TOFDPre-Rev03-Sept.ppt

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Ultrasonic TOFD TechniqueUltrasonic TOFD Technique

Prepared by : Prepared by :

MJMJ Inspection Consultancy, Malaysia Inspection Consultancy, Malaysia

Tel : 60 - 7 - 5568-907 Tel : 60 - 7 - 5568-907

Fax : 60 - 7 - 5568-918Fax : 60 - 7 - 5568-918

Email : [email protected] : [email protected]

Rev .03-Sept

2Conventional UT TechniqueConventional UT Technique

Working PrincipleWorking Principle Probe sends an ultrasonic pulse into metal or Probe sends an ultrasonic pulse into metal or

weldmentweldment This ultrasound is reflected when it comes across This ultrasound is reflected when it comes across

a discontinuity (defect) in the metala discontinuity (defect) in the metal This technique is called This technique is called Pulse EchoPulse Echo Technique Technique

3Disadvantages of Pulse Echo techniqueDisadvantages of Pulse Echo technique

1. 1. Orientation of defect affects detectability.Orientation of defect affects detectability.

A big defect is supposed to produce a large reflection echo


2. 2. No hard copy record. Completely technician No hard copy record. Completely technician dependent.dependent.

Attempt to computerize this technique result Attempt to computerize this technique result in complicated equipment set-upin complicated equipment set-up


3. Time consuming to size defect accurately, use of DAC curve to estimate defect size


As such, Radiography, which produces a As such, Radiography, which produces a picture, is utilized; even though defect picture, is utilized; even though defect detectability is lower than UT.detectability is lower than UT.

Radiography or X’ray produces Radiography or X’ray produces Radiation Radiation Safety Problems Safety Problems

Radiograhpy is time consuming on thick Radiograhpy is time consuming on thick materials or large diameters .materials or large diameters .

7Ultrasonic TOFDUltrasonic TOFD

Late 1970s , AEA ( Atomic Energy Authority) Late 1970s , AEA ( Atomic Energy Authority) of United Kingdom explored new ultrasonic of United Kingdom explored new ultrasonic technique technique

This technique utilizes sound This technique utilizes sound diffractiondiffraction from from defect tips, not defect tips, not reflectionreflection echoesechoes..

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When a sound hits a defect, its tips would When a sound hits a defect, its tips would give out another sound in all directions. give out another sound in all directions. This is termed “Diffraction”This is termed “Diffraction”

Ultrasonic TOFD

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Another probe receives diffracted signals,Another probe receives diffracted signals,

Location and height of defect can be measuredLocation and height of defect can be measured

Ultrasonic TOFD


Lateral Wave

In good metal, lateral wave and backwall echo received. lateral wave = top of the weld. backwall echo = bottom of weld.

BackwallEcho


Diffraction from the tips of defect

Notice the phase change in the top and bottom signals

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When two probes are placed on either sides of the weld, the beam covers the entire weld cross-section in one standing position.

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When two probes are placed on either sides of the weld, the beam covers the entire weld cross-section in one standing position.

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Image shows length and height of defect in a cross-sectional viewalong the axis of weld.

This image is a “D-Scan”

Ultrasonic TOFD

Depth of Defect “s”

Height of Defect “a”

a

s

“l “ defect length l

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1. lack of root penetration / concavity

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1

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2. a long thin defect, e.g. slag line < 1mm height

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1

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2. a long thin defect, e.g. slag line < 1mm height

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3. a small discontinuity with short length, e.g. porosity

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This presentation is a “B Scan”This scan is normally not required in pipe joint inspection

Ultrasonic TOFD

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X’Ray GammaRay

TOFD UT P/E

20

40

60

80

100

0

Defect Detectability of NDT Techniques compared with TOFD

( by Dutch Welding Institute )

%

42TOFD ApplicationTOFD Application

AdvantagesAdvantages Produces picture and hard copy result for record Produces picture and hard copy result for record

keepingkeeping Real-Time Imaging means immediate result if requiredReal-Time Imaging means immediate result if required No Radiation HazardNo Radiation Hazard

NDT in day-time; good control of work progressNDT in day-time; good control of work progress allows fabrication work round the clock if necessaryallows fabrication work round the clock if necessary

Scanning is fast, especially for thick wall materialScanning is fast, especially for thick wall material minimise back logminimise back log

43TOFD ApplicationTOFD Application

LimitationLimitation A dead zone exist in the top 2 to 3 mm.A dead zone exist in the top 2 to 3 mm.

supplement test with creeping wave or MPIsupplement test with creeping wave or MPI No direct indication of defect typeNo direct indication of defect type Minimum thickness 6mm & 4” dia.Minimum thickness 6mm & 4” dia. Not applicable to Stainless Steel, Inconel & Cast Not applicable to Stainless Steel, Inconel & Cast

