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Topic : Non Destructive Testing (NDT)

L&T Heavy Engineering Divison

Hazira

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Outline

What is NDT ? Where is NDT used ?

When is NDT used ?

Types of Discontinuities.

Common NDT methods.

NDT in L&T

Questions & Answers

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What is NDT ?

NDT Non Destructive TestingThe use of noninvasive

techniques to determine

the interity of a materia!"

component or structure orquantitative!y measure

some characteristic of

an o#$ect.i.e. %nspect or

measure without doin harm.

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What is NDT ? Contd..

The fie!d of Nondestructive Testin NDT' is a very#road" interdiscip!inary fie!d that p!ays a critica! ro!e

in assurin that structura! components and systems

perform their function in a re!ia#!e and cost effective

fashion. NDT technicians and enineers define andimp!ement tests that !ocate and characteri(e

materia! conditions and f!aws that miht otherwise

cause p!anes to crash" reactors to fai!" trains to

derai!" pipe!ines to #urst" and a variety of !ess visi#!e"#ut equa!!y trou#!in events.

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What is NDT ? Contd..

)ecause NDT a!!ows inspection without interferinwith a product*s fina! use" it provides an e+ce!!ent

#a!ance #etween qua!ity contro! and cost,

effectiveness. Techno!oy that is used in NDT is

simi!ar to those used in the medica! industry- yet"typica!!y non!ivin o#$ects are the su#$ects of the

inspections.

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When is NDT use! ?

NDT is used #oth #efore and after production of rawmateria!s such as inots and castins" #efore and

after fa#rication" and #efore and after assem#!y of

parts into a comp!eted system.sin NDT /#efore/

prevents a su#standard materia! or part fromwastin time and increasin scrap production. The

/when/ is riht if profit" qua!ity" and safety are the

resu!t of usin NDT.

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Discontinuities %ont!

The definition of defects chanes with the type ofcomponent" its construction" its materia!s and the

specifications or codes in force.

%t is possi#!e that discontinuity in one o#$ect may #e

defect in another.Detection of discontinuities is

!are!y dependent on the discontinuity2s physica!

characteristics.

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Whi!e performin NDT it is a!so important to considerhow the materia! is produced" what manufacturin

process are used to form the finished product and

what discontinuities are typica!!y initiated #y the

process operations. Discontinuity is cateori(ed #ythe stae of manufacturin or use in which it

initiates.

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'nherent !iscontinuities :

When ferromanetic materia!s are produced" mo!ten

meta! so!idifies into inot form producin what is

4nown as inherent discontinuities.

1uch discontinuities then can #e ro!!ed" fored and

section a!on with the materia! in its su#sequent

processin operations.

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'nherent Discontinuities

%ol! shut

Location 0 1urface or 1u#surface

Cause 0 The meetin of two streams of !iquid meta!

that do not fuse toether.

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orosity


Cause 0 5ntrapped ases durin so!idification of

meta!s

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'nclusions


Cause 0 Contaminant introduced durin the castin

process

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Hot tears

Location 0 1urface

Cause 0 6estraints from the core or mo!d durin the

coo!in process.

egregation

Location 0 1urface or su#surface

Cause 0 Loca!i(ed differences in materia!

composition.

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ri*ary rocessing !iscontinuities :

Discontinuities those oriinate durin hot or co!d

formin are said to #e primary processin

discontinuities. The processin of a wrouht product

#y ro!!in" forin" castin or drawin may introduce

specific discontinuities into the product and inherent

discontinuity that were at one time undetecta#!e or

insinificant may propaate and #ecome detrimenta!

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ri*ary rocessing Discontinuities (Wel!)

orosity


Cause 0 7apori(ed constituents in the mo!ten we!d

meta! are entrapped durin so!idification.

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%luster orosity


Cause 0 7apori(ed constituents in the mo!ten we!d

meta! are entrapped durin so!idification.

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Lac+ o" enetration


Cause 0 %nadequate penetration of the we!d $oint root

#y the we!d meta!.

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'nternal .n!ercutLocation 0 1urface

Cause 0 9ver si(ed we!d poo! re!ated to e+cessive

amperae" trave! speed and e!ectrode si(e.'

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E/ternal .n!ercutLocation 0 1urface

Cause 0 9ver si(ed we!d poo! re!ated to e+cessive

amperae" trave! speed and e!ectrode si(e.'

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O""set or *is*atchLocation 0 1urface

Cause 0 where two pieces #ein we!ded toether are

not proper!y a!ined.

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%ol! 0 Hot %rac+Location 0 1urface or 1u#surface.

Cause 0 A com#ination of atomic hydroen"

hardena#!e materia! and hih residua! stress.

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'na!e1uate 2el! rein"orce*ent

Location 0 1urface.

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E/cess 2el! rein"orce*ent

Location 0 1urface.

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Tungsten 'nclusionLocation 0 1u#surface.

Cause 0 :o!ten we!d poo! or fi!!er meta! comes in

contact with the tip of tunsten e!ectrode.

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-urn ThroughLocation 0 1urface.

Cause 0 Too much heat causes e+cessive we!d

meta! to penetrate the we!d (one.

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econ!ary processing Discontinuities

3rin!ing %rac+s

Location 0 1urface

Cause 0 Loca!i(ed overheatin of the materia! due toimproper rindin procedures.

Heat Treating %rac+s

Location 0 1urface

Cause 0 neven heatin and coo!in that producesstresses e+ceedin the tensi!e strenth of themateria!.

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ervice 'n!uce! Discontinuities

,atigueLocation 0 1urface

Cause 0 Cyc!ica!!y app!ied stress #e!ow the u!timate

tensi!e strenth.

%reep

Location 0 1urface

Cause 0 :ateria! su#$ected to e!evated temperatures

and stress #e!ow the yie!d strenth.

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ervice 'n!uce! Discontinuities

tress %orrosion %rac+ingLocation 0 1urface

Cause 0 Com#ined effect of static tensi!e !oad and

corrosive environment.

Hy!rogen %rac+ing

Location 0 1urface

Cause 0 Com#ined effect of app!ied tensi!e or

residua! stress and hydroen enriched environment.

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%o**on NDT 5etho!s

The most common NDT methods used are asfo!!ows 0

!trasonic Testin.

:anetic 3artic!e Testin.

3enetrant Testin.

6adioraphy Testin.

5ddy Current Testin.

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;ih frequency sound waves are introduced into a

materia! and they are ref!ected #ac4 from surfaces orf!aws.

6ef!ected sound enery is disp!ayed versus time" andinspector can visua!i(e a cross section of the specimen

showin the depth of features that ref!ect sound. "

p!ate

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