PAUT Procedure [PDF]

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INDEX NO.

CONTENTS.

PAGE NO.

1

SCOPE

3

2

REFERENCED DOCUMENTS

4

3

PERSONNEL QUALIFICATION & PERFORMANCE

4

4

EQUIPMENT

4

5

CALIBRATION

12

6

EXAMINATION PROCEDURE

14

7

EVALUATION

18

8

ACCEPTANCE CRITERIA

21

9

RECORDING & REPORTING

22

10

APPENDIX – I

23

11

APPENDIX – II

38

12

APPENDIX – III

39

13

APPENDIX – IV

40

14

SCAN PLAN FOR THE JOINT TABULATED IN SCOPE

41

15

PROCEDURE QUALIFICATION METHODOLOGY

71

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1.

R

SCOPE:

This Procedure describes the inspection of weld joints of DSS (UNS No. 31803) piping by using Contact Phased Array (PAUT) / Time of Flight Diffraction (TOFD) Ultrasonic Testing in lieu of Radiography testing for the following conditions: 1.1. Applicable for DSS piping hook-up weld joints at offshore platform (DDW1) 1.2. Material: Duplex Stainless Steel (UNS No. S 31803). 1.3. Thickness: As per table given below :

Sr. No. 1 2 3 4

Table 1 Diameter Thickness In INCH in mm 16 75 16 30.93 6 36 4 24.5

R1

1.4. Welding process: GTAW, SMAW 1.5. Joint Configuration: Groove welds joints as per scan plan 1A a. b. c. d. e. f. g. h. •

2.

Scan Plan (Technique Sheet): Detail scan plan is prepared for each joint configuration, which includes the following information as minimum: Weld Joint details (Thickness, Diameter, Bevel angles). Size of sectorial scan (Start angle, Stop angle, Start Path, End path). Focal Distance. Sufficient coverage of Weld & Heat affected zone (HAZ). Search Unit Placement & movement. Search unit details: element pitch, aperture size and number, gap dimensions, number of element, effective height, and element width & frequency. Wedges, Shoes. Weld axis reference point marking. R1 The TOFD shall be used as supportive for evaluation, characterisation and sizing of discontinuities within weld and HAZ region.

REFERENCED DOCUMENTS: Latest applicable edition to be followed for reference documents: • ASME- Section V- Non-destructive Examination. • ASME B 31.3 process piping. Page 165

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• ASNT - SNT-TC-1A edition 2006 Recommended Practice for Personnel Qualification and Certification in Non Destructive Testing. • L&T NDT Plan: GSPC/DDW1/L&T/QA/2011/NDTP/05- PIPING. • L&T Quality System Work instructions for control and administration of NDE personnel training, examination & certification- MFF/QA/QSI/1040 Issue 1 Rev. 1. 3.

PERSONNEL QUALIFICATION & PERFORMANCE: Personnel performing non-destructive testing to this procedure shall be qualified and certified in accordance with employer’s written practice as per ANSI/ASNT SNT-TC-1A-2006 at UT Level II or Level III and shall be responsible for carrying out calibrations, inspections, evaluations and reporting. In addition, personnel who acquire and analyse Phased array data shall be trained on Omni scan MX equipment. Only UT Level III personnel qualified in Phased array to level II shall perform final examination data package review. • Experience required: For Level III shall have minimum of six months experience using the same or similar equipment for examination of welds in structural or piping. For Level II shall have minimum of three months experience using the same or similar equipment for examination of welds in structural or piping. • In addition to above the operator’s performance shall able to demonstrate the following with PAUT equipment i. ii. iii. iv.

4.

Calibration of equipment Scanning of test object Characterisation of flaw indication Flaw Sizing & location.

EQUIPMENT: During this project, equipment of make RD Tech (Olympus) Model Ominiscan MX or equipment shall be used. For analysis of result TOMO R view software shall be used where as for preparing scan plan ES beam tool 3 or equivalent shall be used. The equipment shall have following features

4.1. PHASED ARRAY

4.1.1 Flaw Detector Instrument: a. b.

Contain minimum 64 independent pulse echo channels. Have attenuation (gain) control stepped in increments of 1 dB or less. Page 166

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c. d. e.

f.

g.

Ability to display A, B, C, E and S scan images. Capable of operation at frequencies of 1 MHz to 10 MHz. Capable of having a pulse repetition rate small enough to assure that a signal from a reflector located at the maximum distance in the examination volume will arrive back at the search unit before the next pulse is placed on the transducer. The reject control shall be in the “off” position for all examinations, unless it can be demonstrated that it does not affect the linearity of the examination. Any control which affects instrument linearity (e.g., filters, averaging, reject) shall be in the same position for calibration, calibration checks, instrument linearity checks, and examination. R

4.1.2 Search Units (Probes):

a. The phased array search unit frequency shall be between 2 MHz to 5 MHz. b. The phased array search unit configuration shall be used 64 elements Table-2 Probe specification and dimension

2L 64-A2

Frequency (MHz) 2.25

Number of elements 64

Elevation (mm) 12.0

Pitch (mm) 0.75

5L 64-A2

5

64

10.0

0.59

Part No.

4.2. TOFD

4.2.1. Flaw Detector: a. The instrument shall provide a linear “A” scan presentation for both setting up scan parameters and for signal analysis. b. Analog to digital conversion of wave forms shall have sampling rates at least four times that of the nominal frequency of the probe. c. Data Display & Recording: The data display allow for the viewing for the unrectified A – Scan so as to position the start and length of a gate that determines the extent of the A – Scan time base that is recorded. d. Equipment shall permit storage of all gated A scan to a magnetic or optical storage medium. Page 167

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e. Equipment shall provide a sectorial view of the weld with a minimum of 64 grey scale levels. f. Computer software for TOFD displays shall include algorithm to linearize cursors to the waveform time – base to permit the depth and vertical extent examination. g. The equipment shall also store positional information indicating the relative position of the wave form with respect to the adjacent waveforms i.e. encoded position. 4.2.2. Search Units: a. b. c. d.

Two probes shall be used in pitch catch arrangements. Each probe in the TOFD pair shall have the same nominal frequency. The TOFD pair shall have the same element dimensions. The pulse duration of the probe shall not exceed 2 cycles as measured to the 20 dB level below peak response. R e. Deleted f. Probe frequency of PAUT probe for 75 mm thickness shall be 2 MHz and for other 5 MHz. also, probe frequency for TOFD shall be 5 Mhz for all thickness range 4.2.3. Mechanics: a. Mechanical holders shall be used to ensure that probe spacing is maintained at a fixed distance. b. The mechanical holder shall also ensure that alignment to the intended scan axis on the examination piece is maintained. c. Probe motion may be achieved using motorised or manual means and the mechanical holder for the probes shall be equipped with a positional encoder that is synchronised with the sampling of A scans. 4.3. Wedges: a. Phased array wedges shall be of a design to accommodate phased array search unit. Nominal refracted-wedge angles shall be used 45, 55, 60 or 70 degrees to ensure coverage of the weld and heat affected zone. b. The curvature wedge shall be used for each nominal pipe size to be examined. Selection of wedge shall be made from table 2; other wedges shall be used after satisfactory demonstration.

