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Radiography Testing Presentation


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Detailed Presentation on Radiography Testing. It is prepared on the lines of ASNT Level II pattern.

A V Abhishek

Published in: Engineering

Radiography Testing Presentation

  1. 1. Presentation on Radiography Testing By Abhishek A V
  2. 2. 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
  3. 3. Advantages & Disadvantages S.No Advantages Disadvantages 1 Can be used to inspect virtually all materials. Extensive operator training and skill required. 2 Detects surface and subsurface defects. Depth of Discontinuity not Indicated 3 Permanent Test Report can be Obtained Access to both sides of the structure is usually required. 4 Ability to inspect complex shapes, Hidden areas and multi-layered structures without disassembly. Orientation of the radiation beam to non- volumetric defects is critical. 5 Minimum part preparation is required. Relatively expensive equipment and investment is required. 6 Technique standardized and Reference standards available Possible radiation hazard for personnel. Application: o Pipe work o Pressure vessels and boilers o Structural steel works o Ship building Note: Testing can be carried out upto 200 mm
  4. 4. Introduction to Radiography o The radiation are of higher energy (shorter wavelength) version of the electromagnetic waves o Source – X ray/ Gamma ray o X-rays are produced by an x-ray generator o Gamma radiation is the product of radioactive atoms. o X-rays and gamma rays can be characterized by frequency, wavelength, and velocity. High Electrical Potential Electrons -+ X-ray Generator or Radioactive Source Creates Radiation Exposure Recording Device Radiation Penetrate the Sample
  5. 5. Principle – Differential Absorption Top view of developed film X-ray film = more exposure = less exposure The 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 object Thinner portion will absorb less radiation and transmit more radiation on to film and hence more black will be on film and vice-versa
  6. 6. Generation of Sources Source Depends on Type of Material Material Thickness Location of Testing Thickness , Energy , Penetration, Radiation Hazards Electrically Generated form X Ray Tube/Tube Heads Requires Power Supply Radiation Controllable  Less Hazardous Generated by decay of unstable atoms Source - Artificial Isotopes Iridium, Cobalt Iridium – Max Penetration -75 mm in steel Cobalt–Max Penetration -200 mm in Steel  Applicable for Onsite No Power Required Radiation is Non – Controllable  Isotopes can be replaced & periodic Inspection More Hazardous
  7. 7. Penetration Level w.r.t Source w.r.t Exposure Steel Aluminum Medical Diagnostics – 50 KV X rays are measured in KV Gamma measured Rays in MeV
  8. 8. Exposing Time Depends on o Material of the Object – Steel/Al/Cu o Material thickness o Type of Film – Slow/Medium/Fast o Film Density o Source to Film Distance – SFD o Source – X Ray/Gamma Ray – Intensity/Energy How to find Exposure Time: o Exposure Chart – X Ray Only o Exposure Scale – Gamma Ray – Onsite Application o Exposure Formulae - Gamma Ray Exposure Scale Exposure Time Formulae = Film Factor x 2 N x (SFD)2 x 60 RHM x S x (100)2 RHM = Roentgen Hour Meter SFD = Source to Film Distance N = Thickness /Half Value Thickness
  9. 9. Exposure Equivalent Chart Exposure Chart Exposure Time for X – Ray Less straight forward because the wavelength and intensity are variable Exposure for X Rays determined by o By Exposure Charts o By Reference to previous exposure records o By Trial and error test shots o By combination of above
  10. 10. Geometric Principle of Shadow Sharpness of the shadow dividing line b/w areas of different density Controlled by Controlled by Note Object Should be kept as close as touch/near to Film Object to be kept parallel to film axis Central ray of beam (Focal Spot) should be perpendicular to film axis
  11. 11. Geometric Unsharpness (Ug) – Width b/w Umbra & Penumbra Sharp Image – Umbra Unsharp Image – Penumbra To minimize penumbra o Source size as small as possible o SOD/FFD as large as possible o OFD as small as possible Ug= f x t /SOD f – focal point t - thickness (for solid object) SOD – Source to Object Distance Object Thickness / Ug Below (50mm) = max. Ug. (0.50mm) (50 - 75mm) = max. Ug. (0.75mm) (75 - 100mm) = max. Ug. (1.00mm) Above (100mm) = Ug (1.75mm)
