) for range calibration

b) Din 54-122 (V2) (BS A4) alternative for range calibration

c) Standard Thickness Calibration Block (ladder step wedge)

Other range setting blocks may be used provided they are demonstrated to provide the accuracyrequired for the materials examined.

6.1.4.2 Sensitivity Setting Calibration Blocks

Prior to fabrication, the block material shall be completely examined with a straight beam searchunit. Areas that contain an indication exceeding the remaining back-wall reflection shall beexcluded from the beam paths required to reach the various calibration reflectors.

When the component material to be examined is clad, the block shall be clad by the samewelding process as the production part.

For ultrasonic examinations the design requirements for the basic calibration block are providedin Table 2. Hole placement and hole dimensions are detailed in Table 2. Aspects of design suchas minimum block dimensions should be considered based on the ultrasonic techniques used.Reference blocks shall be made with thickness and side-drilled holes in accordance with Table 2.



Table 1Ultrasonic Reference Block Requirements

Thickness ofMaterial to be

inspected (mm)

Thickness of block(mm)

Diameter Hole Distance of Hole from Surface

10< t≤50 40 or t

3mm (+/-0.2mm) t/2 and t/4Additional holes areallowed andrecommended

50 < 100 75 or t

100 <t≤ 150 125 or t

6mm (+/-0.2mm)

150 <t≤ 200 175 or t

200 <t≤ 250 225 or t

t > 2500 275 or t

For examinations in materials with diameters greater than 500 mm, a block of essentially thesame curvature, or alternatively, a flat basic calibration block, may be used.

For examinations in materials with diameters 500 mm and less, a curved block shall be used.Unless otherwise specified, a single curved basic calibration block may be used for examinationsin the range of curvature from 0.9 to 1.5 times the basic calibration block diameter

7.0 CALIBRATION

7.1 Equipment Calibration

7.1.1 Instrument Linearity Checks

All instruments are subject to the following linearity checks before use. Details of the stepsinvolved in the set-up of equipment for calibration can be found in the Standard Guide for Use ofTD Handy Scan. The results of these checks are recorded in the Ultrasonic instrument Linearity

Report forms (see standard practice for Verification of TD Handy Scan Linearity Performance)and are kept as part of the Inspection Record.

Instrument Linearity Checks are conducted:

a) on initial receipt of equipmentb) at the commencement of an inspection campaignc) on a twelve month cycled) after any electronic repair or physical damagee) or for any other reason deemed appropriate at intervals less than 12 months

7.1.1.1 Screen Height Linearity - The TD Handy Scan instrument shall provide vertical amplitudepresentation linear to within +/- 3% of full screen height over the range 10% to 100% of fullscreen height. The method for evaluating screen height linearity is outlined in standard practicefor Verification of TD Handy Scan Linearity Performance.

7.1.1.2 Amplitude Control Linearity (Calibrated Gain Control) - The accuracy of amplitude control on theTD Handy Scan instrument is verified. The method for evaluating amplitude control linearity isoutlined in standard practice for Verification of TD Scan Linearity Performance.

7.1.1.3 Sweep Range Linearity (Horizontal Linearity) - The ultrasonic instrument must provide sweep



range linearity accurate to +/-2% of the total base line. The method for evaluating sweep rangelinearity is outlined in standard practice for Verification of TD Scan Linearity Performance.

7.1.2 Search Unit Checks

Because the TD Handy Scan ultrasonic instrument is a phased array instrument many of theparameters associated with standard single element probes such as exit point and nominal angledo not apply. As well, probes using curved wedges to fit the diameter of pipes, and componentswill not permit measurements of nominal angle and exit points using the standard calibrationblocks (IIW and DIN-54) as they cannot be used on flat surfaces. Standard Practice forVerification of Performance of Probes used with TD Handy Scan will be used as appropriate toassess the suitability of the probe and focal laws applied to phased array probes. Guidance forProbe Performance is also found in this Standard Practice for assessment of single elementprobes when used with the TD Handy Scan phased array ultrasonic instrument.

