NDT REPORTT

NON DESTRUCTIVE TESTING
Alfa Institute of Technology,Udupi Page 1
INTRODUCTION TO NON-DESTRUCTIVE TESTING
Testing
It is defined as to take measures to check the quality, performance or reliability of a material,
especially before putting it into wide-spread use or practice
There are two types of testing:
1. Destructive Testing
It is a method of inspecting or measuring materials with doing harm
Eg: Impact Testing, Hardness Testing
2. Non-Destructive Testing
It is a method of inspecting or measuring materials without doing any harm
Eg: Magnetic Particle Testing, Radiographic Testing
Non-Destructive Testing methods:
i. Visual Testing
ii. Radiographic Testing
iii. Magnetic Particle Testing
iv. Liquid or Dye PenetrantTesting
v. Eddy CurrentTesting
vi. Ultra-sonic Testing
vii. Acoustic EmissionTesting
viii. Infrared or ThermalTesting
ix. LeakTesting
x. Vibration Analysis
xi. Neutron RadiographyTesting
Visual Testing
This is the most common and basic inspection method. This includes:
 Fibrescopes, Boroscopes, magnifying glasses and mirrors
 Portable video inspection with zoomed lenses for large tanks and vessels, server lines

 Robotics crawlers to observe hazardous or tight areas such as air ducts, reactors and
pipe lines
Instruments used for Visual Testing
1. Steel Ruler
2. Indirect Calipers
3. VernierCalipers
4. DialCalipers
5. DigitalCalipers
6. Direct ReadingCalipers
7. Mechanical Gauges
8. Fillet WeldGauges
Non-Destructive Evaluation
It is a method of evaluating materials using different non-destructive techniques
Applications of Non-Destructive Evaluation
 To assist in product development
 Screening or sorting the incoming materials
 To monitor, improve or control manufacturing process
 To verify proper processing such as heat treatment
 To verify proper assembly
 To inspect for in-service damage
Homogeneous materials
Materials without cracks are called Homogeneous materials
Non- Homogeneous materials
Materials with cracks are called Non-Homogeneous materials
Defects and Discontinuities
1. Defect

Defect is a material failure
Types of Defects:
 Sensitivity
It is the smallest possible defect in a material
 Resolution
It is represented by two or more straight line or cross line defects
2. Discontinuity
It is a local variation in the material due to transportation or atmospheric conditions
Types of Discontinuities
 Surface Discontinuity
These are open to the surface of the material
Testings’ used are:
i. Visual Testing
ii. Magnetic Particle Testing
iii. Liquid or Dye PenetrantTesting
 Sub-Surface Discontinuity
These are present beneath the surface of the material
Testings’ used are:
i. Ultra-sonic Testing
ii. Radiographic Testing
iii. Magnetic Particle Testing (up to 6mm)
Applications of Non-Destructive Testing
a. Power plant Inspection
b. Wire RopeInspection
c. Storage TankInspection
d. Air craftInspection
e. Pipe-lineInspection
f. RailInspection
g. Bridge Inspection

1.MAGNETIC PARTICLE TESTING
Introduction:
Magnetic particle testing is one of the most widely utilized NDT methods since it is fast and
relatively easy to apply and part surface preparation is not as critical as it is for some other
methods. This method uses magnetic fields and small magnetic particles to detect flaws in
components. The only requirement from an inspectability standpoint is that the component
being inspected must be of ferromagnetic material. Many industries use MPT such as power
generation, automotive, petrochemical and aerospace industries.
Basic principle:
In theory magnetic particle testing is
nothing but combination of two
testing; magnetic flux leakage
testing and visual testing
To explain basic principle in simple
way i.e; when bar magnet is broken
is broken in center of its length ,two
complete bar magnets with magnetic poles end of end piece will result. If the magnet is just
cracked and not broken completely in two, a north and south pole will form at each edge of
the crack as a result of air gap which is formed due to crack,there is a flux leakage which
takes place which is called as flux leakage field
Here if iron particles are sprinkled on the crack , the particles will not only attract towards the
poles at the end of the magnet but also at the poles at the crack
Ferromagnetic material:
These materials have a large positive susceptibility to an external magnetic field. They
exhibit a strong attraction to magnetic field and are able to retain magnetic properties after
the magnetic field has been removed. Some ferromagnetic materials are iron, nickel, cobalt

and their alloys
Fig, 1.2 Ferromagnetic material
Hysteresis loop and Magnetic properties:
Fig, 1.3 Hysteresis loop
A great deal of information can be learned about the magnetic properties of a material
bystudying the hysteresis loop. The loop is generated by measuring the magnetic flux of a
ferromagnetic materialwhile the magnetizing force is changed. A ferromagnetic material
which has never been magnetized or has been properly demagnetized will follow the dashed
line as H is increased. Amongst all the magnetic domains are aligned and an additional
increase in the magnetizing force will produce very little increase in magnetic flux. The
material has reached the point of magnetic saturation. When H is reduced to zero, curve will
from point “a” to point “b”. This is referred to as point of retentivity. As the magnetic force is
reversed the curve moves to point ‘c’ where the flux has been reduced to zero and it is called
as the point of coercivity. As the magnetic force is increased in negative direction, the

material will again become magnetically saturated but in opposite direction, point ‘d’
reducing point H to zero which brings the curve to point ‘e’. It will have a level of residual
magnetism equal to that achieved in other direction. Increasing H back in in the positive
direction which will bring ‘b’ to zero
Basic steps involved in MPT:
1.Pre-cleaning:
Here the material is cleaned by using certain methods such as ;water washing methods
,solvent methods, vapordegreasing, steam cleaning ,ultrasonic cleaning , sand blasting , short
blasting
2. Check the area to be inspected:
Here the supervisor checks the area which is required to be inspected
3. Selection of current:
Here current which is required for carrying out the procedure is selected , current such as
AC/DC is selected
4. Selection of method:
Method which is most suitable is chosen such as longitudinal magnetization or circular
magnetization
5. Applying the method:
Select and apply one type of magnetization method into the component
6. Iron powder application :
There are two types of method by which we can carry out this process
i. Dry method
ii. Wet method
7. Resultsand interpretation:

There are three types of results
i. False indication
ii. Non relevant indication
iii. Relevant indication
We can find variety of interpretation such as tungsten inclusion ,offset mismatch, internal
undercut, lack of fusion ,lack of penetration ,slag inclusion, cluster porousity , porousityetc.
Some magnetizing equipment :
i. Permanent magnet:
It can be used for magnetic particle testing inspection as the source of magnetism.
Fig, 1.4 Permanent magnet
ii. Electromagnetic yoke:
An electromagnetic yoke is common piece of equipment that is used to establish a
magnetic field. A they can powered with AC from a wall socket or by DC from a
battery pack. This type of magnet generates a very strong magnetic field. Some yokes
can lift weights in excess of 40 pounds

Fig, 1.5 Electromagnetic yoke
iii. Prods:
Prods are handheld electrodes that are pressed against the surface of the component
being inspected to make contact for passing electrical current through the metal. Prods
are typically made from copper and have an insulated handle to help protect the
operator. This is the type of dual prodcommonly used for weld inspections
Magnetic field indicators:
It is used to determine whether the magnetic field is of adequate strength and in the proper
direction is critical when performing magnetic particle testing.
i. Hall-effect meter(Gauss Meter):
As discussed earlier, a gauss meter is commonly used to
measure the tangential field strength on the
surface of the part. By placing the probe next to
the surface, the meter measures the intensity of
the field in the air adjacent to the component
when a magnetic field is applied.
ii. Pie Gage:
The pipe gage is a disk of highly permeable material divided into four, six or eight
sections by non-ferromagnetic material. The divisions serve as artificial defects that
radiate out in different directions from the center. The sections are furnace brazed and

copper plated. The gage is placed on the test piece copper side up and the test piece is
magnetized. After particles are applied and the excess removed, the indications
provide the inspector the orientation of the magnetic field
Fig, 1.6 Pie Gage
iii. Slotted Strips:
It are pieces of highly permeable ferromagnetic material with slots of different widths.
These strips can be used with the wet or dry method. They are placed on the test
object as it is inspected. The indications produced on the strips give the inspector a
general idea of the field strength in a particular area
Advantages and disadvantages:
The primary advantages and disadvantages when compared to other NDT methods are
Advantages:
 High sensitivity
 Indication are produced directly on the surface of the part and constitute a visual
representation of the flaw
 Minimal surface preparation
 Portable
Disadvantages:
 Only surface and near surface defects can be detected
 Only applicable to ferromagnetic materials
 Relatively small area can be inspected at a time
 Only materials with relatively nonporous surface can be inspected
 The inspector must have direct access to the surface being inspected

2.LIQUID PENETRANT TESTING
Introduction
Liquid Penetrant Testing is one of the oldest and simplest Non-Destructive Testing methods.
This method is used to reveal surface discontinuities by bleedout of a coloured or fluorescent
dye from the flaw. It is used in inspection of all non-porous materials
Basic Principle
The Liquid Penetrant Testing works on the principle of Capillary action i.e. rise and fall of
liquid. The settling down of penetrant into the discontinuities is called Capillary fall and
rising of penetrant from the discontinuities by the application of developer is known as
Capillary rise.
Fig.2.1 Principle of LPT
Penetrants
Penetrants are carefully formulated to produce the level of sensitivity desired by the
inspector.
Basic types of Penetrants
 Fluorescent Penetrants
 Visible Penetrants

Methods used for excess removal of Penetrants
 Water washable
 Solvent removable
 Post-Emulsifiable
 Lipophilic
 Hydrophilic
Fig. 2.2 Penetrant application and removal process
Application of Penetrants
 By spraying
 By brushing
 By pouring the penetrant on material(when large work material is used
 By dipping the material into the penetrant
Developers
The role of the developer is to pull the trapped penetrant material out of defects and spread it
out on the surface of the part so it can be seen by the inspector.
 Developers used with Visible penetrants create a white background so there is a great
degree of contrast between the indication and the surrounding background
 Developers used with Fluorescent penetrants both reflect and refract the incident UV
light, allowing more of it to interact with the penetrant , causing more efficient

fluorescence. Under UV rays , the defects are visible as green-yellow colour whereas
the developer is visible as black-blue colour.
Basic types of Developers
 Dry developers
 Water soluble developers
 Water suspendable developers
 Non-aqueous developer
Fig. 2.3 Developer application and obtaining of indication
Basic steps involved in Liquid Penetrant Testing
1. Pre- Cleaning
 It is the most critical step in Liquid Penetrant Testing
 All coatings such as paints, varnishes, heavy oxides must be removed to
ensure that defects are open to surface of the part
 Processes like machining, sand blasting, steam cleaning can cause metal
smearing. This layer of metal smearing must removed before inspection.
 Various methods of cleaning are:
i. Water washing
ii. Solvent or Detergent cleaning
iii. Vapour degreasing
iv. Steam cleaning
v. Ultra-sonic cleaning
vi. Sand blasting