  12. 12. Film Characteristics Film Density - Degree of Blackening Low Film/High Film Density Measure by Densitometer For X Rays :1.8 – 4; For Gamma rays : 2-4 Film Speed Film which gives exposing time Exposing Time less – Fast Film Exposing time medium – Medium Film Exposing time Fast – Slow Film Film Sensitivity Ability to detect smallest flaw Film ResolutionSeparation of close lying Defects Film Graininess Small Size- Slow Film – Less Graininess Big Size- Fast Film – More Graininess Film Contrast Degree of Shining More Shining – High Film Contrast Less Shining – Low Film Contrast Film Characteristics Curve / Sensitometric Curve/Hunter & Driffield Curve Density is plotted against log of exposure Film type Material Thickness Class I T < 0.5” Class II T >0.5” to T < 1.0” Class III T >1”
  13. 13. Film Characteristics Curve / Sensitometric /Hunter & Driffield Curve 1. Position of Curve on Exposure axis gives information on film speed 2. Position of Straight line portion of curve against density axis gives density range with which the film is at its optimal 3. Gradient of Curve gives information on films contrast Films are classified into Type 1, Type II and Type III
  14. 14. Intensifying Screens Film is sandwiched between intensifying screens Three types a) Lead Screens b) Fluorescent Screens c) Flurometallic screens Lead Intensifying Screens o Front Screen shortens exposure time and improves quality by filtering backscatter o Back screens act as filter only o Screen thickness 0.02 mm to 0.15 mm Fluorescent Screens o Intensification twice of Lead Screen o Cost effective Flurometallic screens o Front screen act as filter and intensifier o Intensifying Action achieved by emitting light radiation and particulate radiation electrons
  15. 15. Dev. Stop Bath Fix Wash Running Water Dryer Film Processing o Developer - converts latent image into manifest image (10-12 Min- Agitate) o Stop Bath – Removes Excess Developer (10-15 Sec) o Fixer -Clean the film of unexposed, undeveloped AgBr crystals, promotes archival quality (5 Min) o Wash – rid the film of residual chemicals o Wetting the film to swell the emulsion Note :For manual processing a floating thermometer, a timer and the time -temperature chart are essential. Types of Processing 1. Manual 2. Semi Automatic 3. Automatic
  16. 16. Penetrameters /Image Quality Indication o To achieve a radiographic image with highest quality o It provide a means of visually informing the film interpreter of the contrast sensitivity and definition of the radiograph 1% Sensitivity –Aerospace Application 2 % Sensitivity –Industrial Application Sensitivity–Ability to detect smallest flaw Types of IQI Commonly Used 1. Wire Type 2. Step Hole Type 3. Plaque Hole Type (Step – Hole Type) o IQI Thickness = 2 % (Object Thickness) o Unit of IQI Thickness = Thou (40 Thou =1 mm) Suppose, Object – 8 mm Thickness = 2 % (8) = 0.16 mm So, the minimum size of the discontinuity that should be visible in the radiography film is of 0.16mm
  17. 17. Placement of Penetrameters /IQI o To be placed at worst location/Extreme edge of radiographic film o To be placed at Source Side, in case use Film Side ~ DWSI/DWDI (Indicate Letter F) o For Weld, Wire Type IQI to be kept across the weld o For Weld, Plate & Hole, Step Wedge , parallel to weld 3mm away from weld edge o When there is no accessibility , Block/shim to be used & IQI to be placed on it. o Density of radiograph varies from location of IQI by more than -15% to 30 % then another IQI is required o For Circumferential weld in SWSI-Panaromic technique, 3 IQI’s at 120o apart, 4 IQI at 90o apart o Backing rings or strips and root penetration are not to be considered as part of the weld or reinforcement thickness in selection of the IQI. o 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.,
  18. 18. Wire Type Penetrameters /IQI o In Wire Type IQI, Four standards - ATSM, ISO, DIN, EN o ASTM has four Sets- A, B,C,D & its wire identification o All 6 wires are equally spaced and same height o 4 alternative Sets for ASTM Standard available – Selected by End User Alternative Sets- ASTM Selection of Wire Type IQI as per ASTM E 747-97
  19. 19. Plate Hole/Plaque Penetrameters /IQI Selection of Plate Hole IQI Can be differentiated by Notch XX- Thickness of IQI on thou A - 4 T Hole B – 1 T Hole C – 2 T Hole Different Sensitivity Level 2-2T IQI normally used  2- % of thickness of Object 2T- Image to be seen on Film 1-1T 2-2T 4-1T 1-2T 2-2T 4-2T 1-4T 2-4T 4-4T