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Table-3 Wedge Specification and Dimensions Application Part No.

Probe Type

PAUT

SA2N55S

A2

Nominal Refracted beam l i t l 55º SW

TOFD

ST-1 60L ICH

C543

60º LW

R

Sweep (degree)

Probe orientation

30 - 70

NORMAL

NA

NORMAL

4.4. ENCODER: a. The encoder shall be used quadrature type signal. Mini wheel encoder with resolution 12 steps. 4.5. COUPLANT: a. Couplants shall not be detrimental to the material being examined. b. Cellulose Paste, Water, Grease or oil can be used as a Couplants.

Same Couplant shall be used for calibration as well as for testing. 4.6. CALIBRATION & REFERENCE BLOCKS: c.

4.6.1. Phased Array: a. The calibration block shall be made by piece of same material. b. Deleted c. Deleted d. Quality. 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. e. Heat Treatment. Since the calibration block is made by piece of same material, No heat treatment would be required. f. Surface Finish. The finish on the scanning surfaces of the block shall be representative of the scanning surface finishes on the component to be examined g. IIW (V1) Block for checking beam angle, probe index, distance calibration, linearity checks, wedge calibration, Focal law calibration, Index Point. h. Deleted

R

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i. Piping calibration block shall be prepared as per figure 4. j. The temperature of the calibration block must be within +/- 14°C of the component(s) to be examined. 4.6.2. TOFD: a. Deleted. b. Deleted. c. Deleted. d. Deleted. e. Same calibration block as shown in Figure No. 4 can be used for TOFD calibration with notches, ID and OD surfaces as reference reflectors. Figure No. 1 (Deleted)

R

General Notes: Deleted. Figure No. 2 (Deleted) NOTES: •

Deleted

•

Deleted

•

Deleted

R

Deleted R Figure no. 3 PIPING CALIBRATION BLOCK FOR MORE THAN 20” DIAMETER

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Notches shall be located not closer than T or 1 in.(25 mm),whichever is greater to any block edge or to other notches. GERNERAL NOTES: a) The minimum calibration block length l shall be 8 in (200mm) or 8T, whichever is greater. b) For OD 4 in. (100mm) or less, the minimum arc length shall be 270 deg. For OD greater than 4 in. (100mm), the minimum arc length shall be 8 in. (200mm) or 3T, whichever is greater. c) Notches depths shall be from 8% T minimum to 11%T maximum. Notch widths shall be ¼ in.(6mm)maximum. Notch lengths shall be 1 in.(125mm) minimum. d) Maximum notch width is not critical. Notches may be made with EDM or width end mills up to ¼ in.(6 mm)in diameter. e) Notch lengths shall be sufficient to provide for calibration with a minimum 3 to 1 signal to noise ratio.

Figure no. 4 PIPING CALIBRATION BLOCK FOR LESS THAN 20” DIAMETER

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5. CALIBRATION: 5.1. Instrument Linearity Checks: a. To check the instrument linearity as a minimum Screen height linearity and Amplitude control linearity has to be checked for all ‘A’ scan display. In addition to that, checks as mentioned in appendix I shall be verified at intervals of 1 year or prior to first use thereafter. b. The instrument linearity verification shall be recorded on the ultrasonic instrument linearity verification record. c. Side-drilled holes used as target in this document should have diameters less than the wavelength of the pulse being assessed and long enough and 2.5 mm and 20 mm to 25 mm in length. 5.2. Screen Height Linearity: a. Couple a straight beam probe to the IIW V1 block and get multiple echoes from 25mm back wall. b. Select any two echoes whose amplitudes are in the ratio of 2:1 with larger echo set at 80% of full screen height. c. Without moving the search unit, adjust the gain to successively set the larger indication from 100% to 20% of full screen height, in 10% increments or 2 dB steps if a fine control is not available, and read the smallest indication at each setting. d. The reading must be 50% of the larger amplitude, within 5% of full screen height. The setting and reading must be estimated to the nearest 1% of full screen height. 5.3. Amplitude Control Linearity: a. Couple a straight beam probe to the IIW V1 block and get multiple echoes from 25mm back wall. Select any echo and note its amplitude. b. Reduce the gain by 6dB and read the amplitude of the same indication. It must be 50% of the initial amplitude within 20% of the nominal amplitude ratio. Perform this exercise for full range of the gain. c. The setting and reading must be nearest 1% of full screen and the readings should be as mentioned in table 4. Page 172

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Table-4 Indication Set at % of Full Screen 80

Decibel Control Change -6dB

Indication Limits %of Full Screen 32 to 48

80

-12dB

16 to 24

40

+6dB

64 to 96

20

+12dB

64 to 96

5.1. Phased Array Calibration System: a. Calibration shall be performed from the surface of the calibration block which corresponds to the component surface to be examined. System calibration shall include the complete ultrasonic system. b. Screen distance calibration shall be at least 1-1/2 Vee paths (also known as skip) for the minimum angle that will be used during the examination. 5.5.

Focal law verification: a. Find the index point of the transducer. b. By using the Perspex on the IIW V1 block, peak the signal on A-scan display. c. Read the values of Beam path & Surface distance & calculate angle of the transducer. d. Transducer angle shall be within the limits of +/- 2o. e. Focal law used for the examination shall be used for the calibration.

5.6.

Sensitivity Calibration (Straight beam & Angle beam): a. A 3-point TCG (Time Corrected Gain) shall be performed. The TCG function on the system automatically calibrates the reference reflectors to produce an equal amplitude response, regardless of angle of sound path distance. b. The TCG shall be set to a reference level of 80% full screen height. c. Deleted d. When complete, the TCG must encompass the entire area of interest within the S scan. e. The dB displayed once the TCG is completed shall be known as the Page 173

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Standard Sensitivity Level (SSL). f. Refer to the User’s Manual for steps on building a TCG. g. The completed calibration may be saved to an electronic setup file; however, the calibration must be verified whenever the setup file is opened. 5.7.

