TOFD & PA Procedure for 301

PROCEDURE FOR AUTOMATED TOFD

& PA INSPECTION OF BUTT WELD

JOINTS

SIEVERT ARABIA LIMITED

Dammam - Saudi Arabia

Tel. 03 8411 846 Fax. 03 8411 812

Document No. SAL-TECH-SOP-TOFD & PA-010-

2015

05th December 2015

PROCEDURE FOR AUTOMATED PA & TOFD

INSPECTION OF BUTT WELD JOINTS ISSUE 1, Rev.0

Page 2 of 49

Prepared by Reviewed & Approved by NAME Bechan Barai Abdul Habibullah

POSITION ASNT NDT Level II

ASNT NDT Level III

(195519)

SIGNATURE

DATE 05 th December 2015 05 th December 2015

Customer SEPCO Electric Power Construction Corporation

Client Saudi Aramco

Contractor Zamil Steel Industries

Sub-Contractor Sievert Arabia Limited

Project No. ZS-PE-301-01 To 05

ISSUE REVISION DATE REMARKS

1 0 05th Dec 2015 Initial Issue

THIS OPERATING PROCEDURE IS CONTROLLED BY THE SIEVERT ARABIA LIMITED AND MAY NOT BE

AMENDED, REVISED OR ALTERED IN ANY OTHER WAY WITHOUT THE CONSENT OF THAT COMPANY.

THE SIGNATURES BELOW AUTHORISE ALL PAGES OF THIS PROCEDURE FOR USE FROM THE DATE OF

APPROVAL SHOWN



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 3 of 49

Item Comment Resolution Prepared and reviewed

by



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 4 of 49

CONTENTS

1.0 SCOPE: . 6

2.0 PURPOSE: 7

3.0 REFERENCE: .. 7

4.0 SAFETY: . 8

5.0 PERSONNEL QUALIFICATION: 8

6.0 SURFACE PREPARATION: . 8

7.0 INSPECTION EQUIPMENT AND ACCESSORIES: 9

7.1 ACQUISITION UNIT & SOFTWARE: .. 9

7.2 SCANNER DETAILS: ... 10

7.3 SEARCH UNIT & WEDGES: . 11

8.0 COMPUTRIZED IMAGING TECHNIQUE: 12

9.0 COUPLANT: .. 12

10.0 CALIBRATION BLOCKS: 12

11.0 QUALIFICATION BLOCKS: 16

12.0 CALIBRATION: .... 19

12.1 EQUIPMENT CALIBRATION: . 19

12.2 ENCODER CALIBRATION: . 23

12.3 VELOCITY & WEDGE DELAY CALIBRATION: ... 23

12.4 SENSITIVITY CALIBRATION: ... 25

12.5 TCG CALIBRATION.. 26

13.0 CALIBRATION CONFIRMATION: . 27

14.0 SCAN PLAN: .. 28



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 5 of 49

15.0 EXAMINATION COVERAGE & SCANNING: ... 28

16.0 RECORDING AND EVALUATION: 30

17.0 ACCEPTANCE CRITERIA: .. 37

18.0 REPORTING: . 38

ANNEXURE-1- SCAN PLAN DETAILS. 41



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 6 of 49

1.0 SCOPE

This procedure describes the requirement and application of automated Time of Flight

Diffraction (TOFD) examination for detection and evaluation of discontinuities within weld

metal and heat affected zone of weld joints, and TOFD dead zones shall be covered by

Phased array method for deaerator. Final inspection shall be after PWHT in general

arrangement for deaerator. This procedure, when used in combination with specified scan

plan is applicable for single V groove joints configuration and thickness range as per table

given below. Work to this procedure will be in compliance with ASME Sec VIII Div 2.This

procedure is applicable for both circumferential and longitudinal weld seams.

Job no. Joint No. Material Thickness Joint

configuration

Welding

Process

301-01 CS1 TO CS11 &

LS1 TO LS9

SA 516 Gr 70

N

20,24,25 &

28mm Single V

SAW +

SMAW

301-02 TO

05

CS1 TO CS7 & LS1

TO LS5

SA 516 Gr 70

N

22,24,25 &

28mm Single V

SAW +

SMAW

Fig 1 : Single V Configuration



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 7 of 49

2.0 PURPOSE

This procedure shall apply to the general aspect of ultrasonic examination of welds using

TOFD technique along with Phased array and Omniscan equipment coupled with

WeldROVER or HSMT X-03 (in areas inaccessible to WeldROVER Scanner). Main

objective of this procedure is to

Monitor the performance of the equipment used

Set the display and acquisition parameter

Provide details for calibration and sensitivity requirement

Describe the recording criteria

Give the details of the equipment used and extent of volume coverage.

Since the qualification of this procedure is unique to the Omniscan equipment, this procedure

is not valid with any other instrument.

TOFD Sensitivity to near surface indications may be enhanced by using; higher frequency

probes, smaller PCS (Probe Center Separation), Lateral wave straightening or subtraction

algorithms.

3.0 REFERENCE

The following documents shall be referred in conjunction with this procedure:

ANSI/ASNT CP-189-2011: ASNT Standard for Qualification and Certification of

Nondestructive Testing Personnel.

ASME Section V Article 4 (2013): Ultrasonic Examination Methods for Welds.

ASME Sec VIII, Division 2 (2013), Rules for Construction of Pressure Vessels.

ASME Section V Article 5 (2013): Ultrasonic Examination Method for Materials.

