RADIOGRAPHIC TESTING

Radiation Recording Medium, used to detect Three-Dimensional volumnar defects.

It is a Two- Dimensional representation of a Three-Dimensional object Catching the Shadow of an object

LIGHT

Visible Invisible

VIBGYORUltra Violet Infra Red

Non Penetrating RadiationShadow formationby penetrating Radiation

Shadow formed by (Gamma Rays, X-Rays)Non-Penetrating Radiation

Photography

SHADOW

SOURCE

Point Like source(as small as possible)

X-Rays & Gamma Rays

X-Rays and Gamma Rays are made up of High Energy Photons

How to generate X-Rays?

When a fast moving electrons are suddenly stopped by the target X-rays are produced.

X-Rays Production is the reverse of Photo Electric Effect (PEE)

Electron energy only 1% of the 100% is converted into usable X-Rays others is heat.

mA. KV

Intensity/ Quantity Energy/ Penetrating Power

Properties of X-Rays:

1. Poly/ Chromatic in nature (Chromatic = Color, Wavelength)2. Ionization in nature3. Adjustable energy ( It is good for material inspection)4. Currents needed to operate5. Different cooling system necessary (Air cooling, Water cooling and Oil cooling)6. Installation cost high.

Gamma Ray Production:

ISO to PE

Definition:

Same Different

1. No.of Protons No. of nuetrons2. Atomic number Mass number3. Chemical Property Physical Property

Isotope:

ISOTOPE

Natural Artificial

Gamma Ray Majority of Production Gamma RayBeta Particle plus little amount of Beta ParticlesAlpha Particle

Artificial Isotopes: Iridium 192 Cobalt 60 Thulium 170 Ceasium 137 Selenium 75

Description Ir-192 Co-60

Half Life Period 75 days 5-3 years

Steel Penetration Power 3inch (20 to 75mm) 9inch (50 to 225mm)

Energy Output 0.55 RHM 1.35 RHM

Equivalent energy 375 KeV 1200 KeV

Specific Activity 400 Ci/gm 300 Ci/gm

KeV – Kilo Electron Volt RHM – Roentgen per Hour at 1 meter distance per curie

Intensity Energy

Curie Roentgen – In RT it is Milli Roentgen(mR)1R = 1000mR

Properties of Gamma Rays:

Mono / Chromatic Fixed energy, cannot alter its energy No need of current to operate Less installation cost

Camera RadioIsotope

1. Roli – India2. Techops3. Spec 2T4. Gammarid

Basic Concepts:

1. Basic Principle: Change in Radiation Absorptional differenece2. Artificial Defect : Penetrameter3. Probing medical : X-Rays and Gamma Rays4. Testing Media : Weldment, Casting, Forging, etc5. Recording Media : Double side coated film

Ideal Dark Room

Dry Side Wet Area

(Safe Light(Preferably Red in colour), SafeLight, Film Processing, Film Loading and unloading) Developer, Stop Bath, Fixer

Film:

Double side coated films are used in Industrial Radiography.

Film sheets generally available in the size of 12” x 16” It can be used in various sizes like 4x16, 8x16, 8x4, etc

Cassette:

Cassettes are generally used as a pair. Inner cassette and outer cassette will be used to avoid light leakage

Based on its Grain Size films are categorized into three types:

A: Large : Fast speed film – For Trick materiel inspectionB : Medium : Medium speed - For Vessel inspectionC: Fine : Slow speed - For thin material inspection

The following chart showing the characteristics of film. The characteristic curve will be Hurder Drifield curve (H&D)

Screens:

1. Intensification2. Filter – Absorb soft radiation

Films are exposed by electrons only

Note :

Only at 88 KeV, Lead produces electrons, so below 100 KeV no need to use Lead screen.

Classification of Screens:

Screens are classified into two types.

Metallic : Emits electrons Non- Metallic : Emits Light

PENETRAMETER

It is the Artificial defect used in RT

Purpose:

Sensitivity : Size of the defect Technique : Shape of the defect Materiel Identification : Carbon Steel and other then carbon steel

Selection of Penetramenter should be of 2% from the part thickness of the material

Types of Penetrameter:

There are tow types of Penetrameters are used:

1. Hole Type Penetrameter : Place adjacent of the weld2. Wire Type Penetrameter : EN and ASTM standards

Quality Level Subject Contrast level Sensitivity Level

1 2 1T

2 2 2T

3 2 4T

Calculation:

What would be the multiplication factor for Ir-192 decay for 5days

N = No e^-λt/T

No – Present curic strengthN – Curie Strength after 't' daysλ - Decay contrast 0.693t – Time relapsed 5 days T – Half life period of Isotope Ir-192

0.693 x 5------------ = 0.0462 75 x

e^-0.0462 = 0.95

1.8.2012 = 10Ci6.8.2012 = 10 x 0.95 = 9.5Ci11.8.2012 = 9.5 x 0.95 = 9.025Ci

Radiation Level in air:

What would be the radiation level in air for Ir-192 at a distance of 3 meters of 10Ci?