TOFD Calibration System: a. Calibration: Set the TOFD probes on the surface to be utilized for calibration and set the gain control so that lateral wave amplitude is from 40% to 90% of FSH and the noise (Gras) level is less than 5 to 10% of FSH. This is reference sensitivity setting. For multiple zone examination when the lateral wave is not displayed, or barely discernible, set the gain control based solely on the noise level. b. Confirmation of sensitivity: Scan the calibration block’s SDHs with them centred between the probes, at the reference sensitivity level. The SDH responses from the required zone shall be a minimum of 6 dB above the noise and shall be apparent in the resulting digitised grey scale display. c. Deleted d. Deleted R

5.8.

Encoder Calibration: Shall be applicable for both i.e. PA UT / TOFD a. A calibration check shall be performed at intervals not to exceed one month or prior to first use there after by moving the encoder a minimum distance o 500mm. The display distance shall be within 1% of the actual distance moved.

6.

EXAMINATION PROCEDURE:

6.1. Surface Preparation: a. The finished contact surface should be free from weld spatter, scale, rust, dirt etc. and any roughness that could interfere with free movement of search unit or impair the transmission of ultrasonic vibration. b. The weld surface should be free of irregularities that could mask or cause reflections from defects to go undetected and should merge smoothly into the adjacent base material. c. Conditions, which do not meet this requirement, shall be recorded as limitations on the Ultrasonic Report Form. Page 174

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6.2. Straight Beam: a. The scanning of adjacent base material shall be performed to detect reflectors that might affect interpretation of angle beam results. The result of this scanning is not to be used for acceptance or rejection of the weld. Location and areas of such reflectors shall be recorded. b. The scanning shall be performed at a gain setting of at least two times the primary reference level. Evaluation shall be performed with respect to the primary reference level. c. Scanning distance shall be 100 mm or skip distance whichever is greater. 6.3. Angle Beam: 6.3.1. Scanning For Reflectors Oriented Parallel To The Weld Seam: a. The angle beam shall be directed approximately at right angles to the weld axis from two directions wherever possible. The search unit shall be manipulated so that the ultrasonic energy passes through the required volumes of the weld and adjacent base metal. 6.3.2. Scanning For Reflectors Oriented Transverse To The Weld Seam: a. Deleted b. The angle beam shall be directed essentially parallel to the weld axis. The search unit shall be manipulated so that the angle beam passes through the required volumes of the weld and the adjacent weld metal. The scanning shall be performed at a gain setting reference +14 dB.The search unit shall be rotated 180° and the examination shall be repeated. c. If the weld cap is not machined or ground flat, the examination shall be performed from the base metal on both sides of the weld cap in both weld axis direction. 6.3.3. Inaccessible Welds: R

Not applicable

6.3.4. Scanning Overlap and Speed:

R

Not applicable R Page 175

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6.3.5. Procedure: a. A scribe line shall be marked on at least one side of the joint to exactly locate the centre line of the weld. b. Detail the scanning direction and datum marking in the test report to have a known reference point during in service inspection for repeatability and comparison of result. c. Perform the calibrations of PAUT & TOFD as per the applicable clause of this procedure. d. Scan the weld joint as per scan plan attached with this procedure. Incase any variable is changed a separate scan plan has to be prepare. e. Evaluate the offline date with using TOMO view software. f. Prepare the test report as per attached format. 6.4. Examination Coverage: 6.4.1. PAUT a. The required volume of the weld + HAZ + 6 mm of base material to be examined by using linear scanning technique of PAUT with an encoder. b. Each linear scan shall be parallel to the weld axis at a standoff distance with a beam oriented perpendicular to the weld axis. c. The search unit shall be maintained at a fixed distance from the weld axis by a fixed guide or mechanical means. The fixed distance should be as per the applicable scan plan as attached. d. The examination angles for E scan and range of angles in S-scan shall be as per the applicable scan plan for the joint to be examined. e. Scanning speed shall be such that data drop out is less than 2 data lines per R1 inch (25mm) of the linear scan length and that there are no adjacent data line skips. Also, missing data lines shall not exceed 5% of the scan lines to be collected. f. For E-Scan techniques, overlap between adjacent active apertures shall be a minimum of 50% of the effective aperture height. g. For S-Scan technique the angular sweep incremental change shall be a maximum of 1 deg or sufficient to assure 50% beam over lap. h. Not applicable. i. The setup and scan plan is attached at the end of this procedure for the weld joint made as per figure no 6. R

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6.4.2. TOFD: a. For TOFD, The volume to be scanned shall be examined with the TOFD probe pair centred on and transverse to the weld axis and then moving the probe pair parallel to and along the weld axis and again with the offset to the opposite side of the first offset scan. R

b. Not applicable

c. The typical recommendation for setup of TOFD is as per scan plan attached at the end of this procedure. Test Setup plan Top View & Cross Sectional View

Figure no. 5 (Deleted) R

Weld Geometry Details Figure no. 6

(Wedge & Probe Details) R

Figure No. 7. (Deleted)

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7.

EVALUATION: •

Amplitude of A-scan for comparing reflectivity and Size from C scan of Phased Array shall be used for acceptance criteria.

•

All evaluation shall be carried out with the gain setting at Standard Sensitivity Level (SSL). Any imperfection that causes an indication in excess of 20% of SSL shall be investigated.

7.1. Geometrical Indications: It is recognized that not all ultrasonic reflectors indicate flaws, since certain metallurgical discontinuities and geometric conditions may produce indications that are not relevant. Included in this category are plate segregates in the heat-affected zone that become reflective after fabrication. Under straight beam examination, these may appear as spot or line indications. Under angle beam examination, indications that are determined to originate from surface conditions (such as weld root geometry) or variations in metallurgical structure in austenitic materials (such as the automatic-to-manual weld clad interface) may be classified as geometric indications. The identity, maximum amplitude, location and extent of reflector causing a geometric indication shall be recorded. The following steps shall be taken to classify an indication as geometric: a. Interpret the area containing the reflector in accordance with the applicable examination procedure. b. Plot and verify the reflector co-ordinates. Prepare a cross-sectional sketch showing the reflector position and surface discontinuities such as root and counter bore. c. Review fabrication or weld preparation drawings. Other ultrasonic techniques or non destructive examination methods may be helpful in determining a reflector’s true position, size, and orientation. 7.2 SIZING OF THE INDICATION: 7.2.1. PAUT: a. Flaw sizing shall be evaluated using a combination of beam boundary techniques & amplitude calibration. b. Flaw size is to be given in terms of length & through wall extent. Length shall be measured from C scan and by 6 dB drop method whereas through wall R1

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c. d. e.

f. g.

h.