Sievert Arabia Limited Written Practice SAL/WP/QOP/001/2010

Omniscan Manual

SAEP 1142: Qualification of Non-Saudi Aramco NDT Personnel



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 8 of 49

4.0 SAFETY

All personnel are responsible for ensuring that they, as well as their fellow employees

perform their job in a safe and professional manner, while adhering to the safety guidelines

laid out in safety manual SAL-HS-CP-GSE. In addition they will also adhere to any statutory

and local safety requirements along with any Client / Project specific safety requirements.

5.0 PERSONNEL QUALIFICATION

Personnel performing non-destructive testing to this specification shall be qualified and

certified in accordance with employers written procedure at Level-II TOFD & PAUT

minimum, in addition he shall be trained on Omni scan MX equipment and shall have

minimum one year experience in TOFD/PA activities. The personnel shall hold Aramco

approval to do this inspection. The personnel who acquire and interpret the PAUT Data shall

be participated the demonstration on Qualification block. Data acquisition and analysis shall

be performed by a Level II or Level III; however only UT Level III personnel and qualified

in TOFD shall perform final examination data package review.

6.0 PREPARATION OF EXAMINATION AREA

Surface Preparation:

On finished contact surface a minimum area of 150 mm on either side of the weld shall be

free from dirt, weld spatters, corrosion product, surface irregularities or foreign matter that

might interfere with free movement of the search unit and affects the transmission of

ultrasonic vibrations. When the base material or weld surface interferes with the examination,

the base material or weld shall be prepared as needed to permit the examination. Surface

preparation shall be under the clients scope.

In order to exactly locate the centre line of the weld a scribe line shall be marked at least on

one side of the weld.



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 9 of 49

Generally it is assumed that parent material has been tested using normal beam for planar

flaw e.g. lamination, during various stages of fabrication. If the same not documented then

prior to start of the TOFD & PA inspection, the base metal and HAZ area shall be scanned

using normal beam probe to locate reflectors that can limit the capability of the TOFD & PA

inspection to examine the weld volume.

Weld Identification:

Weld joints shall be identified with Weld Seam No. This unique weld numbering system will

be recorded as part of the file storage data. On the prepared area for inspection there will be a

zero reference index and/or position numbers marked on the weld with paint marker arrow

indicating the direction of scanning.

All circumferential measurement shall be made clockwise from the zero reference

position on the weld when looking in the direction of product flow. For vertical long

seams scanning shall start from bottom side of the shell towards topside.

7.0 INSPECTION EQUIPMENT AND ACCESSORIES

7.10 ACQUISITION UNIT & SOFTWARE

Omniscan MX 16/128 Phased array and TOFD inspection unit

(Figure 2 (a)) which can be operated in pulse echo and/or pitch

catch mode, shall be used in association to this procedure.

Omniscan contains 16 independent pulser/receiver channels. The

System is capable of generating the B-Scan, C-Scan, S-Scan display

along with A-scan. Omniscan is equipped with a calibrated stepped

gain controls in units of 2 dB or less.

The data storing capabilities of the system requires the use of an external storage device, flash

card or USB memory stick. In addition to data storage, the PC will also be used by the data-

analysis personnel for analyzing data subsequent to the completion of data collection. Data-

display and analysis software (Tomoview 2.7R6 or higher version) compatible to that residing

Figure 2 (a) Omniscan



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 10 of 49

on the Omni Scan phased array system shall also be used for data play back. Tomoview 2.7R6

It is a powerful and versatile package that will be utilized for offline analysis of previous

acquired data files.

7.20SCANNER DETAIL

WeldROVER

Weld ROVER (Fig. 2 (c)) is a small and easy to operate one

axis encoded, motorized scanner. It can be used on plates and

pipe like structures with up to 6 probes (depends on OD/ID of

the pipe).

HSMT-X03(Fig 2(d)) Scanner is a one axis encoded, semi-

automated scanner. This scanner can hold up to 10 probes for

either phased array or conventional UT. The basic

configuration is intended for construction welding inspection.

In order to be used in more restricted areas, the scanner can

also be reconfigured with the provided short frame bars.

Figure 2 (b) Data display in Tomoview

Figure 2 (c)WeldRover

Figure 2 (d)HSMT-X03



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 11 of 49

Figure 2 (f)

TOFD Probes & Wedges

The Omniscan ultrasonic system will be suitably interfaced with an automatic/semi-automated

scanner drive mechanism that moves the probes in one encoded axis. Four industrial strength

magnetic wheels make it suitable to move on ferromagnetic materials (used in power plant and

petrochemical industries). Mechanical holders are used to ensure that the probe spacing is

maintained at a fixed distance. The mechanical holder for the probes shall be equipped with a

positional encoder that is synchronized with the sampling A-scan of signals. For

WeldROVERMotion controller allows 10 different scan speeds from 5mm/sec to 50mm/sec

with a resolution of 2100 steps/mm. For HSMT X-03 resolution of encoder is 12 steps/mm.

7.30 SEARCH UNIT & WEDGES

Ultrasonic transducers configurations are specified by the technique

used to cover the full volume of the weld. Single element probes

used for TOFD shall have crystal diameter between 3mm to 10mm.

The probe frequency and diameter of the search unit will be determined

by the pertinent parameters for the approved technique. Square or

rectangular transducers of equivalent size and frequency may also be used.Probes shall be

mounted on a wedge of suitable material and refracting angle as to be compatible to provide

required beam steering. Nominal refracting wedgeangle should be 45o, 60

o and 70

o. Wedges

shall have a provision for irrigation hole to provide uniform couplant for scanning.

Table provides recommended search unit parameter for TOFD inspection in the specified

thickness range.

