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NON-DESTRUCTIVE EXAMINATION PROCEDURE
Doc No.: CA - 40 – 12.OSS
Revision No.: 01E
ULTRASONIC EXAMINATION PROCEDURE
01E
26-05-2012
Issued for application
Rev.
Date
Description
N.C Thanh
L.T.Q Thuong
Prepared by
Checked by
CANDT
CLIENT
C.A.
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ULTRASONIC EXAMINATION PROCEDURE
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REVISION RECORD SHEET NN
Rev. No.
Content of Revision
Date
1
01E
Issued for application
26-05-2012
2 3 4 5 6 7 8 9 10 11 12 13 14 15 Note: Third column is to be filled in, when the document is being updated/modified
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TABLE OF CONTENTS REVISION RECORD SHEET....................................................................................................2 TABLE OF CONTENTS.............................................................................................................. 3 1.0INTRODUCTION................................................................................................................... 4 2.0SCOPE.................................................................................................................................. 4 3.0REFERENCES...................................................................................................................... 4 4.0DEFINITION.......................................................................................................................... 4 5.0PERSONNEL QUALIFICATION............................................................................................5 6.0ULTRASONIC EQUIPMENT .................................................................................................5 6.1Ultrasonic Set............................................................................................................. 5 6.2Probes....................................................................................................................... 5 6.3Adaptation of probes to curved scanning surfaces ....................................................5 6.4Couplant.................................................................................................................... 6 6.5Calibration, Reference Block......................................................................................6 7.0Equipment performance check..............................................................................................8 7.1Qualification and Periodically Check of Equipment....................................................8 7.2Probe index of angle probe........................................................................................8 7.3Determination of probe angle.....................................................................................9 7.4Range scale............................................................................................................... 9 7.5Time base linearity...................................................................................................10 7.6Linearity of gain control............................................................................................11 7.7Screen height linearity..............................................................................................11 7.8Resolution................................................................................................................ 11 7.9Profile of angle beam...............................................................................................12 7.10Calibration of amplification (Angle probes).............................................................13 7.11Transfer Correction................................................................................................13 7.12Scanning Sensitivity...............................................................................................17 8.0SURFACE PREPARATION.................................................................................................17 9.0TESTING PROCEDURE.....................................................................................................17 9.1Prior to Examination.................................................................................................17 9.2Testing of Parent Material........................................................................................17 9.3Probe selection........................................................................................................18 9.4Calculation .............................................................................................................. 18 9.5Scanning .................................................................................................................18 9.6Flaw Sizing .............................................................................................................21 10.0EVALUATION OF IMPERFECTIONS IN WELD CONNECTIONS.....................................22 11.0ACCEPTANCE CRITERIA WELD CONNECTIONS..........................................................23 12.0REPORTING/ RECORDING..............................................................................................24 13.0SAFETY............................................................................................................................. 25 14.0SPECIAL REQUIREMENT................................................................................................25 Appendix 1 - ULTRASONIC EQUIPMENT PERFORMANCE CHECK......................................27 Appendix 2 - ULTRASONIC EXAMINATION REPORT............................................................28 Appendix 3 - SKETCH - SUPPLEMENTARY REPORT........................................................29 QUALITY MANAGEMENT SYSTEM
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Appendix 4 - ULTRASONIC TECHNIQUE.........................................................................30 Appendix 5 – DEFECT SIZING ..........................................................................................32
1.0 INTRODUCTION This procedure specification is developed to cover the ultrasonic testing requirements carried out by CANDT.
2.0 SCOPE This procedure is applicable for ultrasonic examinations of groove welds in structural shapes and plates between the thickness of 10mm and 100mm in accordance with DNV Classification notes No.7, December 2004 and Offshore Standard DNV-OS-C401, April 2004.
3.0 REFERENCES o DNV Classification notes No.7, December 2004: Non-destructive testing o EN 1714/EN 1712 acceptable o Offshore Standard DNV-OS-C401 Offshore Standard o ASNT Recommended Practice No. SNT-TC-1A: Personnel Qualification and Certification in Nondestructive testing o CA-30-01 Rev 01E: CANDT NDT’s Written Practice.
