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NON DESTRUCTIVE TESTING

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What is NDT ?

Is procedure , covers the inspection and testing of anymaterial , component or assembly by means which do

not effect ultimate serviceability.

SCOPE OF NDT

Covering the fields : Design , safety engineering.

Quality control of product specifications .

Condition monitoring and maintenance

Industrial standards .

What is the aim of NDT ?

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NDT

The aim of NDT:

Deficiencies in materials and products.

Determination of physical and geometrical properties of

materials and products. Structural behavior of materials , products and installations.

What are the test methods ?

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Visual Inspection. Radiation methods

Leak testing

Liquid penetrate testing

Magnetic particle testing

Ultrasonic testing.

What U R going to see during visual inspectionof Welds and How ?

NDT

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NDT( Visual inspection )

Before welding :Dents , Burrs , scales,

dirt , grease and mill scale on the

fusion faces.

During fit-upGeometry of edge andjoint preparation(Root face ,root

gap, bevel and angle )

After welding :

Removal of spatters and slag.

Appearance of ripples on the weld.

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NDT( Visual inspection )

Undercuts and overlaps.

Unfilled crater.

Gas pockets or porosities.

External cracks.

Size and shape of the bead.

The appearance of the weld

is considered to be goodifripples are spacedregularly.

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NDT (MPT)

Used for detection of surfaceand near surface flaws inferromagnetic materials primarily for crack detection.

Magnetic reluctance Surfacebreaking flaw Magnetic field

will be distorted.

Cause local flux leakagearoundthe flaw.

Magnetic Flux is displayed byvery fine iron particles dry or

wet.

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NDT ( MPT )

Magnetizationcan be produced :

Applying a permanent or electro-magnet to the surface ( Magnetic

flow) Passing a large current to the

specimen or locally by means ofcurrent flow.

Putting the specimen inside acurrent coil or forming a coilaround the specimen.

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NDT ( MPT )

Used may beAC or DCof any wave

form.

Important - current used is correct

for the specimen size.

Dry powder or liquid magnetic inc.

Will be applied while magnetic

current is flowing . or

Residual magnetismis sometimesused when the particles are applied

after magnetization.

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NDT ( MPT )

Magnetic inks are used widelyby low pressure spray, dippingor brushing.

Important to use plenty of inkand to allow time for particlesto flow over the surface andmigrate to any cracks.

On dark surfaces a very thinlayer ofwhite paintcan beapplied to give a heightcontrast indication.

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NDT (MPT)

Defects detected: Surface cracks which may be missed by naked eye .

Give indication of subsurface flaws.

Advantages; Relatively low cost.

Portable

Gives clear indication.

Limitations ;

Only surface cracks

Used only on ferromagnetic materials

No permanent record.

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LIQUID PENETRANT TESTING

Principle is the liquidpenetrant drawn in to thesurface flaw by capillaryaction.

Surface flawssuch ascracks,laps , porosity.

One step up from visualinspection.

Advantages :

Speed ,large area coverage andlow cost.

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LIQUID PENETRANT TESTINGTesting is usually six stages.

1. Surface cleaning (Degreasingetc)

2. Application of penetrant

(Dipping ,spraying or by brush)3. Removal of excess penetrant

(solvent )

4. Application of developer

5. Inspection of test surface

6. Post inspection cleaning.

Matls : Penetrant /developer /cleaner.

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LIQUID PENETRANT TESTING

Can be applied to anynon-porous cleanmaterial ,metallic or non-

metallic. Unsuitable for the dirty or

very rough surfaces.

Surface cleaning is avitalpart of LP testingtechnique.

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RADIOGRAPHY EXAMINATION

Detectingdiscontinuities in testobjects by passing

ionizing radiationonradiography films.

Permanent record.

Industrial radiographycan be Gamma ray and X-ray.

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RADIOGRAPHY EXAMINATION Source Half life

Iridium 192 74days

Cobalt60 5.26 years

Cesium 137 30 years

Thorium 170 127days

X-ray source needs electricpower and continuous

cooling.

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RADIOGRAPHY EXAMINATION Strength of the source:

The old unit is curie(Ci) ,newunit is Bequeral (Bq)

1 curie = 3.7 x 1010disintegrations /sec

1 Bequeral = one transmission/second

1curie = 37G Bq ( G stands for

Giga = 109 Radiography film will be

measured in Densitometrerange 1.5 to 3.0.

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RADIOGRAPHY EXAMINATION Techniques:

Single wall image :Center is

not accessible ,source can be

off the center .

Double wall single image:Noaccess to the inside .Source

can be kept away from the

job.Source film distance

required and accessible.

Double wall double image:

small size below 21/2 inch

.diameter.Elliptical shot.

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RADIOGRAPHY EXAMINATION

Exposure time will be calculated based on the

strength of the source , thickness of the job.

As radiation is harmful , no workmen is

allowed during radiography. As Gamma is

scattered radiation.

Distance coverage depends on the source and

direction.

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Ultrasonic testing

Detection of discontinuitiesgenerally by pulse echomethod.

Using straight and angularbeams.

Flaw can be identified bynoting the reductionin thestrength of the transmittedvibration.

signal will be transmitted atright angleto the surface.

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Ultrasonic testing

Absence of the defect ,travelthrough the thickness andreflected on the other face andreturnto the probe.

Defect shorter distance totravel.

Set the distance between twoechoes as thickness.

Knowing the geometry of thesystem exact location can becalculated.

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THANKS