Thickness

t (mm)

Hole

Dia

(mm)

Number

of

TOFD

set-ups

Depth-

range

(mm)

Frequency

(MHz)

Wedge-

angle

Element

size (mm)

Beam

intersection

As per the Scan

plan, TOFD probe

and Wedge Details

20 to < 25 2.5 1

0-t 5-10 50-70 3-6 2/3t

Transducer Type:

C543-SM, C563-SM

Wedge Type: ST1-

60L-IHC, ST1-70L-

IHC 25 to < 28 3



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 12 of 49

This procedure uses the following probes and wedges for Phased Array

PA Probe Frequency Number of

Elements

Active

Aperture Elevation

Element

Size Supportive Wedge

5L64 A2 5 MHz 64 38.4 mm 10 mm 0.60 mm SA2 N55S IHC

5L32 A5 5 MHz 32 19.2 mm 10 mm 0.60mm SA5 N55S IHC

8.0COMPUTRIZED IMAGING TECHNIQUE

The major attribute of Computerized Imaging Techniques (CITs) is their effectiveness when

used to characterize and evaluate indications: however, CITs may also be used to perform the

basic scanning functions required for flaw detection. Computer-processed data analysis and

display techniques are used in conjunction with automatic or semi-automatic scanning

mechanisms to produce two dimensional images of flaws, which provide an enhanced

capability of examining critical components and structures. Computer processes may be used

to quantitatively evaluate the type, size, shape, location and orientation of flaws detected by

ultrasonic examination or other NDE methods. Phased array ultrasonic examination is one of

the computerized imaging techniques.

9.0 COUPLANT

Acoustic coupling shall be obtained by using a medium (oil, grease, cellulose, water) suitable

for the purpose. Temperature of the part to be scanned shall be taken into considerations while

selecting the couplant. An environmentally safe wetting agent, such as water (up to 50oC) will

be required to promote acoustic coupling, however, no residue will remain on the work-piece

surface after the water has been evaporated. During examination same couplant shall be used as

during calibration.

10.0 CALIBRATION BLOCK

The inspection system shall be calibrated using standard calibration blocks and reference blocks.

The calibration block material shall be, a nozzle dropout from the component or a component



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 13 of 49

prolongation or material of the same specification product form. The calibration block shall

receive the same heat treatment as the part to be tested. The surface of the calibration, at no time

shall be inferior to that of the component. When the component material to be examined is clad,

the block shall be clad by the same welding process as the production part.

Two Cal blocks shall be used to scan different thickness varies from 20mm to 28mm.

alternatively, a thicker block may be utilized provided reflector size is based on the thickness to

be examined and an adequate number of SDHs exist to comply with basic calibration block.



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 14 of 49

The basic calibration block configuration and reflector shall be as shown in figure 3 & 4

Fig 3: 24 mm thick calibration block



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 15 of 49

Fig 4 : 28 mm calibration block

Note :

1) All dimensions are in mm. 2) Runner plates shall be attached after drilling and notch preparation. 3) Notch width shall be 3mm

Tolerance on hole dia. Shall be +/- 0.8mm and tolerance on location through the block

thickness shall be +/- 3mm



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 16 of 49

11.0 QUALIFICATION BLOCKS

Qualification block shall be prepared from the same product form and material specification

or equivalent P-numbers. In case of dissimilar metal welds the material selection shall be

based on the side of the weld from which the examination will be conducted. If examination

will be conducted from both sides, calibration reflectors shall be provided in both the

materials. Prior to the fabrication the block material shall be completely examined with

straight beam search unit.

When the component material is clad, the block shall be clad by the same welding procedure

as the production part. Qualification block shall be prepared by welding or HIP provided the

acoustic properties are similar and shall receive the same heat treatment as the part to be

tested. Blocks weld geometry shall be representative of production joint.

The qualification block shall be within 25% of the thickness to be examined. For welds

joining two different thickness of material, demo block thickness shall be based on thinner of

the two materials.

The qualification block shall contain a minimum of three flaws parallel to the production

weld axis as follows

1. One surface flaw on the OD surface

2. One surface flaw on the ID surface

3. One subsurface flaw

In case the block can be flipped during UT examination then one flaw may represent both ID

and OD surfaces.

When due to obstruction the weld examination can only be performed from one side of the

weld axis, the qualification block shall contain two sets of flaws, one set on each side of the

weld axis.

Flaw size shall be based on the qualification block thickness and shall be no longer than that

specified by Referencing code Section. For this work flaw size is based on

Maximum acceptable flaw height for material thickness as per ASME SECTION VIII

DIVISION 2



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 17 of 49

Qualification block shall be scanned and the qualification data saved as per the procedure and

shall be available to the inspector.

Flaws shall be sized and categorized in accordance with the written procedure being

qualified.

Automated and semi-automated acceptance performance criteria is defined as the

detection of all the flaws in the demonstration block and

a) Recorded responses or imaged lengths, as applicable, exceed the specified evaluation

criteria of the procedure

b) The flaws are sized as being equal to or greater than their actual size (i.e., both length and

height)

c) The flaws are properly categorized (i.e., surface or subsurface)

Supplemental manual technique(s) (For Transverse Reflectors) acceptable performance

criteria is defined as the demonstration blocks flaws being

a) Sized as being equal to or greater than their actual size (i.e., both length and height)

b) Properly categorized (i.e., surface or subsurface)

Demonstration Block Record

The following information shall be recorded:

a) The information specified by the procedure being qualified

b) Demonstration block thickness, joint geometry including any cladding or weld overlays,

and flaw data [i.e., position in block, size (length and height)], separation distance to

nearest surface, category (surface or subsurface)

c) Scanning sensitivity and search unit travel speed

d) Qualification scan data

e) Flaw sizing data [same information as flaw data in]

