Rt Level II Course Notes

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RADIOGRAPHIC TESTING SNT TC-1A 1996 OF ASNT-LEVEL II

Bvk

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INTRODUCTION TO NDT

NDTNDT

1.Visual Testing(VT) 1.Radiography Testing(RT)

2.Magnetic Particle Testing (MT) 2.Ultrasonic Testing(UT)

3.Penetrant Testing (PT)

SURFACE VOLUMINAR

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INTRODUCTION TO NDT

Conventional NDTConventional NDT Methods Methods• Accoustics Emmission Testing (AET)

• Leak Testing(LT)

• Thermal Infrared(IR)

• Eddy Current Testing(ET)

• Neutron Radiography(NRT)

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CONTENTS

• Basic Radiation Physics.• Equipment (x-ray, -ray).• Films Screens & Processing .• Geometric Considerations & Quality.• Radiography Techniques.• Discontinuties & Process.• Interpretation/Codes & Standard.• Safety.

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Basic Radiation Physics(BRP)

Fundamental Particles:Fundamental Particles:

• Basic particles of an atom are Proton, neutron and electron.

• The proton is positively charged and electron is negatively charged, Neutron has no charge.

• The mass of Neutron and Proton are 1 and electron is 1/1840 of a proton.

• Let us see how the atom is arranged.

Nucleus consist of Protons and Neutrons

Electrons revolving around nucleusN

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BRP-Definitions

• Atom:Atom:It is the smallest Particle of an element.

• Atomic No:Atomic No:It is the No.of protons or No.of electrons present in an atom.It is denoted by the letter z.

Z = P = E.

• Atomic Mass or Mass No:Atomic Mass or Mass No:

It is the sum of protons and neutrons present in the nucleus of an atom.It is denoted by the letter ‘A’.

A = P + N.

A = E + N.

A = Z + N.

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BRP-Definitions contd.

• ISOTOPES:ISOTOPES:

Atoms of the same element having the same atomic No. but different Mass No.

eg: Uranium – 92U233, 92U235 ,92U238.

• RADIOACTIVE ISOTOPES:RADIOACTIVE ISOTOPES:

The isotopes that emit radiation.

They are available.

1.Natural Co -59.

2.Artificial Ir-192.

3.Fission fragments. Th-170.

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BRP-Definitions contd.

• RADIOACTIVITY:RADIOACTIVITY:

The spontaneous and continuous emission of Radiation by some Radioactive elements due to atomic disintegration.The activity/ strength is usually measured in Curies(Ci).S.I unit is Bequerel(Bq).

• Half Life Period:Half Life Period:

The time taken by a Radioactive Isotope to reduce its activity to half of its initial amount.

Iridium Ir-192 74.5 days.

Cobalt Co–60 5.3 years.

Thulium Tu-170 130 days.

Cesium Cs-137 33 years.

Radium Rd 1900 years.

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BRP-Radiation Units .

CURIE:CURIE:

1 Ci = 3.7 x 10 10 disintegration per second (dps)

1 Bq = 1 dps

1 Ci = 3.7 x 10 10 Bq

= 37 x 10 9 Bq

= 37 Mega Bq

1 Ci = 37 GBq

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BRP-Radiation Units contd.

ROENTGEN :ROENTGEN :

Roentgen is the unit for measurement of Radiation.

1 Roentgen is the amount of Radiation that can produce 1 e.s.u. of charge in 1cc of air at S.T.P.

1 Roentgen (R) = 1000 milli Roentgen(mR).

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BRP-Properties.

Properies of Electro Magnetic radiation :Properies of Electro Magnetic radiation :

• They travel in a straight line

• They are not effected by magnetic or electric fields

• They start ionisation

• They damage living tissues

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BRP-Electromagnetic spectrum

• Let us see the electro magnetic spectrum

• ------------- Radio waves (m+)• -------------TV Waves (Cm)•-------------Rador Waves (mm)•-------------Infrared (7500Ao)•-------------Visible Spectrum ( 4000Ao)•--------------UltraViolet ( 3650Ao)•--------------X-rays (0.1Ao to 0.001Ao)•--------------Gamma Rays (0.1Ao to 0.001Ao)•Note : 1Ao = 10-7 mm or 100 ηm.

As the wavelength decreases penetration will increase

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BRP-Electromagnetic spectrum

Electro Magnetic Spectrum

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BRP-Radition Types

• Types of Electro Magnetic radiation

1.Alpha rays

2.Beta rays

3.Gamma rays

4.X rays

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BRP-Alpha Rays

• Alpha Particles. Certain radionuclides of high atomic mass (Ra226, U238, Pu239)

decay by the emission of alpha particles. These alpha particles are tightly bound units of two neutrons and two protons each (He4 nucleus). Emission of an alpha particle from the nucleus results in a decrease of two units of atomic number (Z) and four units of mass number (A). Alpha particles are emitted with discrete energies characteristic of the particular transformation from which they originate. All alpha particles from a particular radionuclide transformation will have identical energies.

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BRP-Beta Rays

• Beta Particles. A nucleus with an unstable ratio of neutrons to protons

may decay through the emission of a high speed electron called a beta particle. This results in a net change of one unit of atomic number (Z). The beta particles emitted by a specific radionuclide range in energy from near 0 up to a maximum value characteristic of the particular transformation.

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BRP-Gamma Rays

• Gamma rays. A nucleus which is in an excited state may emit one or

more photons (packets of electromagnetic radiation) of discrete energies. The emission of gamma rays does not alter the number of protons or neutrons in the nucleus but instead has the effect of moving the nucleus from a higher to a lower energy state (unstable to stable). Gamma ray emission frequently follows beta decay, alpha decay, and other nuclear decay processes.

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BRP-X Rays

• X rays. X-rays are also part of the electromagnetic spectrum and are distinguished

from gamma rays only by their source (orbital electrons rather than the nucleus). X-rays are emitted with discrete energies by electrons as they shift orbits following certain types of nuclear decay processes. Internal conversion occurs in a isotope when the energy is transferred to an atomic origin electron that is then ejected with kinetic energy equal to the expected gamma ray, but minus the electron's binding energy. The vacancy in the atomic structure is filled by an external electron, resulting in the production of x-rays. Thulium-170 is a good example of this type of disintegration. When Thulium-170 looses its energy it will exhibit a 60 % probability of interaction with an orbital electron thus producing x-radiation.

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BRP-EMR

Penetration

Power

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Gamma Ray Sources

Industrial Radiography mostly uses gamma radiation sources of Ir-192 and Co –60 for the following range of thickness.

Ir-192 19 to 62 mm of steel.

Co-60 32 to 200 mm of steel.

Radioactive decay measurement:Radioactive decay measurement:

At = Ao e – λt.

Where At Activity after time period ‘t.’

Ao Initial activity.

λ decay constant = 0.693 / Half Life Period.

t time period e exponential constant.

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Gamma Ray Sources

Example Problem:

Find the activity of an Ir-192 source of activity 10 Ci after a time period of 30 days.

Formula: At = Ao e – λt.

= 10 x e – 0.693 / 74.5 x 30.

