38686711-Phased-Array-Ut-Procedure-for-Welds.docx

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]

Q SPACE Engineering Oil & Gas Services

PHASED ARRAY UT PROCEDURE FOR WELDS

CONTENTS DESCRIPTION PAGE COVER PAGE 1 CONTENTS 2 SECTION 1.0 INTRODUCTION 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/JV P.O. Box 534, Doha, State of Qatar, Office Tel +974 4110939, Fax:+974 4764239, Mobile: 0974-3120085 Email: [email protected]

Q SPACE Engineering Oil & Gas Services Revision 00, issued: 03-09-09, page 2 of 2

PHASED ARRAY UT PROCEDURE FOR WELDS 1.0 INTRODUCTION This procedure describes the contact ultrasonic method in which the probe makes direct contact with the material and the ultrasonic instrument is a phased array unit. The probes addressed by the 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 ultrasonic examination of welds. This procedure shall apply to the general aspects of ultrasonic inspection of 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 transverse flaws may be done using either manual, fully automatic or mechanised techniques. This procedure is applicable to ultrasonic examination of welded components for new and in service welds Provisions are incorporated into this procedure and the special adaptations unique to their implementation are described in this procedure and the associated standard practices referenced by this procedure. Since the qualification of this procedure and associated standard practices and techniques is unique to the TD Handy Scan instrument, this procedure is not valid with any other instrument. This procedure is valid for only those techniques that are identified and are recorded in the latest revision 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 NDT Personnel to ASNT SNT-TC-1A GSOP5004, Procedure for Training, Qualification and Certification of NDT Personnel to CP-189 EN 473, Qualification and Certification of NDT Personnel BS 7706, Guide to Calibration and Setting-up of the Ultrasonic Time-of-Flight Diffraction (ToFD) technique for Detection, Location and Sizing of Flaws ASNT SNT-TC-1A, Recommended Practice for Training, Qualification and Certification of NDT Personnel ASNT CP-189, ASNT Standard for Training, Qualification and Certification of NDT Personnel ASME Section V, Non-destructive Examination


Q SPACE Engineering Oil & Gas Services 4.0 PERSONNEL QUALIFICATION 4.1 Personnel shall be qualified in accordance with QSPACE/JV Written Practice as referenced in item 3.0 above. 4.2 Personnel evaluating phased array ultrasonic inspection results shall be qualified to a minimum of Level II. 4.3 The responsibility for the accuracy and completeness of an examination report is verified by either Level II or III qualified ultrasonic personnel. Level I operators may perform specific duties required 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 Preparation The 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 by light brushing and wiping, the Client representative and Q Space/JV shall be advised. The base material or weld shall be prepared as needed to permit examination. 5.2 Weld Marking and Inspection Area Location Numbers allocated to welds being examined shall designate inspection areas. Each weld designated for inspection shall be marked with a reference index and/or position numbers marked on the examination surface during initial examination. This shall include a method 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 clockwise from the zero reference position on the weld when looking in the direction of product flow. When scans are made from a pipe to a flange or fitting where no scan access is had on the flange or fitting, the circumferential measurement shall be made clockwise when looking at the flange or fitting 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 with an A-Scan presentation used for calibration. The instrument is equipped with a stepped gain control calibrated in units of 1dB or less. The equipment is capable of amplitude control over its useful 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 10 MHz. either phased array or single element probes may be used. Phased array linear array configurations shall have 16 elements or more having element width of 6mm to 15mm. Element spacing 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 will P.O. Box 534, Doha, State of Qatar, Office Tel +974 4110939, Fax:+974 4764239, Mobile: 0974-3120085 Email: [email protected]