The basic qualification block configuration and reflector shall be as shown below. Notch

width shall be 3 mm. All dimensions are in mm. Runner plates shall be attached after notch

preparation



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 18 of 49

Fig 5 : 24 mm Single V Qualification block

Fig 6 : 28 mm Single V Qualification block



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 19 of 49

12.0 CALIBRATION

12.10 EQUIPMENT CALIBRATION

Due to the digital control nature of TOFD& PA instruments and also due to the fact that

multiple pulser and receivers are used, instruments are subject to screen height and amplitude

control linearity checks. Linearity checks shall be as per section T-461.1 & 461.2 (Mandatory

appendix I & II) of ASME Section V, Article 4. The results of these checks are recorded in

the ultrasonic instrument linearity forms and are kept as a part of the inspection record. OR

Linearity checks may be performed as per manufacturers standard practice. In this case a

template of verification sheet or a mention regarding manufacturer calibration shall be

provided. Instrument linearity checks are conducted on a twelve month cycle.

Prior to the start of shift operator need to carry out an element check and ensure that probe is

in working condition and ensure that no more than 10% of elements are inactive and no two

adjacent elements are inactive. Ensure the proper couplant between the probe and wedge.

Once data is collected make sure that data missing lines do not exceed the allowable limit.

12.1.1 DISPLAY HEIGHT LINEARITY

1) With the phased array instrument connected to a probe (shear or longitudinal) and coupled

to any block that will produce two signals as shown in fig.7 adjust the probe such that the

amplitude of the two signals are at 80% and 40% of the display screen height.

Display Height Linearity

Fig 7: A-Scan display for display height linearity



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 20 of 49

2) Increase the gain using the receiver gain adjustment to obtain 100% of full screen height

of the larger response. The height of the lower response is recorded at this gain setting as

a percentage of full screen height.

3) The height of the higher response is reduced in 10% steps to 10% of full screen height

and the height of the second response is recorded for each step.

4) Return the larger signal to 80% to ensure that the smaller signal has not drifted from its

original 40% level due to coupling variation. Repeat the test if variation of the second

signal is greater than 41% or less than 39% FSH.

5) For an acceptable tolerance, the response from the two reflectors should bear a 2 to 1

relationship to within 3% of full screen height throughout the range 10% to 100% (99%

if 100% is saturation) of full screen height.

6) The results are recorded on an instrument linearity form.

12.1.2 AMPLITUDE CONTROL LINEARITY

1) A 16/64 phased-array instrument has 16 pulsers and receivers that are used to address up

to 64 elements. Each of the pulser-receiver components is checked to determine the

linearity of the instrument amplification capabilities.

2) Select a flat (normal incidence) linear array phased-array probe having at least as many

elements as the phased-array ultrasonic instrument has pulsers.

3) Using this probe, configure the phased-array ultrasonic instruments to have an electronic

raster scan. Each focal law will consist of one element and the scan will start at element

number 1 and end at the element number that corresponds to the number of pulsers in the

phased-array instruments.

4) Couple the probe to a suitable surface to obtain a pulse-echo response from each focal

law. The backwall echo from the 25 mm thickness of the IIW block or the backwall from

the 20mm thickness of the custom linearity block provides the suitable target option.

5) Select channel of the pulser-receivers of the phased-array instrument. Using the A-scan

display, monitor the response from the selected target. Adjust the gain to bring the singal

to 40% screen height. This is illustrated in fig.8



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 21 of 49

Fig 8: A-Scan Display of Backwall Echo on channel 1 of a phased-Array Instrument

6) Add gain to the receiver in the increments of 1 dB, then 2 dB, then 4 dB then 6 dB.

Remove the gain added after each increment to ensure that the signal has returned to 40%

display height. Record the actual height of the signal as a percentage of the display

height.

7) Adjust the signal to 100% display height, remove 6-dB gain and record the actual height

of the signal as a percentage of the display height.

8) Signal amplitudes should fall within a range of 3% of the display height required in the

allowed height range of Table

9) Repeat the sequence from 5 to 7 for all other pulser-receiver channels.

12.1.3 TIME-BASE LINEARITY (HORIZONTAL LINEARITY)

1) Configure the phased array instrument to display an A-scan presentation.

2) Select any compression wave probe and configure the phased-array instrument to display

a range suitable to obtain at least ten multiple back reflections from a block of a known

thickness. The 25-mm wall thickness of the IIW block is a convenient option for this test.

3) Set the phased-array instrument analog-to-digital conversion rate to at least 80 MHz.

4) With the probe coupled to the block and the A-scan displaying 10 clearly defined multiple

as illustrated in fig.9



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 22 of 49

Fig 9: Horizontal Linearity A-Scan

5) The display software is used to assess the interval between adjacent backwall signals.

6) Acoustic velocity of the test block, determined using the methods described in E 494, is

entered into the display software and the display configured to read out in distance

(thickness).

7) Using the reference and measurement cursors determine the interval between each

multiple and record the interval of the first 10 multiples

8) Acceptable linearity may be established by an error tolerance based on the analog-to-

digital conversion rate converted to a distance equivalent. For example, at 100 MHz each

sample of the timebase is 10 ns. For steel at 5900 m/s each sample along the timebase (10

ns) in pulse-echo mode represents 30 m. A tolerance of 3 timing samples should be

achievable by most analog-to digital systems. Some allowance should be made for

velocity determination error (~ 1%). Typically the errors on the multiples should not

exceed 0.5 mm for a steel plate.