4.0 DEFINITION o ASNT:
American Society of Non-destructive Testing
o PCN:
Personnel Certification of Non-DestructiveTesting
o CSWIP: Certification Scheme of Welding and Inspection Personnel o Manual scanning: Manual displacement of the probe on the scanning surface o Amplitude: Maximum value of the motion or pressure of a sound wave (echoheight) o Probe index: Intersection point of the sound beam axis with the probe surface o Dead zone: Zone adjacent to the scanning surface within which reflectors of interest are not revealed. o DAC: Distance Amplitude Curve o DGS-diagram: Series of curves which shows relationship between distance along a beam and gain in dB for an infinity reflector and different sizes of disc shaped reflectors. o Back wall echo: Pulse reflected from a boundary surface which is perpendicular to the sound beam axis. o 6 dB-drop technique:Method for defect size assessment, where the probe is moved from a position showing maximum reflection amplitude until the echo has decreased to its halfvalue (by 6dB) o dB: Decibel o S: Skip distance QUALITY MANAGEMENT SYSTEM
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o FSH: Full Screen Height o FBH: Flat Bottom Hole SDH: Side Drilled Hole
o
CRT: Cathode Ray Tube Other relevant definitions and symbols, which are defined in DNV Classification, notes No.7, are also applied in this procedure.
5.0 PERSONNEL QUALIFICATION o Personnel performing Ultrasonic Testing of welds shall be qualified and certified in accordance to an appropriate UT level II or III in accordance with ISO 9712, EN 473 or other equivalent recognized standard or certification schemes such as PCN and CSWIP, NORDTEST. o Personnel qualified and certified in accordance with ASNT Recommended Practice No. SNT-TC-1A is subject to evaluate and approve by DNV before commencing UT in the Project.
6.0 ULTRASONIC EQUIPMENT 6.1
Ultrasonic Set The ultrasonic portable flaw detectors for pulse echo technique with following characteristics shall be used: - “A scan” presentation, - Working frequency from 1- 6Mhz, - Single/ double probes mode. - Adjustable gain control with step not more than 2dB The UT set such as USK 7S, USM 35, USM-25, Sonatest 110S, Epoch III or any similar set shall be used. All the functions of the UT set shall be checked in accordance with requirements of this procedure.
6.2
Probes The recommended probes to be used maybe appropriate models from Manufactures such as KRAUTKRAMER, GB, SONATEST, PANAMETRIC, and STRESSTEL etc. -
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6.3
0° probes: 2 – 5 MHz twin/single crystal longitudinal wave probes with norminal element size of 10 mm, 15 mm, 20 mm or 24 mm shall be used. Angle probes: The 45°/ 60°/ 70° single crystal shear wave probes with frequency 2 – 5 MHz shall be used. Generally for all circumstances probe size shall be 8 x 9 mm. If required by code/standard, large probe size shall be used.
Adaptation of probes to curved scanning surfaces -
The gap between the test surface and the bottom of the probe shoe shall not be greater than 0.5 mm. For cylindrical or spherical surfaces
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6.4
Couplant -
6.5
the requirement will normally be met when the following equation is fulfilled: D ≥ 15 A Where: D = the diameter in millimetres of the component A = the dimension in millimetres of the probe shoe in the direction of scanning. If this requirement can not be obtained the probe shoe shall be adapted to the surface and the sensitivity and range shall be set accordingly. Oil, grease, glycerine or cellulose paste is well suited for this purpose. The coupling medium used for calibration shall also be used during testing.
Calibration, Reference Block -
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The IIW or ISO calibration blocks (V1-V2), see Figure 1, shall be used for calibration of range scale, probe index and angle determination. The reference block shall normally be manufactured from the actual material tested and have approved dimensions such as shown in Figure 2. The reference blocks shall be made with thickness and side-drilled holes as described in Table 1 and shown in Figure 3 and shall be used for calibration of amplification and construction of reference curves (DAC). Surface finish from which the scanning is to be conducted is to be representative of the component to be inspected.
Figure 1: Calibration blocks.
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Table 1.Calibration reference block requirements
Figure 2: Basic calibration block.
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Notes: 'Lmin' shall be sufficient to allow a minimum of two half skips (one V path) of the sound beam using the transducer angle to be used. Lmin = 3 x (1/2 skip = T x tang(70o)) + T = 9.25 T Calibration Reflector holes to be drilled parallel to the scanning surface. Surface of reference block shall be the same as tested object surface.