= 10 x e – 0.279.

= 10 x 0.756.

= 7.56 ci.

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Gamma Ray Sources

•Output of Isotope.RHM:RHM:Roentgen hour per metre.

It is the amount of radiation from a 1 ci Isotope at a distance of 1 metre for 1 hour.

For Ir- 192 0.5 RHM.

For Co-60 1.3 RHM.

ENERGY:ENERGY:

For Ir-192 range 0.4 to 0.7 mev.

mean value 0.55 mev.

For Co-60 range 1.17 to 1.33 mev.

mean value 1.25 mev.

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Gamma Ray Sources

Inverse Square Law.Inverse Square Law. I1 D2

2.

-------- = ---------.

I2 D12.

Where I1 = Intensity of Radiation at distance D1.

I2 = Intensity of Radiation at distance D2.

In instance where I1 is not given directly I1 can be calculated as follows.

I1 = Source Strength x RHM x 1000 mR/hr. In this case.

D1 = 1 metre because RHM is for 1 metre distance.

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Gamma Ray Sources

Example Problem:

Find the Radiation intensity at 20 metre distance from a source producing 200 mR/hr at 10 metre distance.Directly substituting the above datas in inverse square law,

200 20 2 I2 200 x 100.

----- = ------ = -------------.

I2 10 2 400.

Thus I2 = 50 mR/ hr.

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Gamma Ray Sources

Example Problem:

Find the Radiation intensity from a 15 ci Ir-192 source at a distance of 30 metres.Substituting I1 = SS x RHM x 1000 and D1 = 1 metres ,

15 x 0.5x 1000 30 2 I2 7500.

------------------ = ------ = -------------.

I2 1 2 900.

Thus I2 = 8.33 mR/ hr.

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Gamma Ray Sources

SHIELDING.SHIELDING.

Half Value Thickness (HVT):Half Value Thickness (HVT):

It is the thickness of Shielding material that can reduce the radiation intensity to half (1/2)of its initial amount.

Tenth Value Thickness (TVT):Tenth Value Thickness (TVT):

It is the thickness of Shielding material that can reduce the radiation intensity to one – tenth (1/10)of its initial amount.

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Gamma Ray Sources

Half Value Thickness (HVT) in mmHalf Value Thickness (HVT) in mm

Material

Source

Depleted

Uranium

Lead Steel Concrete

Ir-192 3.3 5.0 12.5 44.0

Co-60 6.0 12.0 20.0 66.0

1 TVT = 3.323 HVT1 TVT = 3.323 HVT

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Gamma ray Sorces

Radioaction Intensity after shielding measurement:Radioaction Intensity after shielding measurement:

I = Io e – μt.

Where I Intesity of Radiation after shielding.

Io Intesity of Radiation without shielding.

e exponential constant.

μ Linear attenuation / absorption co efficient = 0.693 / HVT.

t thickness of shielding material.

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Gamma Ray Sources

Example Problem:What is the radiation intensity when 200 mR/hr Radiation from an Ir-192 source passes through 50mm of steel.

Formula: I= Io e – μt.

= 200 x e – 0.693 / 12.5 x 50.

= 200 x e – 2.772.

= 200 x 0.0625.

= 12.5 mR/hr.

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Gamma Ray Sources

Example Problem:

What is the radiation intensity from a 20 ci co 60 source at a distance of 40 metres with a shielding of 500 mm concrete.

Soln:

This problem is divided into two steps.First find the intensity without shielding using inverse square law and then use the shielding formula.

Step1:Substituting I1 = SS x RHM x 1000 and D1 = 1 metres ,

20 x 1.3x 1000 40 2 I2 26000.

------------------ = ------ = -------------. = 16.25 mR/hr.

I2 1 2 1600.

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Gamma Ray Sources

Step2:Now 16.25 mR/hr radiation after passing through 50mm of concrete.

Using the formula I = Io e – μt. We get,

= 16.25 x e – 0.693 / 66 x 500.

= 16.25 x e – 5.25.

= 16.25 x 0.0052.

= 0.0845mR/hr.

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Gamma Ray Sources

Equipments:Equipments:

Encapsualtion:

The process of sealing of radioactive pellets in capsules or capsuling pellets .

Packing

Pellets

Capsule

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Gamma Ray Sources

Equipments sketch:Equipments sketch:

Radiography camera with driving unit.

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Gamma Ray Sources

AAccccesoriesesories::

•A Isotope trnsport container.

•Collimator for prevention of radiation passing 360 deg.Best acessory for safety.

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Gamma Ray Sources

Specific Activity:

Activity per unit mass.Its unit is ci/gm.Lets take 1gm each of Ir 192 ,Co 60 and Cs 137 isotopes and load in a nuclear reactor for 2 to 3 months.Note the activity obtained.It shall be approximately.

Ir 192 - 2 ci / gm, Co 60 - 1 ci/gm and Cs 137 – 0.5 ci/gm.These are the Specific activity values.Suppose we want to make 10 ci each we may require as follows.

Ir- 192 Co – 60 Cs – 137.

5gm 10gm 20gm.

From the above we can infer that a source with high specific activity will have smaller physical size.

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X-Ray Sources

X rays are produced when a high speed electrons are suddenly stopped by an obstacle.In other words X rays are produced by decelerating fast electrons.

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X-Ray Sources

X ray tube:

Fast Electrons

Cathode(Filament)

Anode(Tungsten Target)

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X-Ray Sources

Controls in an X ray machineTube VoltageTube CurrentTime

Tube voltage - Kilo voltage (Kv):Tube voltage - Kilo voltage (Kv):When Kv is raised,

•Speed of electrons increase

•Penetration Power increase

•Quality & Quantity of radiation increase

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X-Ray Sources

Controls in an X ray machineTube current – milli Ampere (mA):Tube current – milli Ampere (mA):When mA is raised,

•Amount of electrons increase

•Quantity of Radiation increase

•Intensity of radiation increase Time :Time :Depending on Kv,mA & thickness different exposure time are set

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X-Ray Sources

Types of X ray

Continuous X ray (Brehmstralung Rdn):It occurs due to electrical disturbance

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X-Ray Sources

Types of X ray.Characteristic X ray :

It occurs due to electronic disturbance.The percentage of occurance is less.

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X-Ray Sources

Types of RectificationSelf RectificationGreinisher circuit

Types of X-ray TubeUni Polar Tube ( x ray crawlers)Bi Polar Tube (Generally used)

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X-Ray Sources

Applications

MedicalMedical Less than 100 Kev

Industrial Industrial 100 Kev – 25 Mev

* Kev Kilo electron Volt

* Mev Mega electron volt

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X-Ray Sources

Types of X ray Machines

•Portable

•Mobile•Stationary (High energy X ray Machines):

1. Vandegraff Generator

2. Cyclotron

3. Betatron

4. Linac

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X-Ray Sources

Vandegraff Generator 1 – 5 Mev.An American physicist, R. J. Van de Graaff developed one of the first particle accelerators in the early 1930’s. Known as the Van de Graaff generator, electrostatic generator. This device accelerates electrons to produce high energy radiation. Initially, the generator was capable of producing x-radiation in the 1 to 2 MeV range. Continued design changes produced even higher energies. .