extent shall be measure either in B scan or S scan. In addition, the reflector shall be spherical, cylindrical or planar Identification of type is not required like crack versus incomplete penetration. Isolated, random spherical reflectors are acceptable regard less of signal amplitude. Clustered multiple reflectors with indication above 20% of SSL & two times of branch thickness in length shall be evaluated in terms of width & length limits in acceptance criteria. Cylindrical/ planar reflectors whose dimensions exceeds the limits specified in acceptance criteria are rejected Internal reflectors near the fusion line of a weld shall be evaluated with various probe angles while making an effort to obtain a beam path perpendicular to the fusion line. Reflectors within the base metal of the main member (joint can) at welds shall be evaluated as described in the following. In addition, any such reflector that exceeds the 20% of SSL shall be reported: I. Individual reflectors exceeding the limits of acceptance criteria are rejectable. II. Accumulated reflectors exceeding 8 percent of the area under the weld in any 6-inch (150-millimeter) or D/2 length (whichever is less) are rejectable. III. Rejectable base metal reflectors shall be reviewed by the operator prior to any excavation or attempted repair. Consideration should be given to the risk of causing further problems with additional thermal strain cycles such excavation & repair would entail.

7.2.2. TOFD: a. Demonstration Block (See below figure 2) : The block material and shape shall be the same as that desired to demonstrate the system’s accuracy. The block shall contain a minimum of three notches machined to depths of T/4, T/2 and 3T/4 and with lengths (L) and, if applicable, orientation as that desired to system’s sizing accuracy. Additional notches may be necessary depending on: a) the thickness of the block b) the number of examination zones the block thickness is divided into. c) whether or not the zones are of equal thickness and d) the depth desired to be demonstrated b. System Checks: A free run shall be made on the measuring block. The distance between the lateral wave and first back wall signal shall be within 0.5 mm of the block’s measured thickness, set up failing this check shall have the Page 179

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probe separation distance either adjusted or its programmed value changed and this check repeated. c. Sizing Accuracy Determination: d. Flaw Sizing: Flaw shall be classified as follows: i. Top surface connected flaws: flaw indications consisting solely of a lower tip diffracted signal and with an associated weakening, shift or interruption of the lateral wave signal, shall be considered as extending to the top surface unless further evaluated by other NDE methods. ii. Embedded flaws: flaw indications with both an upper and lower tip diffracted signal or solely an upper tip diffracted signal and with no associated weakening, shift or interruption of the back wall signal shall be considered as embedded flaws. iii. Bottom surface connected flaws: flaw indications consisting solely of an upper tip diffracted signal and with an associated weakening, shift of the back-wall or interruption of the back wall signal, , shall be considered as extending to the bottom surface unless further evaluated by other NDE methods. e. Flaw Height Determination: Not applicable f. Deleted

R

R

Figure 8 (Deleted)

R

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8.

ACCEPTANCE CRITERIA (as per ASME B31.3) :

Acceptance Criteria for Welds(Table K341.3.2) Ultrasonic Type of Imperfection Girth Groove Weld methods Crack * A Lack of fusion * A Incomplete penetration * A Internal porosity ……. B Slag inclusion or elongated indication ……. C Undercutting * A Surface porosity or exposed slag inclusion * A Concave root surface * D Surface finish * E Reinforcement or internal protrusion * F General Note: *= Required examination, = Not required Criterion value Notes For Table K341.3.2 Symbol Measure Acceptable Value Limits(Notes 5) A Extent of imperfection Zero (no evident imperfection) See BPV code, Section VIII ,Division B Size and distribution of internal porosity 1,Appendix 4 6 mm(1/4 in.) for Tw≤19 mm(3/4in.) Slag inclusion or elongated indication. Indication are unacceptable if the amplitude Tw/3 for 19 mm (3/4 in.) 57 mm (2⅟ 4 in.) Cumulative length ≤ Tw in any 12 Tw weld length. Wall Thickness, Depth of Surface Tw,mm (in.) concavity, mm (in.) ≤ 13 (1/2) ≤1.5(1/16) > 13 (1/2)and ≤3(1/8) D Depth of surface concavity ≤ 51 (2) > 51 (2) ≤4(5/32) and total joint thickness including weld reinforcement ≥ ≤ 12.5 μm (500 μin.) Ra (see ASME B46.1 for E Surface roughness definition of roughness average, ) External weld Height of reinforcement or internal Wall Thickness, , reinforcement protrusion (Notes 6) in any plane through of internal weld mm(in.) the weld shall be within the limits of the Protrusion, F applicable height value in the tabulation at mm(in.) the right. Weld metal shall be fused with ≤13(1/2) ≤1.5(1/16) and merge smoothly into component >13(1/2) & ≤ 51(2) ≤3(1/8) surface >51(2) ≤4(5/32) Page 181

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Notes:

 Criteria given are for required examination. More stringent criteria may be specified in the engineering design.

 Longitudinal welds include only those permitted in paras. K302.3.4 and K305. The criteria shall be met by all welds, including those made in accordance with a standard listed in Table K326.1 or in Appendix K.  Fillet weld include only those permitted in para. K311.2.2  Branch connection weld include only those permitted in para. K328.5.4  Where two limiting values are given, the lesser measured value governs acceptance. is the nominal wall thickness of the thinner of two components joined by a butt weld.  For groove welds, height is the lesser of the measurements made from the surface of the adjacent components. R

9.

RECORDING & REPORTING: All test result shall be reported in a report format as attached. More details can be included as per requirement. The recording shall be done as per following:

9.1. Phased Array: A-Scan data shall be recorded for the rate of interest in an unprocessed form with no thresholding, at a minimum digitization rate of five times the examination frequency, and recording increments of a maximum of a. 0.04 in. (1mm) for material< 3 in. (75 mm) thick. b. 0.08 in. (2mm) for material>= 3in. (75mm) thick. 9.2. TOFD a. The unrectified (RF waveform) A scan signal shall be recorded. b. The A scan gated region shall be set to start just prior to the lateral wave and, as a minimum, not end until all of the first back wall to the mode – converted back wall signal shall also be included in the data collected. c. A maximum sample spacing of 1 mm shall be used between A scans collected for thickness up to 50 mm and a sample spacing of 2 mm may be used for thickness greater than 50 mm.

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Sample Report Format

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APPENDIX I Equipment characteristic check of PAUT Determination of Phased Array Beam Profile: For single focal laws the beam is fixed •

For phased-array probes used in a dynamic fashion where several focal laws are used to produce Sectorial or electronic scanning it may be possible to make beam-profile assessments with no or little mechanical motion. Where mechanical motion is used it shall be encoded to relate signal time and amplitude to distance moved. Description made for electronic scan and Sectorial scan beam profile assessments will be made for contact probes.

