NDT examination

7/30/2019 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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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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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



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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

Documents

NDT examination