The generator operates by projecting electrons onto a moving belt. The electrons ride on the belt and are collected at the opposite end on a high voltage terminal. Here a heated filament supplies electrons for acceleration, a glass/metal tube with a vacuum provides a path for particle acceleration away from the high voltage terminal. At the end of the tube is a target, whereby the accelerated particles can interact producing high energy radiation.

Not long after the development of the Van de Graaff generator, it was determined that charged particles could be accelerated to very high speeds by driving them in a circular path. This was accomplished by the application of strong electromagnets. A variety of these have been developed to produce even higher energy radiation than that of the Van de Graaff generator.

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X-Ray Sources

Cyclotron 5 – 10 Mev.

Again in the early 1930’s, E.O. Lawrence also an American physicist developed the Cyclotron. This device is capable of accelerating charged particles (protons) in a circular path to energies that exceed 10 MeV. The Cyclotron is comprised of a large cylindrical box sandwiched between the poles of an electromagnet. The box is evacuated until a high vacuum exists. Charged particles are fed into the cylindrical box. Two `D’ shaped electrodes placed back to back with a gap between them are connected to a high voltage source inside of the box. By rapidly reversing the electric charge on the electrodes, and the due to the presence of the magnetic field of the electromagnets, the charged particles move in a circular fashion. Each time the charged particles cross the gap of the electrodes, the particles gain energy, and begin moving towards the outside of the cylindrical box. Once the charged particles reach the outer edge of the box, they are deflected towards the target, resulting in high energy x-radiation. ..

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X-Ray Sources

Betatron 5 – 10 Mev.

Betatron, was developed in the early 1940’s by a man name Donald Kerst at the University of Illinois. Kerst’s Betatron is used to accelerate electrons (beta particles) to produce high energy x-radiation. The first Betatron developed produced a radiation energy of a little more than 2 MeV. Continued development allowed the Betatron to generate energies as high as 300 MeV. .

The Betatron operates on the principle of the transformer, the primary side consists of a large electromagnet, and the secondary side is the electron stream that is being accelerated. The electrons are accelerated in a circular tube known as a doughnut that has been evacuated. When the electrons have achieved maximum energy, they are directed to a target, the resulting interaction is the production of high energy x-rays.

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X-Ray Sources

Linear accelerator(Linac) 10-25 Mev.

Linear accelerator is designed to move charged particles at high velocities along a straight path to a target. Linear accelerators are comprised of a series of drift tubes mounted inside of an evacuated chamber. The charged particles are fed into one end of the chamber, and accelerated by a alternating high frequency voltage that is applied to the drift tubes. Due to high frequency, the drift tubes alternate charges, resulting in repulsion of the particles as they leave a tube, and attraction by the next tube. It is this alternating high frequency that accelerates the particles as they cross the gaps between tubes/Present day Linear accelerators may be several miles long, capable of producing extremely high energy x-rays.

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X-Ray Sources

Measuring the effective Focal Spot

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Interaction of Radiation with Matter

Photo Elecric Effect:

Only electron is ejected.

less than 100 Kev.

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Compton Scattering

Greater than 100 Kev but less than 1000Kev

Electron + Photon is ejected

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Pair Production

Greater than 1.02 Mev

Electron + Positron ejected

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FILMS,SCREENS & PROCESSING

Structure of film

Super Coating (2-3 microns)

Polyester Base 175 microns

Gelatin Coating 2 microns

Silver bromide 1.5 microns

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Types of film• Slow Film:Slow Film:Fine Grain size,Maximum exposure time and

best quality

• Medium Film:Medium Film: Medium grain size,moderate exposure time and quality

• Fast Film:Fast Film: Coarse grain ,Least exposure time and Poor quality

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Types of Screens.• Metallic Screen:Metallic Screen: Lead foil Screens. Lead + Antimony.Widely used.

• Fluoroscent Screen:Fluoroscent Screen: Calcium Tungstate CaWO4.They absorb X or γ Photons and release

light photons that show fluoroscence.

• Fluorometallic Screen:Fluorometallic Screen: Metallic + Fluoroscent . Not mostly used.

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Function of Screen.

Primary:

It emits electrons thus providing electron intensification.

Secondary:

Reduces Exposure Time.

Reduces Back Scatter.

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Processing Developing Stop bathing Fixing Washing Drying

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DevelopingDevoloping usually takes place in a chemical called developer.Developer is a base with Ph value 9.5 to 11.5 .It reduces Silver bromide crystals on the exposed part to metallic silver and bromine ion.It contains the following chemicals

•Metol,Hydroquinone or phenidione – Developing Action

•Sodium Sulphite – Preservative Controls oxidation

•Sodium carbonate – Accelerator

•Potassium Bromide – Anti fogant

Normal developing time shall be 5 mts at a temperature of 20 deg c

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Developing.Devoloping time is very crucial.As the temperature increases development time reduces and vice versa.

When the developing time increases above the manufacturers recommended time film contrast decreases .

Developer is constantly agitated to maintain uniform supply of electrons.

After prolonged usage,the developer activity reduces and the activity can be maintained by the addition of replenishers.

Typical temperatures and development time.

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Stop Bathing.

The purpose of Stop bath is to stop developing action.

It is a mixture of water + Acetic Acid.

Normal Stop bathing time shall be 1 minute.

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Fixing.Fixing process takes place in a solution called Fixer.The main function of a Fixer is to remove the unexposed silver grains.Fixer is an acid with a Ph value of 4.5.The norml fixing time shall be 10 to 15 minutes and the minimum shall be half the clearing time.It contains the following chemicals.

•Sodium thio sulphate ( Hypo) –Fixing action.

•Sodium sulphite – Control oxidation (Preservative).

•Acetic acid – Accelerator , maintain Ph value.

•Potash Alum - Hardener.

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Washing.To remove the traces of salts of chemicals from solution washing is done.

Washing is done normally in running water.

There are special washing process where it utilises two tanks called cascading.

Normal washing time shall be 2o to 25 minutes.

Washing has a great impact on the storage life of radiographs.

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Drying.Drying shall be done in ordinary air.

Special drying cabinets are available for quicker drying.But care should be taken that the radiograph shall not be kept inside the oven for a long time.

Sometimes wetting agents are added to water during washing proces to enable quicker drying.

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The Process

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Geometric Considerations & Qualities of a Radiograph

QUALITY

Density Sensitivity

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Density.Density is the degree of darkness or blackening in a Radiograph.

D = Log ( Ii / It ).

Where Ii Incident intensity of light.

It Transmitted intensity of light.

The unit of light is Lux.Our eye is sensible to light of.

30 – 100 cd/ m2. whereas the maximum lighting capacity.

is 10,000 cd/ m2. Hence we cannot read more than density 4.