•

Assessments of the beam in the active plane should be made by use of an electronic scan sequence for probes with sufficient number of elements to electronically advance the beam past the targets of interest. For phased – array probes using a large portion of the available elements for the electronic raster may be too small to allow the beam to pass over the target.

•

Side drilled holes should be arranged at various depths in a flaw-free sample of the test material in which focal laws have been programmed for. Using the linear scan feature of the phased-array system the beam is passed over the targets at the various depths of interest.

•

Data collection of the entire waveform over the range of interest shall be made. The display shall represent amplitude as a colour or greyscale time or equivalent distance in the test material shall be presented along one axis and distance displaced along the other axis this is a typical B-scan as illustrated in Fig. Annex 2.1.

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FIGURE ANNEX 2.1 •

Data display for an electronic scan using a phased-array probe mounted on a wedge can similarly made using simple orthogonal representation of time versus displacement or it can be angle corrected as illustrated in Fig. Annex 2.2.

Fig. Annex 2.2.

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•

Resolution along the displacement axis will be a function of the step size of the electronic scan or, if the scan uses an encoded mechanical fixture the resolution will be depended on the encoder step size used for sampling.

•

Resolution along the beam axis will be a function of the intervals between the target paths. For highly focused beams it may be desirable to have small difference between the sound paths to the target paths (for example, 1mm or 2mm).

•

Beam profiling in the passive plane can also be made. The passive plane in a linear – array probe is perpendicular to the active plane and refers to the plane in which no beam steering is possible by passing effects beam profiling in the passive direction will require mechanical scanning.

•

Waveform collection of signals using a combination of electronic scanning in the active plane and encoded mechanical motion in the passive plane provides data that can be projection-corrected to provide beam dimensions in the passive plane.

•

A Through hole may be arranged perpendicular to the required refracted angle to provide a continuous of path length to the target.

•

Projected C-scan can be used to size the beam based on either colour or gray scale indicating amplitude drop or a computer display that plots amplitude with respect to displacement. The projected c-scan option is schematically represented in Fig. Annex 2.3.

Fig. Annex 2.3.

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1.

Determination of Phased Array Beam Steering Limits: •

When used in pulse-echo mode the steering limit is considered to be within the 6-db Divergence envelope of the individual elements.

•

Steering capability may be specified to a sound path distance, aperture and material.

•

Configure the probe focal laws for the conditions of the tests this will include Contact refracting wedge or delay-line, unfocused or a defined focal distance and the test material to be used.

•

Prepare a series of side drilled holes in the material to be used for the application at the distance or distances to be used in the application. The side-drilled-hole pattern should be as illustrated in Fig. Annex 2.4. Holes indicated in Fig. Annex 2.5. are at 5 deg intervals at a 25-mm and 50 -mm distance from a center where the probe is located.

Fig. Annex 2.4 •

Assessments are made placing the probe such the center of beam ray enters the block at the indicated centreline. For the analysis of a probe where all the elements in single plane are used without a delay line or refracting wedge the Page 187

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midpoint of the element array shall be aligned with the center line. For focal laws using only a portion of the total available elements midpoint of the element aperture shall be aligned with the centreline. When delay lines refracting wedges are used corrections will be required to compensate for movement for the apparent exit point along the block entry surface when a probe is used in direct contact with a verification block as illustrated in Fig. Annex 2.5. The lack of symmetry either side of centreline prevents both positive and negative sweep angles being assessed simultaneously. To assess the sweep limit in the two directions when using this style of block requires that the probe be assessed in one direction first and then rotated 180 deg and the opposite sweep assessed.

Fig. Annex 2.5 •

Angular steps between A-scan samples will have an effect on the perceived sweep limits. A maximum of 1 deg between S-scan samples is the recommended for steering assessment. Angular steps are limited by the system timing-delay capabilities between pulses and element pitch characteristics.

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2.

•

Assessment of steering limit shall be made using the dB difference between the maximum and minimum signal amplitudes between two adjacent sidedrilled holes.

•

Acceptable limits of steering may be indicated by the maximum and minimum angles that can achieve a pre specified separation between adjacent holes.

•

Steering capabilities may be used as a prerequisite.

Determination of Phased Array Element Activity: •

Connect the phased-array probe to be tested to the phased-array ultrasonic instrument and remove any delay line or refracting wedge from the probe.

•

Acoustically couple the probe to the 25-mm thickness of an IIW (International Institute of Welding) block with a uniform layer of Couplant.

•

Configure an electronic scan consisting of one element that is stepped along one element at a time for the total number of element in the array. (This should ensure that the pulsar receiver number 1 is used in each focal law or if the channel is selectable it should be the same channel used for each element). Set the pulsar parameters to optimize the response for the nominal frequency of the probe array and establish a pulsar-echo response from the block back wall or water path to 80% display height for each element in the probe.

•

Observe the a-scan display for each element in the array and record the receiver gain required to achieve the 80% single amplitude for each element. Probe Elements Activity Chart : Enter receiver gain for 80% FSH

Elements

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Gain Active ([sqcap]) Inactive (x) •

Note and record any elements that do not provide a backwall.

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• Data collected is used to assess probe uniformity and functionality. Comparison to previous assessment is made using the same instrument settings (including gain) that were saved to file. The receiver gain to provide an 80% response should be within a range of ±2 dB of any previous assessments and within ±2 dB of each other.

3.

•

The total number of inactive elements and number of adjacent inactive elements in a probe should be agreed before testing.

•

The number of inactive element allowed should be based on performance of other capabilities such as focusing and steering limits of the focal law being used. No simple rule for number of inactive elements can be made for all phased-array probes. Typically, if more than 25% of the elements in a probe are inactive, sensitivity and steering capabilities may be compromised. Similarly, the number of the elements allow to be inactive should be determined by the steering and electronic raster resolution required by the application.

•

Stability of coupling is essential for the comparison assessment .if using a contact method and the assessment of elements produces signals outside the ±2 dB range the coupling should be checked and the test run again. If still outside the acceptable rang the probe should be removed from service and corrected prior to further use

•

Prior to removing the probe from service the cable used for test should be exchanged with another cable, when possible, to verify that the inactive elements are not due to bad cable

•

Cable continuity adapters can be made that allow the multi-strand connectors to be tested independently.

Phased Array Focusing: •

Configure the phased array system for the focusing focal laws to be assessed and acoustically couple the phased-array probe to a block with inclined side-drilled holes as illustrated in Fig. Annex 2.6 Compression modes with or without a delay-line and shear modes using a refracting wedge can be assessed by this method.

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•

Focusing at a single refracted angle is assessed by this method. Where several angles are used it will be necessary to assess the focusing ability for each angle separately.