Iron due to coarse grain structureIron due to coarse grain structure

44Validation and AcceptanceValidation and Acceptance

ASME Case Study 2235-4 ASME Case Study 2235-4 ( for ( for 11//22 inch and above ) inch and above )

BS 7706 BS 7706 ( for 6mm and above material thickness )( for 6mm and above material thickness )

European Standard (WGAC9613 rev.10)European Standard (WGAC9613 rev.10) Lloyds RegisterLloyds Register Electric Power Research Institute (EPRI), U.S.A.Electric Power Research Institute (EPRI), U.S.A. Dutch Factory & Machinery Inspectorate Dutch Factory & Machinery Inspectorate

(Stoomwezen BV)(Stoomwezen BV)

45Defect Rejection CriteriaDefect Rejection Criteria

Existing acceptance/ rejection criteria in codes & Existing acceptance/ rejection criteria in codes & standards mainly based on defect length with an standards mainly based on defect length with an assumed defect height (worst case assumed).assumed defect height (worst case assumed).

ASME acceptance criteria for TOFD utilises ASME acceptance criteria for TOFD utilises defect height (defect height (aa) and length () and length (l l ) in Fractured ) in Fractured Mechanics calculation.Mechanics calculation.

46Defect Rejection CriteriaDefect Rejection Criteria

Evaluation is based on defect “Evaluation is based on defect “height-over-height-over-length ratiolength ratio” compared against material ” compared against material thickness. i.e.thickness. i.e. aa//l l againstagainst aa//tt

No necessity to know defect type. No necessity to know defect type.

If necessary, defect type can still be evaluated with If necessary, defect type can still be evaluated with pulse-echo probe.pulse-echo probe.

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Field Application Experience of MJ since 1996

Field Application Experience of MJ since 1996 Project Piping Construction --- in lieu of RTProject Piping Construction --- in lieu of RT

Shell LPG Plant Construction for Foster Wheeler/ Shell LPG Plant Construction for Foster Wheeler/ Kellogg/ JGCKellogg/ JGC

Shell MLNG Plant No.3 Construction for JGC/ Shell MLNG Plant No.3 Construction for JGC/ Kellogg Brown & Root and Slug Catcher for RanhillKellogg Brown & Root and Slug Catcher for Ranhill

Petronas Common Utilities Facilities construction Petronas Common Utilities Facilities construction for Foster Wheeler for Foster Wheeler

Gas Transmission Piping for JGC at Ourhoud, Gas Transmission Piping for JGC at Ourhoud, AlgeriaAlgeria

Ammonia Syn-Gas Plant construction for PetronasAmmonia Syn-Gas Plant construction for Petronas

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Field ApplicationExperience of MJ since 1996

Field ApplicationExperience of MJ since 1996

Project Piping Construction --- in lieu of RTProject Piping Construction --- in lieu of RT Shell Sarawak Offshore M-1 Platform expansion Shell Sarawak Offshore M-1 Platform expansion

projectproject Exxon Pyrolysis Furnace Project for Agra Birwelco Exxon Pyrolysis Furnace Project for Agra Birwelco

LtdLtd Petronas RESAK Offshore Project for ProjassPetronas RESAK Offshore Project for Projass Petronas ANGSI Offshore Project for Sime-Petronas ANGSI Offshore Project for Sime-

SembawangSembawang Titan Chemicals TPP 2 Project for JGCTitan Chemicals TPP 2 Project for JGC

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Field ApplicationExperience of MJ since 1996Field ApplicationExperience of MJ since 1996

Pressure Vessel fabrication --- in lieu of RT Pressure Vessel fabrication --- in lieu of RT Shell Refinery LPG Bullet Tank ConstructionShell Refinery LPG Bullet Tank Construction Insallah Project Algeria for JGC / MechmarInsallah Project Algeria for JGC / Mechmar Shell Sarawak B-11 Platform projectShell Sarawak B-11 Platform project Nippon Oil Helang Field Offshore projectNippon Oil Helang Field Offshore project Petronas/MTBE LPG Bullet Tank for Toyo/ KNMPetronas/MTBE LPG Bullet Tank for Toyo/ KNM Petronas Dagangan Bullet Tank for MechmarPetronas Dagangan Bullet Tank for Mechmar

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Field ApplicationExperience of MJ since 1996Field ApplicationExperience of MJ since 1996

Monitoring Stress Corrosion Cracking in Monitoring Stress Corrosion Cracking in pipings & pressure vessels for refineries pipings & pressure vessels for refineries and chemical plants in Malaysia, Singapore.and chemical plants in Malaysia, Singapore.