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Normal Density: 2.0 to 2.5Acceptable Density: For X ray 1.8 to 4.0 For Gamma ray 2.0 to 4.0 For Castings 1.5 to 4.0

I i (units) It (units) Transmittance % Density

100 100 100 0

100 10 10 1

100 1 1 2

100 0.1 0.1 3

100 0.01 0.01 4

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Density Measurement:Density Measurement:

1.Densitometer

2.Density Strip

Film Factor:Film Factor:

The amount of radiation required by a particular film to reach density 2.0

Film Source NDT 65 NDT 70 AGFA D7 AGFA D4

Ir-192 1.4 1.0 1.1 3.5

Co-60 2.8 2.0 2.2 7.0

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Sensitivity.Sensitivity.Before going to sensitivity in detail lets see the factors that effect sensitivity.

Sensitivity is mainly affected by two factors.

1.Definition or Unsharpness.

2.Contrast.

1.Definition or Unsharpness:

The sharpness of the outline of an image boundary is called Definition or Unsharpness.It is denoted by the letter μ.

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Definition or UnsharpnessDefinition or Unsharpness

1.Geometric Unsharpness μg

2.Movement Unsharpness μm

3.Scatter or Screen Unsharpness μs

4.Film or Inherant Unsharpness μi

Total Unsharpness μ = μg2+ μm

2+ μs2+ μi

2

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Method to find Geometric UnsharpnessMethod to find Geometric UnsharpnessSource(S)

SOD

OFD Object

Film

µg = S x OFD/SOD where S Effective Source size

OFD Object to Film distance

SOD Source to object distance

Method to find Geometric UnsharpnessMethod to find Geometric UnsharpnessSource(S)

SOD

OFD Object

Film

µg = S x OFD/SOD where S Effective Source size

OFD Object to Film distance

SOD Source to object distance

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Acceptable Acceptable µµg or Ug:g or Ug:For thickness upto 50mm 0.5 mm ( 0.020” ).

µµg = S x t / d for Gamma ray.g = S x t / d for Gamma ray.

µµg = f x t / d for X ray.g = f x t / d for X ray.

As a rule of thumb the d/t ratio shall be 8 or more.

Determination of Effective source size:Determination of Effective source size: Source.

Height(h) Effective dia(D) D = h 2 + d 2.

Actual dia(d).

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µg shall always be as low as possible.

To reduce To reduce µµg.g.

Reduce the Source size.

Reduce the OFD.

Increase the SOD.

The nominal source dia shall be 2.5mm and hence the effective source size shall be 4.0mm.

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• RADIOGRAPHIC CONTRAST.RADIOGRAPHIC CONTRAST.The difference in densities between adjacent areas in a radiograph.

Radiographic Contrast.

Subject Contrast Film Contrast. 1.Thickness of material 1.Type of film.

2.Density of material 2.Processing condition.

3.Energy selection.

4.Scattering.

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Scattering.Scattering.Scattering are low energy radiation of longer wave length.Types of Scatter:Types of Scatter:1.Back Scatter ---eg: Flloors,Back walls,film holders etc.2.Side Scatter ---eg: Side walls or side lying objects.3.Forward or internal Scatter ---eg:the object itself.Methods to avoid Scatter:Methods to avoid Scatter:1.Using Filters – Lead,Steel,Copper,Barium,Clay.2.Masks.3.Diaphragms.4.Lead Shots.

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Characteristic Curve or Sensitometric Curve or H& D Curve or Hurther & Characteristic Curve or Sensitometric Curve or H& D Curve or Hurther & Drifield curve.Drifield curve.

6.0.

5.0.

4.0 A - B Under Exposure.

B – C Straight Line.

2.0 C – D Over Exposure.

0.7 E Point of Solarisation.

The slope of the straight line portion in a H & D curve is a measure of. Film contrast or average gradient.

B

D

E

C

A

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Sensitivity:Sensitivity: The least discontinuity that can be visible in a Radiograph.

To measure sensitivity Image Quality Indicators (IQI) are normally kept on the Radiograph.

Types of IQI:

1.Wire Type.

2.Step Hole Type.

3.Strip Hole Type.

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Wire Type IQI 1.DIN Wire Type

DIN – Dutch Industrial Normale 62 - 1962 Year of invention of Penetrameter

Fe – (Ferrous)Steel & Steel Alloys

DIN 62 Fe

1 ISO 7

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DIN Wire Type

The diameter of a DIN wire type penetrameter varies by a geometric progression of 0.8.Each penetrameter will have 7 wires and 2 or 3 wires will be repeated on the next series.The penetrameter material shall be the same or similar material to that of the object being radiographed.For eg radiographing aluminium we need to use Al penetrameter.

DIN Wire Type Thickness range

1 ISO 7 > 50mm

6 ISO 12 >19mm < 50mm

10 ISO 16 <19mm

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DIN Wire DIN Wire DiametersDiameters

Wire No. THICKNESS1 3.22 2.53 24 1.65 1.256 17 0.88 0.6259 0.5

10 0.411 0.3212 0.2513 0.214 0.1615 0.1316 0.1

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ASTM Wire Type :The left side 01,02,03,04,05 gives the material Grouping and on the right A,B,C & D gives the four sets of wires.

Each penetrameter contains 6 wires out of which 1 wires shall be repeated in the next adjacent set.

Totally the four sets A,B,C & D will therefore account 21 wire diameters.

The diameter varies by a geometric progression of 1.25.

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ASTM Wire Type :

Light Metal Group

Group No Material

03 Magnesium

02 Aluminium

01 Titanium

Heavy Metal Group

Group No

Material

01 Steel

02 Aluminium bronzes & Nickel Aluminium bronze

03 Nickel-chromium-Iron alloy

04 Nickel copper

05 Tin bronzeincluding Gun metal & valve bronze.

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ASTM Wire Type :

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Finding Sensitivity:

Sensitivity = Least wire dia visible x 100 % Thickness.

Acceptable sensitivity shall be 2% or < 2 %. (Pressure Vessels & Pipelines).

Hence penetrameter selection shall be 2 % of material thickness.

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STRIP HOLE TYPE PENETRAMETER:

(T)Penetrameter designation/Thickness

in Thou/ mils 1 Thou = 1 / 1000 inch

1 Thou = 1 mil

1 mm = 40 Thou

2020

2T

1T

4T

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STRIP HOLE TYPE PENETRAMETER

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Sensitivity Levels Sensitivity

LevelsEquivalent Sensitivity

1-1T 0.7%

1-2T 1.0%

1-4T 1.4%

2-1T 1.4%

2-2T 2.0%

2-4T 2.8%

4-1T 2.8%

4-2T 4.0%

4-4T 5.6%

Nuclear

Pressure Vessels & Pipelines

Structural

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Sensitivity Level 2 – 1T.Sensitivity Level 2 – 1T.Here 2 implies penetrameter selection shall be 2 % of material thickness and the least visible hole was 1 T.

Obtained Sensitivity.Obtained Sensitivity.

= = 100 TH.

X 2.

Where X - material thickness in Thou.

T - Penetrameter thickness in Thou.

H- Hole dia visible.