•

Using either an electronic scan or encoded mechanical scan in the plane of interest, the full waveforms are collected and displayed in a depth corrected B-scan projection image as illustrated in Fig. Annex 2.7

Fig. Annex 2.6 Page 191

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Fig. Annex 2.7 •

Effectiveness of the focusing algorithm is assessed by sizing the diameter of the projected image based on a dB drop for maximum and comparing that dimension to the actual machined diameter of the side-drilled hole.

•

Working range of the focusing algorithm may be determined by agreement as to the maximum dimension, of the over sizing of the side-drilled hole diameter. For example, if 2-mm diameter SDHs are used are and the 6dBdrop is used to gauge diameter from the B-scan, the working range can be defined as the depth or sound-path distance that B-scan maintain the 6-dBdimension to less than twice the actual diameter.

•

Practical limits for hole diameters and focal spot sizes are required. Practical focal spots for focused beams cannot be made smaller that about 1.5 times the wavelength used. For a 5MHz compression wave in steel this is about 1.7mm. The focal spot size is also a function of sound path; the deeper the holes, the weaker the focusing.

•

It is recommended that at least four samples per hole diameter be used. For example, for a 2-mm diameter SDH target the sample interval of a mechanized encoded scan should be 0.5 mm or for an electronic scan the step between each focal law should not exceed 0.5mm (this will be limited by element pitch of the probe). Page 192

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4.

5.

Assessment of Phased Array Computer Control & Data Display •

Using a contact linear phased-array probe, nominally 5MHz and having at least 16 elements with a pitch not greater than 1mm, configure the software for two separate S-scans one at ±30 deg with a focal distance of 25mm in steel (that is focused at a sound path of 25 in steel), the other at ±30deg with a focal distance of 50mm in steel (that is focused at a sound path of 50 mm in steel).for both sets of focal laws program an angular step interval of 0.5 deg and all focal law shall use 16 adjacent elements.

•

Ensure that the digitizing frequency for data collection is at least 80MHz.

•

Prepare a series of side-drilled holes in a steel block that has acoustic velocity similar to test object. this velocity value will be used in the focal laws.

•

Acoustically couple and align the probe on the block illustrated in Fig. Annex 2.4 such that the centre of the element array aligns with the centre line of the hole pattern.

•

Scan and save the s-scan for the 25-mm focal distance.

•

Scan and save the s-scan for the 50-mmfocal distance.

•

Using the computer display coordinate cursors assess and record the depths, off-sets from the centre-line and angle to the side-drilled hole in a tubular form. For the side drilled hole at 50-mm radius use the results of the focal law configured for 50-mm focus and for the holes at 25-mm radius use the focal law configured for 25 mm.

•

Compare the values assessed using the software to the physical position of the holes in the block. Sound path distance indicated on the computer display should indicate the holes position within ± 0.5 mm. Depth and off-set position holes should be within ± 0.5 mm and all angle to the holes should be within ± 1.0 deg.

WEDGE ATTENUATION COMPENSATION.

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6.

•

Configure the phased-Array for the focal law to be used in the electronic raster Scan application.

•

Acoustically coupled the phased-array probe to the block with a side drilled hole at a known depth. The 1.5-mm diameter SDH in the IIW block shall be used for this purpose

•

Select the A-scan display for the first focal law configured and move the probe forward and backward to locate the maximum amplitude signal from the SDH.

•

Adjust the response from the SDH to 80% full screen height (FSH) and save the parameters in the focal law file.

•

A dynamic assessment of attenuation correction would then be calculated by the phased-array system to ensure that the amplitude of the SDH detected by each focal law would be adjusted to the same amplitude.

•

Assessment of wedge-attenuation compensation requires a constant steel path to ensure that only the effect wedge variations are assessed. For Sscans where 1D linear array probes are used, a single SDH result in a changing steel path for each angle making it unsuitable for this task. A recommended target is radius similar to that of 100-mm radius of the IIW block.

WEDGE –DELAY COMPENSATION •

Configure the phased array system for the focal laws to be used in the S-scan or electronic raster scan application

•

Acoustically couple the phased array probe to a block with known radius of curvature The 50-mm or 100-mm radius of the IIW block shall be used this purpose.

•

Select the A- Scan display for the first focal law configured and move the probe forward and backward to locate the maximum amplitude signal from the radius selected

•

Adjust the delay setting s to indicate the sound path in the metal correctly indicate the radius used and save the focal law parameters.

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7.

•

A dynamic assessment of delay adjustment shall calculated by the computer. A dynamic assessment would simply require that the operator move the probe back & forth.

•

Small angle compression wave focal law may require a custom block to carry out this compensation

PAUT Display Height Linearity •

With the phased-array instrument connected to a probe (shear or longitudinal) and coupled to any block that will produce two signals adjust the probe such that the amplitude of the two signals are at 80% and 40% of the display screen height. If the phased-array instruments has provision to address the single element probe in pulse echo more than the two flat bottom holes with adjustable acoustic impedance inserts in the custom linearity block to provide such signals.

•

Increase the gain using the receiver gain adjustments to obtain 100% of full screen height of the larger response. The height of the lower response is recorded at this gain setting as a percentage of full screen height. (NOTE For 8-bit digitization systems this value should be 99%, 100% would provide a saturation signal.)

8.

•

The height of the higher response is reduced in 10% steps to 10% of full screen height and the height of the second response is recorded for each step.

•

Return the larger signal to 80% to ensure that the smaller signal has not drifted from its original 40% level due to coupling variation. Repeat the test if variation of the second signal is greater than 41% or less than 39% FSH.

•

For an acceptable tolerance, the response from the two reflector should bear a 2-to-1 relationship to within ± 3% of full screen height throughout the range 10% to 100% (99% if 100% is saturation) of full screen height.

Amplitude Control Linearity •

A 16/64 phased-array instrument has 16 pulsars and receiver that are used to address up to 64 elements. Each of the pulsar-receiver components is checked to determine the linearity of the instrument amplification capabilities. Page 195

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•

Select a flat (normal incidence) linear array phased-array probe having at least as many elements as the phased-array ultrasonic instruments has pulsers.

•

Using the probe configures the phased-array ultrasonic instrument to have an electronic raster scan. Each focal law will consist of one element and the scan will start at element number 1 and end at the element number that corresponds to the number of pulsers in the phased-array instrument.

•

Couple the probe to a suitable surface to obtain a pulse-echo response from each focal law. The back wall echo from the 25-mm thickness of the IIW block or the back wall from the 20-mm thickness of the custom linearity block illustrated in Fig Annex 2.8. Provides a suitable target option. Alternatively, immersion testing can be used.