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Figure3: Reference blocks.
7.0 EQUIPMENT PERFORMANCE CHECK 7.1
Qualification and Periodically Check of Equipment -
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7.2
The ultrasonic testing system shall be qualified and verified in accordance with the procedure described in ASME Code, section V, Article 4, Appendix 1 and 2 for Screen height linearity and Gain control accuracy at the beginning of each period of extended use or every one week, whichever is less. At approximately four-hourly intervals the range scale, probe angle and primary gain must be checked and corrected. Checks shall also be carried out whenever a system parameter is changed or changes in the equivalent settings are suspected. If deviation is found to be > 2% of range scale, >4dB of primary gain setting or >2o of nominal angle probe, the examinations carried out with the equipment over the previous period shall be repeated. All data of the qualification and equipment performance check shall be recorded and documented.
Probe index of angle probe -
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The index point of angle probe is to be determined by placing the probe as shown in Figure 4 and by maximizing the echo against the cylinder surface with radius 100mm (IIW V1 block), the echo height is adjusted to about 80% FSH. The probe index can now be read off against the mark on the calibration block and marked off on the probe. Figure 4: Determination of probe index. Daily check before the test and at least every four hours is required.
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7.3
Determination of probe angle -
The probe angle is to be checked on the IIW block using the index found. The echo from the circular perplex reflector is maximized and put at 80% FSH. The probe angle can now be read off on the calibration block against the engraved center point, see Figure 5.
Figure 5: Checking the probe angle. -
7.4
Daily check before the test and at least every four hours is required.
Range scale -
The calibration of range scale with straight beam probe is to be carried out with an IIW V1 or V2 block. The range scale is to be selected such that there are always at least 2 back-wall echoes on the screen. Figure 6 shows some typical calibrations.
Figure 6: Calibration of range with straight beam normal probe QUALITY MANAGEMENT SYSTEM
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The calibration of angle beam probe is to be carried out on an IIW V1 or V2 block. The range is to be selected in order to cover minimum 1.25 x full V-path distance. The required V-path distance (SP) is depending of the object thickness and can be calculated as follows: SP=2T/cosα, where T = thickness of object to be tested and α = probe angle. Some typical calibrations are shown in Figure 7
Figure 7: Figures b and c calibration of range with angle probe.
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7.5
Daily check before the test and at least every four hours is required.
Time base linearity -
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Place the probe on position A, B or C of IIW V1 block (Fig.6). Adjust the time base so that the first and fifth back wall echo indications coincide with the particular graticule line on the CRT screen. Bring successive back wall echoes, in turn, to approximately the same height (e.g. 80% FSH). The leading edge of each echo should line up with the appropriate graticule line. Record any deviation from the ideal positions. For range less than 250 mm, place the probe at B; for the range greater than 250 mm, place the probe at A or C. Tolerance: Deviation of the base line linearity shall be not exceeded ± 2% of the full time- base range, otherwise re-calibration is required.
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7.6
Frequency of calibration: Checks shall be carried out at least once per week if the unit is used daily or prior to production testing.
Linearity of gain control -
Place the probe on position B (Fig.6) Adjust the gain to set the signal to 80% of full screen height (FSH) and note the value of the calibrated control (dB). Adjust the calibrated control to increase the gain by 2 dB. The signal should increase to full screen height (100%). Restore the gain to its original value and than reduce it by 6dB.The signal should fall to 40% of full screen height. Reduce the gain by a further 12 dB. The signal should fall to 10% of full screen height. Reduce the gain by 6 dB. The signal should fall to 5% of full screen height. The signal height should fall within the following tolerances: Gain dB 2 0 -6 - 12 - 18 - 24
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7.7
Limits
Actual screen height (%)
Not less than 95% (reference line) 37% - 43% 17% - 23% 8% - 12% Visible, below 8%
Frequency of calibration: Checks shall be carried out at least once per week if the unit is used daily or prior to production testing.
Screen height linearity -
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7.8
Expected screen height (%) 101 80 40 20 10 5
Place the probe on position B (Fig.6). Adjust the probe position to give a 2 to 1 ratio of amplitudes between the first and the second back wall signal with the first signal set at 80% FSH. Without moving the probe, adjust the gain control to successively set the first signal from 100% to 20% FSH, in 10% or 2 dB increments. Read the amplitude of the second signal at each setting. Record the amplitudes of both signals. Tolerance: Difference between smaller signal and ½ larger signal height to be better than 5% FSH or 25% smaller signal height whichever is the less. Frequency of Checking: Checks shall be carried out at least once per week if the unit is used daily or when maintenance service is carried out on the test equipment.