12.1.4 PHASED-ARRAY ELEMENT ACTIVITY VERIFICATION

1) The Phased Array probe shall be checked to determine that all elements of the phased

array probe are active and of uniform acoustic energy. Because, during normal

operation in a timed sequence, each of the elements is addressed by a separate

pulser and receiver, a method from element to element and any differences are



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 23 of 49

attributable to the probe itself. To ensure channel is selected to address each element.

2) Any Phased Array Probe that has greater than 25% defective element of the usable

aperture should be replaced with a new probe.

Fig 10: Continuity Display for Phased-Array Instrument or Cable

12.2 ENCODER CALIBRATION

The encoder shall be connected to the Omni Scan equipment and the calibration wizard shall

be used to calibrate the encoder. Through the menu wizard set up, all the parameters are fed

and the encoder is made to scroll on a pre-determined known length from initial position,

press calibrate, get the calibration done. Encoder calibration shall be confirmed by moving a

minimum distance of 500mm and the distance displayed being 1% of the actual distance

moved. Encoder calibration shall be carried out prior to the first use and not to exceed one

month.

12.3 VELOCITY & WEDGE DELAY CALIBRATION

For contact examinations the temperature differential between the calibration block and

examination surface shall be within 14o C.



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 24 of 49

TOFD

After initial UT parameter and PCS setting for the given weld configuration and weld

thickness, an inspection pass is performed on the calibration block and a location is chosen in

the B-scan image by choosing the data cursor, where the lateral wave and Back wall signal is

seen. The velocity and wedge delay calibration is performed by choosing the ultrasound

reference cursor (Ur) on the lateral wave and place the TOFD (Tr) value as 0. Place the

ultrasound measurement cursor (Um) on the phase reversal amplitude of the back wall signal

and place the TOFD (Tm) value part thickness. Accept calibration and the TOFD

calibration shows the value of the part thickness in the B-scan display. In case, if the part is

divided into multiple zones where back wall or lateral wave or both may not be available,

calibration can be performed using SDHs at known depth.

Phased Array

Compensation for delay in the wedge is required so as to ensure that indications detected are

poisoned correctly. The wedge delay calibration shall be carried out for both linear scan and

as well as sectorial scan. The velocity & wedge delay calibration can be carried out in sound

path (using 50mm, 100mm radius of V1 block) mode or true depth (using SDHs) mode with

known reflector having fixed sound path or depth respectively. 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 of focal laws. When the signal for all angles and focal laws lies within the threshold,

Omniscan system dynamically adjusts delay setting to correctly indicate radius (depth).

Figure (11) shows the screen display during wedge delay calibration.

Figure 11: Wedge delay calibration



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 25 of 49

12.4SENSITIVITY CALIBRATION

TOFD

The maximum diffraction efficiency occurs when the included angle is about 120o the probes

should be arranged such that beam centre lines intersect at about this angle (approximately at

2/3 of the zone thickness). The time window and PCS shall be set to those values that will be

used in subsequent examination. The time window should start at least 1s prior to the time

of arrival of the lateral wave, and should at least be extended up to the first back wall echo

with allowance for thickness and mismatch variation. Useful data can be obtained from mode

converted signals so it is recommended that the time window recorded also includes the time

of arrival of the first mode converted backwall echo signal.

Sensitivity calibration shall be performed on the calibration block or on the test object itself.

Set the TOFD probes on the surface to be utilized for calibration and set the gain control so

that the lateral wave amplitude is from 40% to 90% of the full screen height(FSH) and the

noise (grass) level is less than 5% to 10% FSH. This is the reference sensitivity. For multiple

zone examinations when the lateral wave is not displayed, or barely discernible, set the gain

control based solely on the noise (grass) level.

Phased Array

Variation between electronics of pulsers and receivers and variation between probe elements

results in small gain variation from one focal law to the next. Also the variation in path

distance in both wedge and steel will result in some focal laws requiring more gain. So to

compensate for this Omniscan shall be calibrated for sensitivity, which can be carried out

dynamically. The sensitivity calibration shall provide the required gain adjustments for each

refracted angle and sound path used. Select a calibration reflector, which is 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 of focal laws. The Omniscan

System calculates the required gain needed at each focal law to adjust the amount of gain

required to obtain the sensitivity.



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 26 of 49

Figure 12 illustrates the example of special screen feature used to ensure the sensitivity

(amplitude response) from each focal law. All focal laws provide a uniform amplitude

response to the calibration reflector. As the operator moves the probe back and forth over a

calibration reference reflector, unit software automatically adjusts gain to the prescribed

amplitude 80% with +5% tolerance limit. The horizontal scale is the virtual probe aperture

(VPA) which defines the group of elements i.e. focal law that is sequenced in the scan. These

focal laws are either linear or sectorial depending on whether E-scan of S-scans is being

calibrated.

Figure 12: Sensitivity Calibration (S-Scan)

12.5 TCG CALIBRATION

Time corrected gain calibration shall be applied to compensate for attenuation in the material

for the sound paths used during calibration and examination. Generally Phased array

inspection is being done in full skip so in order to compensate for the attenuation; calibration

shall be performed as per the plan shown below (Fig 13). To obtain the TCG calibration, peak

the signal from the respective SDHs and adjust the gain to obtain 80% of amplitude from the

reflector. Place the phased array probe perpendicular to the SDHs axis. Move the phased

array probe forward and backward to equal the amplitude for all the focal laws and angles

and plot the first point. The same process is repeated to set the response from each reflector



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 27 of 49

for each focal law at 80% FSH. Omniscan uses the gain compensation required due to

attenuation in the sound travel and adjust the gain for all focal laws/angles. Once all the

points are picked the TCG can be accepted. TCG calibration has to be carried out for all scan

plans in a multi group option while using phased array probe. The examination system

calibration shall be stored in the Omni scan System with electronic memory, on an external

chip or data storage device. This calibration may be used at a later date provided that the

system calibration is verified prior to the examination. A complete ultrasonic system

calibration shall be performed at least once prior to the examination.