Search unit Checks are conducted:

a) on initial receipt of equipmentb) at the commencement of an inspection campaignc) on a one month cycled) after any electronic repair or physical damagee) or for any other reason deemed appropriate at intervals less than 1 month

7.2 Calibration - Weld Examination

7.2.1 Range and Signal Amplitude (TCG) Calibration

The TD HandyScan is calibrated for each examination specified on the detailed technique forboth range and signal amplitude.

a) Range setting for both shear and longitudinal wave examination is detailed in Standard Practice for Setting Range using TD Handy Scanb) Time Corrected Gain is applied as detailed in Standard Practice for Distance Amplitude Correction using TD Handy Scan.

7.2.2 Calibration Confirmation

A system calibration confirmation shall be used to verify the sweep range calibration and DACand or TCG curve at the start and finish of each examination and at a minimum of once each dayduring an examination session using the appropriate calibration block

Any change in search units, shoes, couplants, cables, ultrasonic instruments, personnel or otherparts of the examination system is cause for a calibration check.

Calibration checks are performed as follows:

a) The sensitivity control settings are adjusted to match those recorded for the calibrated reference sensitivity of the middle focal law of a single angle Phased Array scanning technique or the single element probe for non-phased array probe applications.

b) The search unit is positioned to detect the first and last points on the TCG using the reference reflectors on the appropriate basic calibration block. The maximum signalresponse amplitudes and horizontal sweep positions are observed.

c) If either point along the time base using the TCG has decreased by greater than 2 dB in



amplitude, all recorded data sheets since the last calibration check are marked void. A newcalibration is made and recorded and the voided examination areas re-examined.

d) If any point along the time base using the TCG has increased by greater than 2 dB inamplitude, only recorded indications taken since the last valid calibration check need be reexaminedwith the correct calibration and their values changed on the data sheets or filesrescanned.

e) If during system confirmation of calibration, any point on the time base has moved on thesweep line more than 5% of the total base line, correct the sweep range calibration. Ifrecordable reflectors are noted on the data sheets, these data sheets are voided, a newcalibration is recorded and the voided examination is repeated.

7.3 Transfer Values

Loss of sound transmission due to surface geometry, or surface condition (roughness orcoatings), can be compensated using a transfer value. Transfer value shall be determined usingStandard Practice for Determining Acoustic Compatibility using TD Handy Scan.

Any difference between the transfer value obtained on the basic calibration block and the testpiece is added to the Primary Reference and this noted in the report. If a negative dB valueresults from the transfer value determination, no adjustment to the primary Reference shall bemade.

7.4 Temperature Control

For contact examination, the temperature differential between the calibration block and theexamination surface shall be within +/-10C°.

7.5 Instrument Controls

Any controls affecting the linearity of the instrument shall be in the same position for calibration,calibration checks, instrument linearity checks and examinations.

7.6 Encoding

Automated scanning shall use position encoders that are verified to provide position accuracy ofscans within +/-1mm in 100mm of scan length. All encoders shall be verified daily to be correctlycalibrated. Moving the scanning apparatus over a fixed distance (e.g. 150mm) and comparingthe start and end readings is sufficient to verify the calibration of the encoder. All encodeddistances recorded by the data acquisition system shall be accurate to within 2mm over 100mmof actual travel. Encoders failing to maintain this tolerance shall be re-calibrated.

8.0 EXAMINATION AND RECORDING CRITERIA

8.1 Weld Examination - General Description

Each weld configuration has its own individual technique that describes in detail the type andextent of the examination. Techniques will be described using the format detailed in StandardPractice for Technique Layout and TD Handy Scan parameters.

8.1.1 Inspection Area

Each inspection area is identified with a unique "weld" number. The width of the inspection areaextends beyond the point of maximum width of the final weld preparation for a minimum distanceof one-half the material thickness or 25 mm, which ever is less.



The weld zone is defined as the weld and the base metal up to 10 mm (Heat Affected Zone -HAZ), from the edge of the final weld preparation, as illustrated in Figure 1. The base material oneither side of the inspection area of pipe welds need not be examined for laminations that wouldinterfere with shear wave examination if these materials have been inspected for laminarinclusions at some previous stage in fabrication. .