  20. 20. Back Scatter Radiation o 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. o If a light image of the “B” appears on a darker background of the radiograph, protection from backscatter is insufficient and the radiograph shall be considered unacceptable. IQI Sensitivity For the wire type IQI: %Sensitivity = (Diameter of the smallest visible wire / Thickness of metal) * 100 For the step-hole IQI: %Sensitivity = Diameter of the smallest visible hole / Thickness of metal * 100 For 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 thickness B is the diameter of the smallest hole visible, expressed as a percentage of metal thickness
  21. 21. Radiography Techniques Selection of Technique based on o Test Object – material/thickness/configuration o Weld/Casting/Forging/Assembled part o Anticipate location and nature of discontinuities o Critical and vulnerable locations o Sensitivity level required o Accessibility of Film
  22. 22. Radiography Techniques Types of Techniques Single wall Single Image (SWSI) o Flat Surfaces/Plates/sheets/Large Pipe Joints (Dia> 8”) o Film Inside, Source Outside Single Wall Single Image (SWSI) – Panoramic o Film Outside, Source Inside Double Wall Single Image (DWSI) o Film Outside, source outside (External Exposure), Dia of Pipe > 3inch Double Wall Double Image (DWDI) o Film Outside, source outside (Elliptical Exposure), Dia of Pipe <3inch
  23. 23. For Panaromic, Multiple films are used and films must be same type One Inch film to be overlapped with other Single Shot, No of IQI to be calculated
  24. 24. Double Wall Single Image Double Wall Double Image SOD wrt Top wall 0 SOD=Pipe Dia Source Outside, Film Outside Source Displacement Angle Ø = 360 /n where n is odd, n= no of shots Ø = 180 /n where n is even Source Outside, Film Outside Exposing Time will be double Only 2 Shots required Elliptical image will be observed (OD/ID > 1.4)x1.7 = XX shots (OD/ID < 1.4) =2 shots OD – Outer Diameter, ID – Inner Diameter For Example OD= 50mm, t=12.5, ID = 25 N=? (OD/ID > 1.4)x1.7 =3.4 ~ 4 Shots
  25. 25. Reference Source - ASNT Section 5
  26. 26. Reference Source - ASNT Section 5
  27. 27. Defects o Casting o Welding o Forging o Rolling o Assembly o Faults occurred during Handling/ Film Processing
  28. 28. Type of Defects - Casting Defect Shape Location Indication Shrinkage Linear Surface/Internal Black Line Hot Tears Linear Surface Black Line Cold Shuts Linear Surface Black Line Porosity Round Surface/Internal/Root Black Spot Non Metallic/Metallic Inclusions Round Surface/Internal Black/White Spot Defect Shape Location Indication Lack of Penetration Linear Root Black Line Lack of Sidewall Fusion Linear Internal Black Line Porosity Round Surface/Internal/Root Black spot Slag Inclusions Round Internal Black/White Spot Type of Defects - Welding
  29. 29. Four Pases in Weld a) Root b) Hand pass c) Fill d) Cap Root Pass(Bottom side of Welded piece) Cap Pass (Top side of Welded piece) Defects in Welding
  30. 30. Defects in Welding o Lack of Penetration o Lack of Fusion o Porosity Cluster Porosity o Slag Inclusions o Root Undercut o Crown Undercut o Mismatch oInadequate Weld Reinforcement o Excess Weld Reinforcement o Cracks o Weld Spatter o Arc Strike o Tungsten/Oxide Inclusions (In TIG Welding) o Whiskers / Burn through ( In MIG Welding) Types of Defects
  31. 31. Defects in Welding
  32. 32. Defects in Welding
  33. 33. Defects in Welding
  34. 34. Casting Defects Can be classified as Filling related defect oBlow Hole oSand Burning oSand Inclusion Cold Lap/Cold Shut oMisrun oGas Porosity Shape related defect oMismatch /Misrun oDistortion/Wrap oFlash Thermal defect oCrack/Tears oShrinkage - Cavity/ Dendritic/Filamentary/Sponge oSink Mark  Defect by appearance oMetallic Projections oCavities oDiscontinuities oIncomplete casting oRat Tail/ Buckles Types of Defects
  35. 35. Defects in Casting Sand Inclusions Porosity Cavity Shrinkage Dendrite Shrinkage Cracks Slag Inclusion Core Shit Sponge Shrinkage
  36. 36. Defects in Forging Process oUnfilled Section oCold Shut oScale Pits oDie Pits oImproper Grain Flow Defects in Parent Material o Surface Irregularities – Rust/weld spatter/notches/ grooves/ loose scale o Surface Roughness oPorosity oInclusions Metallic/Non Metallic oLaminations/High Hydrogen Content Types of Defects
  37. 37. Faults Associated with Storage o Light Fog – Exposed to light while yet covered with interleaving paper o Radiation Fog – Exposed to X Rays or Gamma rays during storage Faults Associated with Safelight o 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 o Dirt Deposit on intensifying screens o Dark Spots due to low density and Hugh density o Water Spattered/Fixer Solution on film Types of Defects