Figure 13: PA Calibration Using SDHs

13.0 CALIBRATION CONFIRMATION

A system calibration confirmation shall be used to verify sensitivity at the start and finish of

each examination using the appropriate calibration block. The sensitivity control settings are

adjusted to match those recorded for reference sensitivity. The search unit is positioned to

detect the first and last point on the TCG using the reference reflectors. The examination

deemed to be void if any point on the TCG decreased by 20% or 2dB of its amplitude. All

inspection since last valid calibration needs to be rescanned. If the sensitivity has increased

all recorded indications since last valid calibration or calibration check shall be reexamined

and there values shall be changed on data sheet. Any change in search unit, wedge and

ultrasonic instrument cause for a new calibration.

For confirmation of TOFD calibrations; scan the calibration block at the reference sensitivity

level with SDHs at the centre of the pair of probes. The SDH responses from the required

zone shall be a minimum 6dB above the grain noise and shall be apparent in the resulting

digitized grayscale display.



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 28 of 49

14.0SCAN PLAN

A documented examination strategy shall be provided showing search unit placement and

movement that provides a standardized and repeatable methodology for the examination.

Scan plan shall include beam angles and direction with respect to the weld axis reference

point, weld geometry and number of zones.

Scan plan provides clear view of scanning, helping to clearly convey weld coverage, HAZ

coverage and probe position, in addition to critical dimensions. The beamset parameters

dialog displays a visual representation of the transducer elements that are used to form the

beamset. Varying the focus of the beam is the capability of TOFD &PAinstrument, but

generally focusing is not the norm for weld inspection.

Beam spread visualization allows you to more accurately see the beam coverage and near

field visualization ensures that any focusing being performed is within the near field. True

Depth, Projection and Half Path focus types can be visualized in the workspace and

documented as a technique report. These all is achieved with the help of ESbeam software

tool. The scan plan for inspection of full volume of given weld geometry and thickness are

given in Annexure: 1

Note: Scan plan given below may require modification based on the actual field conditions to

achieve optimum inspection results. Such improvements are applicable provided it has been

demonstrated successfully on the qualification block.

15.0 EXAMINATION COVERAGE & SCANNING

The ultrasonic examination area shall include the volume of the weld plus the lesser of 25mm

or thickness on each side of the weld or Alternatively, examination volume may be reduced

to include the actual heat affected zone (HAZ) plus 6 mm (1/4 in.) of base material beyond

the heat affected zone on each side of the weld provided the following requirements are met:

1) The extent of the weld HAZ is measured and documented during the weld qualification

process; and



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 29 of 49

2) The ultrasonic transducer positioning and scanning device is controlled using a reference

mark (paint or low stress stamp adjacent to the weld) to ensure that the actual HAZ

plus an additional 6 mm (0.25 in.) of base metal is examined.

The required volume of the base material and weld to be examined shall be scanned from

outer surface/inner surface using a linear scanning technique with encoder.The level of gain

used for scanning shall be appropriate for the configuration being examined and shall be

capable of detecting the calibration reflectors at the maximum scanning speed. Each linear

scan shall be parallel to the weld axis and at a constant standoff distance with the beam

oriented perpendicular to the weld axis from the zero datum point. Scanning mechanisms

shall be used to maintain a constant distance and alignment between the index points of the

two probes. Scanning mechanisms can either be motor or manually driven with encoder.

They shall be guided by means of a suitable guiding mechanism (steel band, belt, automatic

track following systems, guiding wheels etc.). Guiding accuracy with respect to the centre of

a reference line (e.g. the centre line of a weld) should be kept within a tolerance of 10 % of

the probe index point separation.

The scan plan shall demonstrate by plotting or with using a computer simulation the

appropriate examination angles for zones at different depth. This scan plan shall be

documented to show that the examination volume was examined. This scan plan shall be a

part of the final examination report. More than one line scan may be required to ensure

complete coverage of the weld and heat affected zone. Transverse defects can be identified

with manual UT. Prior to scanning, calibration data shall be recorded and stored. The

Restricted access welds like T-Joints shall have to be dressed for its weld cap and examined.

During inspection over this dressed weld surface, if data acquisition is not acceptable due to

missing data lines, then the weld cap shall be removed for inspection.

A maximum sampling of 1mm shall be set for and be used between A-scans collected for

thickness up to 50mm. A 2mm resolution can be used for thicknesses more than 50mm.

Scanning speed shall not exceed 150 mm/sec. Scanning speed will be limited by mechanical

ability to maintain acoustic coupling and by the systems electronic ability to ensure full



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 30 of 49

wave forms are captured without missing data points. Scanning speed shall not exceed that

qualified. Missing of data lines shall not exceed 5% of the total acquisition with adjacent data

shall not be missed. Omni Scan equipment has the capability of rewriting the data while

observed loss of data. The encoder is retrieved back to home position whenever data is

missed. Missing data is represented by black lines in the display. Between two consecutive

scans there should be an overlap of 50 mm. Repaired weld area shall be rescanned with an

overlap of minimum 50mm at the start and end of the scan.

