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INSPECCION TECNICA DEL NORTE

ULTRASONIC TESTING (UT) OF GROVES WELDS

Procedure N 003.-.AWS

PR-END-UT-iNDTecnor

Date 09-08-2012

Review 03

PROCEDURE OF INSPECTION ULTRASONIC TESTING (UT)

OF GROOVE WELDS

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INDICE

1 PURPOSE .. 3

2 SCOPE ........ 3

3 UT EQUIPMENT..... 3

4 EQUIPMENT QUALIFICATION ... 4

5 CALIBRATION FOR TESTING ....... 4

6 TESTING PROCEDURES . 5

7 CRITERIA OF ACCEPTATION OF WELDINGS THROUGH THE

ULTRASONIC TEST .... 7

8 ANNEXES 8

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1.- PURPOSEThis proceeding has been made to ensure and guarantee the Ultrasonic Inspection of splicesof weldings in Flanges and Webs, of Beams and Columns of Structures in stages ofManufacture..

2.- SCOPEUltrasonic Testing of butt welds and fillet and partial penetration, according to the requirementsof Structural Welding Code AWS D1.1 2010 edition, part F, for thicknesses between 8 mm and200 mm.

3.- UT Equipment

3.1.1 Equipment Requirements. The UT instrument shall be the pulse echo type suitable for usewith transducers oscillating at frequencies between 1 and 6 megahertz. The display shall bean "A" scan rectified video trace.

3.1.2 Horizontal Linearity. The horizontal linearity of the test instrument shall be qualified over thefull sound path distance to be used in testing.

3.1.3 Calibration of Test Instruments. The test instrument shall have a calibrated gain control(attenuator) adjustable in discrete 1 or 2 dB steps over a range of at least 60 dB. The accuracyof the attenuator settings shall be within plus or minus I dB.

3.1.4 Display Range. The dynamic range of the instrument's display shall be such that a differenceof I dB of amplitude can be easily detected on the display.

3.2.- Transducers

3.2.1 Straight-Beam (Longitudinal Wave) Search Units. Straight-beam (longitudinal wave) searchunit transducers shall have an active area of not less than 112 in2 [323 mm2] nor more than 1in2 [645 mm2]. The transducer shall be round or square. Transducers shall be capable ofresolving the three reflections

3.2.2 Angle-Beam Search Units. Angle-beam search units shall consist of a transducer and anangle wedge. The unit may be comprised of the two separate elements or may be an integralunit.

3.2.3 Frequency. The transducer frequency shall be between 2 and 2.5 MHz, inclusive.3.2.4 Transducer Dimensions. The transducer crystal shall be square or rectangular in shape and

may vary from 5/8 in to 1 in [15 mm to 25 mm] in width and from 5/8 in to 13/16 in [15 mm to20 mm] in height (see Figure 6.17). The maximum width to height ratio shall be 1.2 to 1.0, andthe minimum width-to-height ratio shall be 1.0 to 1.0.

3.2.5 Angles. The search unit shall produce a sound beam in the material being tested within plusor minus 2 of one of the following proper angles: 70, 60, or 45

3.2.6 Marking. Each search unit shall be marked to clearly indicate the frequency of the transducer,nominal angle of refraction, and index point.

3.2.7 Internal Reflections. Maximum allowable internal reflections from the search unit shall be asverified at a maximum time interval of 40 hours of instrument use

3.2.8 Edge Distance. The dimensions of the search unit shall be such that the distance from theleading edge of the search unit to the index point shall not exceed 1 in [25 mm].

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4.- EQUIPMENT QUALIFICATION4.1.1 Horizontal Linearity. The horizontal linearity of the test instrument shall be requalified at two-

month intervals in each of the distance ranges that the instrument will be used.4.1.2 Horizontal Linearity. The horizontal linearity of the test instrument shall be requalified at two-

month intervals in each of the distance ranges that the instrument will be used.5. - CALIBRATION FOR TESTING5.1.- Position of Reject Control. All calibrations and tests shall be made with the reject (clipping

or suppression) control turned off. Use of the reject (clipping or suppression) control may alter

the amplitude linearity of the instrument and invalidate test results.5.2.- Technique. Calibration for sensitivity and horizontal sweep (distance) shall be made by the UT

operator just prior to and at the location of testing of each weld.5.3.- Recalibration. Recalibration shall be made after a change of operators, each two-hour

maximum time interval, or when the electrical circuitry is disturbed in any way which includesthe following:

Transducer change

Battery change

Electrical outlet change

Coaxial cable change

Power outage (failure)

5.4 Straight-Beam Testing of Base Metal. Calibration for straight-beam testing of base metalshall be made with the search unit applied to Face A of the base metal and performed asfollows:

Sweep. The horizontal sweep shall be adjusted for distance calibration to present the

equivalent of at least two plate thicknesses on the display.