vii. Shot or Abrasive blasting
2. Penetrant application
 The penetrant material can be applied in a number of ways, such as spraying,
brushing or immersing the part in a penetrant bath
 The penetrant must entirely cover the part of the material to be tested
3. Penetrant Dwell Time
 It is defined as the time taken by the penetrant to settle inside the cracks of the
material to be tested
 Penetrants require a dwell time of 5-10 minutes
 The dwell time depends upon:
i. The contact angle of the penetrant
ii. The capillary pressure at the flaw opening
iii. The specific gravity of the penetrant
4. Excess Penetrant Removal
 The penetrant removal procedure must effectively remove the penetrant from
thesurface of the part without removingan appreciable amount of entrapped
penetrant from the discontinuity
 Excess penetrant removal methods
i. Water washable
ii. Penetrant removable
iii. Post-Emulsifiable
a. Lipophilic: The emulsifier is oil-based and interacts with the oil
soluble penetrant to make removable possible
b. Hydrophilic: The emulsifier is water soluble detergent which
lifts excess penetrant from surface of part with a water wash
5. Developer Application
 The main function of the developer is to provide a contrast background for
indications and the developer must be bright
 Commonly a white contrast developer is used
 Types of developers are:
i. Dry developers
ii. Water soluble developers

iii. Water suspendable developers
iv. Non-aqueous developers
 Non-aqueous developers are generally recognized as the most sensitive when
properly applied
6. Developing Time
 It is defined as the time taken by developer to pull the penetrant out from the
defect to make an indication
 Developing time is around 2-5 minutes
7. Result and Interpretation
 Results:
i. False Indications: It can be caused by improper cleaning. It should be
eliminated by using proper lint-free clothes and air covers
ii. Non-Relevant Indications: These are caused due to geometrical
changes in the part
iii. Relevant Indications: These are produced by actual discontinuities in
the part
a. Acceptable: If the indications matches the codes and standards
b. Reject-able: If the indications does not matches the codes and
standards
 Interpretations(Weld Discontinuities):
1. Tungsten Inclusions:
2. Offset or Mismatch
3. Internal Undercut
4. Lack of Fusion
5. Lack of Penetration
6. Slag Inclusions
7. Cluster Porosity
8. Porosity
9. Suck Back

Fig. 2.4 Various discontinuities obtained on a weld part
8. Post Cleaning
 It is the method of cleaning the material after inspection
9. Final Report
 The final report is obtained by providing the photo copy of the procedure or by
drawing
Emulsifier
 The function of the emulsifier is to remove the excess of penetrant from the
surface of the material
 Emulsifier is give enough time to react with penetrant, but not enough time to
diffuse into the penetrant trapped in the defect
 When there is excess penetrant, Post-Emulsification method is used
 In this method, emulsifier is applied on the part and given some time for
dwelling
Functions of Emulsifiers
 Penetrant inside the defect should not be over-washed
 Excess penetrant should be removed easily
 Emulsifier should have good sensitivity
Types of Emulsifiers
 Lipophilic Emulsifiers

 Hydrophilic Emulsifiers
Basic Steps involved in Post-Emulsification Method
1. Pre-Cleaning
2. Penetrant Application
3. Penetrant Dwell Time
4. Application of Emulsifier
5. Emulsifier Dwell Time
6. Excess Penetrant Removal
7. Developer Application
8. Developing Time
9. Result and Interpretation
10. Post Cleaning
11. Final Report
Safety Precautions
Two types of problems may cause to the inspector
 Skin Irritation
Precaution: Wearing gloves, hand crings
 Breathing problem/Air pollution
Precaution: Wearing masks and install exhaust fans
Fig. 2.5 A Inspector carrying out LPT process with wearing safety equipments

Wetting Ability and Contact Angle
 The ability of the liquid to wet the surface of material is called as wetting ability
 Liquids having good wetting ability have very low contact angle
 Contact angle is represented by ’’
 Liquids having contact angle less than 90, have a good wetting ability
Fig. 2.6 Wetting ability and contact angle diagram
Advantages of Liquid Penetrant Testing
 High sensitivityi.e., small discontinuities can be detected
 Rapid inspection of large areas and volumes
 Suitable for parts with complex shapes
 Indications are produced directly on the surface of the part and constitute avisual
representation of the flaw
 Low cost i.e., the materials and related equipment are relatively inexpensive
Dis-advantages of Liquid Penetrant Testing
 Only surface defects can be detected
 Pre-cleaning is critical since contaminants can mask defects
 Only materials with a relatively non-porous surface can be inspected
 Surface finish and roughness can affect inspection sensitivity
Applications of Liquid Penetrant Testing
 This method is used in the inspection of grinding, casting, welding defects

3. RADIOGRAPHIC TESTING
Introduction:
Radiography is used in a very wide range of applications including medicine, engineering,
forensic etc. Radiographic Testing is the method of inspecting materials for hidden flaws by
using the ability of short wavelength electromagnetic radiations to penetrate various
materials. The intensity of the radiation that penetrates and passes through the material is
either captured by a radiation sensitive film or by a planar array of radiation sensitive sensors.
Radiographic Testing offers a number of advantages over other NDT methods, however, one
of its major disadvantages is the health risk associated with the radiation.
Basic Principle:
The Radiographic Testing works on the principle of differential absorption and shadow
formation.
Fig. 3.1 Basic principle of Radiographic Testing
 In Radiographic Testing, the part to be tested is placed between the radiation source
and a piece of radiation sensitive film.
 The radiation source can either be an X-Ray machine or a radio-active source.
 The radiation that passes through the part will expose the film and forms a shadow
graph of the part.
 The film density will vary with the amount of radiation reaching the film through the
test object.

