PA TOFD Procedure

LARSEN & TOUBRO LIMITED

PROCEDURE NO: H02-5666-536

HED, HAZIRA Manufacturing Complex

1.0

REV NO: R1

SCOPE: This procedure describes the requirements and application of contact based Time of Flight Diffraction (TOFD) ultrasonic examination for both detection and sizing of discontinuities in the weld joints thickness range from 19mm to 46 mm. The clad restoration over the weld and blind zones of TOFD Shall be volumetrically examined by the contact based semi automated encoded PHASED ARRAY (PA) ultrasonic technique. Procedure is only applicable for Shell long seams , circumferential seams and Y-ring with skirt. Procedure is not applicable for shell to nozzle joints.

2.0

APPLICABLE CODES, STANDARDS AND SPECIFICATIONS: ASME Section V Edition, 2010 ASME Sec. VIII Div 1 Edition 2010 ASME code case 2235-9

3.0

QUALIFICATION OF PERSONNEL FOR EXAMINATIONS:

3.1

The personnel employed for conducting the examination shall be trained, examined, qualified and certified for Ultrasonic testing Level II or III as per L&T written practice No. WP-NDT-01. Recommendations of SNT-TC-1A 2006 edition, ASME Section V and Section VIII are fully incorporated in the written practice.

3.2

In addition to above, only the personnel that have successfully demonstrated the scan plans on the qualification block which is prepared in line with para (c) of CODE CASE 2235-9 are eligible to perform the job. The evaluation of results and preparation of reports and their review and signature shall be done only by Level II or Level III personnel that have been qualified as per L & T’s written practice and have participated in the demonstration as above.

4.0

APPLICATION: Main objective of this procedure is to describe computerized Semi-automated “Time of flight Diffraction ” technique for location and evaluation of defects in the volume of the weld and adjacent parent material (Lesser of 1 in. or t on each side of the weld).Examination shall be conducted from outside of weld surface so that 100% (full) volume of weld is covered. The clad restoration shall be examined by the PHASED ARRAY technique in addition to blind zones associated with TOFD for detection, evaluation and sizing of flaws.

5.0

EQUIPMENT AND DETAILS:

5.1

APPARATUS

For TOFD Calibrated Ultrasonic system “Sonomatic Microplus 2 Digital flaw detector with single/dual axis encoded hand scanner” shall be used for the testing. Software  Line II or  TOFD II shall be used for scanning and post processing of data. Software TOFD Aids shall be used as a tool to determine probe centring separation (PCS) and volumetric coverage of weld. For PHASED ARRAY Calibrated Ultrasonic system “Omni Scan Digital flaw detector with single axis encoded hand scanner” shall be used for the testing. software Tomo View shall be used for scanning and post processing of data. Software ES Beam Tool shall be used as a tool to determine probe spacing and volumetric coverage of weld. OR Calibrated Ultrasonic system TD Focus scan or TD Handy scan Digital flaw detector with single/dual axis encoded hand scanner” shall be used for both TOFD and PA Ultrasonic testing. Software TD scan, 17.07, 17.08, 18.03 shall be used for scanning and post processing of data.

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5.2

REV NO: R1

CALIBRATION OF EQUIPMENTS: 5.2.1

SCREEN HEIGHT LINEARRITY:

Screen height linearity shall be checked as per ASME Sec.V, Article 4, and clause T-461.1.Position an angle beam search unit on a calibration block, as shown in Fig 1 so that indications from both the ½ and ¾ T Holes give a 2:1 ratio of amplitudes between the two indications. Adjust the sensitivity (gain) so that The larger indication is set at 80% of full screen height (FSH). 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 2dB steps if a fine control is not available), and read the smaller indication at each setting. The reading shall be 50% of the larger amplitude, within 5% of full screen height. The setting and readings must be estimated to nearest 1% of full screen height. Alternatively, a straight beam search unit may be used on any calibration block that provides amplitude differences, with sufficient signal separation to prevent overlapping of the two signals.

5.2.2

AMPLITUDE CONTROL LINEARITY:

Amplitude control linearity shall be checked as per ASME Sec.V, clause T-461.2 Couple an angle beam probe to IIW – V1 block and get multiple echoes from 100mm quadrant. Select any echo and note its amplitude. Reduce the gain by 6 dB and read the amplitude of 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. The settings and readings must be estimated to the nearest 1% of full screen and the readings shall be as shown in the following table. AMPLITUDE CONTROL LINEARITY INDICATION SET AT % OF FULL SCREEN HEIGHT 80 % 80 % 40 % 20 %

5.3

dB CONTROL CHANGE - 6 dB -12 dB + 6 dB +12 dB

INDICATION LIMITS % OF FULL SCREEN HEIGHT 32 to 48 % 16 to 24 % 64 to 96 % 64 to 96 %

PROBES: 5.3.1

TOFD PROBE

Table for TOFD Transducer selection Center REF NUMBER Type of probe Frequency 5 MHz PHOENIX ISL TOFD Broad Band and VERTIC SONOMAIC Longitudinal Wave 2MHz PHOENIX ISL TOFD Broad Band 10 MHz VERTIC SONOMAIC Longitudinal Wave