Sensitivity. The sensitivity shall be adjusted at a location free of indications so that the

first back reflection from the far side of the plate will be 50% to 75% of full screenheight.

5.5 Calibration for Angle-Beam Testing. Calibration for angle-beam testing shall be performed asfollows:

Horizontal Sweep. The horizontal sweep shall be adjusted to represent the actual

sound-path distance by using the IIW ~ block or alternative. the distance calibration

shall be made using either the 5 in [125 mm] scale or 10 in [250 mm] scale on thedisplay, whichever is appropriate. If, however, the joint configuration or thicknessprevents full examination of the weld at either of these settings, the distance calibrationshall be made using 15 in or 20 in [400 mm or 500 mm] scale as required.

Zero Reference Level. The zero reference level sensitivity used for discontinuity

evaluation ("b" on the ultrasonic test report) shall be attained by adjusting the calibratedgain control (attenuator) of the discontinuity detector, so that a maximized horizontaltrace deflection (adjusted to horizontal reference line height with calibrated gain control[attenuator]) results on the display between 40% and 60% screen height,

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6.- TESTING PROCEDURES6.1 "X" Line. An "X" line for discontinuity location shall be marked on the test face of the weldment

in a direction parallel to the weld axis. The location distance perpendicular to the weld axisshall be based on the dimensionalfigures on the detail drawing and usually falls on the centerline of the butt joint welds, andalways falls n the near face of the connecting member of T and comer joint welds (the faceopposite Face C).

6.2 "Y" Line. A "Y" accompanied with a weld identification number shall be clearly marked on the

base metal adjacent to the weld that is subject to UT. This marking is used for the followingpurposes:

Weld identification

Identification of Face A

Distance measurements and direction (+ or -) from the "X" line

6.3 Cleanliness.All surfaces to which a search unit is applied shall be free of weld spatter, dirt,grease, oil (other than that used as a couplant), paint, and loose scale and shall have acontour allowing intimate coupling.

6.4 Couplants.A couplant material shall be used between the search unit and the test material.The couplant shall be either glycerin or cellulose gum and water mixture of a suitableconsistency. A wetting agent may be added if needed. Light machine oil may be used forcouplant on calibration blocks.

6.5 Extent of Testing. The entire base metal through which ultrasound must travel to test the weldshall be tested for laminar reflectors using a straight-beam search unit. If any area of basemetal exhibits total loss of back reflection or an indication equal to or greater than the originalback reflection height is located in a position that will interfere with the normal weld scanningprocedure, its size, location, and depth from the A face shall be determined and reported , onthe UT report.

6.6 Inaccessibility. If part of a weld is inaccessible to testing due to laminar content, the testingshall be conducted using one or more of the following alternative procedures as necessary toattain full weld coverage:

Weld surface(s) shall be ground flush

Testing from Faces A and B shall be performed.

Other search unit angles shall be used.6.7 Testing of Welds. Welds shall be tested using an angle beam search unit using the angle asshown in Table 6.7. Following calibration and during testing, the only instrument adjustmentallowed is the sensitivity level adjustment with the calibrated gain control (attenuator).The reject (clipping or suppression) control shall be turned off. Sensitivity shall be increasedfrom the reference level for weld scanning in conformance with Table 6.2 or 6.3, as applicable.

6.8 Butt Joints.All butt joint welds shall be tested from each side of the weld axis. Corner and

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T-joint welds shall be primarily tested from one side of the weld axis only. All welds shall betested using the applicable scanning pattern as necessary to detect both longitudinal andtransverse discontinuities.