•

Select channel 1 of the pulser-receivers of the phased-array instrument. Using the A-scan display, monitor the response from the selected target. Adjust the gain to bring the signal to 40% screen height.

Fig. Annex 2.8 •

Add gain to the receiver in the increments of 1dB, then 2 dB, then 4 dB. Remove the gain added after each increment to ensure that the signal has returned to 40% display height. Record the actual height of the signal as a percentage of the display height.

•

Adjust the signal to 100% display height remove 6-db gain and record the actual height of the signal as a percentage of the display height.

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9.

•

Signal amplitude should fall within a range of ± 3% the display height required in the allowed height range of linearity verification report form.

•

Repeat the sequence for all other pulser-receivers channels.

Time Base Linearity (Horizontal Linearity) •

Configure the phased-array instruments to display an A-scan presentation.

•

Select any compression wave probe and configure the phased-array instruments to display a range suitable to obtain at least ten multiple back reflections from block of a known thickness. The 25 mm wall thickness of the IIW block is a convenient option for this test.

•

Set the phased-array instrument Analog-to-digital conversion rate to at least 80 MHz

•

With the probe coupled to the block and the A-scan displaying 10 clearly defined multiples. The display software is used to assess the interval between adjacent back wall signals.

•

Acoustic velocity of the test block is entered into the display software and the display configured to read out in distance (thickness).

•

Using the reference and measurement cursors determine the interval between each multiple and record the interval of the first 10 multiples.

•

Acceptable linearity may be established by an error tolerance based on the Analog-to-digital conversion rate converted to a distance equivalent. For example, at 100MHz each sample of the time base is 10ns. For steel at 5900 m/s each sample along the time base (10ns) in pulse-echo mode represents 30 m. A tolerance of 3 timing samples should be achievable by most Analog-to-digital systems. Some allowance should be made for velocity determination error ( .Typically the errors on the multiples should not exceed 0.5 mm for a steel plate.

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Appendix – II ESSENTIAL VARIABLE FOR ULTRASONIC TESTING SL. NO.

REQUIREMENT

ESSENTIAL

1

Weld configurations to be examined, including thickness dimensions and base material product form (pipe, plate, etc.)

X

2

The surface from which the examination shall be performed

X

3

Technique(s) (straight beam, angle beam, contact, and/or immersion)

X

4

Angle(s) and mode(s) of wave propagation in the material

X

5

Search unit type(s), frequency (ies), and element size(s)/shape(s)

X

6

Special search units, wedges, shoes, or saddles, when used

X

7

Ultrasonic instrument(s)

X

8

Calibration [calibration block(s) and technique(s)]

X

9

Directions and extent of scanning

X

10

Scanning (manual vs. automatic)

X

11

Method for discriminating geometric from flaw indications

X

12

Method for sizing indications

X

13

Computer enhanced data acquisition, when used

X

14

Scan overlap (decrease only)

X

15

Personnel performance requirements, when required

X

16

Personnel qualification requirements

X

17

Surface condition (examinassions surface, calibration block)

X

18

Couplant: brand name or type

X

19

Automatic alarm and/or recording equipment, when applicable

X

20

Records, including minimum calibration data to be recorded (e.g., instrument settings)

X

NON ESSENTIAL

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Appendix – III ESSENTIAL VARIABLE FOR PHASED ARRAY SL. NO.

1 2 3

REQUIREMENT (As Applicable)

Search unit (element pitch, size and number, and gap dimensions) Focal range (identify plane, depth, or sound path as applicable) Virtual aperture size (i.e. number of element, effective height, and element width)

ESSENTIAL

X X X

4

Wedge Angle

X

5

Wedge natural refracted angle

X

6

Scan plan

X

7

Weld axis reference point marking

8

Computer Software

X

9

Scanning Technique (automated vs. Semi- automated)

X

10

Flaw characterization methodology

X

11

Flaw sizing (length) methodology

X

12

Scanner and adhering and guiding mechanism

13 14 15 16

Additional E scan requirement Range of Element number used(i.e., 1-126, 10-50, etc.) Raster angle(s) Aperture start and stop element number Aperture incremental changes (number of element stepped)

NON ESSENTIAL

X

X X X X X

Additional S scan requirement

18 19

Angular Range used (i.e., 40 deg—50 deg, 50 deg—70 deg, etc.) Angle incremental change (i.e., ½ deg, 1 deg, etc.) Sweep angular range(s)

X X

20

Angular sweep increment (increment angle change deg)

X

21

Aperture element number (first & Last)

X

17

X

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NOTE: 1.

Any change in above described Essential Variable would require Re Demonstration of NDE Procedures.

2. Any change in Non Essential Variables may be addressed by incorporating required change and revising existing procedure without Re Demonstration.

Appendix – IV ESSENTIAL VARIABLE FOR TOFD OTHER THAN PAUT AS APPLICABLE SL. NO.

REQUIREMENT (As Applicable)

ESSENTIAL

1

Instrument manufacturer and model

X

2

Instrument software

X

3

Direction & Extent of Scanning

X

4

Method for sizing flaw length

X

5

Method for sizing flaw height

X

6

Data sampling spacing (Increase only)

X

NON ESSENTIAL

NOTE: 1. Any change in above described Essential Variable would require Re Demonstration of NDE Procedures. 2.

Any change in Non Essential Variables may be addressed by incorporating required change and revising existing procedure without Re Demonstration.

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Scan plans

R

Page 201

PROCEDURE FOR

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OFFSHORE

OF DSS PIPING WELD JOINTS FOR OFFSHORE HOOKUP JOINTS

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SCAN PLAN FOR 16 Inch 75 mm THICK – PIPE TO PIPE WELD JOINT

Page 202

PROCEDURE FOR

LARSEN & TOUBRO

PHASED ARRAY/TOFD ULTRASONIC TESTING

OFFSHORE

OF DSS PIPING WELD JOINTS FOR OFFSHORE HOOKUP JOINTS

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Basic Test Information Material

Thickness

Shear Velocity

Compression Velocity

Stainless Steel

75mm

3.1mm/µs

5.8mm/µs

HAZ Width

HAZ

Wedge Details (used for all scans) No.

Type

Velocity

Primary Offset

Height 1st Element

Length

Width

Angle

1

SA2-N55S-IHC Dual 2L64

2.33mm/µs

64.59mm

5.38mm

68.55mm

40mm

36

o

Transducer Details (used for all scan) Probe No.

Type

Total Aperture

No of Element

Element Pitch

1

2.25L64-A2

48 mm

64

0.75 mm

Scan Setup Scan No.