Crystal Size

Manufacturer

3-6 mm

Phoenix/Sonomatic

3-6 mm

Phoenix/Sonomatic

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REV NO: R1

Unfocused probes shall be used for detection and focused probes are recommended for improved resolution for sizing Wave propagation: Wave propagation for the TOFD shall be longitudinal in nature with broad beam coverage. 5.3.2

PHASED ARRAY PROBE:

Table for Transducer & Wedges selection Type of probe 5L- 64 A2 5L60PWZ1 2L – 32 A4 SA2 N55S PWZ1N55S SA4N55S Note : Other equivalent probes may

Center Frequency Elements 5 MHz 64 5 MHz 60 2 MHz 32 Wedge Wedge Wedge be used after validating the same on the mock up

Manufacturer R/D Tech/agr R/D Tech/agr R/D Tech/agr R/D Tech R/D Tech R/D Tech blocks to TPI.

Wave Propagation: Wave propagation for the Phased Array shall be Shear in nature.

5.4

DEAD ELEMENT VERIFICATION IN PA PROBES:

Following procedure shall be adopted to check the dead elements in PA probes: For TD Focus scan and handy scan dead element verification can be determined automatically with the software. Alternatively to perform manually, following procedure to be followed: Put the PA probe on V1 calibration block and select the following settings: Calibration reflector: 25 mm thickness back wall echo on V1 block Velocity: 5920 m/s Sensitivity: 80% BWE Display: A Scan and S scan Scan Type

Start element

Linear at 0 degree

1

No of active element/element group 1

Stop Element Last element the probe

of

By selecting each focal law/VPAs (virtual probe aperture) each element can be verified by verifying S scan display and A scan signal amplitude. If any element is dead /not working the same will show white strip on S scan display. Allowable dead elements are maximum 2 nos adjacent or 3 per focal law. 6.0

COUPLANT : A couplant shall be used which provides optimum wetting, transmission of ultrasound, resistance to corrosion, viscosity and removal characteristics. For this inspection couplant shall be Liquid starch or water or any other similar material, which permits satisfactory transmission of ultrasonic waves. Same couplant shall be used for calibration as well as for testing. Couplants used on nickel base alloy and austenitic stainless steel/titanium shall not contain more than 250ppm of sulphur and halides respectively.

6.1

7.0

Post cleaning of Couplant : The Couplant shall be removed after the completion of the inspection by means of damp cloths or allowed to dry in ambient condition.

CO-ORDINATE/REFERENCE SYSTEM The seams to be tested shall be divided in to spot numbers each having length of 250 to 300mm and shall be punched by using low stress punching (Bradma) on the job prior to inspection. The spot punching shall be started from O degree. orientation for cir-seam and for long-seam the spot punching to start from down side of the equipment towards topside (in vertical direction). The scanning shall be carried out by combining the group

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REV NO: R1

of spots with maximum length up to 3000mm in single scan. A calibrated encoder, which is an integral part of the system, shall be used to establish the location of coordinates of flaws. Sketch for Datum point marking attached.(Ref. Annexure 10) 8.0

BASIC CALIBRATION BLOCK (Ref Annexure1A, 1B, 1C, 1D & 1E) Basic calibration block shall be used for the sensitivity setting in accordance with Article 4, ASME Section V. The block shall be within +6mm of the nominal thickness of the job. The material from which the block is fabricated shall be of the same as of the job or equivalent P-Number grouping. Prior to fabrication, the block material shall be completely examined with a straight beam search unit. Areas that contain and indication exceeding the remaining back wall reflection shall be excluded from the beam paths required to reach the various calibration reflectors. The calibration block shall receive at least the minimum tempering treatment required by the material specification for the type and grade. If the calibration block contains welds other than cladding, and the component weld at the time of examination has been heat treated, the block shall receive the same heat treatment. TOFD scanning shall be performed on the above calibration block that the lateral wave amplitude is from 40 to 90 % of FSH. For multi-zone examinations where the lateral wave may appear feeble and below 40% FSH,( Eg.60degree for far-zone), the nearest SDH in the adjoining zone shall be detected at least with a difference of 6dB when compared to that of noise. The width of coverage shall be confirmed with the probe offset scanning to either side of the applicable zone’s weld edge +13mm. If required holes are not detected, two additional offset scans shall be performed. As job having dia more than 508mm, it is not required to have any curved block.