Resolution 7.8.1 Straight beam probes
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At position A (Fig.8): The probe / flaw detector combination shall be able of resolving the 85, 91 and 100 mm steps in the IIW V1 block. Echoes shall be considered resolved when they are observed to be separated by 60 % FSH when displayed at 80 % FSH. CANDT
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Positions B and C is to determine near surface resolution and dead zone of the probe. If the reflection from the Perspex disc at 10 mm or 5 mm cannot be displayed, reflectors within the corresponding range shall not be detected (dead zone). B
A
C 85
91
100
Figure 8
7.8.2 Angle beam probes
7.9
The combination of search unit and instrument shall resolve three holes in the RC resolution reference test block.
Near surface resolution can be determined by using the block with side drilled holes near to surface.
The signal amplitude of subsequent signals should be clearly separated.
Frequency of checking: The resolution check of probe-unit combined shall be carried out for a new probe, when the beam index / angle has changed or at least once a week.
Profile of angle beam The 20 dB beam profile in the vertical plane shall be determined for each angle probe using the 1.5 mm holes in the IOW block. Procedure is as following: -
Maximize the response from 1.5 mm SDH at 12.5 mm depth and amplitude will be adjusted to 100% FSH. The distance between the holes index and the beam index will be measured and recorded. Move the probe forward until the response drops to 10% FSH. The distance between the hole index and the beam index will be measured and recorded Move the probe backward until the response drops to 10% FSH. The distance between the hole index and the beam index will be measured and recorded Plot the three distances recorded on full – size graph. This procedure shall be repeated utilizing the responses from the two further reflectors at varying depths (as a minimum requirement) to provide a beam profile chart.
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7.10
Calibration of amplification (Angle probes) -
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7.11
Drawn a straight line through the center line points and extend the line to the probe. This indicates the beam centerline of the probe. Frequency of checking: The profile shall be checked on a weekly basis and re-plotted when new probes are used, when there is a change of probe index, beam angle and when the probe shoe has worn down. The calibration of the amplification shall include the whole ultrasonic testing system, which are the ultrasonic flaw detector, probes (Angle probes), cables and coupling medium. In order to compensate for attenuation and sound beam spread with increasing sound path a DAC-curve is to be constructed. DAC is to be constructed using reference block with side-drilled holes as described in 6.5. The echo reflected from the drilled hole in the reference block is maximized and the gain control regulated so that the echo amplitude is 80% of FSH. This gain setting is called the primary gain and is to be noted. Without altering the primary gain, the probe is positioned in various skip distances as indicated on Figure 3 and the respective echo amplitudes are marked on the screen. These points are connected with a smooth line with a length, which covers the required scanning area. This is the reference curve (DAC). This first point of DAC must be selected so that the distance in sound path from the probe index to the drilled hole is not less than 0.6N where N is the near field length of the relevant probe.
Transfer Correction -
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A correction of instrument sensitivity is required to compensate for the differences between the reference block and test component due to test surface roughness, contact area and acoustical attenuation characteristic. Measurement is achieved by employing two angle probes of the same type, one acting as a transmitter and the second as a receiver. The probes are directed at each other on the reference block at one skip distance and the signal adjusted to the DAC using the gain control. The gain setting is noted. The procedure then shall be repeated on the scanning surface adjacent to the weld to be tested. The differences between two-gain settings are the transfer correction to be noted for the test, see Figure 9. Any difference in echo amplitude between the two materials can now be determined with the aid of the gain control. If the differences are less than 2 dB, correction is not required.
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Figure 9: Attenuation and surface correction.
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7.12
If the differences are greater than 2 dB but smaller 12 dB, they shall be compensated for. If transfer losses exceed 12 dB, the reason shall be considered and further preparation of the scanning surfaces shall be carried out, if applicable. When there are no apparent reasons for high correction values, the attenuation, at various locations on the test object shall be measured. Where it is found to vary significantly, corrective actions must be considered.