RL = Ci x RHM / d²

Here, R= 1000mR, RHM = 0.55 for Ir-192

RL = 10 x 0.55 x 1000 / 3 x 3

RL = 10 x x550 / 9

RL = 5500 / 9

RL = 611.11 mR/Hr

At what distance Radiation level would 5mR/Hr?

RL = Ci x RHM / d²

d² = Ci x RHM / RL

= 10 x x0.55 x 1000 / 5

= 550 x 2

d² = 1100

d = √1100

d = 33.16 meters

Shielding Thickness :

Half Value Layer (HVL):

After crossing Particular material trick by particular Isotope the Intensity reduced to halfits initial value.

Ir – 192: HVL Steel thickness : 12.5mm

Tenth Value Layer (TVL):

Reduced to 1/10 of its initial.

1 TVL = 3.33 HVL

1 TVL of Steel = 41.66mm

Calculate how many TVL's and HVL's required to reduce the radiation level 600mR/Hr to 3mR/Hr?

1. Radiation in air.

______________________________________________________ 600 mR/Hr

2. At 1st TVL

______________________________________________________ 600/10 = 60mR/Hr

3. At 2nd TVL

_____________________________________________________ 600/100 = 6mR/Hr

4. At 1st HVL

_____________________________________________________ 6/2 = 3mR/Hr

= 2TVL + 1 HVL

= 2 x (41.66) + 1(12.5)

= 83.2 + 12.5

= 95.7mm

Exposure Time Calculation:

It is the combination of

1. Radiation level formula2. Shielding Thickness value3. Film factor

ET = FF x RRV x (SFD)² / Ci x RHM

ET = 60 / (40 x40)

Particle thickness = 25mm

SFD = 24inch

Ci = 10Ci

Medium speed film = 1.6

RHM = 0.55

RRV = 4

= (1.6 x 4 x 24 x 24 / 10 x 0.55) x 60 / (40 x 40)

= 25 minutes

Geometrical Unsharpness:

Uɡ = Source Size x Object to Film Distance (OFD) ----------------------------------------------------------

Source to Film Distance - OFD

Uɡ = SS x OFD--------------SFD – OFD

Uɡ value maximum 1% of the part thickness

Part thickness = 25mm

SS = 1.5 mm

SFD = 600mm

1% of 25mm = 0.25mm

1.5 x 25----------- = 0.065 mm600 – 25

Equivalent Penetrameter sensitivity (EPS):

Expressed in 1%

100 IQI Thickness x Visible Hole PenetrameterEPS = ------------------ ------------------------------------------------------

Part Thickness 2

EPS = 100 TH-------------- ----------- X 2

X = 2 inch

T = ASTM 40 = 0.040 inch

H = 2T

100 0.040 x 2 x 0.040 = --------- -------------------------

2 2

= 50 x 0.040EPS = 2%

Film Processing:

At controlled room temp 20°C or 68°F

1. Developer : Make latent image visible2. Stop Bath : Stop the function of the developer temporarily3. Fixer : (a) Remove unexposed Silver (Clearing time)

(b) Fix the image (Twice the clearing time)4. Running Water : Remove all the processing chemicals5. Wetting agent : Help to water quick to drain6. Drier : Helps to film dry and view

Wrapper:

• Edge screen• Center screen

Viewers:• Strip viewer (Weld)• Spot Viewer (Casting)

Density:

• Amount of film darkness

It varies depending upon:

• Particle thickness• Type of Radiation• Internal Scattering• Film• Degree of development

Density expressed in number:

No units expressed , only in numbers

D = Log10 II

------ TI

Radiation Safety:

Personnel Safety:

1 Hr = 1.5mR

1 Day = 12mR

1 year = 3000mR

Banking Concept:

13 = 3R (N-18)

if Age = 30

= 3R(30-18) = 3R(12) = 3.6R or 36000mR

Defect Image:

Black:1. Reduction of Metal

a. Artificial (Hole type IQI)b. Natural (LOF, LOP, Crack)

2. Low atomic number material inclusiona. Porosity b. Slag

White:

• Addition of the metal:◦ Excess penetration

• Inclusion:◦ High atomic number material◦ Tungsten inclusion

CODE:

ASME Section V, Article 2

Standard:

• ASTM E94 / E1742• ASTM E747 - Wire type IQI• ASTM E999 - Manual Film processing• ASTM E1025 - Hole type IQI• ASTM E1030 - Casting• ASTM E1032 - Welding• ASTM E1079 - Calibration of Densitometer

Reference Radiographs:

• E446 upto 2inch• E186 2 to 4½• E280 4½ to 12

Acceptance Standard:

• ASME BPVC Sec VIII, Div 1◦ Appendix 4, Porosity Chart◦ AWS 51 : Linear Indication Chart

• Crack, LOP, LOF rejected without grading