9.0

QUALIFICATION BLOCK FOR THE DEMONSTRATION (Ref Annexure1A, 1B, 1C, 1D & 1E) Qualification block shall be prepared by welding. The block shall contain a minimum of three flaws, oriented to simulate flaws parallel to the production weld’s fusion line as follows: 1. One surface flaw on the side of the block representing the vessels OD surface. 2. One surface flaw on the side of the block representing the vessels ID surface. 3. One subsurface flaw. 4. 3 to 4 number of EDM NOTCHES in the overlay The scanning surface of the block shall be same as that of job. Flaw size shall be no larger than the flaw in the table 2 mentioned for Acceptance Criteria. Qualification block shall be made according to the code case 2235-9 Para (c). Material for the qualification blocks shall have same P number with the surface finish as of job. Fingerprinting of qualification block shall be carried out using RT (Radiography) to ensure Flaw size and location are as per plan. Fingerprinting report will be used for validating qualification scans as per the procedure. New qualification scan shall be performed in case of any change in the equipment, equipment setting (Gain, filtering, Rejection, PRF), probes, cables, wedges, direction and extent of scanning, method for discriminating geometric indications from flaw indications, Level II person or using different accessories & same shall be performed on the job.

10.0

TEST SURFACE PREPARATION:

10.1 BASE METAL: The area to be scanned shall be free from loose scale, loose rust, weld spatter, indentations, burrs and waviness which may adversely affect free passage of the transducer over the scanning area of the transmission of ultrasound. Prior to conducting an ultrasonic examination the operator shall ensure that the weld deposit and surrounding area are sufficiently smooth to avoid false or misleading indications. The weld seam shall be flush ground and weld centre Line shall always be marked. At intersection of seams (longitudinal seams to circumferential seams), both the weld must be flush grounded to cover the total area in scanning. The scanning surfaces of the block shall be representative of that of the component to be examined.

Page 5 of 37

LARSEN & TOUBRO LIMITED HED, HAZIRA Manufacturing Complex

PROCEDURE NO: H02-5666-536 REV NO: R1

Prior to TOFD, A scan shall be performed in terms of base material scanning up to the scanning area. For further detail refer A-scan procedure H02-100045D-UT Rev0.

10.2 TEMPERATURE The maximum surface temperature when using conventional probes and couplants shall not exceed 50°C. The temperature difference between the calibration block and examination surface shall be with in 14 degree centigrade. 11.0

CALIBRATION:

11.1 POSITIONAL ENCODER CHECK ( TOFD) The positional encoder shall be moved through a measured distance of 20 inch (500mm). Calibrate the equipment over the moved distance to calculate the number of encoder count. Move the encoder in reverse direction from 500mm to 0mm to verify the encoder count, the system read-out shall be within 1% [0.02 inch (5mm)] of the measured distance. Encoder failing this check shall be recalibrated and this check is repeated.

11.2 THICKNESS CHECK ( TOFD) The probe set up is made on scanner and equipment as per scan plan (for Far Zone). A free run shall be made on the Calibration Block with this set up and data is acquired. The distance between the lateral wave and first back wall signal in the image shall be measured and compared with that of physical thickness of the block. The difference between the same shall be within 0.02 inch (0.5mm) of the block’s measured thickness. Set-ups failing this check shall have the probe separation distance either adjusted or its programmed value changed and this check is repeated.

11.3 SENSITIVITY SETTING 11.3.1 For TOFD Technique : Set the TOFD probes on the surface to be utilized for calibration and see the gain control so that the lateral wave amplitude is from 40% to 90% of the full screen height and the noise (grass) level is less than 5-10% of FSH. For multiple zone examination when the lateral wave is not displayed, or barely discernible, set the gain control based solely on the noise (grass) level. The side drill hole amplitude response in the focussed zone must be at least 80% of FSH. The SDH response from the required zone shall be a minimum of 6dB above the grain noise and shall be apparent in the resulting digitized gray-scale display. The sensitivity calibration shall be executed at the beginning and at the end of the examination of each weld scan by comparing the sensitivity to the lateral wave & back wall echo of the job and the block. 11.3.2 For Phased Array Technique System calibration:

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Fig: 1-Probe movement for system calibration   

The Phased array system shall be calibrated for Wedge Delay and Sensitivity/Focal Law Calibration. The Wedge Delay Calibration shall be calibrated for True Depth with the angles/VPA used in calibration. Wedge delay calibration can be done by taking reference side drilled holes on calibration block. The Wedge Delay Calibration shall be calibrated for True Depth with the angles used in calibration. Select a calibration reflector, which is of the known depth in the calibration block. Peak up this signal from the calibration reflector and scan the phased array probe backwards through all the different angles or focal laws. Scan forward over the calibration reflector through all the refracted angles or focal laws. The system will calculate the required wedge delay needed at each focal law to adjust the amount needed.

   

Fig:2- Sensitivity / Focal Law Calibration display The Sensitivity/Focal Law Calibration will provide the required gain adjustments for each refracted angle and sound path used. Select a calibration reflector, which is approximately one half the thickness of the component to be examined, or within the zone of material to be examined. Peak up this signal from the calibration reflector and scan the phased array probe backwards through all the different angles or focal laws. Scan forward over the calibration reflector through all the refracted angles or focal laws. The system will calculate the required gain needed at each focal law to adjust the amount needed

o o o o o

Fig: 3- Wedge Delay Calibration display. o o

o

A Time Corrected Gain (Auto-TCG) calibration shall be used to compensate for attenuation in the material at the sound paths utilized during calibration and examination. . The examination system calibration may be stored in the System with electronic memory or on an external chip or data storage device. This calibration may be used at a later date provided the system calibration is verified prior to examination. A complete Ultrasonic System Calibration shall be performed at least once prior to the examination.