04/11/23 89


Example Problem:

Job thicknes X = 20 mm = 800 Thou

IQI Thickness T = 15 Thou

Hole dia H = 2T = 2 x 15 Thou = 30 Thou

Sensitivity = 100 15 x 30

800 2

= 1.875%

04/11/23 90

RADIOGRAPHY TECHNIQUES

• Single Wall Single Image (SWSI)

• Double Wall Single Image(DWSI)

• Double Wall Double Image(DWDI)

• Single Wall Panaromic (SWP)

04/11/23 91


SWSI.For Radiographing Tanks,Vessels and large dia open end pipes.

Best Technique.

IQI Selection:

SWT + one Reinforcement.

Minimum SFD:

Length of Coverage & Ug requirements.

04/11/23 92


DWSI.For pipes with OD > 89mm.

Minimum 3 exposures placed at 120 deg apart.

IQI Selection:

SWT + one Reinforcement.

Minimum SFD:

Normally Pipe OD.

Ug requirement & not less than pipe OD.

04/11/23 93


DWDI (Elliptical Exp).For Radiographing pipe with.< 89mm OD.Minimum 2 exposures placed at 90 deg apart.

IQI Selection: DWT + one Reinforcement.

Minimum SFD:Ug requirement.Rule of thumb d/t shall be 8 or more.

04/11/23 94


DWDI(Super imposed).For Radiographing pipe with.

< 89mm OD particularly on.

Nozzles,Flanges etc.Minimum 3 exposures placed at 120 deg apart.

IQI Selection:

DWT + Two Reinforcement.

Minimum SFD:

Ug requirement.

Rule of thumb d/t shall be 8 or more.

04/11/23 95


SWP.For radiographing large dia pipelines, cirseam welds in Pressure vessels & Tanks where source is positioned on axis.The entire circumference is completed in a single exposure.IQI Selection: SWT + One Reinforcement.Minimum 3 IQI placed at 120 deg apart.Minimum SFD:Half the Diameter of pipe.

04/11/23 96


Exposure Time:

E = F.F * 2 X/HVT * SFD2 * 60

S.S * RHM * 1002

Where FF - Film Factor

X - Material thickness in mm

HVT - Half Value Thickness in mm

SFD - Source to Film Distance in cm

SS - Source Strength

RHM - Roentgen hour per metre

04/11/23 97

RADIOGRAPHY TECHNIQUESSTEEL EQUIVALENT FACTOR.

.X-rays.

Gamma Rays.Material.50 kV.

100 kV.150 kV.220 kV.400 kV.

1000 kV.2000 kV.4 to 25 .

MeV.Ir .

192.Cs .137.Co. 60.

Radium.Magnesium.0.6.0.6.0.5.0.08. . . . . . . . .Aluminum.1.0.1.0.0.12.0.18. . . . .0.35.0.35.0.35.0.40.2024 (aluminum) alloy.2.2.1.6.0.16.0.22. . . . .0.35.0.35.0.35. .Titanium. . .0.45.0.35. . . . . . . . .Steel. .12.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.18-8 (steel) alloy. .12.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.Copper. .18.1.6.1.4.1.4. . .1.3.1.1.1.1.1.1.1.1.Zinc. . .1.4.1.3.1.3. . .1.2.1.1.1.0.1.0.1.0.Brass.

. .1.4.

1.3.

1.3.

1.2*.

1.2*.

1.2*.

1.1*.

1.1*.

1.1*.

1.1*.

Inconel X alloy. .16.1.4.1.3.1.3.1.3.1.3.1.3.1.3.1.3.1.3.1.3.Zirconium. . .2.3.2.0. .1.0. . . . . . .Lead. . .14.12. .5.0.2.5.3.0.4.0.3.2.2.3.2.0.Uranium. . . .25. . . .3.9.12.6.5.6.3.4. .

04/11/23 98

RADIOGRAPHY TECHNIQUESX-ray Exposure Chart:

.X-rays.

Gamma Rays.Material.50 kV.

100 kV.150 kV.220 kV.400 kV.

1000 kV.2000 kV.4 to 25 .

MeV.Ir .

192.Cs .137.Co. 60.

Radium.Magnesium.0.6.0.6.0.5.0.08. . . . . . . . .Aluminum.1.0.1.0.0.12.0.18. . . . .0.35.0.35.0.35.0.40.2024 (aluminum) alloy.2.2.1.6.0.16.0.22. . . . .0.35.0.35.0.35. .Titanium. . .0.45.0.35. . . . . . . . .Steel. .12.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.18-8 (steel) alloy. .12.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.Copper. .18.1.6.1.4.1.4. . .1.3.1.1.1.1.1.1.1.1.Zinc. . .1.4.1.3.1.3. . .1.2.1.1.1.0.1.0.1.0.Brass*.

. .1.4*.

1.3*.

1.3*.

1.2*.

1.2*.

1.2*.

1.1*.

1.1*.

1.1*.

1.1*.

Inconel X alloy. .16.1.4.1.3.1.3.1.3.1.3.1.3.1.3.1.3.1.3.1.3.Zirconium. . .2.3.2.0. .1.0. . . . . . .Lead. . .14.12. .5.0.2.5.3.0.4.0.3.2.2.3.2.0.Uranium. . . .25. . . .3.9.12.6.5.6.3.4. .

04/11/23 99


Time Distance Formula.Time Distance Formula.

T1 D1 2.

-------- = ---------.

T2 D22.

Where T1 = Exposure time at distance D1.

T2 = Exposure time at distance D2.

Exposure time is directly proportional to the distance.

This formula is also called as Direct square Law.

04/11/23 100

SPECIAL RADIOGRAPHY TECHNIQUES

Parallax PrincipleParallax Principlea/ b = (D-d) / d ad = bD –

bd ad + bd = bD

d(a + b) = bDd = bD/ (a + b) = defect shift x SFD

(source shift + defect shift)

a

b

Source Positions

d

D

Object

Film

defect

04/11/23 101


Parallax Principle(Lead Marker Parallax Principle(Lead Marker Method)Method)

By similar triangles ratio

a = d

b t

d = at / b

Depth of defect d =

defect shift(a) x thickness(t)

marker shift (b)

a bd

t

Marker

Source positions

04/11/23 102


Double Exposure Parallax Double Exposure Parallax PrinciplePrinciple

04/11/23 103


Stereo Radiography.Stereo Radiography.

• Three dimensional effect is obtained using a stereoscope.

04/11/23 104


FluoroscopyFluoroscopy

04/11/23 105


Flash Radiography.Flash Radiography.

FreezFreezing the motion of projecties ing the motion of projecties & Trajectories.& Trajectories.

High Speed radiography.High Speed radiography.

Cuurent- 2000A.Cuurent- 2000A.

Exposure time – nano seconds.Exposure time – nano seconds.

04/11/23 106


Proton RadiographyProton Radiography

• Very high sensitivity 0.05 %

• Attenuation only after the proton passes through 90% of material thickness

• No burning of edges

04/11/23 107


Xero Radiography or Xonics Electron Radiography.Xero Radiography or Xonics Electron Radiography.

• Selenium coated Aluminium Plate.

• Well polished aluminium plate coated with selenium oxide.

• When exposed to xrays charge on weld portion remain.

• Image obtained by developing charged particle.

04/11/23 108


Micro Focus Radiography.Micro Focus Radiography.

• Image enlargement is possible.