Index Offset

Scan Offset

Mirror status

1

80 mm

10 mm

False

2

120 mm

10 mm

False

3

80 mm

10 mm

True

4

120 mm

10 mm

True

5

0 mm

10 mm

False

6

0 mm

10 mm

True

7

45 mm

10 mm

False

8

45 mm

10 mm

True

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Linear Law Configuration Scan No. 1 2 3 3 4 5 6 7 8 9

Law Configurati on

Wave Type

Element Qty.

1st Element

Last Element

No. Of Beam

Refracted Angle

Focus Depth

Linear

Shear

16

1

64

49

55o

150 mm

Linear

Shear

16

1

64

49

38o

150 mm

Linear

Shear

16

1

64

49

55o

150 mm

Linear

Shear

16

1

64

49

38o

150 mm

Linear

Shear

16

1

64

49

37

o

150 mm

Linear

Shear

16

1

64

49

37o

150 mm

Linear

Shear

16

1

64

49

55o

150 mm

Linear

Shear

16

1

64

49

55o

150 mm

Linear

Shear

16

1

64

49

55o

150 mm

Linear

Shear

16

1

64

49

55o

150 mm

Sectorial Law Configuration 1 2 3 4

Sectorial

Shear

16

16

40o

55o

1.0o

150 mm

Sectorial

Shear

16

1

40o

55o

1.0o

150 mm

Sectorial

Shear

16

16

40o

55o

1.0o

150 mm

Sectorial

Shear

16

1

40o

55o

1.0o

150 mm

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TOFD SCAN PLAN

Page 205

PROCEDURE FOR

LARSEN & TOUBRO

PHASED ARRAY/TOFD ULTRASONIC TESTING

OFFSHORE

OF DSS PIPING WELD JOINTS FOR OFFSHORE HOOKUP JOINTS

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Rev.

Date : 04/01/2013 Page 44 of 50

Basic Test Information Material

Thickness

Shear Velocity

Compression Velocity

Stainless Steel

75mm

3.1mm/µs

5.8mm/µs

HAZ Width

HAZ

Wedge Details (used for all scans) No.

Type

Velocity

Primary Offset

Height 1st Element

Length

Width

Angle

1

ST1-60L-IHC

2.33mm/µs

20.3 mm

N/A

20.3 mm

31.75 mm

20o

Transducer Details (used for all scan) Probe No.

Type

Shape

Diameter

Frequency

1

C543-SM

Round

6.35

5 MHZ

Scan Setup Scan No.

PCS

Scan Offset

Beam angle

1

160 mm

10 mm

60o

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PROCEDURE FOR

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OFFSHORE

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SCAN PLAN FOR 4 Inch 25 mm THICK – PIPE TO PIPE WELD JOINT

Page 207

PROCEDURE FOR

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PHASED ARRAY/TOFD ULTRASONIC TESTING

OFFSHORE

OF DSS PIPING WELD JOINTS FOR OFFSHORE HOOKUP JOINTS

GSPC/DDW1/L&T/QA/2011/QPC14B

Doc No.

2

Rev.

Date : 04/01/2013 Page 46 of 50

Basic Test Information Material

Thickness

Shear Velocity

Compression Velocity

Stainless Steel

25mm

3.1mm/µs

5.8mm/µs

HAZ Width

HAZ

Wedge Details (used for all scans) No.

Type

Velocity

Primary Offset

Height 1st Element

Length

Width

Angle

1

SA2-N55S-IHC Dual 5L64

2.33mm/µs

56.8mm

11.02mm

68.53mm

40mm

36o

Transducer Details (used for all scan) Probe No.

Type

Total Aperture

No of Element

Element Pitch

1

5L64-A2

38.4 mm

64

0.6 mm

Scan Setup Scan No.

Index Offset

Scan Offset

Mirror status

1

23mm

10mm

False

2

23mm

10mm

True

Linear Law Configuration Scan No. 1 2 3 3

Law Configurati on

Wave Type

Element Qty.

1st Element

Last Element

No. Of Beam

Refracted Angle

Focus Depth

Linear

Shear

16

1

64

49

56o

50 mm

Linear

Shear

16

1

50

35

45o

50 mm

Linear

Shear

16

1

64

49

56o

50 mm

Linear

Shear

16

1

50

35

45o

50 mm

Sectorial Law Configuration 1 2

Sectorial

Shear

16

27

39o

57o

1.0o

50 mm

Sectorial

Shear

16

27

39o

57o

1.0o

50 mm

Page 208

PROCEDURE FOR

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PHASED ARRAY/TOFD ULTRASONIC TESTING

OFFSHORE

OF DSS PIPING WELD JOINTS FOR OFFSHORE HOOKUP JOINTS

Doc No. Rev.

GSPC/DDW1/L&T/QA/2011/QPC14B

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Date : 04/01/2013 Page 47 of 50

TOFD SCAN PLAN

Page 209

PROCEDURE FOR

LARSEN & TOUBRO

PHASED ARRAY/TOFD ULTRASONIC TESTING

OFFSHORE

OF DSS PIPING WELD JOINTS FOR OFFSHORE HOOKUP JOINTS

Doc No.

GSPC/DDW1/L&T/QA/2011/QPC14B

2

Rev.

Date : 04/01/2013 Page 48 of 50

Basic Test Information Material

Thickness

Shear Velocity

Compression Velocity

Stainless Steel

25mm

3.1mm/µs

5.8mm/µs

HAZ Width

HAZ

Wedge Details (used for all scans) No.

Type

Velocity

Primary Offset

Height 1st Element

Length

Width

Angle

1

ST1-60L-IHC

2.33mm/µs

20.3 mm

N/A

20.3 mm

31.75 mm

20o

Transducer Details (used for all scan) Probe No.

Type

Shape

Diameter

Frequency

1

C543-SM

Round

6.35

5 MHZ

Scan Setup Scan No.

PCS

Scan Offset

Beam angle

1

60 mm

10 mm

60o

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OFFSHORE

OF DSS PIPING WELD JOINTS FOR OFFSHORE HOOKUP JOINTS

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Date : 04/01/2013 Page 49 of 50

R

PROCEDURE QUALIFICATION

A piece of DSS pipe of having length around one meter, thickness 75 and diameter 16(see figure-1) & thickness 25 mm and diameter 4.5 inch(see figure-2) were cut from the pipe to prepare the demonstration block. Various notches were prepared at the HAZ and weld metal on OD as well as ID side. The drawing for same is attached below. Also, few slags were introduced at intermittent depth. Radiography testing has completed for the joint and the same joint has to be tested with PAUT+TOFD. Once the result of both NDT methods are comparable the procedure for using UT in lieu of RT shall be consider suitable to use for production joints.

Figure-1

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Figure-2

R

Page 212