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o


Focal law shall be the same for calibration and Phased Array examination.

Fig:4- TCG Calibration display All the above calibration shall be saved and stored in the machine with specific folder name so that same can be retrieved at the time of data acquisition.

11.4 System Calibration Verification ( PA ): System calibration verification shall include the entire examination system. Sweep range and TCG calibration shall be verified on the appropriate calibration block or simulator block, as applicable, under the following conditions:  With any substitution of the same type and length of search unit cable.  With any substitution of power utilizing the same type source At least every 4 hours during the examination  At the completion of a series of examinations  Whenever the validity of the calibration is in doubt  When examination personnel are changed. 11.5 Encoder Calibration (PA ): calibrate an Encoder Select Encoder from list Enter the start point. Enter the end point. Note this distance. It will be used as reference for the calibration distance travelled. Mark this distance. Physically move the encoder to mark point and note the distance travelled. Choose calibrate: This automatically calibrates the encoder. At this point, a resolution and the encoder position are displayed.  Recheck the calibration by moving the encoder moving reverse to the start point verify the count; 5 count over 500mm calibration distance.  Accept it.  Encoder shall be calibrated prior to start the examination. During nozzle inspection encoder calibration shall be done by taking weld centreline as reference

To      

12.0

TOFD CALIBRATION and VALIDATION SCANS on QUALIFICATION BLOCK. Select the relevant calibration block based on the weld geometry under test. A calibration scan to be done by placing the probes as per the scan plan provided in this procedure, on the side face of a relevant calibration block /qualification block, collecting minimum of 20 A-scans without moving the probes such that the lateral wave and direct compression wave reflection from the far surface are contained within the resultant image. This enables set-up or calibration errors to be traced. Select the frequency and probe diameter, which has sufficient beam spread for the coverage of weld to inspect. Set the pulse length accordingly. Set the Gain such that lateral wave is between 40 to 90% of full screen height.

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Set the pulse repetition rate at the lowest level possible. Same shall be demonstrated on the mockup to cover the far surface indication. The selection of the pulse repetition rate shall be according to thickness and scan speed. (As Job thickness is in 19mm mm to 49 mm, PRF shall be set between 800 to 1000). The ultrasonic instrument pulse repetition rate is sufficient to pulse the search unit at least six times within the time necessary to move one-half the transducer (piezoelectric element) dimensions parallel to the direction of the scan at maximum scanning speed. A dynamic calibration is performed on multiple reflectors, which are +2 dB. Of a static calibration. For a thickness up to 100mm, through thickness accuracy shall be adjusted to 0.5mm, for a wall thickness exceeding 100mm the through thickness accuracy shall be adjusted to 1mm. The through thickness accuracy shall be obtained by physically adjusting the PCS to the value as defined in the scan plan rather than adjusting the software value for the PCS. For dB references, lateral wave amplitude is from 40% to 90% of the full screen height and the noise (grass) level is less than 5-10% of FSH. The side drill hole (70/60 degree) amplitude response in the focussed zone must be at least 80% of FSH. The SDH response from the required zone shall be a minimum of 6dB above the grain noise and shall be apparent in the resulting digitized gray-scale display. Scanning over the appropriate calibration block to confirm the detection of the true diffracted responses shall prove this sensitivity setting. The sensitivity setting shall be checked on areas of clean, parent plate adjacent to the weld to be inspected. When required small changes (order of few dB) are permitted in order to compensate for a too low or too excessive noise level. If a change of –6dB is required the reason shall be considered and the validation tests repeated with the new settings. If any variation in sensitivity setting by more than 20% or 2dB of its amplitude whichever is less or distance range point has moved on the sweep line by more than 10% of the distance reading or 5% of full seep, whichever is greater, re-examination shall be performed since the last valid calibration check. After the calibration scan completed, the scanning is being done on qualification block to validate the scan plan. The image captured on the qualification block is evaluated for detection, sizing and location of flaws revealed. The same are compared with that of fingerprint results. A successful scan plan is considered only when all the relevant flaws are detected with the dimensions of the flaws equal to or greater than the finger print values and the complete coverage of the HAZ area and base material as per the code requirement is ensured. 13.0

SCANNING ON THE JOB:

13.1 TOFD SCAN DETAILS : TOFD scans are to be performed on each weld area to ensure adequate inspection coverage. TOFD scan shall be performed to evaluate the far surface region of the weld; 700 TOFD scan concentrated at near surface (Annexure 2 & 3) and All scans shall be performed from the vessel either external or internal surface as per scan plan. Each scan shall be performed with the TOFD probe array symmetrically astride the weld. The data shall be collected by moving the probes or rotating the vessel on rollers, at uniform speed ensuring the probe array remains central to the weld. The scanning speed shall be less than 1m/min. A maximum of 5% of the total number of lines collected in one single scan may be missed but no adjacent line shall be missed. The scanning speed used for the job shall be demonstrated on the calibration block by catching all the reference reflector. Same setup, gain setting shall be put same for the scanning. The collected data shall be presented in D-scan format i.e., vertical axis representing time/depth into the material and the horizontal axis representing distance along the weld. Indications evident in the lateral wave region shall require re-scanning at high frequency and/or closer probe center separations Phased array shall be done to cover the clad restoration weld area and BLIND ZONES associated with TOFD as per scan plan (Annexture-6)

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REV NO: R1

13.2 SCAN PARAMETERS FOR TOFD SCANS : Circumferential welds and longitudinal welds - Far Surface 5MHz with 3 or 6mm dia TOFD probes with 60° wedges and/or 70° wedges shall be applied. A probe center separation (PCS) shall be selected to cover the weld and HAZ region. Circumferential welds and longitudinal welds - Near Surface 10 MHz, 3-6mm dia TOFD probes with 700 wedges shall be applied. A probe center separation (PCS) shall be selected to cover the near surface.

13.3 SCAN LENGTHS & OVERLAP : Each PA and TOFD scans shall be performed by collecting 1 A-scan every 1mm of probe travel and each one degree in sectorial scan of PA. Typically, each scan shall be collected in maximum lengths of 5000mm and there shall be a minimum of 25mm overlap between successive scans.

13.4 SUPPLEMENTARY SCANNING FOR BLIND ZONE OF TOFD : Recordable Phased array UT annexure-7). 14.0

shall be done to cover blind zone of centre scan TOFD (Refer

RECORDING DATA For TOFD, A-scan gated region shall be set to start 1µ(s) prior to the lateral wave and up to 1µ(s) after mode-converted back-wall signal shall be recorded. For PA, range shall be adjusted so that that the data acquisition shall be of area of interest of relevant weld geometry. Same co-ordinate shall be followed in TOFD and PA.

15.0

DATA SAMPLING SPACING : For TOFD: A maximum sample spacing of 0.04 in. (1 mm) shall be used between A-scans collected for thicknesses under 2 in. (50 mm) and a sample spacing of up to 0.080 in. (2 mm) may be used for thicknesses greater than 2 in. (50 mm). For PA: A maximum sample spacing of 0.04 in. (1 mm) shall be used between A-scans collected for thicknesses under 3 in. (75 mm) and a sample spacing of up to 0.080 in. (2 mm) may be used for thicknesses equal to or greater than 3 in. (75 mm).

15.1 MISSING DATA LINES : For TOFD: Missing lines in the display shall not exceed 5% of the scan lines to be collected, and no adjacent lines shall be missed. For PA: The scanning speed shall be such that data drop out is less than 2 data lines per inch (25 mm) of linear scan length and there are no adjacent data line skip.

15.2 DATA DISPLAY AND RECORDINGS : The data display shall allow for the viewing of 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. Equipment shall permit storage of all gated A-scans to a magnetic or optical storage medium. Equipment shall provide a sectional view of the weld with a minimum of 64 gray scale or colour levels. (Storage of just sectional images without the underlying A-scan RF waveforms is not acceptable.) Computer software for TOFD displays shall include algorithms to linearize cursors or the waveform time-base to permit depth and vertical extent estimations. In addition to storage of waveform data including amplitude and time-base details, the equipment shall also store positional information indicating the relative position of the waveform with respect to the adjacent waveform(s), i.e., encoded position

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16.0

DATA STORAGE:- The acquired data for TOFD and PA shall be stored & archived with following file structure AA-BB-CC-DD-EE-FF AA: - Project No. BB: - Seam No (with revision) CC: - Iteration no. DD: - Operator ID EE:- Spot No. FF:- Detail of Scan (Probe angle/ Direction Of Scan )

17.0

EVALUATION:

17.1 FOR TOFD TECHNIQUE : For weld in materials equal to or less than 38mm thick at the weld images with indicated lengths greater than 4mm (5/22 in) shall be investigated. For weld in greater that 38mm at the weld images indicated lengths greater than 5mm shall be investigated. (Ref. Annexure 7) When the indication is determined to be a flaw, the acceptance criteria of CC 2235-9, Table 1 or 2 of Para. 13.0 shall apply (According to the thickness of the Job). Initial data evaluation shall be carried out using the unprocessed data only. Advanced algorithms as straightening and subtraction of lateral and/or back wall echoes shall only be carried out when signal detection has improved, or when indications require more accurate evaluation. The flaw length and the through thickness shall be measured by the distance between end fitting hyperbolic cursor.