6.9 Maximum Indication. When a discontinuity indication appears on the screen, the maximumattainable indication from the discontinuity shall be adjusted to produce a horizontal referencelevel trace deflection on the display. This adjustment shall be made with the calibrated gaincontrol (attenuator), and the instrument reading in decibels shall be used as the "IndicationLevel, a," for calculating the "Indication Rating, d," as shown on the test report

6.10- Attenuation Factor. The "Attenuation Factor, c," on the test report shall be attained bysubtracting 1 in [25 mm] from the sound-path distance and multiplying the remainder by 2 for

U.S. Customary Units or be 0.08 for SI Units. This factor shall be rounded out to the nearestdB value. Fractional values less than dB shall be reduced to the lower dB level and those of dB or greater increased to the higher level.

6.11 Indication Rating. The "Indication Rating, d," in the UT Report, represents the algebraicdifference in decibels between the indication level and the reference level with correction forattenuation as indicated in the following expressions:

Instruments with gain in dB:a b c = d

Instruments with attenuation in dB:b a c = d

12 Length of Discontinuities. The length of such indication shall be determined by measuringthe distance between the transducer centerline locations where the indication rating amplitudedrops 50% (6 dB) below the rating for the applicable discontinuity classification. This lengthshall be recorded under "discontinuity length" on the test report. Where warranted bydiscontinuity amplitude, this procedure shall be repeated to determine the length of Class A, B,and C discontinuities.

6.13 Severity of IndicationOnce the D value is obtained, the indication severity of the indication for 70 beam shall bedetermined as follows:

Plate thickness between 5/16 and D Value

+ 10 or less Class A+ 11 Class B+ 12 Class C+ 13 Class D

Plate Thickness thru 1 D Value

+ 8 or less Class A+ 9 Class B

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+ 10 Class C+ 11 Class D

6.14 Identification of Rejected Area. Each unacceptable discontinuity shall be indicated on theweld by a mark directly over the discontinuity for its entire length.The depth from the surface and indication rating shall be noted on nearby base metal.

6.15 Repair. Welds found unacceptable by UT shall be repaired by methods allowed. Repairedareas shall be retested ultrasonically with results tabulated on the original form (if available) oradditional report forms.

7.- CRITERIA OF ACCEPTATION OF WELDINGS THROUGH THE ULTRASONICTEST

7.1 Effecting the survey of elevations and values indicated, the same ones shall be set over sheetand their acceptation or reject shall be indicated, which shall be marked with metalmarker of acolor highlighting the zone to be repaired, according to the following considerations:

7.1.1 Discontinuities Class AWhichever indication in this category shall be rejected independently from its length.

7.1.2 Discontinuities Class BWhichever indication in this category which length overpasses 19 mm, shall be rejected.

7.1.3 Discontinuities Class CWhichever indication in this category which length is greater than 50 mm in the medium zoneof the bead or greater than 20 mm in the root or upper quarter of the same, shall be rejected.

7.1.4 Discontinuities Class DWhichever indication in this category, shall be accepted independently from its length and/orposition in the bead.

7.2 Additional Requirements

7.2.1 Indications type B and C shall be separated at least with a distance of 2L, L being the length ofthe greatest homogeneousness. If not, they shall be considered as unique fault, computing the

real separation between them, in order to determine the total length.7.2.2 Indications of type B or C shall not be accepted at distances less than 2L from the end of

welding.

7.2.3 Discontinuities detected with the equipment calibrated at Level of the Indication , but in the

root of butt welding and qualified as resistant welding, shall be appraised subtracting 4 dB fromvalue D

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8.- ANNEXES8.1 Report Format of Ultrasonic Inspection of Welding

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8.2 Table 6.7 Test Angles

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8.3 Table 6.2 UT Acceptance-Rejection Criteria (Statically Loaded Nontubular Connections)

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8.4 Plan View of UT Scanning Patterns

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8.5 Level III

Certificate

This Certificate is issued based on the DCTA Portaria 25-T/IFI of 8 October 2009 on Acerequalification tests in Nondestructive Testing, ultrasound modality Level 3 (three) performedbetween 22 and 26 November 2010 certifies that

Mr. MAURICIO REYES MORALES

was qualified and obtained approval of the media: 95 %

This reclassification is valid until November 26, 2015.

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8.6 Level II

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8.7 Transducer

1.1.1 SNAIL WEDGES

Snail Wedge Dimensions*

(in inches)

(A)(B) (C) (D)

45 2.15 0.62 1.78 1.25

60 1.910.65

1.81 1.25

70 2.17 0.67 1.92 1.25

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