 The darker areas indicate more exposure i.e., high radiation intensity
 The lighter areas indicate less exposure i.e., low radiation intensity
Properties of X-Rays and Gamma Rays:
 They travel in straight lines at the speed of light
 Their degree of penetration depends upon their energy and matter they are travelling
through
 Their paths cannot be changed by electrical or magnetic fields
 They can be diffracted, refracted to a small degree at interfaces between two different
materials, and in some cases be reflected
Isotopes:
 The atoms having same number of protons and different number of neutrons are
known as isotopes
 They are also known as Unstable atoms
 Natural Isotopes and Artificial Isotopes are its two types
 Half Life: It is defined as the time required for the activity of any radionuclide to
decrease to one-half of its initial value
 Radiation Intensity: It is amount of energy passing through the given area, that is
perpendicular to the direction of radiation travel in a given unit of time
 Exposure: It is the amount of ionization in the air. Its SI unit is Roentgen
 Various Isotopes are:
i. Cobalt-60
 This is hard grain magnetic material having melting point of 1480C
 Density is 8.9 gm/cm3
 It has a half-life of 5.3 years
 It is used for the inspection of iron, copper and other medium weight
metals
ii. Iridium-192
 This isotope belongs to Platinum family and has a density of 22.4
gm/cm3

 It has a half-life of 74.3 days
 It is used for radiography of steel up to 100mm
iii. Helium-170
 It is generally in the form of Helium Oxide and has a density of 4
gm/cm3
 It has a half-life of 129 days
 It is used in the inspection of steel of 0.8mm and 30mm of aluminium
iv. Caesium-137
 It is a man made isotope and it can be extracted from Sulphate or
Fluorite
 It has a half-life of 33.1 years
 It is used for the inspection of steel of thickness between 40-100mm
v. Selenium-75
 This isotope provides radiation energies considerably lower than
Ir-192, which results in largely improved quality of weld radiographs
 It has a half-life of 120 days
 It is highly volatile and chemically reactive
 Its mass is about 7kg
 These isotopes are commonly used in mid-thickness gamma
radiography applications requiring high image quality
 Its code is EN1435, ISO 5579
Attenuation:
 When X-Rays or Gamma rays are directed into an object, some of the photons interact
with the particles of the matter and their energy can be absorbed or scattered. This
absorption and scattering is called as Attenuation
 The number of photons transmitted through a material depends on the thickness,
density and atomic number of the material, and the energy of the individual photons
 The Linear Attenuation Co-efficient() describes fraction of a beam of X-rays or
Gamma rays that is absorbed or scattered per unit thickness of the absorber

 Linear Attenuation Co-efficient() can be normalized by dividing it by the density of
the element. This constant(/)is known as Mass Attenuation Co-efficient and its unit
is cm2/gm
 Half Value Layer: The thickness of any given material where 50% of the incident
energy has been attenuated
HVL= 0.693/
 Scattering processes:
i. Photo-electric Effect: The proton of low radiation energy transfers all its
energy to electron, at that time, it will impart kinetic energy and electrons will
be ejected by the atom
ii. Rayleigh’s(Coherent) Scattering: It occurs due to direct interaction between
proton and orbitory electron
iii. Compton Scattering: It occurs due to direct interaction between
proton(0.123meV) and obituary electron
iv. Pair Production: It occurs due to creation of two protons(0.51meV). It scatters
an energy of 1.02meV
Types of Radiography:
1. X-Ray Radiography
Fig. 3.2 Working Principle of X-ray Radiography

 The tube cathode is heated with a low-voltage current of a few amps.
 The filament heats up and the electrons in the wire become loosely held.
 A large electrical potential is created between the cathode and the anode by the high-
voltage generator. Electrons that break free of the cathode are strongly attracted to the
anode target.
 The stream of electrons between the cathode and the anode is the tube current. The
tube current is measured in milliamps and is controlled by regulating the low-voltage
heating current applied to the cathode.
 The higher the temperature of the filament, the larger the number of electrons that
leave the cathode and travel to the anode. The milliamp or current setting on the
control console regulates the filament temperature, which relates to the intensity of
the X-ray output Fig 3.3 X-Ray
camera
 A focusing cup is used to concentrate the stream of electrons to a small area of the
target called the focal spot
 Cooling of the anode by active or passive means is necessary. Water or oil re-
circulating systems are often used to cool tubes
 To prevent the cathode from burning up and to prevent arcing between the anode and
the cathode, all of the oxygen is removed from
the tube by pulling a vacuum
 X-ray generators usually have a filter along
the beam path (placed at or near the x-
rayport). Filters consist of a thin sheet of
material (often high atomic number
materialssuch as lead,copper, orbrass) placed
in the useful beam to modify the spatial
distribution of the beam.
2. Gamma Radiography