Q SPACE Engineering Oil & Gas Services be placed on a refracting wedge of suitable material and refracting angle as to be compatible with the requirement to provide beam steering of +/- 20°. In addition to phased array search units, pulse-echo single element probes may be used where geometry or resolution or other factors dictate that there is advantage to do so such as for thickness assessments, transverse scanning and TOFD techniques. 6.1.3 Couplant Couplant used shall contain no ingredients deemed harmful to the test piece. For automated or mechanised scanning, water shall be used. Alternatively, Ultragel or Glycerine may be used and diluted 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 manual transverse scans. 6.1.4 Calibration Blocks Weld inspections using the TD Handy Scan shall be calibrated using standard calibration blocks and blocks fabricated from material that is acoustically similar to that being inspected and which has been subjected to minimum heat treatment required by the material specification. The surface of calibration blocks is finished to approximately 10 micron Ra. At no time shall the calibration block surface be inferior to the test piece surface. Calibration blocks are of 2 types i.e. range setting calibration blocks and sensitivity setting calibration 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 accuracy required 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 search unit. Areas that contain an indication exceeding the remaining back-wall reflection shall be excluded 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 same welding process as the production part. For ultrasonic examinations the design requirements for the basic calibration block are provided in Table 2. Hole placement and hole dimensions are detailed in Table 2. Aspects of design such as 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 1 Ultrasonic Reference Block Requirements P.O. Box 534, Doha, State of Qatar, Office Tel +974 4110939, Fax:+974 4764239, Mobile: 0974-3120085 Email: [email protected]

Q SPACE Engineering Oil & Gas Services Thickness of Material to be inspected (mm) 10< t≤50

Thickness of block (mm)

50 < 100

75 or t

100
125 or t

150
175 or t

200
225 or t

t > 2500

275 or t

Diameter Hole

Distance of Hole from Surface

40 or t 3mm (+/-0.2mm)

t/2 and t/4 Additional holes are allowed and recommended

6mm (+/-0.2mm)

For examinations in materials with diameters greater than 500 mm, a block of essentially the same 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 examinations in 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 steps involved in the set-up of equipment for calibration can be found in the Standard Guide for Use of TD 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 equipment b) at the commencement of an inspection campaign c) on a twelve month cycle d) after any electronic repair or physical damage e) 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 amplitude presentation linear to within +/- 3% of full screen height over the range 10% to 100% of full screen height. The method for evaluating screen height linearity is outlined in standard practice for Verification of TD Handy Scan Linearity Performance. 7.1.1.2 Amplitude Control Linearity (Calibrated Gain Control) - The accuracy of amplitude control on the TD Handy Scan instrument is verified. The method for evaluating amplitude control linearity is outlined 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 range linearity is outlined in standard practice for Verification of TD Scan Linearity Performance. P.O. Box 534, Doha, State of Qatar, Office Tel +974 4110939, Fax:+974 4764239, Mobile: 0974-3120085 Email: [email protected]

Q SPACE Engineering Oil & Gas Services 7.1.2 Search Unit Checks Because the TD Handy Scan ultrasonic instrument is a phased array instrument many of the parameters associated with standard single element probes such as exit point and nominal angle do not apply. As well, probes using curved wedges to fit the diameter of pipes, and components will not permit measurements of nominal angle and exit points using the standard calibration blocks (IIW and DIN-54) as they cannot be used on flat surfaces. Standard Practice for Verification of Performance of Probes used with TD Handy Scan will be used as appropriate to assess the suitability of the probe and focal laws applied to phased array probes. Guidance for Probe Performance is also found in this Standard Practice for assessment of single element probes when used with the TD Handy Scan phased array ultrasonic instrument. Search unit Checks are conducted: a) on initial receipt of equipment b) at the commencement of an inspection campaign c) on a one month cycle d) after any electronic repair or physical damage e) 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 for both 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 Scan b) 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 DAC and or TCG curve at the start and finish of each examination and at a minimum of once each day during an examination session using the appropriate calibration block Any change in search units, shoes, couplants, cables, ultrasonic instruments, personnel or other parts 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 signal response 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 new calibration is made and recorded and the voided examination areas re-examined. P.O. Box 534, Doha, State of Qatar, Office Tel +974 4110939, Fax:+974 4764239, Mobile: 0974-3120085 Email: [email protected]