16.0 RECORDING AND EVALUATION

A scan data shall be recorded for the area of interest in an unprocessed form with no

thresholding at a minimum digitization rate of five times the examination frequency and

recording increment of a maximum of 1mm for material less than 50mm thick and 2mm for

material having thickness greater than 50mm. Calibration check data shall also be recorded.

Only Trained Level II - UT operators with hands on training Omni Scan shall calibrate and

carry out UT inspection. Only personnel certified Level II or III in Ultrasonic testing along

with knowledge of phased array and Omni Scan equipment shall evaluate the results of

ultrasonic examinations for acceptance.

For amplitude base technique, the location, amplitude and extent of all reflectors that

produces a response greater than 20% of the reference level shall be investigated.

For non-distance amplitude based techniques (TOFD), all indication images that have

indicated lengths greater than the following shall be evaluated in terms of the acceptance

criteria of the referencing code section:

a) 0.15 in. (4 mm) for welds in material equal to or less than 1 in. (38 mm) thick

b) 0.20 in. ( 5 mm) for welds in material greater than 1 in. (38 mm) thick but less than

4 in. (100 mm)

For welds joining two different thickness of material, material thickness shall be

based on the thinner of the two material.



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 31 of 49

Non Relevant Indications

Signals which are determined to originate from metallurgical discontinuities (such as

cladding to base material interface) and/or geometrical features (such as weld reinforcement

or root geometry) may be classified as geometric indication. Such reflectors are not

characterized as indications nor compared with allowable indication standard.

The presence of geometric reflectors is confirmed either by reviewing the fabrication drawing

of the weld preparation or by plotting the reflectors co-ordinates or by supplemental

inspection (PT or MT) result. In addition to reporting indications, area of restricted access

which cannot be scanned shall be recorded and reported.

Relevant Indications

Signals that are determined to result from welding flaws will be assessed according to the

acceptance criteria in ASME Sec VIII Div2.For PA, flaw sizing shall be performed using -6

dB Drop technique. Flaw length parallel to the surface can be measured from the distance

encoded D- or C-scan images using amplitude drop techniques by placing vertical cursors on

the extents of the flaw displayed on the D- or C- scan display. Flaw height normal to the

surface can be measured from the B-, E-, or S-scan images using amplitude drop techniques.

Using amplitude drop techniques, the horizontal cursors are placed on the displayed flaws

upper and lower extents.

For TOFD, flaw lengths parallel to the surface can be measured from the TOFD image by fitting

hyperbolic cursors to the ends of the flaws. Flaw height perpendicular to the surface can be

measured from the TOFD image by fitting cursors on the top and bottom tip signals. A sizing

procedure qualified by performance demonstration will be used to assess all indications

interpreted to be flaws.

TomoView software should be used for further processing (e.g. lateral wave synchronization,

lateral wave removal and to apply soft gains) which enhances the interpretation of the

discontinuities.

Size & Category

Dimensions of the flaw shall be determined by rectangle that fully contains the area of the flaw.

Length of the flaw is the dimension of the rectangle parallel to pressure retaining surface, and



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 32 of 49

the height of the flaw is the dimension of rectangle perpendicular to the pressure retaining

surface.

Flaws shall be characterized as being surface or subsurface based on their separation from the

nearest component surface:

1. If space is equal to or less than one half of the height of the flaw than flaw shall be

categorized as surface flaw.

2. If space is greater than one half of the height of the flaw than flaw shall be categorized as

subsurface flaw.

Surface Indications S a

Figure 14: Classification of Surface & Sub surface Indications

Flaws shall be evaluated for acceptance using the applicable criteria for the respective thickness,

with the following additional requirements-Flaws identified as surface flaws during the UT

examination may or may not be surface connected. Therefore, unless the UT data analysis

confirms that the flaw is not surface connected, it shall be considered surface connected or a



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 33 of 49

flaw open to the surface, and is unacceptable unless surface examination is performed. If the

flaw is surface connected, the requirements above still apply. However, in no case shall the flaw

exceed the acceptance criteria in this Division for the material employed. Acceptance surface

examination techniques are as follows:

(1) Magnetic particle examination (MT) in accordance with ASME 2013 SECTION VIII,

DIVISION 2 paragraph 7.5.6

(2) Liquid penetrant examination (PT) in accordance with ASME 2013 SECTION VIII,

DIVISION 2 paragraph 7.5.7

Figure 15: Multiple Planar Flaws Oriented in a Plane Normal to the Pressure Retaining

Surface



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 34 of 49

i. Discontinuous flaws shall be considered a singular planar flaw if the distance between

adjacent flaws is equal to or less than the dimension S as shown in Figure (15).

ii. Discontinuous flaws that are oriented primarily in parallel planes shall be considered a

singular planar flaw if the distance between the adjacent planes is equal to or less than 13

mm. (see Figure 16).

iii. 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 as shown in Figure 17.

iv. For Subsurface Flaws the flaw length shall not exceed 4t.

Figure 16: Surface and Subsurface Flaws



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 35 of 49

Figure 17: Non-Aligned Coplanar Flaws in a Plane Normal to the Pressure Retaining

Surface



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 36 of 49

Flaw sizing technique for PA

Flaw sizing can be performed using a -6 dB Drop, amplitude drop techniques

Flaw Length.

Flaw lengths parallel to thesurface can be measured from the distance encoded DorC-scan

images using amplitude drop techniques by placingthe vertical cursors on the extents of the

flaw displayedon the D- or C-scan display.