  38. 38. Faults Associated with Loading and Unloading o Film Adhesion – Cassette adhered to intensifying lead screens o Static Marks - Contact, peeling of foreign matter bcoz of electricity o Kink Marks – Bents occurred during handling Faults Associated with Post Development Process o Uneven Fixing o Uneven Drying Types of Defects
  39. 39. Radiographic Interpretation in Steel Casting ASTM E 446 - Reference Radiographs for Steel Castings Up to (51 mm) in Thickness ASTM E 186 - Reference Radiographs for Heavy-wall (51 mm- 114 mm)) Steel Castings ASTM E 280 - Reference Radiographs for Heavy-walled (114 to 305 mm)) Steel Castings MIL STD 1265 A Radiographic Inspection, Classification & Sound Requirements for Steel Castings Classification of Classes:
  40. 40. Radiographic Interpretation in Steel Casting
  41. 41. Aluminium Casting Defects ASTM E 155 - Reference Radiographs for Inspection of Al & Mg Castings MIL STD 139 A Radiographic Inspection, Soundness Requirements for Al & Mg Castings Classification of Classes:
  42. 42. Acceptance Criteria for Al & Mg
  43. 43. Copper base & Nickel Copper Castings ASTM E 155 - Reference Radiographs for High Strength Copper–base & Nickel-Cu Alloy Castings
  44. 44. 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 Identification 2. Component, Casting, Pressure Vessel or Piping identifications 3. Seams or welds identification 4. R for repair, R2, R3 etc. if more than one repair. 5. C for new weld following complete cut out 6. Date of radiography 7. Welders identification
  45. 45. Film Viewing o Equipment used to view radiographs for interpretation shall have a variable light 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 o Light from the viewer not transmitted through the film shall be masked when viewing the radiograph. o Calibrated densitometers or step wedge films shall be used to assure film density compliance Film Interpretation o Radiographs shall be interpreted by Level II or Level III personnel o Acceptance level shall be as per relevant Standard / project code
  46. 46. Quality Of Radiographs All 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) Fogging b) Processing defects such as streaks, watermarks, or chemical stains c) Scratches, finger marks, crimps, dirtiness, static marks, smudges or tears d) False indications due to defective screens.
  47. 47. Radiographic Testing Acceptance Standard For Weld As per ASME Sec VIII, Div. I a) 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. b) 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 57mm Where: 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
  48. 48. Defect Removal for Welding Repair 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
  49. 49. Report Format (General Electric, US)
  50. 50. Checklist for Reviewing Radiographic Inspection
  51. 51. Precautions for Radiation Safety o Shielded Enclosures and Exposure Devices are manufactured in compliance with authorizations, appropriately surveyed and followed by quality objectives o Personnel are trained and competent to operate the exposure devices safely o Approved Operational procedures are to be followed o Sources are sealed and leak free o Source to be maintained in safe and secure condition at end of use or are decommissioned properly o Every personnel involved in radiography shall wear personal monitoring film badge. o Radiation warning signs shall be posted at sufficient locations along the rope and monitored by the technician. o Fire and safety regulations of clients shall be adhered to at all times.
  52. 52. Measurement of radiation as per MIL – HDBK 728 Used to monitor amount of radiation received by man Measured in REM- Roentgen Equivalent Man Wrist Watch DosimeterPocket Dosimeter
  53. 53. Computed Tomography o Computed Tomography (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. o Characteristics of the internal structure of an object such as dimensions, shape, internal defects, and density are readily available from CT images. o The component is placed on a turntable stage , b/w radiation source and imaging system. o The turntable and the imaging system are connected to a computer. o The imaging system produces a 2-D shadowgraph image of the specimen just like a film radiograph. Schematic View of a CT system
  54. 54. 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.
  55. 55. Thank You…