Fig 3.4 Working principle of Gamma Radiography
 The source capsule and the pigtail are housed in a shielding device referred to
as a exposure device or camera.
 Depleted uranium is often used as a shielding material for sources.
 The exposure device for Iridium-192 and Cobalt-60 sources will contain 22
kgand 225 kgof shielding materials, respectively.
 Cobalt cameras are often fixed to a trailer and transported to and from
inspection sites
 To make a radiographic exposure, a crank-out mechanism and a guide tube are
attached to opposite ends of the exposure device.
 The guide tube often has a collimator (usually made of tungsten) at the end to
shield the radiation except in the direction necessary to make the exposure.
 The end of the guide tube is secured in the location where the radiation source
needs to be to produce the radiograph.
 The crank-out cable is stretched as far as possible to put as much distance as
possible between the exposure device and the radiographer.
 To make the exposure, the radiographer quickly cranks the source out of the
exposure device and into position in the collimator at the end of the guide
tube.
 At the end of the exposure time, the source is cranked back into the exposure
device.

 Physical size of isotope materials varies between manufacturers, but generally
an isotope material is a pellet that measures 1.5 mmx 1.5 mm
 The disadvantage of a radioactive source is that it can never be turned off and
safely managing the source is a constant responsibility
 In comparison to an X-ray generator, Cobalt-60 produces energies comparable
to a 1.25 MVX-ray system and Iridium-192 to a 460 kVX-ray system
Types of Gamma-Ray cameras:
1. Indian Cameras
 They have a Radio-active Source Power of 35 Ci
 The shielding of Lead is provide
 They weigh about 37kg
 The cost of these cameras is estimated around 3.5 to 4 lakhs
 Various Indian cameras are:
i. Roli 1
ii. Roli 2
iii. Delta
 The most commonly used camera is Delta
 It uses Ir-192 isotope
Fig. 3.5 Delta Camera

2. Foreign Camera
 They have a Radio-active Source Power of 100 Ci
 The shielding of Depleted Uranium is provided
 They weigh about 25kg
 The cost of these cameras is estimated around 5 to 6 lakhs
 The most commonly used camera is TechOps USA
 It uses Ir-192 isotope
Radiographic Film:
 X-ray films for general radiography basically consist of an emulsion-gelatine
containing radiation-sensitive silver halide crystals (such as silver bromide or
silverchloride).
 The emulsion is usually coated on both sides of a flexible, transparent, blue-tinted
base in layers about 0.12 mmthick
 The typical total thickness of the X-ray film is approximately 0.23 mm.
 When X-rays, gamma-rays, or light strike the film, some of the halogen atoms are
liberated from the silver halide crystal and thus leaving the silver atoms alone. This
change is of such a small nature that it cannot be detected by ordinary physical
methods and is called a latent (hidden) image.
 When the film is exposed to a chemical solution (developer) the reaction results in the
formation of black, metallic silver
 Types of films
i. Agfa:
 D7, D4, D5, D2
ii. Kodak:
 AA400,MX125,MX200,DR50
 D7 has high thickness and it is commonly used film
 D7 is equivalent to AA400
Film Density
 It is defined as the amount of degree of blackening or darkening the film

 This density can be measured with an instrument called Densitometer
 A good film density on a Densitometer will have a reading of 2.5
 Radiographic density is the logarithm of two measurements: the intensity of light
incident on the film and the intensity of light transmitted through the film
 Industrial codes and standards typically require a radiograph to have a density
between 2.0and 4.0for acceptable viewing with common film viewers. Fig. 3.6
Radiographic Film
 Film density is measured with a densitometer which simply measures the amount of
light transmitted through a piece of film using a photovoltic sensor
Fig. 3.7 Densitometer
Film Factor:
It is the amount of radiation required to produce the
desired density
Radiographic Contrast:
It is the density difference between two areas on a
radiograph. It has two types
 Subject Contrast
Contrast appearing in the film because of density or thickness of part
 Film Contrast
It is the density difference on the film due to the type of film used. It depends upon
the exposure and type processing of the film
Types of Contrast:

 Low contrast poor Definition
 High contrast poor Definition
 Low contrast goodDefinition
 High contrast goodDefinition
Details to be included in the film before radiographic action:
 Diameter of the work material
 Line number
 Piping class
 Joint number
 Welder number
 Radiography or X-Ray number
 Thickness of the work material
 Date on which the operation is carried out
Fig. 3.8 Details on the film
Penetra-meters or Image Quality Indicators:
 IQI is a device, whose image on a radiograph is used to determine radiographic
quality level
 IQIs should be placed on the source side of the part over a section with a material
thickness equivalent to the region of interest.
 Image quality indicators take many shapes and forms due to the various codes or
standards that invoke their use
 The two most commonly used IQI types are:
 Hole type IQI

 Hole-type IQIs are classified in eight groups based on their radiation
absorption characteristics.
 The numbers on the IQI indicate the sample thickness that the IQI
would typically be placed on.
 ASTM Standard Of Hole type is E1025
 Holes of different sizes are present where these holes should be visible
on the radiograph.
Fig. 3.9 Hole type IQI
 Wire type IQI
 Wire IQIs are grouped in four sets each having different range of wire
diameters
 ASTM Standard of Wire type is E747
 ASTM Wire types consists of 6 wires whereas, DIN Wire types
consists 0f 7 wires
 Wire IQIs are grouped in four sets each having different range of wire
diameters. The set letter (A, B, C or D) is shown in the lower right
corner of the IQI

