Download - NDT examination
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NON-DESTRUCTIVE
TESTINGby
GROUP-E
MEMBERS
1 JUDE RINALDO
2 JUDE PRADEEP
3 AARYL DSA4 SWAROOP SUNDER
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Describe the five types of
non-destructive test used inship construction
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NON-DESTRUCTIVE TESTING
In this process the material is tested for any flawswithout applying any kind of stress
The test piece is not destroyed or deformed Non-destructive tests are desirable for materials that are
costly or difficult to fabricate or that have been formedinto finished or semi finished products.
At the end of these tests there are no damage to thecomponents
Non-destructive testing is required to enable thesoundness of ship welds to be assessed
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There are five of non destructive tests:
Visual examination
Dye penetrant test
Magnetic particle inspection
Radiographic inspection
Ultra sonic inspection
NON-DESTRUCTIVE TESTING
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VISUAL EXAMINATION
Any surface defects are noticed by the
experienced and responsible personnel
Some of the defects are: Incorrect bead shape
High spatters Under cutting
Bad stop and start points
Incorrect alignment
Surface cracks
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Visual inspection can be simply visual i.e. with the nakedeye or at magnifications up to 40 times.
This test can be done in conjunction with NDT or as
stand alone. When this test is done as stand alone then it is used for
identifying macro manufacturing defects.
VISUAL EXAMINATION
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When used in conjunctionwith NDT it is essentiallyapplied at every stageinvolving human eye e.g.reading measuring
instrument screens.
This forms the simplestform of investigation usedas there are no
sophisticated and costlyinstruments used.
VISUAL EXAMINATION
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Advantages It is a routine procedure
The cost of visual inspection is low
It can be very effective where examination ismade before,during, and after welding
VISUAL EXAMINATION
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DYE PENETRANT TEST
Process Liquid ( containing either dye or ultra violet-sensitive
substances) is sprayed onto specimen
The liquid is drawn into the crack by capillary action, then
by highlighting its presence after application of adeveloping agent
It will show up a surface flaw
To aid the detection of a surface crack, the dye is oftenluminous and is revealed under an ultra violet light
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The dye penetrant test consists of the following steps:
The surface of the metal to be inspected is cleaned first and alow viscosity penetrant is sprayed on.
After a set time the surface is cleaned again.
Then a developer is coated on the surface the dye seeps out ifthere is any crack and stains the developer red
DYE PENETRANT TEST
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Advantages A simple way to detect surface opening cracks and
porosities in non porous and clean specimen
Low-cost
It can detect small defect on smooth and clean
surfaces
Disadvantages Cannot be used for rough and dirty surfaces
DYE PENETRANT TEST
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MAGNETIC PARTICLE INSPECTION
Process It is carried out by locally magnetizing the specimen by
a yoke or a coil
Then by spreading a fluid of magnetic particles e.g. iron
fillings suspended in paraffin on its surface Any discontinuity such as a surface crack will show up
as the particles will concentrate at the point where thereis an alteration in the magnetic field
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MAGNETIC PARTICLE INSPECTION
A component is place between two poles of a
magnet The lines of magnetism concentrate aroundflaws.
Magnetic particles are then applied, in a light oil ordry sprayed, onto the surface where they indicate the
lines of magnetism and any anomalies
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MAGNETIC PARTICLE INSPECTION
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Advantages
Portable
Fast and rapid
Low cost
Defects like cracks, slag inclusions and gas porosities
can be detected
Disadvantages
Can be used only in Ferro-magnetic material
only
MAGNETIC PARTICLE INSPECTION
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RADIOGRAPHIC INSPECTIONProcess
A material is subjected toradiation from one side, andrecord the radiation emittedfrom the opposite side
Either x ray or gamma raydevices may be used to providethe source of radiation
Ant obstacle in the path of theradiation will affect the radiationdensity emitted and may berecorded
As radiation will expose photographic plates, they are used torecord the emitted rays
The photographic platesrecords changes in radiationdensity emitted
Thus any defects in welding canbe found out by this method
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Equipment used
RADIOGRAPHIC INSPECTION
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Advantages
It can give a permanent record of the test for futureevidence It is a quick process Accurate results
Disadvantages Cannot use for thick sections Cannot use in places of difficult access The process fails without electricity To interpret the weld radiograph a large amount of
experience is requiredgamma rays is an alternative to x rays
because of this disadvantages
RADIOGRAPHIC INSPECTION
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ULTRASONIC INSPECTIONProcess
The principle of
ultrasonic inspectiondepends on the fact thatpulses of ultrasonicenergy are reflectedfrom any surface whichthey encounter
Virtually total reflectionoccurs at an air-metalinterface, and thereforeto get the ultrasonicwave into the metal aliquid (usually grease) isplaced between thesource and metal
Pulsed beams ofultrasonic waves passthrough the object
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Waves traveling through a plate may be reflected from
the surface of the metal and also from the surfaces of anyflaws in the metal
A receiver detects the reflected waves signal, which is
displayed after signal amplification and analysis by theinstrument
The pattern of reflection is revealed on either Cathoderay tube or liquid crystal display
From that we will be able to recognize type and locationof flaws
ULTRASONIC INSPECTION
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Advantages
Low cost
Equipments used are easy to handle
No health hazards
The technique is used for locating fine cracks, whichare missed by radiography
They can also be used for assessing the thickness ofstructural members
ULTRASONIC INSPECTION