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Presentation on Radiography TestingByAbhishek A Vabhishek.agyarapu@gmail.com

Outline Application, Pros & Cons Principle/Source Generation Exposing Time, Film & its Characteristics Penetrameters / IQI Type of Technique Defects/Identification Film Interpretation Acceptance Criteria Report Format Safety Precaution

RT- Radiography Testing

Advantages & DisadvantagesS.NoAdvantagesDisadvantages1Can be used to inspect virtually all materials.Extensive operator training and skill required.2Detects surface and subsurface defects.Depth of Discontinuity not Indicated3Permanent Test Report can be ObtainedAccess to both sides of the structure is usually required.4Ability to inspect complex shapes, Hidden areas and multi-layered structures without disassembly.Orientation of the radiation beam to non-volumetric defects is critical.5Minimum part preparation is required.Relatively expensive equipment and investment is required.6Technique standardized and Reference standards availablePossible radiation hazard for personnel.

Application: Pipe work Pressure vessels and boilers Structural steel works Ship building

Note:Testing can be carried out upto 200 mm

Introduction to Radiography The radiation are of higher energy (shorter wavelength) version of the electromagnetic waves Source X ray/ Gamma rayX-rays are produced by an x-ray generator Gamma radiation is the product of radioactive atoms. X-rays and gamma rays can be characterized by frequency, wavelength, and velocity.

High Electrical Potential

Electrons-+X-ray Generator or Radioactive Source Creates RadiationExposure Recording Device

Radiation Penetrate the Sample

Principle Differential Absorption

Top view of developed film X-ray film

= more exposure

= less exposureThe film darkness (density) will vary with the amount of radiation reaching the film through the test object.

Different parts of object will absorb the radiation differently depending on thickness, density and the atomic no of the objectThinner portion will absorb less radiation and transmit more radiation on to film and hence more black will be on film and vice-versa

Generation of SourcesSource Depends on Type of MaterialMaterial ThicknessLocation of Testing

Thickness , Energy , Penetration, Radiation Hazards

Electrically Generated form X Ray Tube/Tube HeadsRequires Power SupplyRadiation Controllable Less Hazardous

Generated by decay of unstable atomsSource - Artificial Isotopes Iridium, CobaltIridium Max Penetration -75 mm in steelCobaltMax Penetration -200 mm in Steel Applicable for OnsiteNo Power RequiredRadiation is Non Controllable Isotopes can be replaced & periodic InspectionMore Hazardous

Penetration Level w.r.t Source w.r.t ExposureSteel AluminumMedical Diagnostics 50 KVX rays are measured in KVGamma measured Rays in MeV

Exposing TimeDepends on Material of the Object Steel/Al/CuMaterial thickness Type of Film Slow/Medium/FastFilm Density Source to Film Distance SFDSource X Ray/Gamma Ray Intensity/Energy

How to find Exposure Time:Exposure Chart X Ray Only Exposure Scale Gamma Ray Onsite ApplicationExposure Formulae - Gamma Ray

Exposure ScaleExposure Time Formulae= Film Factor x 2 N x (SFD)2 x 60 RHM x S x (100)2

RHM = Roentgen Hour MeterSFD = Source to Film Distance N = Thickness /Half Value Thickness

Exposure Equivalent Chart

Exposure ChartExposure Time for X Ray Less straight forward because the wavelength and intensity are variableExposure for X Rays determined by By Exposure Charts By Reference to previous exposure records By Trial and error test shots By combination of above

Geometric Principle of ShadowSharpness of the shadow dividing line b/w areas of different density

Controlled byControlled byNoteObject Should be kept as close as touch/near to FilmObject to be kept parallel to film axis Central ray of beam (Focal Spot) should be perpendicular to film axis

Geometric Unsharpness (Ug) Width b/w Umbra & PenumbraSharp Image UmbraUnsharp Image PenumbraTo minimize penumbra Source size as small as possible SOD/FFD as large as possible OFD as small as possible

Ug= f x t /SODf focal pointt - thickness (for solid object)SOD Source to Object Distance Object Thickness / UgBelow (50mm) = max. Ug. (0.50mm)(50 - 75mm) = max. Ug. (0.75mm)(75 - 100mm) = max. Ug. (1.00mm)Above (100mm) = Ug (1.75mm)

Film CharacteristicsFilm Density - Degree of BlackeningLow Film/High Film DensityMeasure by DensitometerFor X Rays :1.8 4; For Gamma rays : 2-4 Film SpeedFilm which gives exposing timeExposing Time less Fast FilmExposing time medium Medium FilmExposing time Fast Slow FilmFilm SensitivityAbility to detect smallest flawFilm ResolutionSeparation of close lying DefectsFilm GraininessSmall Size- Slow Film Less GraininessBig Size- Fast Film More Graininess Film Contrast Degree of Shining More Shining High Film Contrast Less Shining Low Film ContrastFilm Characteristics Curve / Sensitometric Curve/Hunter & Driffield Curve Density is plotted against log of exposure