Fig. 3.10 Wire type IQI
Film Processing:
Radiographic film consists of a transparent, blue-tinted base coated on both sides with an
emulsion. The emulsion consists of gelatin containing microscopic, radiation sensitive silver
halide crystals, such as silver bromide and silver chloride. When the film is processed, it is
exposed to several different chemical solutions for controlled periods of time.
Film processing basically involves the following five steps:
1. Development:
 The developing agent gives up electrons to convert the silver halide grains to
metallic silver.
 Grains that have been exposed to the radiation develop more rapidly, but
given enough time the developer will convert all the silver ions into silver
metal.
 Proper temperature control is needed to convert exposed grains to pure silver
while keeping unexposed grains as silver halide crystals
 The developer consists of chemicals like Metol, Phenidoletc
 A p.H value of 9.8 is maintained so as to keep the developer solution alkaline
2. Stopping the development:
 The stop bath simply stops the development process by diluting and washing
the developer away with water

3. Fixing:
 Unexposed silver halide crystals are removed by the fixing bath. The fixer
dissolves only silver halide crystals, leaving the silver metal behind
 The Fixer consists of Sodium Thio-sulphate(NaH2O3)
 A p.H value of 4.5 is maintained so as to keep the developer solution acidic
4. Washing: The film is washed with water to remove all the processing chemicals
5. Drying: The film is dried for viewing.
Fig. 3.11 Steps of Film Processing
Positive Material Identification (PMI):
 It is the identification and analysis of various metal alloys by their chemical
composition through non-destructive methods
 It can be conducted on-site or in the lab
Fig. 3.12 Positive Material Identification (PMI)

Benefits:
 Highly specific and accurate results, essential for good quality control
 Field testing with lab quality
 Assurance for verification of special metal parts
 Quick results for product verification and sorting of product that may have been
inadvertently mixed
Ferrite Tester:
 It is used to measure the ferrite content in different applications of steel
 It uses a method called magnetic induction to measure ferrite content in given sample
 It is carried out to ensure that ferrite content is at correct levels specified for material
testing
 A device called Feritoscope is used to determine the iron content in the material
Fig. 3.13 Feritoscope used to determine the iron content in the material
Advantages of Ferrite Tester:
 Rapid and accurate analysis
 Highly portable digital technology
 Testing instruments meet all requirements of ANSI/AWS A4.2 and DIN EN ISO
8249
 Calibration is trace-able to internationally approved IIW secondary calibration
standards

Limitations of Ferrite Tester:
 Surface preparation is very important for result accuracy
 Minimum material thickness and Minimum specimen size are required
 Not recommended where material is at temperature greater than 125F
Film Interpretations:
 Interpretations(Weld Discontinuities):
1. Tungsten Inclusions
2. Offset or Mismatch
3. Internal Undercut
4. Lack of Fusion
5. Lack of Penetration
6. Slag Inclusions
7. Cluster Porosity
8. Porosity
9. Suck Back
Fig. 3.14 Interpretations obtained on the film after processing
Radiographic Safety:
Radiographic Safety depends upon TIDS system i.e., Time Distance Shielding
Time: Less time spent near the source, less radiation received
Distance: More distance from source, less radiation received
Shielding: Behind the shielding from the source, less radiation received

General Safety Precautions:
1. Safety suit
2. Radiation Alarm
3. Radiation Badges
4. Radiation Barrier
5. Maintain a qualified technician inside the radiographic areas
6. Sign Boards
Fig. 3.15 various sign boards used in radiographic areas
 Sign boards should be in English
 The colour of the board must be Yellow whereas, the colour of the writings
must be Red
 The size of sign boards must be 450X450mm
Fig. 3.16 Direct Read Pocket Dosimeter
Single Wall Single Image (SWSI):
 In this method, the source is made to fall on single wall of work material
 The film is placed behind the wall of the work material
Double Wall Single Image (DWSI):

 In this method, the source is passed through two walls of the work material
 Here the film is placed behind only one of the wall and thus single image
Double Wall Double Image (DWDI):
 The source is kept at 1/4th of the SFD (Source to Film Distance) from weld
 The image formed on the film is in the form of Ellipse
 Two film are used in this method
Panoramic Method:
 This method is used in the inspection of very large circular work materials
 In this method, the source is kept at the centre and a number of films are placed
throughout the diameter of the work material
 It works on the same principle as Single Wall Single Image (SWSI)
Advantages of Radiographic Testing:
 Both surface and internal discontinuities can be detected.
 Significant variations in composition can be detected.
 It has a very few material limitations.
 Can be used for inspecting hidden areas (direct access to surface is not required)
 Very minimal or no part preparation is required.
 Permanent test record is obtained.
 Good portability especially for gamma-ray sources
Dis-advantages of Radiographic Testing:
 Hazardous to operators and other nearby personnel.
 High degree of skill and experience is required for exposure and interpretation.
 The equipment is relatively expensive (especially for x-ray sources).
 The process is generally slow.
 Highly directional (sensitive to flaw orientation).
 Depth of discontinuity is not indicated.