Scanning Sensitivity. -
Scanning is then performed at the reference sensitivity (primary gain) + transfer correction + 6 dB. Indication shall be evaluated at the reference sensitivity + transfer correction.
8.0 SURFACE PREPARATION The surfaces of welds and base metal shall be prepared as follows: o Contact surfaces shall be free of weld spatter and any condition that might interfere with free movement of the probe. o Finished weld surfaces shall be adequate to prevent interference with interpretation of the examination. o Surfaces of the calibration reference blocks shall be of a similar finish to the part under examination. o Shipbuilding Manufacturer or Contractor of Construction shall be responsible for insuring all surface preparation are acceptable prior to any ultrasonic testing work being carry out.
9.0 TESTING PROCEDURE 9.1
Prior to Examination -
9.2
Verify actual angle, probe index of each probe, calibration and reference levels where deemed necessary. Prepare a cross sectional drawing of the weld design on paper and determine... Check surface preparation as required refer to 8.0 of this procedure. Establish beam spreads and DAC curves for each probe. Carry out function tests on ultrasonic flaw detector and probes.
Testing of Parent Material -
The examination is to be performed in order to reveal possible imperfections, which might influence the angle probe testing. The whole of the area (1.25 x T x tg(α)) which will transfer ultrasound when using angle probes shall be tested. The gain setting shall be calibrated on a defect free place on the parent material. The second back wall echo shall be set to 75% or 80% of FSH imperfections with a cross section larger than sound beam (loss of back wall echo) shall be
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reported. The extent of the imperfections is measured with the aid of the 6 dB-drop method when complete loss of back wall echo occurs.
9.3
Probe selection Minimum two angle probes shall be used for the testing. -
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Angle of probe to be used for inspection is depend on thickness of material, weld bevel and type of defect being sought and to be selected as recommend below: Table 2 Parent material thickness, T
Probe angle
10 – 20 mm
600 and 700
20 – 40 mm
450, 600, 700
T > 40 mm
450, 600 (700 when ½ V or K groove)
A favorable probe angle when the weld connection in the transition between welds and parent material is the angle which gives incident sound normal to the angle of the weld bevel. The optimal angle for a Vgroove is given by the groove geometry and can be calculated as shown in Figure 10. If the calculated angle does not comply with any standard probe angle, the nearest larger probe angle shall be selected.
Figure 10: Detection of sidewall lack of fusion
α= 90O –β
9.4
Calculation -
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9.5
Skip distance: ½ S = T x tan (α) Where: α - Angle probe T - Thickness of Base metal ½ Sound V-Path Distance: SP = T/cos(α) Depth of flaw detected: - In case < 1/2 skip: d = sound path to defect x cos(α) - In case > 1/2 skip: d = 2T - (sound path to defect x cos(α))
Scanning
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The scanning for weld examination shall investigate the total weld volume plus the region either side of the weld considered to be the heat affected zone. (H.A.Z.). The angle probe is placed on the parent material in such a way that the sound beam is normal to the weld. The probe is to moved forwards and backwards in the scanning area of 1.25 x T x tg(α), see Figure 11.
Figure 11: Probe movement for testing of butt weld – for X-groove and V-groove.