• Application:Segregation & Coring in alloys.

04/11/23 109


Hot Radiography.Hot Radiography.

• Radiography of radioactive materials.

04/11/23 110


Photo Electron Radiography.Photo Electron Radiography.

•Application:

Radiography of Bank notes, stamps, Coins & clothes.

04/11/23 111


Neutron radiography.Neutron radiography.

•Suitable for hydrogeneous material & Radioactive material.

•Does not depend on density & thickness.

•Applications:

Corrosion in space and aircraft components,explosives,organic compound,plastics.

04/11/23 112

Discontinuities & Process

Classification of Discontinuties:Classification of Discontinuties:1.Inherent- Mostly at the molten stage.eg.Gas inclusions.

2.Process-During Process eg. Discontinuties occuring durinng process like welding,casting, forging,rolling

etc.

3.Service-During Service eg: Fatigue crack,Intergranular.

Corrosion Cracking.

04/11/23 113

Discontinuities -Casting

Types of Casting:1.Temporary Casting:a.Sand casting

b.Shell Casting

c.Invest ment casting

2.Permanent Casting:a.Centrifugal casting

b.Pressure die casting

c.Continuous casting

114 04/11/23


Gas porosity or blow holes are caused by accumulated gas or air which is trapped by the metal. These discontinuities are usually smooth-walled rounded cavities of a spherical, elongated or flattened shape. If the be trapped as the molten metal begins to solidify. Blows can also be caused by sand that is too fine, too wet, or by sand that has a low permeability so that gas can't escape. Too high a moisture content in the sand makes it difficult to carry the excessive volumes of water vapor away from the casting. Another cause of blows can be attributed to using green ladles, rusty or damp chills and chaplets.

115 04/11/23


Shrinkage is a form of discontinuity that appears as dark spots on the radiograph. Shrinkage assumes various forms but in all cases it occurs because molten metal shrinks as it solidifies, in all portions of the final casting. Shrinkage is avoided by making sure that the volume of the casting is adequately fed by risers which sacrificially retain the shrinkage. Shrinkage can be recognized in a number of characteristic by varying appearances on radiographs. There are at least four types: (1) cavity; (2) dendritic; (3) filamentary; and (4) sponge types. Some documents designate these types by numbers, without actual names, to avoid possible misunderstanding.

116 04/11/23


Dendritic shrinkage is a distribution of very fine lines or small elongated cavities that may vary in density and are usuallyunconnected.

Filamentary shrinkage usually occurs as a continuous structure of connected lines or branches of variable length, width and density, or occasionally as a network.

117 04/11/23


• Cavity shrinkage appears as areas with distinct jagged boundaries. It may be produced when metal solidifies between two original streams of melt, coming from opposite directions to join a common front; cavity shrinkage usually occurs at a time when the melt has almost reached solidification temperature and there is no source of supplementary liquid to feed possible cavities

118 04/11/23


Core shift shows itself as a variation in section thickness, usually on radiographic views representing diametrically opposite portions of cylindrical casting portions.

119 04/11/23


Inclusions are nonmetallic materials in a supposedly solid metallic matrix. They may be less or more dense than the matrix alloy and will appear on the radiograph, respectively, as darker or lighter indications. The latter type is more common in light metal castings.

120 04/11/23


Sand inclusions and dross are nonmetallic oxides, appearing on the radiograph as irregular, dark blotches. These come from disintegrated portions of mold or core walls and/or from oxides (formed in the melt) which have not been skimmed off prior to introduction of the metal into the mold gates. Careful control of the melt, proper holding time in the ladle and skimming of the melt during pouring will minimize or obviate this source of trouble.

121 04/11/23


Sponge shrinkage shows itself as areas of lacy texture with diffuse outlines, generally toward the mid-thickness of heavier casting sections. Sponge shrinkage may be dendritic or filamentary shrinkage; filamentary sponge shrinkage appears more blurred because it is projected through the relatively thick coating between the discontinuities and the film surface.

122 04/11/23


Cracks are thin (straight or jagged) linearly disposed discontinuities that occur after the melt has solidified. They generally appear singly and originate at casting surfaces.

Cold shuts generally appear on or near a surface of cast metal as a result of two streams of liquid meeting and failing to unite. They may appear on a radiograph as cracks or seams with smooth or rounded edges.

04/11/23 123

Discontinuties-Casting

• Hot tears are linearly disposed indications that represent fractures formed in a metal during solidification because of hindered contraction. The latter may occur due to overly hard (completely unyielding) mold or core walls. The effect of hot tears, as a stress concentration, is similar to that of an ordinary crack; how tears are usually systematic flaws. If flaws are identified as hot tears in larger runs of a casting type, they may call for explicit improvements in technique.

• Misruns appear on the radiograph as prominent dense areas of variable dimensions with a definite smooth outline. They are mostly random in occurrence and not readily eliminated by specific remedial actions in the process.

• Mottling is a radiographic indication that appears as an indistinct area of more or less dense images. The condition is a diffraction effect that occurs on relatively vague, thin-section radiographs, most often with austenitic stainless steel. Mottling is caused by interaction of the object's grain boundary material with low-energy X-rays (300 kV or lower). Inexperienced interpreters may incorrectly consider mottling as indications of unacceptable casting flaws. Even experienced interpreters often have to check the condition by re-radiography from slightly different source-film angles. Shifts in mottling are then very pronounced, while true casting discontinuities change only slightly in appearance.

.

04/11/23 124

Discontinuties-Casting• Radiographic Indications for Casting Repair Welds.

• Most common alloy castings require welding either in upgrading from defective conditions or in joining to other system parts. It is mainly for reasons of casting repair that these descriptions of the more common weld defects are provided here. The terms appear as indication types in ASTM E390. For additional information, see the Nondestructive Testing Handbook, Volume 3, Section 9 on the "Radiographic Control of Welds."

• Slag is nonmetallic solid material entrapped in weld metal or between weld material and base metal. Radiographically, slag may appear in various shapes, from long narrow indications to short wide indications, and in various densities, from gray to very dark.

• Porosity is a series of rounded gas pockets or voids in the weld metal, and is generally cylindrical or elliptical in shape.

• Undercut is a groove melted in the base metal at the edge of a weld and left unfilled by weld metal. It represents a stress concentration that often must be corrected, and appears as a dark indication at the toe of a weld.

• Incomplete penetration, as the name implies, is a lack of weld penetration through the thickness of the joint (or penetration which is less than specified). It is located at the center of a weld and is a wide, linear indication.

• Incomplete fusion is lack of complete fusion of some portions of the metal in a weld joint with adjacent metal; either base or previously deposited weld metal. On a radiograph, this appears as a long, sharp linear indication, occurring at the centerline of the weld joint or at the fusion line.

04/11/23 125

Discontinuties-Casting• Melt-through is a convex or concave irregularity (on the surface of backing ring, strip, fused root or

adjacent base metal) resulting from complete melting of a localized region but without development of a void or open hole. On a radiograph, melt-through generally appears as a round or elliptical indication.