HAZ HAZ

Inspection Area / Weld zone / Scanning zone

Weld Profile Will Showing Inspection Area and Weld Zone

Non-Relevant Indications

Signals which are determined to result from metallurgical discontinuities and/or geometricalconditions (such as weld root geometry, or weld to base metal interface) are classified asgeometric reflectors. Such reflectors are not characterised as indications nor compared withallowable indication standards. They are clearly identified, located, and recorded in theInspection Record for future reference.

The presence of geometric reflectors is confirmed either by reviewing the fabrication drawings ofthe weld preparation, the previous Inspection Records or by supplemental inspection results.

TOFD scanning may be used to aid in discriminating between flaws and geometric reflectorswhere surface scanning areas permit. When TOFD is carried out, guidance on its use shall followthe instructions in BS7706.Every “root” indication shall be carefully examined to determine its nature (crack / LOF / LOP /



geometrical).

In respect to weld configuration: With a single V a root indication will be masked by a surfaceindication as per 10.0 note 5.

In a 50/50 double V ToFD can support findings like LOP / LOF / centre line cracking.

8.1.2 Inspection Scan Types

Automated weld inspection for laminar flaws is carried out using a phased array linear rasterscan using focal laws providing a 0° beam in the inspection volume when possible. Restrictionsdue to geometries of surroundings shall be reported.

Automated weld inspection for axial flaws is carried out using a phased array linear raster scanusing focal laws providing angled beam examination of the inspection volume. Restrictions dueto geometries of surroundings shall be reported.

Manual or automated transverse scans in two directions either side of the weld cap will also becarried out where access permits. Restrictions due to geometries of surroundings shall bereported.

All automated scanning shall be position encoded at sampling intervals of 1mm.

8.1.3 Recording

a) General

The fundamental criterion for the evaluation of the existence of an ultrasonic examinationindication is the amplitude of the indication in relation to a specified reference level. Thereference level is established during calibration of the test instrument on the sensitivitycalibration block and set so that the amplitude from the applicable notches or holes are set to80% full screen height using TCG. Scanning shall be done at the Primary Reference levelplus any gain required for transfer value.

TD Handy Scan Phased Array ultrasonic instrument is a digital instrument. Analogue toDigital Conversion will be at a rate suitable to ensure that the recorded peak signal is within1dB of the analogue peak. This shall be considered achieved when the digitisation rate isset to at least 5 times the nominal frequency of the probe used1. Actual digitisation settingsshall be specified in the Technique.

b) Sequence of Examination Reporting

The Site Examination Record is a record prepared by the ultrasonic technician containing thedata pertaining to an examination of a particular weld. This is the raw data collected in theTD-Scan software.

The Ultrasonic Inspection Data Record Sheet 2 is the official source of ultrasonic records onwhich observed reflectors are plotted, and all inspection results are permanently recorded.

This form will include weld number, technique number, project information, minimumthickness noted and the status of the inspection (accept/reject) with pertinent indicationsnoted if repairs are required. Standard Practice for Report and Data Display using TD HandyScan provides instruction on the preparation of the Report.The site examination record data file shall be kept on file with the Ultrasonic Inspection DataRecord Sheet.

8.2 Detailed Examination and Recording Sequence



8.2.1 Calibration of Equipment

The examination equipment shall be calibrated as described in item 8.0 herein to verify linearityand set range and sensitivity.

8.2.2 Thickness Measurements

Thickness Measurements - Weld Inspection

At the examination site, the ultrasonic operator takes an initial thickness measurement. Thethickness is compared to the thickness indicated on the detailed technique to confirm that thetechnique and related range settings are applicable. This thickness assessment may be madeusing a separate zero degree probe with TD Handy Scan unit or as part of any required scanresults from a 0° scan.

Thickness measurements are to be noted at the edge of the weld cap and at 50 mm either sideof the weld at 3 points around the circumference of the weld. The minimum thickness reading isrecorded.