Film typeMaterial ThicknessClass IT < 0.5Class IIT>0.5 toT 1

Film Characteristics Curve / Sensitometric /Hunter & Driffield Curve Position of Curve on Exposure axis gives information on film speedPosition of Straight line portion of curve against density axis gives density range with which the film is at its optimalGradient of Curve gives information on films contrast

Films are classified into Type 1, Type II and Type III

Intensifying ScreensFilm is sandwiched between intensifying screensThree types a) Lead Screensb) Fluorescent Screensc) Flurometallic screensLead Intensifying Screens Front Screen shortens exposure time and improves quality by filtering backscatter Back screens act as filter only Screen thickness 0.02 mm to 0.15 mmFluorescent Screens Intensification twice of Lead Screen Cost effectiveFlurometallic screens Front screen act as filter and intensifier Intensifying Action achieved by emitting light radiation and particulate radiation electrons

Dev.StopBathFixWash Running Water

DryerFilm Processing

Developer - converts latent image into manifest image (10-12 Min- Agitate) Stop Bath Removes Excess Developer (10-15 Sec) Fixer -Clean the film of unexposed, undeveloped AgBr crystals, promotes archival quality (5 Min) Wash rid the film of residual chemicals Wetting the film to swell the emulsionNote :For manual processing a floating thermometer, a timer and the time -temperature chart are essential.

Types of ProcessingManualSemi AutomaticAutomatic

Penetrameters /Image Quality Indication To achieve a radiographic image with highest quality It provide a means of visually informing the film interpreter of the contrast sensitivity and definition of the radiograph

1% Sensitivity Aerospace Application2 % Sensitivity Industrial ApplicationSensitivityAbility to detect smallest flaw

Types of IQI Commonly UsedWire Type Step Hole TypePlaque Hole Type (Step Hole Type)

IQI Thickness = 2 % (Object Thickness) Unit of IQI Thickness = Thou (40 Thou =1 mm)

Suppose, Object 8 mm Thickness= 2 % (8) = 0.16 mmSo, the minimum size of the discontinuity that should be visible in the radiography film is of 0.16mm

Placement of Penetrameters /IQITo be placed at worst location/Extreme edge of radiographic filmTo be placed at Source Side, in case use Film Side ~ DWSI/DWDI (Indicate Letter F)For Weld, Wire Type IQI to be kept across the weld For Weld, Plate & Hole, Step Wedge , parallel to weld 3mm away from weld edgeWhen there is no accessibility , Block/shim to be used & IQI to be placed on it.Density of radiograph varies from location of IQI by more than -15% to 30 % then another IQI is requiredFor Circumferential weld in SWSI-Panaromic technique, 3 IQIs at 120o apart, 4 IQI at 90o apartBacking rings or strips and root penetration are not to be considered as part of the weld or reinforcement thickness in selection of the IQI.The material of the IQI shall be of similar radiographic density to that of the material under examination, i.e. use steel for steel, aluminium for aluminium, etc.,

Wire Type Penetrameters /IQIIn Wire Type IQI, Four standards - ATSM, ISO, DIN, ENASTM has four Sets- A, B,C,D & its wire identificationAll 6 wires are equally spaced and same height4 alternative Sets for ASTM Standard available Selected by End User

Alternative Sets- ASTM Selection of Wire Type IQI as per ASTM E 747-97

Plate Hole/Plaque Penetrameters /IQI

Selection of Plate Hole IQICan be differentiated by NotchXX- Thickness of IQI on thouA - 4 T HoleB 1 T HoleC 2 T Hole

Different Sensitivity Level

2-2T IQI normally used 2- % of thickness of Object2T- Image to be seen on Film

1-1T2-2T4-1T1-2T2-2T4-2T1-4T2-4T4-4T

Back Scatter Radiation A lead symbol B with minimum dimensions of 1/2 inch in height and 1/16 inch in thickness, shall be attached to the back of film holder to determine if backscatter radiation is exposing the film. If a lightimage of the B appears on a darker background of the radiograph, protection from backscatter is insufficient and the radiograph shall be considered unacceptable.