A flaw shall be considered a surface flaw if the separation of the flaw from the nearest surface of the component is equal to or less than half of the through dimensional height of the flaw. The dimension of the flaw shall be determined by the rectangle that fully contains the area of the flaw. Discontinuous flaws shall be considered a singular planar flaw if the distance between adjacent flaws is equal to or less than S. Discontinuous flaws that are oriented primarily in parallel planes shall be considered a singular planar flaw if the distance between adjacent planes is equal to or less than 12.7mm. Discontinuous flaws that are coplanar and nonaligned in the through wall thickness direction of the component shall be considered a singular planar flaw if the distance between adjacent flaws is equal to or less than S. Discontinuous flaws that are coplanar in the through wall thickness direction within two parallel planes 12.7mm apart (i.e., normal to the pressure retaining surface of the component) are unacceptable if the

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REV NO: R1

additive flaw depth dimension of the flaws exceeds the limit.

17.2

PHASED ARRAY TECHNIQUE : 17.2.1 Validation:

Select the relevant Qualification block based on the weld geometry under test. The scanning to be done (at + 6dB of reference level) as per the scan plan provided in this procedure on the above block with the calibration set up file from respective folder of that block . The scanning is being done on qualification block to validate the scan plan. The image captured on the qualification block is evaluated for detection, sizing and location of flaws revealed. The same are compared with that of fingerprint results. A successful scan plan is considered only when all the relevant flaws are detected with the dimensions of the flaws equal to or greater than the finger print values and the complete coverage of the HAZ area and base material as per the code requirement is ensured. 17.2.2 Sizing of Indication Flaws shall be sized in accordance with a procedure demonstrated. Sizing of discontinuity (location, length and through thickness dimension) shall be done using equipment software on the captured image of discontinuity as mentioned in the sketch below. All indications above 20% amplitude of FSH ( at reference level) shall be evaluated. Gain may be increased for the indications above 20% amplitude to approximately 80% of FSH for sizing with 12 dB drop method at the ends of the discontinuities. Data cursor can be moved on the indication and with the help of A scan, 12dB drop method at the ends of discontinuities can be done for sizing of the indication. Indication length can be calculated by placing two cursors as shown below on C scan image and similarly through thickness height of the indication can be calculated by placing two cursors (at the back diffracted signals) as shown below on S scan image.

18.0

GEOMETRIC OR METALLURGIC INDICATIONS : In order to distinguish geometric or metallurgical discontinuities. Other NDE methods or techniques may be applied to classify an indication as geometric (e.g., alternative UT beam angles, radiography, ID and/or OD profiling). It is recognized that not all ultrasonic reflectors indicate flaws, since certain metallurgical discontinuities and geometric conditions may produce indications that are not relevant. This indication of geometric and metallurgical origin which are non-relevant shall be classified as follows: a)

Indications that are determined to originate from the surface configurations(such as weld reinforcement or root geometry) or variations in metallurgical structure of materials(such as cladding to base metal interface may be classified as geometric indications, and 1) Need not be characterized or sized in accordance with Para. 13.0 2) Need not be compared to allowable flaw acceptance criteria as

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REV NO: R1

per Para. 13.0 The maximum indication amplitude and location shall be recorded, for example: internal attachments, 200% DAC maximum amplitude, 25 mm above the weld centreline, on the inside surface, from 90 to 95 deg. 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-tomanual 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. 3)

19.0

RESTRICTED ACCESS WELD OR INACCESSIBLE WELD : Welds which are restricted or inaccessible with respect to TOFD/PA shall be covered by using RT (Radiography Technique).

20.0

SUPPLEMENTARY EXAMINATION: Due to the presence of Dead zone at scanning surface locations Recordable PA/A-SCAN UT to be done to compliment & Manual A Scan ( Conventional UT) shall be done for the indications oriented transverse to the weld. A-scan shall be done to examine the weld volumetrically as per approved & latest version of A Scan Procedure No.H02-100045D-UT.

20.1 RADIOGRAPHY : In case of doubt, if required local spot radiography may be taken for the confirmation or sizing of indications revealed in above methods.

R1

21.0

R1

20.2 MPT / PT: Any indication found opened to surface shall be examined by MPT/PT, whichever is more appropriate, and Respective procedure and acceptance criteria shall be applicable. ACCEPTANCE/REJECTION STANDARDS (AS PER CODE CASE: 2235-9) Indications shall be measured as aspect ratio (a/l) and acceptance/rejection shall be as per the table given below. For definitions of surface & subsurface flaws and their separation follow as per ASME CODE CASE 2235-9. Flaw size shall not be larger than the flaws in the bellow mentioned table. For “Sub surface flaws. Flaw length (l) shall not exceed 4t” where t is the thickness of the weld excluding any reinforcement. Surface Connected Flaws. Flaws identified as surface flaws during the UT examination may or may not be surface connected. Therefore, unless the UT data analysis confirms that that flaw is not surface connected, it shall be considered surface connected or a flaw open to the surface, and is unacceptable unless a surface examination is performed i.e M.T or P.T. If the flaw is surface connected, the requirements above still apply; however, in no case shall the flaw exceed the acceptance criteria in the applicable Construction Code for the method employed. Table 1: Flaw acceptance criteria for 1/2 in. to less than 1 in. thick weld a/t l Surface flaw ≤ 0.087 ≤ 0.25 in. (6.4 mm) Subsurface flaw ≤ 0.143 ≤ 0.25 in. (6.4 mm) Table 2: Flaw acceptance criteria for 1 in. to 12 in. thick weld 1 in. < t < 21/2 in. Aspect ratio Surface Subsurface Flaw Flaw a/l a/t a/t