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Scanning speed should be slow enough to maintain coupling and ensure the operator can monitor all events on the screen/displays. Typical scanning speeds are as follows: - Parent material ≤ 150mm/sec. - Weld root ≤ 25mm/sec. - Weld body ≤ 100mm/sec. Butt weld: All fusion faces shall be scanned with a probe whose angle strikes the fusion line within ± 10o of the normal. All single sided welds shall be subjected to a critical root scan. The weld cross-section shall be scanned with the full range of angle probes. For transverse weld cracking by scanning along the weld cap using a 45 o probe shall be examined for SAW in material 25 mm and above. Each weld is
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examined with angle probes (45o, 60o or 70o) using 1/2 (half) and full skip techniques refer to scanning techniques. - Testing of T-joint: Examination of T-joints with ½ V or K-groove is carried out as for butt weld. The scanning area for the probes is shown in Figure 12 - Reflectors oriented parallel to the weld: The angle beam shall be directed at approximate right angle to the weld axis from two sides where possible. The probe shall be manipulated so that the ultrasonic energy passes through the required volumes of the welds and adjacent metal. The scanning shall be performed at a gain setting at least two times the primary reference level. Evaluation shall be performed with respect to primary reference level. - Reflectors oriented transverse to the weld: The angle beam shall be directed at approximate 100 to the weld axis. The Probe shall be manipulated so that the angle beam passes through the required volumes of the welds and adjacent metal (HAZ). The scanning shall be performed at a gain setting at least two times the primary reference level. The probe shall be rotated 180 o. And the examination repeated. Figure 12: inspection of T-or corner joint (Single bevel or double bevel groove welds)
9.6
Flaw Sizing
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Indications shall be investigated from all possible angles to obtain the highest possible response to confirm the position of the flaw and to determine the orientation of the flaw. The UT operator will determine the position of the flaw in the weld as follows: − An actual size drawing of the weld profile will be produced. − The probe will be positioned to obtain the maximum response from the flaw. − The distance from the weld to index point of the probe shall be measured − The position of index point shall be marked on the drawing of weld profile − At the angle of probe being used, the beam path will be measured along a distance equal to that of the flaw indication from the zero on the flaw detector screen, and point marked − The shape, the orientation and therefore the possible type of flaw shall be determined by the use of the scanning patterns. − Indications of discontinuities those remain on the screen as the probe is moved toward and away from the discontinuity may be indicative of planar discontinuities with significant through throat dimensions. For those indications a more detailed evaluation of discontinuity by the other methods may be required, e.g. radiography, MPI or grinding / gouging for visual inspection. The through throat dimension of discontinuity may be evaluated by using either maximum amplitude technique or the dB drop techniques. − For the flaw longer than the beam width the 6dB-drop technique will be used to determine the extremities along the length of weld, and for those of flaws smaller then the beam width the 20 dB drop technique will be used − Where the width, i.e. the through thickness dimension of the flaw is required, this will be determined by either the maximum amplitude technique or the 20 dB drop technique. − Defect areas found by lamination checking are sized by means of 6dB-drop technique and the result shall report on the ultrasonic lamination check report. − Discontinuities shall be classified as linear, planar or spherical. Reporting of defective areas shall be referred to a datum point and the defective area is physically marked adjacent to the defective joint.
10.0EVALUATION OF IMPERFECTIONS IN WELD CONNECTIONS o Imperfections, from which the reflected echo response is greater than 20% of the reference level shall be investigated to the extent that the operator can determine the shape, identity and location of all such imperfections and evaluate them in terms of the acceptance criteria. QUALITY MANAGEMENT SYSTEM
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o The length of the imperfection shall be determined by measuring the distance along the length over which the echo amplitude exceedes the acceptance criteria. o All defects exceeding the acceptance criteria shall be reported unless more stringent requirements to reporting are agreed.
11.0ACCEPTANCE CRITERIA WELD CONNECTIONS o Whenever acceptance criteria are defined in the rules, approved drawings, IACS recommendations or the agreed product standard, there criteria are mandatory. o If no acceptance criteria are defined, acceptance criteria as specified below may be applied for welds in C, C-Mn steels, alloy steels, aluminum, austenitic stainless steel and ferritic-austenitic stainless steel. o DAC is based on a ∅ 3mm drilled hole. Table 3A. Object thickness 10 mm ≤ T ≤ 15 mm Indication length, L (mm)
Max. permitted echo amplitude
L≤ T
Reference level (DAC)
L>T
DAC – 6 dB
Table 3B. Object thickness 15 mm ≤ T ≤ 100 mm Indication length, L (mm)
Max. permitted echo amplitude
L ≤ 0,5 T
DAC + 4 dB
0,5 T < L ≤ T
DAC – 2 dB
L>T
DAC – 6dB
o The above levels are equal to acceptance level 2 and 3 of EN1712 and correspond to quality levels B and C of EN 25817/ISO 5817, ref. correlation given in EN 12062. o Acceptance criteria for Offshore Standard DNV-OS-C401 Offshore Standard as in table 4 below:
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Table 4: Ultrasonic testing - Acceptance criteria Indication 1)2)3) Echo height above Maximum length 4), mm
Structural category Special
Primary
Secondary
50% of reference level
100% of reference level
100% of reference level
t/3 or maximum 10
t/2 or maximum 10
t or maximum 20
Cracks are not acceptable regardless of size or amplitude. 1) Indications which the operator based on experience, knowledge of the welding method and joint geometry deems likely to be cracks, lack of fusion or lack of penetration may be unacceptable regardless of echo amplitude and length. In such cases an independent examination by another operator shall be per-formed. 2) If only one side of the weld is accessible for examination, all indications with a length > t /4 and exceeding 20% of the reference curve for the special category and 50% otherwise, may be regarded as cracks, lack of fusion or lack of penetration unless otherwise proven. In such cases an independent exam-ination by another operator or by different methods shall be performed. 3) For longitudinal defects where the indications intermittently are above and below the acceptance level, the type of defect shall be determined when the areas exceeding the acceptance level are repaired. If the defect is found to be crack, lack of fusion, lack of penetration or slagline(s) the whole defect length is unacceptable regardless of echo amplitude. 4) Length is defined as distance between points where the echo amplitude reaches or passes the stated percentages of reference level.