8.2.3 Shear Wave Scanning and Recording

The instrument is calibrated as described in Standard Practice for Verification of Performance ofProbes used with TD Handy Scan, Standard Practice for Setting Range using TD Handy Scan,Standard Practice for Distance Amplitude Correction using TD Handy Scan and StandardPractice for Determining Acoustic Compatibility using TD Handy Scan.Calibration checks are performed when required as outlined in item 8.0 herein.

8.2.4 Scanning Sensitivity

Scanning of all welds is performed at a gain setting equal to the Primary Reference Sensitivityplus any transfer value. On the Data Acquisition display an evaluation threshold is set using acolour threshold at 6dB below the Primary Reference level. Typically Primary Reference level isset at 80% Full Screen Height and the evaluation level is then 40% FSH.

8.2.5 Scanning Normal to the Weld (Axial Scan)

The probe is directed at 90° to the weld centre line and mechanically moved so that theultrasonic beam passes through all of the inspection area. This is accomplished by an electronicraster or S-scan. Where possible, the weld is scanned from both sides of the same surface. Thespeed of scanning is such as to ensure that coupling and data acquisition integrity is maintained.

Data recorded will ensure encoded samples along the weld are at 1mm intervals and not greaterthan 10% of data points shall be missed in a weld scan with not more than 3 adjacent samplesmissing in a single scan.

8.2.6 Scanning Parallel to the Weld (Transverse Scan)

The search unit is aimed essentially parallel to the weld centre line and moved along the weld sothat the ultrasonic beam passes through the weld zone. Scanning is done in two directionsessentially 180° to each other. Swiveling of the probe is not possible when using shapedwedges.

Probe motion may be made manually. The speed of scanning is such as to ensure that coupling



is maintained. Where access permits the weld is scanned from both sides on the same surface.

Due to weld cap configurations the surface of the weld may not be a suitable scan surface.When the weld cap is not a suitable scan surface the probe will need to be positioned close tothe weld cap edge and the beam directed towards the weld centerline (i.e. “essentially” parallel tothe weld axis) where curvature permits.

8.2.7 Recording and plotting – Axial Shear Scan

All A-scan waveforms shall be recorded using a digitisation not less than 5 times the nominalfrequency of the probe. Recording shall be in the form of an “RDT” data file and evaluation of thescan results shall be made using B-scan or S-scan and C-scan projections with colour palletsthat allow the operator to discriminate between signals above or below the evaluation threshold.

Relevant indications greater than or equal to -6dB reference shall be evaluated against theapplicable acceptance criteria. Rejectable indications are plotted showing dimensions, locationrelative to the weld centre line and vertical extent when required. Length shall be determinedusing the 6 dB drop method for signals less than 80% and for flaw signals with amplitudesgreater than 80% length shall be determined to the 40% limits

When vertical extent is required it shall be determined using the tip diffraction sizing technique.Vertical sizing methods are described in Standard Practice for Determining Vertical Extent withTD Handy Scan.

9.0 ACCEPTANCE CRITERIA

Results of weld inspections to this procedure will be compared to the requirements of thereferencing code unless otherwise instructed by written instructions.

10.0 REPORTING

After each inspection an Inspection Report shall be prepared. This report describes the workdone, the equipment used, the qualification of the inspection personnel and the results.Additional inspection results (if any) are also reported and alternate methods of inspectiondescribed.

The final report for each weld shall include;

a) Project name, contract detailsb) Procedure and technique identificationc) Equipment used (UT instrument, probes, cables, manipulators, couplant)d) Computer programme identification and versione) Instrument gain settings sensitivity or reference targetf) Weld Identificationg) Scan Surfaceh) Record of rejectable indications locations or areas clearedi) Areas of restricted accessj) Personnel and their qualificationsk) Date and Time of the examination

_______________1 This is not addressed in EN 1714 but it is an essential variable and the 5 times nominal is documented in IIW AUT guides2 This is intended to be a summary sheet that includes weld number, status, applicable technique # and any relevant findings andrepair information of reject able flaws.


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Ultrasonido Por Arreglo de Fases