4 in. < t < 12 in. Surface Flaw a/t

Subsurface Flaw a/t

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0.00

0.031

0.034

0.019

0.020

0.05

0.033

0.038

0.020

0.022

0.10

0.036

0.043

0.022

0.025

0.15

0.041

0.049

0.025

0.029

0.20

0.047

0.057

0.028

0.033

0.25

0.055

0.066

0.033

0.038

0.30

0.064

0.078

0.038

0.044

0.35

0.074

0.090

0.044

0.051

0.40

0.083

0.105

0.050

0.058

0.45

0.085

0.123

0.051

0.067

0.50

0.087

0.143

0.052

0.076

(a) Thickness of the weld excluding any allowable reinforcement. For butt weld joining two members having different thickness at the weld, t is the thinner of these two thicknesses. If a full penetration weld includes a fillet weld, the thickness of the throat of the fillet weld shall be included in t. (b) A subsurface indication shall be considered as a surface flaw if separation (S in Fig. 1) of the indication (2d in Fig.1), sketch[b]) of the surface indication. 9c) If the acceptance criteria in this table results in a flaw length, L, less than 0.25in. (6.4mm), a value of 0.25in (6.4mm) may be investigated. Note: For intermediate flaw aspect ratio a/l and thickness (64mm
REPORT AND DOCUMENTATION A report of the examination shall be made as per the format. The report shall be made after the evaluation of both, TOFD and PA data (Ref. Annexure 7) Examination Records shall contain:  Procedure identification & revision  Ultrasonic instrument identification (Including manufacturer’s serial number)  Search units identification (Sr. No. , Frequency, and size)  Beam angle  PCS (probe center separation)  Focused angle (if used)  Couplant used  Search unit cable used, type and length  Computerized program identification and revision  Calibration data reference reflectors, distance reading and block identification  Instrument reference level gain, if used, damping and reject settings  Identification and location of weld  Surface from which examination was conducted including surface condition  Record of rejectable indication  Area of restricted access or inaccessible  Examination personnel identity  Date of examination  Data sampling spacing  Flaw height NOTE: File Name for the data storage: The soft copy of the scan data shall be stored as per below link.

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Project Folder Name > Seam No > scanned file Scanned file shall have the name in terms of: Spot No > Angle of probe > PCS Example: For seam no. X and spot no. 1-10 Go to project file name: 45666, Select Seam No. X, Select file for spot 1-10 (60 and/or 70 degree) The above image data shall be stored for five years in the main Server of L&T. The reports shall be part of final document dossier and shall be submitted to the customer along with the completion of Vessel.

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Annexure 1A TOFD Calibration and Qualification Block 52 # 52 mm Thickness

Sr. No. 1

Distance from datum spot -1 ( mm ) 85

Length ( mm )

Depth ( mm )

Height ( mm)

Y value ( mm )

15

3-7

4

0

2

140

15

45 - 49

4

20

3

185

20

13 - 17

4

-17

4

220

20

34 - 37

4

0

5

110

10

48 – 55.5

7.5

-16

6

165

10

52 – 55.5

3.5

0

7

255

10

51 – 55.5

4.5

19

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Annexure 1B TOFD Calibration and Qualification Block 52 # 39 mm Thickness

Sr. No. 1


Length ( mm )

Depth ( mm )

Height ( mm)

Y value ( mm )

10

2–5

3

0

2

140

10

34 – 37

3

15

3

185

20

16 - 19

3

-13

4

220

20

25 - 28

3

0

5

110

10

38 - 42.5

4.5

-12

6

165

10

39 – 42.5

3.5

0

7

255

10

35 – 42.5

7.5

14

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Annexure 1C TOFD Calibration and Qualification Block Thickness 39 # 39 mm

Sr. No. 1


Length ( mm )

Depth ( mm )

Height ( mm)

Y value ( mm )

10

2–5

3

0

2

140

10

34 – 37

3

15

3

185

20

16 - 19

3

-13

4

220

20

25 - 28

3

0

5

110

10

38 – 42.5

4.5

-12

6

165

10

39 – 42.5

3.5

0

7

255

10

35 - 42.5

7.5

14

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Annexure 1D TOFD Calibration and Qualification Block 26 # 26 mm Thickness

Sr. No. 1


Length ( mm )

Depth ( mm )

Height ( mm)

Y value ( mm )