Inspection of Spherical Tank & Reactors for Inspection of Spherical Tank & Reactors for service-induced defects for oil refineries in service-induced defects for oil refineries in Malaysia and Singapore & ThailandMalaysia and Singapore & Thailand

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LPG Bullet Tank Fabrication at Shell Refinery Port Dickson, 1996

48.5m x 8m dia x 43mm thick

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Performing TOFD Inspection on LPG Bullet Tankfor Shell Port Dickson Refinery

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TOFD Scanning on Pressure Swing Absorber

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TOFD Inspection at Shell Seraya Chemicals SingaporeTOFD Inspection at Shell

Seraya Chemicals Singapore

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TOFD Scanning on Pipe Joints in Shell LPG Plant Construction for JGC / Hyundai

56LPG Plant Piping for JGC/ HyundaiLPG Plant Piping for JGC/ Hyundai

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SlugCatcher Piping at MLNG-3 PlantSlugCatcher Piping at MLNG-3 Plant

58Piping Inspection in Algeria for JGCPiping Inspection in Algeria for JGC

59Offshore Platform Piping --ShellOffshore Platform Piping --Shell

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Top Surface

Backwall

Primary Image

Secondary Image

Typical TOFD image

61Porosi ty

Defec t Wi th L ength

Hi-low B ac k-wal l

La ck-Of-Root-Penet ra ti on

Ultrasonic TOFD Images

Porosity

Linear InclusionHi-low on Root

Lack of Root Penetration

How defect images look like in TOFD

Porosi ty

Defec t Wi th L ength

Hi-low B ac k-wal l

La ck-Of-Root-Penet ra ti on

Ultrasonic TOFD Images

Porosity

Linear InclusionHi-low on Root

Lack of Root Penetration

How defect images look like in TOFD

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Comparison between RT & TOFD Images

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Note that TOFD shows 2 defects at different depths while RT shows only one combined defect.

65Stress Corrosion CrackingStress Corrosion Cracking

66Crack in Pressure VesselCrack in Pressure Vessel

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Cracks in a Support Ring Weld

A

B

A

B

SupportRing

VesselWall

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Embedded crack in Spherical TankEmbedded crack in Spherical Tank

LongSeam

LongSeam

Note the phase change in TOFD indication. Yellow arrow shows top of defect (black /white) Pink arrow shows bottom of defect (white /black)

69 Corrosion under Cladding Corrosion under Cladding

BaseMetal

Cladding

70Corrosion / Erosion on Weld-Root

See more detail in next slide

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Corrosion on Weld-Root

B- scan

D-scan

D-scan

72Field Application Field Application

Equipment Equipment consist of :consist of : 1 unit Computer --- lap-top size1 unit Computer --- lap-top size, ,

inclusive of Ultrasonic Cardsinclusive of Ultrasonic Cards

1 unit Scanner --- hand-held size, 1 unit Scanner --- hand-held size, to hold a pair of probes and to hold a pair of probes and to hold encoder which give information of probe movement to to hold encoder which give information of probe movement to

computercomputer

Cables --- up to 120 meters longCables --- up to 120 meters long CD drive & Printer CD drive & Printer

use in office for reportinguse in office for reporting

73Field ApplicationField Application

Equipment MobilizationEquipment Mobilization Computer may be stationed on ground level, Computer may be stationed on ground level,

mounted on trolley or pick-upmounted on trolley or pick-up Computer connected to scanner via 40m to 120m Computer connected to scanner via 40m to 120m

long cableslong cables Communication between Technicians via Communication between Technicians via

headphones, independent of background noiseheadphones, independent of background noise


ManpowerManpower

A team normally consists of 3 personnelA team normally consists of 3 personnel 1 number Level II Technician1 number Level II Technician 2 numbers Level I Technician2 numbers Level I Technician

Additional helper for cleaning weldAdditional helper for cleaning weld


Weld Preparation for TOFDWeld Preparation for TOFD Avoid grindingAvoid grinding base metal --base metal --

--favorite practice of welder to remove undercut and spatter by favorite practice of welder to remove undercut and spatter by grinding grinding

Grinding creates uneven surface and makes probe contact Grinding creates uneven surface and makes probe contact difficultdifficult

Use scrapper, chisel or sanding disc, to remove spatterUse scrapper, chisel or sanding disc, to remove spatter

Make weld cap as narrow as possible. Avoid Make weld cap as narrow as possible. Avoid excessive weld reinforcement. This also reduces excessive weld reinforcement. This also reduces amount of welding.amount of welding.

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The EndThe End

Thank YouThank You

For further enquiry, please contact us at :For further enquiry, please contact us at :

Email : [email protected] : [email protected]

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TOFDPre-Rev03-Sept.ppt