4.ULTRASONIC TESTING (UT)
Introduction:
Ultrasonic testing uses high frequency sound waves to conduct examination and make
measurements. Besides its wide use in engineering applications
(such as flaw detection and evaluation, dimensional
measurements, material characterization, etc), ultrasonic
arealsoused in medical field. In general, ultrasonic testing is on
capture and quantification of either the reflected waves. Each of
the two types are in certain applications, but generally, pulse echo
systems are more useful since they require one sided access to the
object being inspected
Fig, 4.1 Introduction to UT
Basic principle:
Fig, 4.2 Basic principle of UT
A typical pulse-echo UT inspection system consists of several functional units, such as the
pulser/receiver, transducer and display device. A pulser/receiver is an electrical device which
can produce high voltage electrical pulses. Driven by the pulser, the transducer produces high
frequency ultrasonic energy. The sound energy is introduced and propagates through the
materials in the form of waves. When there is an discontinuity in the wave path, path of
energy will be reflected back from the flaw surface . The reflected wave signal is transformed
into electrical signal by the transducer and explained on the screen. Knowing the velocity of
the signal, information about the reflector location, size, orientation and other features can be
gained

WAVE PROPAGATION:
Ultrasonic testing is based on the vibration in materials which is generally referred to as
acoustics. All material substances are comprised of atoms, which may be forced into
vibrational motion about their equilibrium positions. Many different patterns of vibrational
motion with at the atomic level; however, most are irrelevant to acoustics and ultrasonic
testing. Acoustics is focused on particles that contain many atoms that move in harmony to
produce a mechanical wave. When a material is not stressed in tension or compressionbeyond
its elastic limit, its individual particles perform their elastic oscillations. When the particles of
a medium are displaced from their equilibriumposition, internal restoration forces arise.
These elastic restoring between particles lead to the oscillatory motions of the medium. In
solids, sound waves can propagate in four principal modes
that are based on the way the particles oscillate. Sound can
propagate as longitudinal waves, shear waves surface waves
and in thin materials as plate waves longitudinal and shear
waves are the two modes of propagation used in the ultrasonic
testing as shown in the figure
Fig, 4.3 Wave propagation
Snell’s law:
It describes the relationship between the angles and the velocities of the waves. Snell’s law
equates the ratio of material velocities to the ratio of the sine’s of incident and refracted
angles, as shown in the following equation
Transducers:
There are two types of transducer
i. Contact type transducer
ii. Immersion transducer

Piezoelectric transducer(contact type):
The conversion of electrical pulses to
mechanical vibrations and conversion
of returned mechanical vibration into
electrical energy is the basis of UT
.The conversion is done by the
transducer using piezoelectric material
with electrodes attached to the two of
the opposite faces .When an electric
field is applied across the material, the
molecules will align themselves with
the electrical field causing the material
to change dimensions. In addition, a permanently polarized material such as quartz and
barium titanate will produce an electric field the material will change dimensions as a result
of imposed mechanical force. The phenomenon is known as piezoelectric effect
Immersion type:
These transducers are designed to operate in the liquid environment and all the connections
are water tight.Immersion transducers usually have an impedance matching layer helps to get
more sound energy into water and in into components being inspected. Immersion
transducers can be purchased with a planer focused or spherically focused lens. A focused
transducer can improve the sensitivity and axial resolution by concentrating the sound energy
to a smaller area. It is used inside a water tank or as part of a squitter or bubbler system in
scanning application

Fig, 4.5 Immersion type transducers
Ultrasonic Testing Techniques:
There are three types of techniques which are mainly used during inspection
i. A-scan technique:
It displays the amount of received ultrasonic energy as a function of time. The relative
amount of received energy is plotted along the vertical axis and the elapsed time is
displayed along the horizontal axis. Most instruments with a an A-scan display allow
the signal to be displayed allow the signal to be displayed in its natural radio
frequency form, as a fully rectified RF signal, or as either the positive or negative half
of the RF signal, or as the positive or negative half of the RF signal. In the A-scan
presentation, relative discontinuity size can be estimated by comparing the signal
amplitude obtained from unknown reflector. Reflector depth can be determined by the
signal on the horizontal time axis
Fig, 4.6 A, B & C-scan technique
ii. B-scan technique:
The B-scan presentation is a type of presentation that is possible for automated linear
scanning systems where it shows a profile of the test specimen. In the B-scan, the time
of flight of the sound waves is displayed along the vertical axis and the linear position of

the transducer is displayed along the horizontal axis. From the B-scan, the depth of the
reflector and its approximate linear dimensions in the scan direction can be determined.
The B-scan is typically produced by establishing a trigger gate on the A-scan. Whenever
the signal intensity is great enough to trigger the gate, appoint is produced on the B-
scan. The gate is triggered by the sound reflected from the back wall of the specimen
and by smaller reflector within the material. In the B-scan image shown previously, line
A is produced as the transducer moves to the right of this section, the back wall line BW
is product. When the transducer is over flaws B and C, lines that are similar to the
length of flaws and at similar depth of the material are drawn on the B-scan .It should be
noted that limitation to this display technique is that reflectors may be masked by large
reflector near surface
iii. C-scan technique:
The C-scan presentation is a type of presentation that is possible for automated for two-
dimensional scanning systems that provides a plan type view of the location and size of
test specimen features. The plane of the image is parallel to the scan pattern of the
transducer. C-scan presentations are typically produced with an automated data
acquisition system, such as computer controlled scanning system. Typically, a data
collection gate is established on the A-scan and the amplitude or the time-of-flight of the
signal is recorded at regular intervals as the transducer is scanned over the test piece. The
relative signal amplitude or the time-of-flight is displayed as a shade of grey or a colour
for each of the positions where data was recorded. The C-scan presentation provides an
image of the features that reflect and scatter the sound within and on the surfaces of the
test piece
Calibration method:
Calibration refers to the act of evaluating and adjusting the precision and accuracy of
measurement equipment. In UT, several forms of calibrations must occur. First, the
electronics of the equipment must be calibrated to ensure that they are performing as
designed. In UT reference standards are achieved a general level of consistency in
measurements and to help interpret and quantify the information contained in the receive
signal. The fig shows some of the commonly used to validate that the equipment and the
setup provide similar results from one day to the next and that similar results are
produced by different systems

