NON-DESTRUCTIVE TESTING

by GROUP-E

MEMBERS 1 JUDE RINALDO2 JUDE PRADEEP3 AARYL D’SA4 SWAROOP SUNDER

Describe the five types of non-destructive test used in ship construction

NON-DESTRUCTIVE TESTING

In this process the material is tested for any flaws without 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 formed into finished or semi finished products.

At the end of these tests there are no damage to the components

Non-destructive testing is required to enable the soundness of ship welds to be assessed

There are five of non destructive tests:

Visual examinationDye penetrant testMagnetic particle inspectionRadiographic inspectionUltra sonic inspection

NON-DESTRUCTIVE TESTING

VISUAL EXAMINATIONAny 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

Visual inspection can be simply visual i.e. with the naked eye 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

When used in conjunction with NDT it is essentially applied at every stage involving human eye e.g. reading measuring instrument screens.

This forms the simplest form of investigation used as there are no sophisticated and costly instruments used.

VISUAL EXAMINATION

Advantages It is a routine procedure The cost of visual inspection is low It can be very effective where examination is

made before,during, and after welding

VISUAL EXAMINATION

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 a developing agent

It will show up a surface flaw To aid the detection of a surface crack, the dye is often

luminous and is revealed under an ultra violet light

The dye penetrant test consists of the following steps: The surface of the metal to be inspected is cleaned first

and a low 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 if there is any crack and stains the developer red

DYE PENETRANT TEST

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

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 there is an alteration in the magnetic field

MAGNETIC PARTICLE INSPECTION A component is place between two poles of a

magnet The lines of magnetism concentrate around flaws.

Magnetic particles are then applied, in a light oil or dry sprayed, onto the surface where they indicate the lines of magnetism and any anomalies

MAGNETIC PARTICLE INSPECTION

Advantages Portable Fast and rapid Low cost Defects like cracks, slag inclusions and gas porosities

can be detected

DisadvantagesCan be used only in Ferro-magnetic

material only

MAGNETIC PARTICLE INSPECTION

RADIOGRAPHIC INSPECTION Process A material is subjected to

radiation from one side, and record the radiation emitted from the opposite side

Either x ray or gamma ray devices may be used to provide the source of radiation

Ant obstacle in the path of the radiation will affect the radiation density emitted and may be recorded

As radiation will expose photo graphic plates, they are used to record the emitted rays

The photographic plates records changes in radiation density emitted

Thus any defects in welding can be found out by this method

Equipment used

RADIOGRAPHIC INSPECTION

Advantages It can give a permanent record of the test for future

evidence 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 required gamma rays is an alternative to x rays

because of this disadvantages

RADIOGRAPHIC INSPECTION

ULTRASONIC INSPECTION Process The principle of

ultrasonic inspection depends on the fact that pulses of ultrasonic energy are reflected from any surface which they encounter

Virtually total reflection occurs at an air-metal interface, and therefore to get the ultrasonic wave into the metal a liquid (usually grease) is placed between the source and metal

Pulsed beams of ultrasonic waves pass through the object

Waves traveling through a plate may be reflected from the surface of the metal and also from the surfaces of any flaws in the metal

A receiver detects the reflected waves signal, which is displayed after signal amplification and analysis by the instrument

The pattern of reflection is revealed on either Cathode ray tube or liquid crystal display

From that we will be able to recognize type and location of flaws

ULTRASONIC INSPECTION

Advantages Low cost Equipments used are easy to handle

No health hazards The technique is used for locating fine cracks, which

are missed by radiography They can also be used for assessing the thickness of

structural members

ULTRASONIC INSPECTION