Q SPACE Engineering Oil & Gas Services d) If any point along the time base using the TCG has increased by greater than 2 dB in amplitude, only recorded indications taken since the last valid calibration check need be reexamined with the correct calibration and their values changed on the data sheets or files rescanned. e) If during system confirmation of calibration, any point on the time base has moved on the sweep line more than 5% of the total base line, correct the sweep range calibration. If recordable reflectors are noted on the data sheets, these data sheets are voided, a new calibration is recorded and the voided examination is repeated. 7.3 Transfer Values Loss of sound transmission due to surface geometry, or surface condition (roughness or coatings), can be compensated using a transfer value. Transfer value shall be determined using Standard Practice for Determining Acoustic Compatibility using TD Handy Scan. Any difference between the transfer value obtained on the basic calibration block and the test piece is added to the Primary Reference and this noted in the report. If a negative dB value results from the transfer value determination, no adjustment to the primary Reference shall be made. 7.4 Temperature Control For contact examination, the temperature differential between the calibration block and the examination 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 of scans within +/-1mm in 100mm of scan length. All encoders shall be verified daily to be correctly calibrated. Moving the scanning apparatus over a fixed distance (e.g. 150mm) and comparing the start and end readings is sufficient to verify the calibration of the encoder. All encoded distances recorded by the data acquisition system shall be accurate to within 2mm over 100mm of 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 and extent of the examination. Techniques will be described using the format detailed in Standard Practice 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 area extends beyond the point of maximum width of the final weld preparation for a minimum distance of 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 on


Q SPACE Engineering Oil & Gas Services either side of the inspection area of pipe welds need not be examined for laminations that would interfere with shear wave examination if these materials have been inspected for laminar inclusions 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 geometrical conditions (such as weld root geometry, or weld to base metal interface) are classified as geometric reflectors. Such reflectors are not characterised as indications nor compared with allowable indication standards. They are clearly identified, located, and recorded in the Inspection Record for future reference. The presence of geometric reflectors is confirmed either by reviewing the fabrication drawings of the weld preparation, the previous Inspection Records or by supplemental inspection results. TOFD scanning may be used to aid in discriminating between flaws and geometric reflectors where surface scanning areas permit. When TOFD is carried out, guidance on its use shall follow the instructions in BS7706. Every “root” indication shall be carefully examined to determine its nature (crack / LOF / LOP / geometrical).


Q SPACE Engineering Oil & Gas Services In respect to weld configuration: With a single V a root indication will be masked by a surface indication 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 raster scan using focal laws providing a 0° beam in the inspection volume when possible. Restrictions due to geometries of surroundings shall be reported. Automated weld inspection for axial flaws is carried out using a phased array linear raster scan using focal laws providing angled beam examination of the inspection volume. Restrictions due to geometries of surroundings shall be reported. Manual or automated transverse scans in two directions either side of the weld cap will also be carried out where access permits. Restrictions due to geometries of surroundings shall be reported. 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 examination indication is the amplitude of the indication in relation to a specified reference level. The reference level is established during calibration of the test instrument on the sensitivity calibration block and set so that the amplitude from the applicable notches or holes are set to 80% full screen height using TCG. Scanning shall be done at the Primary Reference level plus any gain required for transfer value. TD Handy Scan Phased Array ultrasonic instrument is a digital instrument. Analogue to Digital Conversion will be at a rate suitable to ensure that the recorded peak signal is within 1dB of the analogue peak. This shall be considered achieved when the digitisation rate is set to at least 5 times the nominal frequency of the probe used 1. Actual digitisation settings shall be specified in the Technique. b) Sequence of Examination Reporting The Site Examination Record is a record prepared by the ultrasonic technician containing the data pertaining to an examination of a particular weld. This is the raw data collected in the TD-Scan software. The Ultrasonic Inspection Data Record Sheet 2 is the official source of ultrasonic records on which observed reflectors are plotted, and all inspection results are permanently recorded. This form will include weld number, technique number, project information, minimum thickness noted and the status of the inspection (accept/reject) with pertinent indications noted if repairs are required. Standard Practice for Report and Data Display using TD Handy Scan provides instruction on the preparation of the Report. The site examination record data file shall be kept on file with the Ultrasonic Inspection Data Record Sheet. 8.2 Detailed Examination and Recording Sequence 8.2.1 Calibration of Equipment P.O. Box 534, Doha, State of Qatar, Office Tel +974 4110939, Fax:+974 4764239, Mobile: 0974-3120085 Email: [email protected]