• Burn-through is a void or open hole into a backing ring, strip, fused root or adjacent base metal.• Arc strike is an indication from a localized heat-affected zone or a change in surface contour of a

finished weld or adjacent base metal. Arc strikes are caused by the heat generated when electrical energy passes between surfaces of the finished weld or base metal and the current source.

• Weld spatter occurs in arc or gas welding as metal particles which are expelled during welding and which do not form part of the actual weld: weld spatter appears as many small, light cylindrical indications on a radiograph.

• Tungsten inclusion is usually denser than base-metal particles. Tungsten inclusions appear most linear, very light radiographic images; accept/reject decisions for this defect are generally based on the slag criteria.

• Oxidation is the condition of a surface which is heated during welding, resulting in oxide formation on the surface, due to partial or complete lack of purge of the weld atmosphere. Also called sugaring.

• Root edge condition shows the penetration of weld metal into the backing ring or into the clearance between backing ring or strip and the base metal. It appears in radiographs as a sharply defined film density transition.

• Root undercut appears as an intermittent or continuous groove in the internal surface of the base metal, backing ring or strip along the edge of the weld root.

126 04/11/23

Discontinuities -Welding

Welding Discontinuties:1.Mechanical - Mismatch or offset

2.Inadequate - LP,LF

3.Metallurgical - Porosity,Cracks

Welding Discontinuties:1.Planar --LF

2.Voluminar --Slag,porosity

127 04/11/23


Discontinuities.Discontinuities.

Discontinuities are interruptions in the typical structure of a material. These interruptions may occur in the base metal, weld material or "heat affected" zones.

Defects.Defects.

Discontinuities, which do not meet the requirements of the codes or specification used to invoke and control an inspection, are referred to as defects.

128 04/11/23


Offset or mismatch are terms associated with a condition where two pieces being welded together are not properly aligned. The radiographic image is a noticeable difference in density between the two pieces. The difference in density is caused by the difference in material thickness. The dark, straight line is caused by failure of the weld metal to fuse with the land area.

Fluoroscopy

appearance

129 04/11/23


Incomplete penetration (IP) or lack of penetration (LOP) occurs when the weld metal fails to penetrate the joint. It is one of the most objectionable weld discontinuities. Lack of penetration allows a natural stress riser from which a crack may propagate. The appearance on a radiograph is a dark area with well-defined, straight edges that follows the land or root face down the center of the weldment

Fluoroscopy

appearance

130 04/11/23


Incomplete fusion is a condition where the weld filler metal does not properly fuse with the base metal. Appearance on radiograph: usually appears as a dark line or lines oriented in the direction of the weld seam along the weld preparation or joining area.

Fluoroscopy

appearance

131 04/11/23


Cracking can be detected in a radiograph only the crack is propagating in a direction that produced a change in thickness that is parallel to the x-ray beam. Cracks will appearas jagged and often very faint irregular lines. Cracks can sometimes appearing as "tails" on inclusions or porosity.

Fluoroscopy

appearance

132 04/11/23


Internal or root undercut is an erosion of the base metal next to the root of the weld. In the radiographic image it appears as a dark irregular line offset from the centerline of the weldment. Undercutting is not as straight edged as LOP because it does not follow a ground edge

Fluoroscopy

appearance

133 04/11/23


External or crown undercut is an erosion of the base metal next to the crown of the weld. In the radiograph, it appears as a dark irregular line along the outside edge of the weld area.

Fluoroscopy

appearance

134 04/11/23


Slag inclusions are nonmetallic solid material entrapped in weld metal or between weld and base metal. In a radiograph, dark, jagged asymmetrical shapes within the weld or along the weld joint areas are indicative of slag inclusions.

Fluoroscopy

appearance

135 04/11/23


Oxide inclusions are usually visible on the surface of material being welded (especially aluminum). Oxide inclusions are less dense than the surrounding materials and, therefore, appear as dark irregularly shaped discontinuities in the radiograph.

Fluoroscopy

appearance

136 04/11/23


Tungsten inclusions. Tungsten is a brittle and inherently dense material used in the electrode in tungsten inert gas welding. If improper welding procedures are used, tungsten may be entrapped in the weld. Radiographically, tungsten is more dense than aluminum or steel; therefore, it shows as a lighter area with a distinct outline on the radiograph.

Fluoroscopy

appearance

137 04/11/23

Discontinuities -WeldingPorosity is the result of gas entrapment in the solidifying metal. Porosity can take many shapes on a radiograph but often appears as dark round or irregular spots or specks appearing singularly, in clusters or rows. Sometimes porosity is elongated and may have the appearance of having a tail This is the result of gas attempting to escape while the metal is still in a liquid state and is called wormhole porosity. All porosity is a void in the material it will have a radiographic density more than the surrounding area.

Fluoroscopy

appearance

138 04/11/23


Cluster porosity is caused when flux coated electrodes are contaminated with moisture. The moisture turns into gases when heated and becomes trapped in the weld during the welding process. Cluster porosity appear just like regular porosity in the radiograph but the indications will be grouped close together.

Fluoroscopy

appearance

139 04/11/23


Internal concavity or suck back is condition where the weld metal has contracted as it cools and has been drawn up into the root of the weld. On a radiograph it looks similar to lack of penetration but the line has irregular edges and it is often quite wide in the center of the weld image.

Fluoroscopy

appearance

140 04/11/23


Cold lap is a condition where the weld filler metal does not properly fuse with the base metal or the previous weld pass material (interpass cold lap). The arc does not melt the base metal sufficiently and causes the slightly molten puddle to flow into base material without bonding.

Fluoroscopy

appearance

141 04/11/23


Inadequate weld reinforcement is an area of a weld where the thickness of weld metal deposited is less than the thickness of the base material. It is very easy to determine by radiograph if the weld has inadequate reinforcement, because the image density in the area of suspected inadequacy will be more (darker) than the image density of the surrounding base material.

Fluoroscopy

appearance

142 04/11/23

Discontinuities -WeldingExcess weld reinforcement is an area of a weld, which has weld metal added in excess of that specified by engineering drawings and codes. The appearance on a radiograph is a localized, lighter area in the weld. A visual inspection will easily determine if the weld reinforcement is in excess of that specified by the individual code involved in the inspection.

Fluoroscopy

appearance

143 04/11/23

Discontinuities -WeldingBurn through (icicles) results when too much heat causes excessive weld metal to penetrate the weld zone. Lumps of metal sag through the weld creating a thick globular condition on the back of the weld. On a radiograph, burn through appears as dark spots surrounded by light globular areas.They are most commonly found in GMAW welds.

Fluoroscopy

appearance

04/11/23 144

Interpretations,Standards & Codes

Acceptance Considerations:Acceptance Considerations:1.Stresses

2.Type of Stress

3.Environment

4.Thickness

5.Consequences of failure

6.Rectification cost

7.Standards

04/11/23 145


Qualities of a good Interpreter:Qualities of a good Interpreter:1.Enhance knowledge on Techniques.

2.Knowledge of Product.

3.Nature of Product.

4.Acceptance Standards.

Functions of a good Interpreter:Functions of a good Interpreter:1.Check the quality of the rdiograph or weld image.

2.Identify the discontinuty.