7

14 - 17

3

0

2

140

5

2-5

3

10

3

170

5

21 - 24

3

-8

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Annexure 1E TOFD Calibration and Qualification Block 22 # 22 mm Thickness

Sr. No. 1


Length ( mm )

Depth ( mm )

Height ( mm)

Y value ( mm )

5

8 - 11

3

0

2

140

5

2-5

3

8

3

210

5

15 - 18

3

-8

4

115

10

21 – 25.5

4.5

-7

5

180

10

22 – 25.5

3.5

0

6

250

10

19.5 – 25.5

6

7

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Annexure 2 Scan plan Far Zone Coverage

T1 WEP of weld seams as per Drawing Table : TOFD scan plan GEOMETRY Group Butt

  

Thickness (mm)

PCS (mm)

Probe Frequency (MHz)

Probe Element Diameter (mm)

Probe Angle (Degrees)

Offset (mm)

Transducer (Type)

32 to 46

100 to 120

5

6

60

-

Broadband TOFD probes

PCS mention in above table is tentative; the final PCS will be decided on the basis of the calibration check. Above scan plan shall be read in conjunction with Annexure 4 &5 The far surface blind zone associate with TOFD shall be covered in supplementary PA scan (Refer Annexure 7)

.

.

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Annexure 3 Scan plan Near Surface Coverage

T WEP of weld seams as per Drawing Table: TOFD scan plan

group

Thickness (T) (mm)

PCS (mm)

Probe Frequency (MHz)

Probe Element Diameter (mm)

Probe Angle (Degrees)

Offset (mm)

Transducer (Type)

Butt

19-46

60-80

5-10

3-6

70

-

Broadband TOFD probes

GEOMETRY

   

PCS mention in above table is tentative; the final PCS will be decided on the basis of the calibration check. Above scan plan shall be read in conjunction with Annexure 2 & 4. The blind zone at top surface for the above scans: 3mm The above blind zone covered in supplementary PA scan (Ref Annexure 7)

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Annexure-4 MOCK-UP BLOCK FOR PHASED ARRAY



The above WEP (weld edge preparation ) details will vary depends upon actual job condition based on drawings

EDM NOTCHESLENGTH- 10mm WIDTH- 0.4mm HEIGHTis 2mm; 4mm; 6mm; & 8mm Note: distance from reference zero, (in mm), total 14 numbers of slits.

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Crossectional view of indications

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Annexure-5 PROBE-WEDGE: 5L64A2-SA2N55SDUAL Reference for skip distance: WELD CENTRE to WEDGE FRONT Scanning shall be done from both side of weld 1. SCAN-1:

Probe scanning line number

scan 1

Distance from weld centre [mm]

Angular beam scan [from ... to] [degree]

Overall depth Zone inspected [mm]

Number of used probe elements

Element Pitch

Start elemen t

T(X)/R(X)

(mm)

(mm)

Transmitt er focus Depth [mm]

0

45°

20 - 34

16

1

30

0.6

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REV NO: R1

2.SCAN-2 (Group-1):


scan 2

Group 1





Element Pitch

Start elemen t

T(X)/R(X)

(mm)

(mm)


25

45°

0 - 34

16

1

35

0.6

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REV NO: R1

3.SCAN-2 (Group-2):


SCAN 2

Group 2





Element Pitch

Start elemen t

T(X)/R(X)

(mm)

(mm)


25

35°- 47°

0 - 13

16

1

35

0.6

Notes:

Scan plan may change based on selection of probe and wedge

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Annexure-6 PHASED ARRAY SCAN PLAN FOR JOB THICKNESS 1.

SCAN PLAN FOR JOB THICKNESS 26 MM


scan 2

2.

Group 1 Group 2





Element Pitch

Start elemen t

T(X)/R(X)

(mm)

(mm)


45°

0 - 26

16

1

25

35°- 47°

0 - 13

16

1

25

5

0.6 0.6

SCAN PLAN FOR JOB THICKNESS 39 MM + 3 MM Clad






Element Pitch

Start elemen t

T(X)/R(X)

(mm)

(mm)


45°

0-42

16

1

35

45°

0 - 42

16

1

35

35°- 47°

0 - 13

16

1

35

scan 1

Group 1

10

scan 2

Group 1 Group 2

35

3.

0.6 0.6 0.6

SCAN PLAN FOR JOB THICKNESS 52 MM + 3 MM Clad






Element Pitch

Start elemen t

T(X)/R(X)

(mm)

(mm)


45°

0-55

16

1

50

45°

0 - 55

16

1

50

35°- 47°

0 - 13

16

1

50

scan 1

Group 1

30

scan 2

Group 1 Group 2

60

0.6 0.6 0.6

NOTE: (SCANNING SHALL BE DONE FROM BOTH SIDE i.e. at 90º & 270º SKEW) 

Above scan plan shall be read in conjunction with Annexure 2,3 & 4.

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Annexure 7 Flaw Evaluation

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Annexure8A Sample TOFD UT Report

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PA TOFD Procedure

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