NONDESTRUCTIVE TESTING by GROUPE MEMBERS 1 JUDE RINALDO

NON-DESTRUCTIVE TESTING by GROUP-E MEMBERS 1 JUDE RINALDO 2 JUDE PRADEEP 3 AARYL D’SA 4 SWAROOP SUNDER

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

NON-DESTRUCTIVE TESTING Ø In this process the material is tested for any flaws without applying any kind of stress Ø The test piece is not destroyed or deformed Ø 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. Ø At the end of these tests there are no damage to the components Ø Non-destructive testing is required to enable the soundness of ship welds to be assessed

NON-DESTRUCTIVE TESTING There are five of non destructive tests: Ø Visual examination Ø Dye penetrant test Ø Magnetic particle inspection Ø Radiographic inspection Ø Ultra sonic inspection

VISUAL EXAMINATION Ø Any surface defects are noticed by the experienced and responsible personnel Some of the defects are: Ø Ø Ø Incorrect bead shape High spatters Under cutting Bad stop and start points Incorrect alignment Surface cracks

VISUAL EXAMINATION Ø Visual inspection can be simply visual i. e. with the naked eye or at magnifications up to 40 times. Ø This test can be done in conjunction with NDT or as stand alone. Ø When this test is done as stand alone then it is used for identifying macro manufacturing defects.

VISUAL EXAMINATION Ø When used in conjunction with NDT it is essentially applied at every stage involving human eye e. g. reading measuring instrument screens. Ø This forms the simplest form of investigation used as there are no sophisticated and costly instruments used.

VISUAL EXAMINATION Advantages Ø It is a routine procedure Ø The cost of visual inspection is low Ø It can be very effective where examination is made before, during, and after welding

DYE PENETRANT TEST Process Ø Liquid ( containing either dye or ultra violet-sensitive substances) is sprayed onto specimen Ø The liquid is drawn into the crack by capillary action, then by highlighting its presence after application of a developing agent Ø It will show up a surface flaw Ø To aid the detection of a surface crack, the dye is often luminous and is revealed under an ultra violet light

DYE PENETRANT TEST The dye penetrant test consists of the following steps: Ø The surface of the metal to be inspected is cleaned first and a low viscosity penetrant is sprayed on. Ø After a set time the surface is cleaned again. Ø 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 Ø A simple way to detect surface opening cracks and porosities in non porous and clean specimen Ø Low-cost Ø It can detect small defect on smooth and clean surfaces Disadvantages Ø Cannot be used for rough and dirty surfaces

MAGNETIC PARTICLE INSPECTION Process Ø It is carried out by locally magnetizing the specimen by a yoke or a coil Ø Then by spreading a fluid of magnetic particles e. g. iron fillings suspended in paraffin on its surface Ø 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 Ø A component is place between two poles of a magnet The lines of magnetism concentrate around flaws. Ø 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

MAGNETIC PARTICLE INSPECTION Advantages Ø Ø Portable Fast and rapid Low cost Defects like cracks, slag inclusions and gas porosities can be detected Disadvantages Ø Can be used only in Ferro-magnetic material only

RADIOGRAPHIC INSPECTION Process Ø A material is subjected to radiation from one side, and record the radiation emitted from the opposite side Ø Either x ray or gamma ray devices may be used to provide the source of radiation Ø Ant obstacle in the path of the radiation will affect the radiation density emitted and may be recorded Ø As radiation will expose photo graphic plates, they are used to record the emitted rays Ø The photographic plates records changes in radiation density emitted Ø Thus any defects in welding can be found out by this method

RADIOGRAPHIC INSPECTION Equipment used

RADIOGRAPHIC INSPECTION Advantages Ø It can give a permanent record of the test for future evidence Ø It is a quick process Ø Accurate results Disadvantages Ø Ø 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

ULTRASONIC INSPECTION Process Ø The principle of ultrasonic inspection depends on the fact that pulses of ultrasonic energy are reflected from any surface which they encounter Ø 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 Ø Pulsed beams of ultrasonic waves pass through the object

ULTRASONIC INSPECTION Ø 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 Ø A receiver detects the reflected waves signal, which is displayed after signal amplification and analysis by the instrument Ø The pattern of reflection is revealed on either Cathode ray tube or liquid crystal display Ø From that we will be able to recognize type and location of flaws

ULTRASONIC INSPECTION Advantages Ø Low cost Ø Equipments used are easy to handle Ø No health hazards Ø The technique is used for locating fine cracks, which are missed by radiography Ø They can also be used for assessing the thickness of structural members