3.Interpret the discontinuity.

4.Evaluate the discontinuity in terms of codes and standard.

04/11/23 146


Code:Code:It is a collection of relative standards and specification often applied to a particular product line.

Standard:Standard:It is a published specification,test method or practice that has been prepared by an isolated body.

Specification:Specification:It is a document which states in detail the set of requirements associated with the product.

Procedure:Procedure:It is the specific way to perform an activity which says performed by whom ,when, where and in what way.

04/11/23 147


International Organisations that prepare a code:International Organisations that prepare a code:

•ASME ASME - American Society for Mechanical Engineers

•AWS AWS - American Welding Society

•AWI AWI - American Welding Institute

•ANSIANSI - American National Standards Institute

•ASNTASNT - American Society for Non Destructive Testing

•API API - - American Petroleum Institute

•EN EN – European Nations

04/11/23 148


04/11/23 149

RADIATION SAFETY

ALARA - AAs s LLow ow AAs s RReasonably easonably AAchievablechievable

TDS - TTime ime DDistance istance SShieldinghielding• Spend the least time near radiation

• Spend maximum distance

• Ensure adequate shielding

• T D S

04/11/23 150

Radiation Units

• Radiation level - exposure rate - R per hour (or)

- mR per hour• Exposure - charge released in air

- Coulomb per kg or esu per cc

• Activity - Bq - 1 transformations /per second

1Ci = 3.7 x 1010 transformations / second

1Ci = 37 GBq

04/11/23 151

Radiation Units

• Absorbed Dose : Energy absorbed

- 1 joule / kg - gray ( Gy)

- 100 ergs/gm - rad

- 1 Gy = 100 rad• Biological effects depend uponBiological effects depend upon• - Spatial distribution of energy• - Energy loss per unit path length• - Different for different radiation's

04/11/23 152

Radiation Units

• Equivalent Dose :

Dose x Radiation Weighting Factor (WR)

- 1 Joule / kg - Sievert ( Sv)

- 100 ergs/gm - Rem

- 1 Sv = 100 Rem

- 1mSv = 100 mRem

• Effective Dose - for Non Uniform Exposure or

Individual Organ Exposure

Dose x Tissue Weighting Factor ( WT)

04/11/23 153

RADIATION SAFETY

Biological EffectsBiological Effects : :

• Inhibition of Cell division• Chromosome abberation• Gene Mutation• Cell death

04/11/23 154

RADIATION SAFETY

Background Radiation:Background Radiation:Terrestial Cosmic Rays.

1995 – 125 mR/ year ,Latest – 240 mR/year.

Because of ozone depletion and other factors.

Radiation Limits(MPD -Maximum Permissable Dose):Radiation Limits(MPD -Maximum Permissable Dose):

Radiation Worker --- 5000 mR/ Year (Old).

--- 2000 mR/ Year (New).

General Public --- 5% of Rdn worker. ie 100 mR/year(New).

04/11/23 155

RADIATION SAFETY

Radiation Limits (MPD):Radiation Limits (MPD):

Radiation WorkerRadiation Worker General PublicGeneral Public

20 mSv/Year 1 mSv/Year

40 mR/Week 40 mR/Week

8 mR/Day 8 mR/Day

1 mR/Hour 1 mR/Hour

04/11/23 156

RADIATION SAFETY

DOSEDOSE::

1.Acute Dose:Sudden dose.

e.g.Dose received during one operation or in a day.

2.Chronic Dose:Cumulative dose.

e.g.Dose received for 1 year year.

04/11/23 157

RADIATION SAFETY

EFFECT:EFFECT:

1.Stochastic Effect:No threshold value or limits.

e.g.Cancer,Leukamia,Genetic effects.

2.Non Stochastic Effect:Threshold value or limits.

e.g.Cataract, skin erythma.

158 04/11/23

RADIATION SAFETY

Whole Body Dose and Effects:Whole Body Dose and Effects:Upto 0.1 Gy No detectable effect

0.1 – 0.25 Gy Chromosome abberation

0.25 – 1.0 Gy Blood Picture Changes.

Reduction in blood count etc.

1.0 – 3.0 Gy NVD Nausea Vomitting & Diarrhoea

3.0 – 5.0 Gy LD 50/60. Lethal Dose.

50%of exposed individual die within 60 days

> 5.0 Gy Death within Few days.

159 04/11/23

RADIATION SAFETY

Local Radiation or Organal Dose:Local Radiation or Organal Dose:

ORGAN DOSE EFFECT

Testes 1.25Gy Temporary sterlity

Ovary 3.0 Gy Temporary sterlity

Ovary 4.5 Gy Permanent sterlity

Testes 6.5 Gy Permanent sterlity

Eye 6.0 Gy Cataract(delayed effect)

Skin 8.0 Gy Skin Erythma

160 04/11/23

RADIATION SAFETY

Radiation Monitoring DevicesRadiation Monitoring Devices

Area Monitor Personnel Monitor1.Survey Meters: 1.Film Badge

a.Geiger Muller Counter-Low level Rdn

b.Ionisation Chamber-Low level Rdn. 2.TLD Badge

c. Scintillation Counter

d. Proportional counter 3.Pocket Dosimeters

2.Audible alarms

04/11/23 161

RADIATION SAFETY

Survey Meter

04/11/23 162

RADIATION SAFETY

Audible Alarm:

04/11/23 163

RADIATION SAFETY

Film Badge:Film Badge:Useful Range:20 mR – 2000R.

It can be used to detect the effects of all ionising radiations Alpha,Beta,Gamma,Neutons,Low energy Xrays,High energy Xrays & Gamma Rays.

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TLD Badge:Lithium Fluoride,Calcium Zinc Sulphate.

20mR – 20,000 R.When certain materials are exposed to ionising radiation, some of the energy absorbed is stored. This stored energy is released in the form of light when the material is heated. Lithium fluoride has this property which is called thermoluminescence. The amount of light emitted on heating the lithium flouride, is proportional to the amount of radiation that had been incident on it. Its response is relatively independent of the energy of the radiation.

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Pocket Dosimeter:0 – 200 mR or 0- 2 mSv.

Advantage:Advantage:

• On the spot indication.

• Measures total dose.

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Permissable Leakage RadiationPermissable Leakage Radiation

Type of Device

Max.at Surface

At 1 metre Distance

Portable 100 mR/hr 2 mR/hr

Mobile 100 mR/hr 10 mR/hr

Stationary 200 mR/hr 20 mR/hr

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SHIPPING.SHIPPING.Dangerous Goods. Class 7. UN 2972.

Transport Index:

The value of Leakage radiation measured in mR/hr at 1 metre distance from the surface of the package.

Type Maximum Contact Reading

Transport Index

White I 0.5 mR/hr < 0.05

Yellow II 50 mR/hr Upto 1.0

Yellow III 200 mR/hr 1.0 – 10.0

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RADIATION SAFETY

SHIPPING.SHIPPING.Radiation warning Transport label:Radiation warning Transport label:49 CFR 172.403.

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THE END

Thank You.

Good Luck for Your Examination

Documents

Rt Level II Course Notes