IQI SensitivityFor the wire type IQI: %Sensitivity = (Diameter of the smallest visible wire / Thickness of metal) * 100For the step-hole IQI:%Sensitivity = Diameter of the smallest visible hole / Thickness of metal * 100For the plaque hole IQI, % of Sensitivity = square root of (AxB/2)A is thickness of the smallest plaque image visible, expressed as a percentage of metal thicknessB is the diameter of the smallest hole visible, expressed as a percentage of metal thickness

Radiography TechniquesSelection of Technique based on Test Object material/thickness/configuration Weld/Casting/Forging/Assembled partAnticipate location and nature of discontinuitiesCritical and vulnerable locationsSensitivity level required Accessibility of Film

Radiography TechniquesTypes of TechniquesSingle wall Single Image (SWSI) Flat Surfaces/Plates/sheets/Large Pipe Joints (Dia> 8) Film Inside, Source OutsideSingle Wall Single Image (SWSI) Panoramic Film Outside, Source InsideDouble Wall Single Image (DWSI) Film Outside, source outside (External Exposure), Dia of Pipe > 3inchDouble Wall Double Image (DWDI) Film Outside, source outside (Elliptical Exposure), Dia of Pipe 1.4)x1.7 = XX shots(OD/ID < 1.4) =2 shots OD Outer Diameter, ID Inner DiameterFor Example OD= 50mm, t=12.5, ID = 25 N=?(OD/ID > 1.4)x1.7 =3.4 ~ 4 Shots

Reference Source - ASNT Section 5

Reference Source - ASNT Section 5

Defects Casting Welding Forging Rolling Assembly Faults occurred during Handling/ Film Processing

Type of Defects - Casting

DefectShapeLocationIndicationShrinkageLinearSurface/InternalBlack LineHot TearsLinearSurfaceBlack LineCold ShutsLinearSurfaceBlack LinePorosityRoundSurface/Internal/RootBlack SpotNon Metallic/Metallic InclusionsRoundSurface/InternalBlack/White Spot

DefectShapeLocationIndicationLack of PenetrationLinearRootBlack LineLack of Sidewall FusionLinearInternalBlack LinePorosityRoundSurface/Internal/RootBlack spotSlag InclusionsRoundInternalBlack/White Spot

Type of Defects - Welding

Four Pases in WeldRootHand passFillCap

Root Pass(Bottom side of Welded piece)Cap Pass (Top side of Welded piece)Defects in Welding

Defects in Welding Lack of Penetration Lack of Fusion Porosity Cluster Porosity Slag Inclusions Root Undercut Crown Undercut MismatchInadequate Weld Reinforcement Excess Weld Reinforcement Cracks Weld Spatter Arc Strike Tungsten/Oxide Inclusions (In TIG Welding) Whiskers / Burn through ( In MIG Welding)

Types of Defects

Defects in Welding

Defects in Welding

Defects in Welding

Casting Defects Can be classified asFilling related defectBlow HoleSand BurningSand Inclusion Cold Lap/Cold ShutMisrunGas PorosityShape related defectMismatch /MisrunDistortion/WrapFlashThermal defectCrack/TearsShrinkage - Cavity/ Dendritic/Filamentary/SpongeSink Mark Defect by appearanceMetallic ProjectionsCavitiesDiscontinuitiesIncomplete castingRat Tail/ BucklesTypes of Defects

Defects in Casting

Sand Inclusions

Porosity

Cavity Shrinkage

Dendrite Shrinkage

Cracks

Slag Inclusion Core Shit

Sponge Shrinkage

Defects in Forging Process Unfilled SectionCold ShutScale Pits Die Pits Improper Grain Flow

Defects in Parent Material Surface Irregularities Rust/weld spatter/notches/ grooves/ loose scale Surface RoughnessPorosityInclusions Metallic/Non MetallicLaminations/High Hydrogen Content

Types of Defects

Faults Associated with Storage Light Fog Exposed to light while yet covered with interleaving paper Radiation Fog Exposed to X Rays or Gamma rays during storage

Faults Associated with Safelight Safelight Fog Higher capacity lamp used Film has been allowed to stand under safelight Illumination too long period White light is leaking from a slit in the safelight box

Faults Associated with Before Development Dirt Deposit on intensifying screens Dark Spots due to low density and Hugh density Water Spattered/Fixer Solution on film

Types of Defects

Faults Associated with Loading and Unloading Film Adhesion Cassette adhered to intensifying lead screens Static Marks - Contact, peeling of foreign matter bcoz of electricity Kink Marks Bents occurred during handlingFaults Associated with Post Development Process Uneven Fixing Uneven Drying

Types of Defects

Radiographic Interpretation in Steel CastingASTM E 446 - Reference Radiographs for Steel Castings Up to (51 mm) in ThicknessASTM E 186 - Reference Radiographs for Heavy-wall (51 mm- 114 mm)) Steel CastingsASTM E 280 - Reference Radiographs for Heavy-walled (114 to 305 mm)) Steel CastingsMIL STD 1265 A Radiographic Inspection, Classification & Sound Requirements for Steel CastingsClassification of Classes:

Radiographic Interpretation in Steel Casting

Aluminium Casting DefectsASTM E 155 - Reference Radiographs for Inspection of Al & Mg CastingsMIL STD 139 A Radiographic Inspection, Soundness Requirements for Al & Mg Castings