Reference standards are mainly used for
 Checking the performance of both angle beam and normal beam transducers
 Determining the sound beam exit point of angle beam transducers
 Determining the refracted angle produced
 Evaluating instrument performance
IIW Type US-1 Calibration Block:
This block is a general purpose calibration block that can be used for calibrating angle; beam
transducers as well as normal beam transducers. The material from which IIW blocks are
prepared is specified as killed, open hearth or electric furnace, low carbon steel in the
normalized condition and with a grain size of McQuaid-Ehn No.8. Official IIW blocks are
dimensioned in the metric system of units. The block has several features that facilitate
checking and calibrating many of the parameters and functions of the transducer as well as
the instrument where that includes; angle beam exit, beam angle, beam speed spared, time
base, linearity, resolution, dead zone, sensitivity and range setting.T
Fig, 4.7 IIW Type US-1 Calibration Block
ASTM-Miniature Angle-Beam Calibration Block (V2):
The miniature angle-beam block is used in a somewhat similar manner as the IIW block,
but is smaller and lighter. The miniature angle-beam block is primarily used in the field
for checking the characteristics of angle-beam transducers.
With the miniature block, beam angle and exit point can be checked for an angle-beam
transducer. Both the 25 and 50 mm radius surfaces provide ways for checking the
location of the exit point of the transducer for calibrating the time base of the instrument

in terms of the metal distance. The small hole provides a reflector for checking beam
angle and for setting the instrument gain.
Inspection Technique:
i. Normal Beam Inspection
Pulse-echo ultrasonic measurementscan determine location of a discontinuity in a
part of a structure by accurately measuring the time required for short ultrasonic
pulse generated by a transducer to travel through a
thickness of a material reflect from the back of a surface
of a discontinuity and be returned to the transducer. In
most applications, this time interval is a few
microseconds or less. The two way transit time
measured is divided by two to account down-and-back travel path and multiplied
by the velocity of sound in the test material. The result is expressed in the well-
known relationship
Where d is the distance from the distance to the discontinuity in the test piece, V
is the velocity of sound waves in the material, and t is the measured round-trip
transit time.
Precision ultrasonic thickness gages usually operate at frequencies between 500
kHz and 100 MHz, by means of piezoelectric transducers that generate bursts of
sound waves when excited by electrical pulses. Typically, lower frequencies are
used to optimize penetration when measuring thick, highly attenuating, non-
scattering materials. It is possible to measure most engineering materials
ultrasonically, including metals, plastic, ceramics, composites, epoxies, and glass
as well as liquid level and the thickness of certain biological specimens. On-line
or in-process measurement of extruded plastics or rolled metal often is possible, as
is measurements of single layers or coatings in multilayer materials.

ii. Angle Beam Inspection
Fig, 4.9 Angle Beam Inspection
Angle beam transducers and wedges are typically used to introduce a refracted
shear wave into the test material. An angled sound path allows the sound beam to
come in from the side, thereby improving detectability of flaws in and around
welded areas. Angle beam inspection is somehow different than normal beam
inspection. In normal beam inspection, the back wall echo is always present on the
scope display and when the transducer basses over a discontinuity a new echo will
appear between the initial pulse and the back wall echo. However, when scanning
a surface using an angle beam transducer there will be noreflected echo on the
scope display unless a properly oriented discontinuity or reflector comes into the
beam path.If a reflection occurs before the sound waves reach the back wall, the
reflection is usually referred to as “first leg reflection”.
Fig, 4.10 Second leg Reflection
If a reflector came across the sound beam after it has reached and reflected off the
back all, the reflection is usually referred to as “second leg reflection”. In this
case, the “Sound Path” (the total sound path for the two legs) and the “Surface

Distance” can be calculated using the same equations given above; however the
“Depth” of the reflector will be calculated as
Advantages and Disadvantages:
Advantages:
 It is sensitive to both surface and sub-surface discontinuities.
 The depth of penetration for flaw detection or measurement is superior to other NDT
methods
 Only single-sided accurate in determining reflector position and estimating size and
shape
 Minimal part preparation is required
 It provides instantaneous results
 Detail images can be produced with automated systems
 It has other uses, such as thickness measurement, an addition to flaw detection
 Its equipment can be highly portable or highly automated
Disadvantages:
 Surface must be accessible to transmit ultrasound
 Skill and training is more extensive than with some other method
 It normally requires a coupling medium to promote the transfer of sound energy into
the test specimen
 Cast iron and other coarse grains are difficult is difficult due to low sound
transmission and high signal noise
 Linear defects oriented parallel to the sound beam may go undetected
 Reference standards are required to both equipment calibration and the
characterization of flaws

NDT REPORTT

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