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Part 3.
Radiographic InterpretationRadiographic Interpretation
Course Reference WIS 20
M.S.RogersCopyright © 2004 TWI Ltd
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TechniquesTechniques
M.S.RogersCopyright © 2004 TWI Ltd
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- film inside, source outside
Single Wall Single Image (SWSI) panoramic
- film outside, source inside (internal exposure)
Double Wall Single Image (DWSI)
- film outside, source outside (external exposure)
Double Wall Double Image (DWDI)
- film outside, source outside (elliptical exposure)
Radiographic TechniquesRadiographic Techniques
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IQI’s should be placed source side
Film
Film
Single Wall Single ImageSingle Wall Single Image
SWSI
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IQI’s are placed on the film side
Source inside film outside (single exposure)
Film
SWSI panoramic
Single Wall Single Image PanoramicSingle Wall Single Image Panoramic
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Film
IQI’s are placed on the film side Source outside film outside (multiple exposure) This technique is intended for pipe diameters over
100mm
Double Wall single ImageDouble Wall single Image
DWSI
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Radiograph
Identification
ID MR11
• Unique identificationEN W10
• IQI placing
A B• Pitch marks indicating readable film length
Double Wall single ImageDouble Wall single Image
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Radiograph
Double Wall single ImageDouble Wall single Image
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Film
IQI’s are placed on the source or film side Source outside film outside (multiple exposure) A minimum of two exposures This technique is intended for pipe diameters less than
100mm
Double Wall Double ImageDouble Wall Double Image
DWDI
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Shot A Radiograph
Identification
ID MR12
• Unique identification EN W10
• IQI placing
1 2• Pitch marks indicating readable film length
4 3
Double Wall Double ImageDouble Wall Double Image
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Elliptical Radiograph
1 2
4 3
Double Wall Double ImageDouble Wall Double Image
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Film
IQI’s are placed on the source or film side Source outside film outside (multiple exposure) A minimum of three exposures Source side weld is superimposed on film side weld This technique is intended for small pipe diameters
Double Wall Double Image perpendicularDouble Wall Double Image perpendicular
DWDI
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intensifying screens
There are three main there are three main types of intensifying screens
Lead screens
Fluorescent screens
Fluorometallic screens
Intensifying ScreensIntensifying Screens
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Intensification action achieved by emitting
particulate radiation (electrons/beta)
Generally lead of 0.02mm to 0.15mm
Front screen shortens exposure time and
improves quality by filtering out scatter
Back screen acts as a filter only
Lead Intensifying ScreensLead Intensifying Screens
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Intensification action achieved by emitting
Light radiation (Visible or UV-A)
Intensification action twice that of lead
screens
No filtration action achieved
Salt used calcium tungstate
Salt Intensifying ScreensSalt Intensifying Screens
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Intensification action achieved by emitting light
radiation (Visible or UV-A) and particulate
radiation electrons)
High cost
Front screen acts as a filter and intensifier
Salt used calcium tungstate
Fluoromatallic Intensifying ScreensFluoromatallic Intensifying Screens
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image quality
None
Fluorescent
Fluorometallic
Order of speed
Intensification factor
How intensification
is achieved
Electrons -veBeta radiation
1
4
3
Lead
2
3
1
2
4
2-3
8-15
5-10
N/A
Light radiation
Light radiation
None
An intensification factor of 3 will reduce exposure from six minutes to two minutes
Comparison Chart, Intensifying ScreensComparison Chart, Intensifying Screens
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Radiographic FilmRadiographic Film
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Base
Radiographic FilmRadiographic Film
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Base
Subbing
Subbing
Radiographic FilmRadiographic Film
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Base
Subbing
Subbing
Emulsion AgBr
Emulsion AgBr
Supercoat
Supercoat
Radiographic FilmRadiographic Film
M.S.RogersCopyright © 2004 TWI Ltd
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G YWhat are the advantages of Double Coated Film?