12.0REPORTING/ RECORDING o The certified personnel who perform the Ultrasonic Testing shall report the results on the attached form. o Identification of first repair on reports and weld identification shall be indicated, as ‘R1’ and the subsequent weld repair shall be identified as ‘R2’ and joints that has been cut out and re-weld shall be denoted as ‘RW’. o The final report shall include, as minimum, the following information: −
Object and drawing references
−
Place and date of examination
−
Material type and dimensions
−
Post weld heat treatment, if required
−
Location of examined areas, type of joint
−
Welding process used
−
Name of the company and operator carrying out the testing including certification level of the operator
−
Surface conditions
−
Temperature of the object
−
Number of repairs if specific area repaired twice or more
−
Contract requirements e.g. order no., specifications, special agreements etc.
−
Sketch showing location and information regarding detected defects.
−
Extent of testing
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Revision No.: 01E Issued date: 26-05-2012 Page 25 of 35
−
Test equipment used
−
Description of the parameters used for each method
−
Description and location of all recorded indications
−
Examination results with reference to acceptance level.
−
Probes, type and frequency
−
Identification of reference blocks used
−
Couplant medium
−
Reporting level, if different from acceptance level
−
Example of report sheet with defect notes, see Figure 13
13.0SAFETY o The Equipment Manager is responsible for ensuring that all the ultrasonic equipment at the worksite is maintained in good working order. o Operators of ultrasonic equipment are responsible for performing all work in accordance with Shipbuilding Manufacturer’s safety procedure with regard to the project.
14.0SPECIAL REQUIREMENT Ultrasonic test will only be carried after 24 hours after welding has been completed on mild steel will yield strength (YS) less than 40 ksi and for continue overleaf higher strength steel the time delay shall be a minimum of 48 hours.
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Figure 13: Example of sketch with notes.
o All report to be recorded follow company’s document control procedure, see Appendix.
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ULTRASONIC EXAMINATION PROCEDURE
Issued date: 26-05-2012 Page 27 of 35
Appendix 1 - ULTRASONIC EQUIPMENT PERFORMANCE CHECK ROUTINE OPERATOR CHECKS ON THE PERFORMANCE OF ULTRASONIC FLAW DECTECTOR Form No. : CA-40-12.02 Rev. 01E Project Name:
Location:
Date:
Flaw Detector Make:
Type:
Serial No.:
Instrument Equipment Certification:
Date Calibrated:
Expiry Date:
Performance calibration date:
For period from
To
Note: ALL RESULT MUST BE RECORDED TEST
TOLERANCE
Time Base Linearity
± 2%
Attenuator Accuracy (Datum point 80% F.S.H)
± 2 dB Not less than 95% FSH
RANGE
TEST RESULT
PASS/FAIL
of full range across the screen
0 - 6dB
35% to 45% FSH
- 18dB 8% to 12% FSH - 24dB To be visible above base line Amplifier Linearity
Difference between smaller signal and ½ larger signal height to be better than 5% FSH or 25% smaller signal height (whichever is the less)
Main Signal 100% 80% 60% 40% 20%
Equipment Resolution
All three echoes to be clearly resolved
Maximum Penetrative Power
Minimum of 3 echoes
Probe used
Operator Name
Checked By
Qualification
Qualification
Signature
Signature
Date
Date
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Appendix 2 - ULTRASONIC EXAMINATION REPORT Report No.:
ULTRASONIC EXAMINATION REPORT Form No. : CA-40-12.01 Rev. 01E
Page:
Project Name:
Procedure No.:
Job No.:
Client Name:
Item:
Drawing No.:
Acceptance Standard:
Flaw Detector: S/N No.:
Calibration Block: DAC Block:
00
Probes
450
600
700
of:
Weld Preparation:
Type Serial No. Size (mm)
Welding Process:
Frequency (MHz) Range (mm)
Surface Condition:
Sensitivity (dB) Transfer (dB)
Parent Metal Examined:
Couplant: No
Weld Identification
ABBREVIATION :
Welder No.
