radiography testing

7/29/2019 Radiography testing

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RADIOGRAPHY

TESTING


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Principle of Radiography


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Principle of Radiography

Electromagnetic radiation of certain wavelengths

penetrate materials and are absorbed differentially

by different materials. The emergent radiation from the job is recorded

normally on a film

The film after processing is called a radiograph

and contains the shadow image of the

discontinuities which produce differential degree

of darkness on the radiograph


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ELECTROMAGNETIC SPECTRUM


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Characteristics of X rays and Gamma

Rays

Capable of Penetrating most of the

industrial materials

Travels in straight lines

Can affect photographic films

Can ionize gases

Can affect living cells

Invisible, Odorless


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Sources of Electromagnetic

Radiation

X Rays

X ray Generator, Linear Accelerator, Betatron

Gamma Rays

Natural and Artificial Radioactive elements

Natural : Radium, Polonium, Uranium, Radon

Artificial : Iridium 192, Cobalt 60, Cesium 137

Ytterbium 170, Thulium 169


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X RAY

X rays are produced when high speed

electrons hit a material target in an

evacuated chamber ( 10 ^ -12 to 10^ -13torr )


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CONSTRUCTION OF

X RAY GENERATOR


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FOCAL SPOT


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Parameters in X Radiography

KVControls thickness to which can be

radiographed

Exposure affects the density of image in

the radiographs

ExposuremA * Mins


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X RAY UNIT - CONTROLS


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Gamma radiography

Gamma rays are

produced during

radioactive decay of

elements

Alpha particles are

He++

Beta particles are (-)

Gamma radiation is

a electromagnetic

radiation


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Radioactive decay


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RADIOACTIVE

SOURCE CAMERA


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GAMMA RAY

CAMERA OPERATION

Source in stored

position in pig

Source cranked partially out

source no longer shielded

Source in exposure

position all the way


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Source Pencil


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Co 60

Created by Neutronbombardment,

capsuled pellet

1.17, 1.33 MeV

Penetration 1 - 8 steel

Requires thick shielding Container is bulky and

handling difficult

Iridium 192

Produced by neutron

bombardment 0.31, 0.47 & 0.60 MeV

Capsuled pellet

Easy shielded and less

bulky widely used

0.253 inches thick steel


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EXPOSURE CHART


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Characteristics of sources

Isotope Cobalt60 Ir 192 Cs 137c

Half life 5.3 yrs 75 days 30 yr

Form Co Ir CsCl

Energy 1.33,1.17 0.45 0.66

Practical Sources

Ci 20 50 75Rhm 27 60 30

Dia, app, 3 mm 3 mm 10 mm


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Characteristics of Isotopes

Curie is a measure of disintegration of source 1 Ci

= 3.7 x 10 10 disintegrations per sec

In SI System it is 1 Becquerel = 1 disintegrations /sec

Half Life : length of time required for the activity

to decay to one half of the original value

Energy is expressed as KeV or MeV

Specific Activity : Ci/ gm of isotope


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Parameters in Gamma

radiography Source determines the thickness limit of

radiography

Exposure determines the density ofradiographic image

Exposure = Curie * min

CurieStrength of source


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RADIOGRAPHIC FILM


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CHARACTERISTIC CURVE


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FILM PROCESSING


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ASTM Penetrameters

Hole Type Wire Type


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LOCATION OF PENETRAMETERS

AWS D1.1


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Sensitivity Level

Equivalent

Sensitivity %

Quality Level T of

Penetrameter

Perceptible

hole dia

0.7 1-1T 1 1T

1.0 1-2T 1 2T

1.4 2-1T 2 1T

2.0 2-2T 2 2T

2.8 2-4T 2 4T

4 4-2T 4 2T


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DIN Wire Penetrameter

DIN 1-7

1- 3.2; 2-2.5; 3-2.0; 4-1.6;

5-1.25; 6-1.00; 7-0.8 DIN 6-12

6-1.00; 7-0.8; 8-0.63; 9-0.5

10-0.4 11-0.32;120.25

DIN 10-16

10-0.4; 11-0.32; 12- 0.25 13-0.2

14-0.16; 15 - 0.125 16-0.1


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ASTM Wire Penetrameter

SET A

No 10.08 mm, 2-0.1,30.13 4-0.16, 5-0.2, 6-0.25

SET BNo 6-0.25,7-0.33, 8- 0.4, 9-0.51, 10-0.64,11-0.81

SET C

No 11-0.81, 12-1.02, 13- 1.27, 14-1.6 15-2.03 16-2.5 SET D

No 16-2.5 17- 3.2 18-4.06 19-5.1 20-6.4 218


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Wire Penetrameter Sensitivity

SENSITIVITY

S = ( D / T ) * 100

SSensitivity in %

D - Dia of smallest wire seen in mm

T

Thickness of Job in mm


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Effect of angle of radiation


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RT Techniques

Double wall Single imageSingle Wall Single Image

Job WeldFilm Source Radiation


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RT Techniques

Job WeldFilm Source Radiation

Double Wall Double Image Panoramic Exposure


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Radiation Safety

Radiation safety is ensured by

Radiation Protection

Radiation monitoring


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Radiation Protection

Radiation Protection is ensured by

Undertaking RT in an enclosure

Maintaining safe distances

Providing local temporary enclosure around the

source

Retaining the source in the camera when not inuse


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Radiation Monitoring

Ensuring that radiation intensity

is within limits

Thermo Luminescent Dosage(TLD) badge is used for

monitoring the dosage received

by the operator

TLD Badges are processed every

month by BARC or its

authorised agency


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AWS D1.1

RT Evaluation

* Pl refer to codes for details

w

e

ld

s

i

ze

Gap between defects


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AWS D1.1

RT Evaluation

* Pl refer to codes for details


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RADIOGRAPHIC INDICATIONS

INTER-PASS SLAG INCLUSIONS


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SLAG INCLUSION


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SLAG INCLUSION


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CLUSTER PORES


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LACK OF PENETRATION


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PORES


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WORM HOLE


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THANK YOU

radiography testing

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