•Improve contrast
• Reduce the exposure time
M.S.RogersCopyright © 2004 TWI Ltd
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Grain size Speed Quality Film Factor
Coarse
Medium
Fine
Ultra Fine
Fast
Medium
Slow
V Slow
Poor
Medium
Good
V Good
10
35
90
200
Note: Some film manufactures my use different film factor systems
Radiographic FilmRadiographic Film
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When radiation passes through an object it is differentially
absorbed depending upon the materials thickness and any
differing densities
The portions of radiographic film that receive sufficient
amounts of radiation undergo minute changes to produce the
latent image (hidden image)
1. The silver halide crystals are partially converted into
metallic silver to produce the latent image
2. The affected crystals are then amplified by the
developer, the developer completely converts the
affected crystals into metallic silver
3. The radiograph attains its final appearance by fixation
Image FormationImage Formation
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Developer tank - alkali
Stop bath or rinse tank - slightly acidic
Fixer tank - acidic
Final wash tank - running water
Wetting agent - detergent
Drying - drying cabinet or drying room
Film ProcessingFilm Processing
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DevelopmentDevelopment Metallic Silver converted into Black metallic silver
3-5 min at 20OC
Main ConstituentsMain Constituents Developing agent metol-hydroquinone Accelerator keeps solution alkaline Restrainer ensures only exposed silver halides converted Preservative prevents oxidation by air
Processing Systems
Replenishment Replenishment
Purpose – to ensure that the activity of the developer and the
developing time required remains constant
Guideline – 1. After 1m2 of film has been developed,
about 400 ml of replenisher needs to be added
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Supplied as a liquid concentrated alkali mixed to 1 part developer to 4 parts water
Developer temperatures for manual processing 20oC
Development times are 4 to 5 minutes During the development process agitation should
take place to avoid bromide streaking Replenishment may be added to maintain
development times and the activity of the developer
Film ProcessingFilm Processing
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Supplied as a liquid concentrated acid mixed to 1 part fixer to 3 parts water
Fixing temperatures for manual processing 20oC
Fixing times are twice the clearing time, clearing time about 3 minutes, fixing time about 6 minutes
During the fixing process agitation should take place to avoid light spots on the radiograph
When fixing times exceed 10 minutes the fixer should be replaced, replenishment is not normally added
Film ProcessingFilm Processing
M.S.RogersCopyright © 2004 TWI Ltd
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G Y After washing in running water the films may be placed in a
wetting agent to reduce surface tension this results in even
drying, preventing black streaky marks on the radiograph
Before drying excess water should be removed with the use
of a squeegee
Drying should take place in a dust free environment
Typical drying times in a drying cabinet 15 minutes
Typical drying times in a drying room 45 minutes Care should be taken not to allow drops of water to appear
on the drying films, this may cause black marks to appear
on the radiograph
Washing / Drying
Film ProcessingFilm Processing
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Sensitometric curve
H & D Curve (Hurter & Driffield)
Log Relative Exposure
Density (Log)
The point of solarisation
0.5
1.0
2.0
2.5
3.0
3.5
Maximum inherent film density 0.3
Film Characteristic CurveFilm Characteristic Curve
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films characteristic curve The position of the curve on the exposure axis
gives information about the films speed
Film Characteristic CurveFilm Characteristic Curve
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Log Relative Exposure
Density
A B C D E
Film A is faster than Film B
Film B faster then C
Film Characteristic CurveFilm Characteristic Curve
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M.S.RogersCopyright © 2004 TWI Ltd
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characteristic curve
The position of the curve on the exposure axis gives
information about the films speed
The gradient of the curve gives information on the films
contrast
Film Characteristic CurveFilm Characteristic Curve
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Log Relative Exposure
Density (Log)
Density obtained in a photographic emulsion does not vary linearly with applied exposure
Steeper gradientHighest contrast
Film Characteristic CurveFilm Characteristic Curve
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curve
The position of the curve on the exposure axis gives
information about the films speed
The gradient of the curve gives information on the films
contrast
The position of the straight line portion of the curve against
the density axis will show the density range within which the
film is at its optimal
Film Characteristic CurveFilm Characteristic Curve
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Log Relative Exposure
Density (Log)
Shoulder
Toe
Straight line section
Film Characteristic CurveFilm Characteristic Curve
M.S.RogersCopyright © 2004 TWI Ltd
T E