Q SPACE Engineering Oil & Gas Services The examination equipment shall be calibrated as described in item 8.0 herein to verify linearity and 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. The thickness is compared to the thickness indicated on the detailed technique to confirm that the technique and related range settings are applicable. This thickness assessment may be made using a separate zero degree probe with TD Handy Scan unit or as part of any required scan results from a 0° scan. Thickness measurements are to be noted at the edge of the weld cap and at 50 mm either side of the weld at 3 points around the circumference of the weld. The minimum thickness reading is recorded. 8.2.3 Shear Wave Scanning and Recording The instrument is calibrated as described in Standard Practice for Verification of Performance of Probes 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 Standard Practice 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 Sensitivity plus any transfer value. On the Data Acquisition display an evaluation threshold is set using a colour threshold at 6dB below the Primary Reference level. Typically Primary Reference level is set 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 the ultrasonic beam passes through all of the inspection area. This is accomplished by an electronic raster or S-scan. Where possible, the weld is scanned from both sides of the same surface. The speed 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 greater than 10% of data points shall be missed in a weld scan with not more than 3 adjacent samples missing 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 so that the ultrasonic beam passes through the weld zone. Scanning is done in two directions essentially 180° to each other. Swiveling of the probe is not possible when using shaped wedges. 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. P.O. Box 534, Doha, State of Qatar, Office Tel +974 4110939, Fax:+974 4764239, Mobile: 0974-3120085 Email: [email protected]

Q SPACE Engineering Oil & Gas Services When the weld cap is not a suitable scan surface the probe will need to be positioned close to the weld cap edge and the beam directed towards the weld centerline (i.e. “essentially” parallel to the 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 nominal frequency of the probe. Recording shall be in the form of an “RDT” data file and evaluation of the scan results shall be made using B-scan or S-scan and C-scan projections with colour pallets that 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 the applicable acceptance criteria. Rejectable indications are plotted showing dimensions, location relative to the weld centre line and vertical extent when required. Length shall be determined using the 6 dB drop method for signals less than 80% and for flaw signals with amplitudes greater 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 with TD Handy Scan. 9.0 ACCEPTANCE CRITERIA Results of weld inspections to this procedure will be compared to the requirements of the referencing code unless otherwise instructed by written instructions. 10.0 REPORTING After each inspection an Inspection Report shall be prepared. This report describes the work done, the equipment used, the qualification of the inspection personnel and the results. Additional inspection results (if any) are also reported and alternate methods of inspection described. The final report for each weld shall include; a) Project name, contract details b) Procedure and technique identification c) Equipment used (UT instrument, probes, cables, manipulators, couplant) d) Computer programme identification and version e) Instrument gain settings sensitivity or reference target f) Weld Identification g) Scan Surface h) Record of rejectable indications locations or areas cleared i) Areas of restricted access j) Personnel and their qualifications k) Date and Time of the examination _______________ This is not addressed in EN 1714 but it is an essential variable and the 5 times nominal is documented in IIW AUT guides This is intended to be a summary sheet that includes weld number, status, applicable technique # and any relevant findings and repair information of reject able flaws. 1 2


38686711-Phased-Array-Ut-Procedure-for-Welds.docx

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