Classification of Classes:

Acceptance Criteria for Al & Mg

Copper base & Nickel Copper Castings

ASTM E 155 - Reference Radiographs for High Strength Copperbase & Nickel-Cu Alloy Castings

Film Identification

Each radiograph shall be identified through the use of lead markers(numbers and letters). The identification shall be as specified by the client but should consist of :-1. Project Identification2. Component, Casting, Pressure Vessel or Piping identifications3. Seams or welds identification4. R for repair, R2, R3 etc. if more than one repair.5. C for new weld following complete cut out6. Date of radiography7. Welders identification

Film Viewing Equipment used to view radiographs for interpretation shall have a variablelight source sufficient for the essential designated IQI wire to be visible for the specified density range of 2.0 to 4.0 High intensity light sources shall have exhaust arrangements for cooling to prevent film damage Light from the viewer not transmitted through the film shall be masked when viewing the radiograph. Calibrated densitometers or step wedge films shall be used to assure film density compliance

Film Interpretation Radiographs shall be interpreted by Level II or Level III personnel Acceptance level shall be as per relevant Standard / project code

Quality Of RadiographsAll radiographs shall be free from mechanical, chemical or other blemishes to the extent that they do not mask and are not confused with the image of any discontinuity in the area of interest of the object being radiographed. Such blemishes include

a)Foggingb)Processing defects such as streaks, watermarks, or chemical stainsc)Scratches, finger marks, crimps, dirtiness, static marks, smudges or tearsd)False indications due to defective screens.

Radiographic Testing Acceptance Standard For WeldAs per ASME Sec VIII, Div. I

All Welded joints surfaces shall be sufficiently free from coarse ripples,grooves, overlaps and abrupt ridges & valleys to permit proper interpretation of radiographic and the required non-destructive examinations. If any Default found on Surface, the film shall be compared to the actual weld surface for determination of acceptability.Indications shown on the radiographies of welds and characterized as imperfections are un-acceptable under the following condition:

1) Any indications characterized as a crack or zone of incomplete fusion or penetration.2) Any other elongated indication at radiography, which has length greater than:(a) 6mm for t up to 19mm(b) 8 mm for t from 19mm to 57mm(c) 19mm for t over 57mmWhere: t= thickness of weld excluding any allowable reinforcement.

3) Any group of aligned indications that have an aggregate length greater than t in a length of 12t , except when the distance between the successive imperfections exceed 6L where L is the length of the longest imperfection in the group.

4) Rounded indications in excess of that specified by the acceptance standards given in ASME sec. VIII, DIV I, appendix 4 fig. 4-2 to 4-8

Defect Removal for WeldingRepair area shall be located on the weld line after evaluation & interpretation of radiograph defects shall be removed by suitable method such as grinding, chipping or gouging (if permitted) welding of the repair area shall meet the requirement of related WPS,PQR.

Certification And Personnel Qualification In Radiographic Testing.Personnel performing radiography examination to this procedure shall be qualified and certified by XXX Company also shall meet the requirements of ASNT-SNT-TC-1A-2001 EDITION at least level II and on ASNT-SNT-TC-IA for code section I and sec VII div 2. Film interpreter shall have level II as a minimum

Report Format (General Electric, US)

Checklist for Reviewing Radiographic Inspection

Precautions for Radiation SafetyShielded Enclosures and Exposure Devices are manufactured in compliance with authorizations, appropriately surveyed and followed by quality objectives Personnel are trained and competent to operate the exposure devices safely Approved Operational procedures are to be followedSources are sealed and leak freeSource to be maintained in safe and secure condition at end of use or are decommissioned properlyEvery personnel involved in radiography shall wear personal monitoring film badge.Radiation warning signs shall be posted at sufficient locations along the rope and monitored by the technician.Fire and safety regulations of clients shall be adhered to at all times.

Measurement of radiation as per MIL HDBK 728

Used to monitor amount of radiation received by manMeasured in REM- Roentgen Equivalent Man Wrist Watch Dosimeter

Pocket Dosimeter

Computed Tomography ComputedTomography(CT) is a powerful non destructive evaluation (NDE) technique for producing 2-D and 3-D cross-sectional images of an object from flat X-ray images. Characteristics of the internal structure of an object such as dimensions, shape, internal defects, and density are readily available from CT images. The component is placed on a turntable stage , b/w radiation source and imaging system. The turntable and the imaging system are connected to a computer. The imaging system produces a 2-D shadowgraph image of the specimen just like a film radiograph.

Schematic View of a CT system

Pressure Vessel Inspection

The failure of a pressure vessel can result in the rapid release of a large amount of energy. To protect against this dangerous event, the tanks are inspected using radiography testing.

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