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G Y Information which can be obtained from a films
characteristic curve
The position of the curve on the exposure axis gives
information about the films speed
The gradient of the curve gives information on the films
contrast
The position of the straight line portion of the curve against
the density axis will show the density range range within
which the film is at its optimal
A new exposure can be determined for a change of film
type
Film Characteristic CurveFilm Characteristic Curve
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Changing DensityChanging Density
Log Relative Exposure
DensityDensity achieved 1.5
Density required 2.5
Determine interval between logs
1.8 - 1.3 = 0.5
2.5
1.5
1.3 1.8
Antilog of 0.5 = 3.18
Therefore multiply exposure by 3.18(measured density is lower than the required density)(measured density is lower than the required density)
Original exposure 10 mA mins
New exposure 31.8mA mins
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Changing FilmChanging Film
Log Relative Exposure
Density Obtain Logs for Films A and B at required density
Interval between logs = 0.15
1.7 1.85
Antilog of 0.15 = 1.42
Multiply exposure by 1.42
Original exposure 10 mA mins
New exposure 14.2 mA mins
2.5
A B
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G Y Wavelength - Gamma fixed, X-ray variable
Intensity - Gamma curies fixed, X-ray mA variable
Film density to be achieved
Film speed
Source to film distance
Material type
Material thickness
Determination of ExposureDetermination of Exposure
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of a gamma calculators/slide rule
Gamma calculators take into consideration Film density to be achieved Source type Activity of the source Film speed Source to film distance Material type Material thickness
Determination of ExposureDetermination of Exposure
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because the wavelength and intensity are variable
X-ray exposures are determined by the following
By using exposure charts
By reference to previous exposure records
By trial and error test shots
By a combination of the above
Determination of ExposureDetermination of Exposure
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5 10 15 20 25 30 35 40 4550
0.5
1.0
1.5
2.5
3.5
4.5
5.5
6.5
Chart based on
• Philips 300kV
• Screen = pb
• Dev = to spec
• Density = 2.0
300280250220200180150120100M
illi A
mps
Material thickness
Kilo VoltsExposure ChartExposure Chart
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1.50 2.00 2.50 3.0
1st DensityAchieved
0.50 5.00 7.50 10.00 12.00
0.75 2.60 3.90 4.90 6.00
1.00 1.75 2.50 3.33 4.00
1.50 1.00 1.40 1.90 2.40
2.00 0.75 1.00 1.25 1.60
2.50 0.55 0.80 1.00 1.20
2.75 0.50 0.70 0.95 1.10
3.00 0.45 0.60 0.80 1.00
3.50 0.38 0.55 0.70 0.86
3.75 0.36 0.53 0.65 0.80
4.00 0.35 0.50 0.60 0.75
Multiply 1st exposure by the above factors to achieve the density required.
Density Equivalent FactorDensity Equivalent Factor
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5 10 15 20 25 30 35 40 4550
0.5
1.0
1.5
2.5
3.5
4.5
5.5
6.5
Chart based on
• Philips 300kV
• Screen = pb
• Dev = to spec
• Density = 2.0
• Material C/S
300280250220200180150120100M
illi A
mps
Material thickness
Kilo VoltsExposure ChartExposure Chart
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50kv 100kV 150kV 220kV 400kV
Mg 0.6 0.6 0.5 0.08
Al 1 1 0.12 0.08
Ti 0.45 0.35
Cu 18 1.6 1.4 1.4
Steel 12 1 1 1
Zi 1.4 1.3 1.3
Radiographic Equivalence Chart
Exposure Equivalent ChartExposure Equivalent Chart
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5 10 15 20 25 30 35 40 4550
0.5
1.0
1.5
2.5
3.5
4.5
5.5
6.5
Chart based on
• Philips 300kV
• Screen = pb
• Dev = to spec
• Density = 2.0
• Material C/S
• Film Type
300280250220200180150120100M
illi A
mps
Material thickness
Kilo VoltsExposure ChartExposure Chart
M.S.RogersCopyright © 2004 TWI Ltd
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Agfa
Kodak
Fuji
2 2.5 3 3.5 4 5 6 7 8 10 12 14
150 100 80
CX AX MX
D7 D5 D4
Relative Film ExposuresRelative Film Exposures
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Original Exposure 4 mins
Film factor for CX 2.5
Film factor for MX 10
New Exposure = New film type X original exposureoriginal film
New Exposure = 10 x 4 = 16mins2.5
Relative Film ExposuresRelative Film Exposures
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5 10 15 20 25 30 35 40 4550
0.5
1.0
1.5
2.5
3.5
4.5
5.5
6.5
Chart based on
• Philips 300kV
• Screen = pb
• Dev = to spec
• Density = 2.0
• Material C/S
• Film Type
• FFD = 900
300280250220200180150120100M
illi A
mps
Material thickness
Kilo VoltsExposure ChartExposure Chart
M.S.RogersCopyright © 2004 TWI Ltd
M.S.RogersCopyright © 2004 TWI Ltd
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example 3 mA at 2 minutes = 6 mA minutes1 mA at 6 minutes = 6 mA minutes
Exposure formula
old exposure = old distance2
new exposure new distance2
E1 = D12
E2 D22
Exposure CalculationExposure Calculation
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Exposure control• For FFD/SFD change
T1 D1 2
T2 D2 2
=
T1 = New exposure time
T2 = Original exposure time
D1 = New FFD
D2 = Original FFD
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Exposure control• For FFD/SFD change
Example:
Calculate new exposure time for FFD = 600 mm
Original exposure at 500mm was 10 min
T1 =(600) 2
(500) 2 X 10 = 14.4 mins
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??
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