Sample Scan image Showing Flaw Length Sizing Using Amplitude Drop Technique

Flaw Height

Flaw height normal to the surfacecan be measured from the B-, E-, or S-scan images

using amplitude drop

Using amplitude drop techniques, the horizontalcursors are placed on the displayed flaws

upper and lowerextents.

Sample Scan image Showing Flaw Height Sizing Using Amplitude Drop Technique



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 37 of 49

17.0 ACCEPTANCE CRIETERIA

Results of weld inspections to this procedure shall be compared to the requirement of

acceptance criteria as defined in ASME Sec VIII Div 2.

Flaw Acceptance Criteria for Inch (13mm) to less than 1 inch (25mm) Thick Weld

a/t L

Surface Flaw 0.087 0.25 In. (6.4mm)

Sub Surface Flaw 0.143 .025 In (6.4mm)

GENERAL NOTES:

(a) The parameter t is the thickness of the weld excluding any allowable reinforcement, and

the parameter l is the length of the flaw. For a 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, then 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 the separation (S in Figure

13) of the indication from the nearest surface of the component is equal to or less than half

the through dimension (2d in Figure 14) of the subsurface indication.

(c) The acceptance limits specified here are based upon workmanship considerations and are

not necessarily intended for use in evaluating flaws identified after the vessel has gone into

service.

(d) The length (l) of the flaw shall be drawn parallel to the inside pressure-retaining surface

of the component.

(e) The depth of the flaw shall be drawn normal to the inside pressure retaining surface and

shall be denoted as a for a surface flaw or 2a for a subsurface flaw.



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 38 of 49

Flaw Acceptance Criteria for 25mm to 64mm Thick Weld

GENERAL NOTES:

(a) The parameter t is the thickness of the weld excluding any allowable reinforcement, and

the parameter l is the length of the flaw. For a 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, then 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 the separation (S in Figure

10) of the indication from the nearest surface of the component is equal to or less than half

the through dimension (2d in Figure 14) of the subsurface indication.

(c) The acceptance limits specified here are based upon workmanship considerations and are

not necessarily intended for use in evaluating flaws identified after the vessel has gone into

service.

(d) For intermediate flaw aspect ratio a/l and thickness t (64 mm (2 in.) < t < 100 mm (4

in.)), linear interpolation is permissible.

(e) If the acceptance criteria in this table results in a flaw length, l , less than 6.4 mm (0.25

in.), a value of 6.4 mm (0.25 in.) may be used.

(f) For materials exceeding 655 MPa (95 ksi) ultimate tensile strength, the use of this table is

limited to a thickness of 200 mm (8 in.).

18.0 REPORTING

The following data shall be reported in the final report

a. Procedure identification and revision.



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 39 of 49

b. Instrument Identification including manufacturers serial number.

c. Transducer type, serial number, angle and frequency.

d. Cables used, type and length.

e. Probe center spacing (PCS), Data sampling spacing.

f. Couplant used

g. Special equipment when used (search units, wedges, shoes, automatic scanning equipment,

recording equipment etc)

h. Computerized programmed identification and revision when used

i. Calibrations block identification.

j. Instrument reference level gain and, if used damping and reject settings.

k. Calibration data including reference reflectors, indication amplitude and distance reading.

l. Data correlating simulation blocks and electronic simulator, when used, with initial

calibration.

m. Identification and location of weld or volume scanned.

n. Surface condition.

o. Record of indications identified to be rejected.

p. Areas of restricted access or inaccessible welds.

q. Examination personnel identity and when required by referencing code section, qualification

level.

r. Date and time examinations were performed.



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 40 of 49

REPORT FORMAT (SAMPLE)



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 41 of 49

Annexure: 1

SCAN PLAN DETAILS Surface of scanning : OD



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 42 of 49

Surface of scanning : ID

Note:- scanning from ID surface shall be done when scanning from OD surface is not

possible.



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 43 of 49

SURFACE OF SCANNING : OD

Scan Plan for 301-01 : CS1 & CS5

Thickness:25-20MM SHELL-DISH (A2 & A5)

Scan Plan for 301-01 : CS2 TO CS4 & LS1 TO LS4 & 301-02 TO 05 :

CS2 & LS1 TO LS2

Thickness: 25MM SHELL-SHELL



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 44 of 49

Scan Plan for 301-01 : CS6 & 301-02 TO 05 : CS4



CS5, CS6 & LS3 TO LS5

Thickness:28MM SHELL-SHELL



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 45 of 49



Scan Plan for 301-02 TO 05 : CS1 & CS3




Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 46 of 49

SURFACE OF SCANNING : ID

Scan Plan for 301-01 : CS1 & CS5



CS2 & LS1 TO LS2




Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 47 of 49

Scan Plan for 301-01: CS6 & 301-02 TO 05 : CS4


Scan Plan for 301-01: CS7 TO CS10 & LS5 TO LS9 & 301-02 TO 05:

CS5, CS6 & LS3 TO LS5




Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 48 of 49


Thickness: 28-24MM SHELL-DISH (A2 & A5)

Scan Plan for 301-02 TO 05 : CS1 & CS3

Thickness: 25-22MM SHELL-DISH (A2 & A5)



Tel. 03 8411 846 Fax. 03 8411 812


2015

05th December 2015



Page 49 of 49

Transverse Scanning

The angle beam shall be directed essentially parallelto the weld axis. The search unit shall be

manipulatedso that the ultrasonic energy passes through the requiredvolume of weld and adjacent

base material. The searchunit shall be rotated 180 deg and the examination repeated.

If the weld cap is not machined or ground flat, theexamination shall be performed from the base

metal onboth sides of the weld cap in both weld axis directions.

Documents

TOFD & PA Procedure for 301