ACC-Accepted PL-Planar Defect
CANDT
Dia. & Thick (mm)
Defect Location
REJ-Rejected CL-Cylindrical
CLIENT
Defect Length
Type of Defect
Result ACC/REJ
SP-Spherical Defect
C.A.
Evaluated by: Qualified: Signature: Date:
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CANDT
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Signature: Description:
Page:
of:
Report No:
SKETCH
Date:
Appendix 3 - SKETCH - SUPPLEMENTARY REPORT
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Appendix 4 - ULTRASONIC TECHNIQUE Technique No.: UT1 Application : Butt weld in Plate and Pipe Thickness : ≥ 10 mm 00, 450, 600, 700 to one skip
00, 450, 600, 700 to one skip
Fig. 1A For welds access one side only Backing, if any 00, 450, 600, 700 to one skip
00, 450, 600, 700 to one skip
Fig. 1B
For welds access two sides
00, 450, 600, 700 to one skip
00, 450, 600, 700 to one skip
00, 450, 600, 700 to one skip
00, 450, 600, 700 to one skip
Fig. 1C
For welds access one side only
00, 450, 600, 700 to one skip
00, 450, 600, 700 to one skip
Fig. 1D
For welds access two sides
00, 450, 600, 700 to one skip
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CANDT
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Technique No.: UT2 Application : T, Y, K fillet weld on plates Thickness : ≥ 10 mm
Fig. 2 A: Single bevel T joint, full penetration
00, 450, 600, 700 to one skip 00, 450 probe if accessible
450, 600, 700 to one skip if accessible
Fig 2A: Double bevel T joint, full penetration 00, 450, 600, 700 to one skip
00, 450 probe if accessible
450, 600, 700 to one skip if accessible
QUALITY MANAGEMENT SYSTEM
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Revision No.: 01E Issued date: 26-05-2012 Page 32 of 35
Technique No.: UT3 Application : Tubular Node welds Thickness : ≥ 10 mm
Main member
Appendix 5 – DEFECT SIZING QUALITY MANAGEMENT SYSTEM
CANDT
Doc No. : CA-40-12.OSS Revision No.: 01E
ULTRASONIC EXAMINATION PROCEDURE
Issued date: 26-05-2012 Page 33 of 35
Technique : 20 dB drop Application : Height of Defect sizing
A
A1
20 dB
20 dB
Variation on peak signal amplitude Echo A at 20 dB below maximum height
Echo A1 at 20 dB below maximum height
A-scan
A-scan
20 dB edge
A 20 dB edge
Note: Defect edge A & A1 are plotted along 20 dB beam edges. A1
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CANDT
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Revision No.: 01E Issued date: 26-05-2012 Page 34 of 35
Technique : Maximum amplitude Application : Height of Defect sizing
A1
A
Variation on peak signal amplitude Echo A at maximum height
Echo A1 at maximum height
A-scan
A-scan
Echo A will be the first to A appear when moving probe backward.
A1
Echo A1 will be the first to appear when moving probe forward.
Note: Defect edges A and A1 are plotted along the beam axis when their individual echoes are at maximum height.
QUALITY MANAGEMENT SYSTEM
CANDT
Doc No. : CA-40-12.OSS Revision No.: 01E
ULTRASONIC EXAMINATION PROCEDURE
Issued date: 26-05-2012 Page 35 of 35
Technique : 6 dB drop Application : Length of Defect sizing
Measured reflector length A
A1
6 dB
6 dB
A
A1
Variation in peak signal amplitude
A1-scan
A-scan Reflector (A-6) dB
( A1-6) dB
A dB
A1 dB
All values are in decibels
QUALITY MANAGEMENT SYSTEM
CANDT A-scan
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