FIGURE
2
RADIOGRAPHIC TECHNIQUE:
•
SINGLE WALL TECHNIQUE
•
DOUBLE WALL TECHNIQUE
•
3 ½ OR LESS IN NOMINAL OD. RADIATION PASSES TWO WALL
AND BOTH WALLS ARE REVIEWED – OFF SET METHOD OR
SUPER IMPOSED.
FOR OFF SET METHOD MIN. 2 SHOTS IN 90 DEG.
APART.
SUPER IMPOSED –3 SHOTS IN 60 DEG. APART.
•
DOUBLE WALL SINGLE
EXPOSURES AT 120 DEG.
IMAGE
AT
LEAST
3
3
4
5
6
7
8
9
10
11
12
13
14
15
STEREORADIOGRAPHY
THE RIGHT EYE SEES THE IMAGE
OF THE RIGHT SHIFT POSITION
OF THE X-RAY TUBE, AND THE
LEFT EYE SEES THE IMAGE OF
THE LEFT SHIFT POSITION. THE
BRAIN COMBINES AND MERGES
THE TWO IMAGES INTO ONE IN
WHICH TRUE PERSPECTIVE AND
SPATIAL RELATIONSHIPS ARE
APPARENT. STEREOGRAPHY IS
LITTLE USED IN INDUSTRIAL
RADIOGRAPHY BUT IS OF VALUE
IN
FLAW
LOCATION
OR
STRUCTURAL
VISUALIZATION
(FIG 6.51).
16
17
QUALITY OF A GOOD RADIOGRAPH
• GOOD DEFINITION
• GOOD CONTRAST
• LEAST DISTORTION
TO ACHIEVE THE ABOVE
• REDUCE UN-SHARPNESS TO MINIMUM
• SELECT CONDITIONS FOR HIGH CONTRAST
• ENSURE PERPENDICULARITY OF THE RADN. TO THE
SPECIMEN
18
RADIOGRAPHIC SENSITIVITY
19
ASME CLASSIFICATION
TYPES OF INDUSTRIAL RADIOGRAPHIC FILM
FILM TYPE SPEED
CONTRAST GRAINNESS
1
LOW
VERY HIGH
VERY LOW
2
MEDIUM
HIGH
LOW
3
HIGH
MEDIUM
HIGH
4
HIGH
FOR SCREEN
TYPE FILMS
20
CHARACTERISTICS OF GAMMA SOURSES
Isotope
Ir 192
Co 60
Cs 137
Gamma
Energies
MeV
RHM /Ci
0.31, 0.47,
0.64
1.17, 1.33
0.66
0.5
1.33
0.37
Opt. Thick
10-70 mm
HVL mm
of lead
Approx.
Dia.
50-150 mm 20-100 mm
2.8
13
8.4
3
3
6
21
Where Ug is the geometric un-sharpness, F is the size
of the radiation source, D0 is the source object distance,
and t is the object-film distance. Since the maximum unsharpness involved in any radiographic procedure is
usually the significant quantity, the object-film distance
(t) is usually taken as the distance from the source side
of the specimen to the film.
Ug = F (t /D0)
22
FIGURE
23
24
Geometric Representation
of Radiographic Image
25
SHARPNESS OF RADIOGRAPHIC IMAGE
GEO. UNSHARPNESS: Ug = F t/do
F-RADIATION SOURSE SIZE.
t-SPECIMEN THICKNESS.
do- SOURSE TO OBJECT DISTANCE.
Ug RECOMMENDATIONS. (ASME)-2004
FOR WELDS & CASTINGS
MATERIAL THICK IN mm
Ug (max),mm
UP TO 50
0.5
50-75
0.75
OVER 75-100
1.00
MORE THAN 100
1.75
26
IQI
- A DEVICE EMPLOYED TO OBTAIN EVIDENCE
ON RADIOGRAPH THAT TECHNIQUE WAS
SATISFACTORY.
- NOT INTENDED FOR JUDGING THE SIZE &
ACCEPTABILITY OF DEFECTS.
- MADE OF RAD. SIMILAR MATL. THAT OF
PART. SAME ALLOY OR AN ALLOY WITH LESS
RAD. ABSORPTION.
- GEN. 2% THICKNESS OF PART (ALL CODES)
27
28
29
IQI SELECTION (T-276)
 AS PER TABLE T-276.
 SMALLER HOLE IN A THICH IQI SELECTION IS
BASED IN THINNER IQI PERMITTED, PROVIDED
EQUIVALENT IQI SENSITIVITY (EPS) IS MET.
 WELDS WITH REINFORCEMENT, IQI SELECTION IS
BASED ON NOMINAL SINGLE WALL THICKNESS PLUS
ESTIMATED WELD REINFORCEMENT.
 BACKING RINGS OR STRIPS NOT CONSIDERED.
30
 WELDS WITHOUT REINFORCEMENT, IQI
SELECTION IS BASED ON NOMINAL SINGLE
WALL THICKNESS.
EQUIVALENT IQI SENSITIVITY (EPS)
= (100/X))√(TH/2)
X- SELTION THICKNESS OF COMPONENT (in)
T- IQI THICKNESS (in)
H-HOLE DIAMETER (in)
31
PLACEMENT OF IQIs
-
ALWAYS SOURCE SIDE
NORMAL TO RADIATION BEAM
SHIM, UNDER IQI, IF REINFORCEMENT EXISTS.
FILM SIDE ALLOWED, IF INACCESSIBILITY EXISTS.
A LEAD LETTER ‘F’ SHALL BE PLACED ADJACENT TO
IQI.
SHIMS- RAD. SIMILAR
- ONLY WHEN DENSITY IS MORE THAN MINUS
15% FROM DENSITY THRO’ PENETRAMETER.
32
FIGURE
33
SOURSE SELECTION – GAMMA RAYS:
ASME SEC. V. ART-2 & 3
MIN. THICKNESS – WELDS & CASTINGS.
MATL
IR-192
CO-60
STEEL
19 MM
38 MM
CU. & HIGH NI.
16.5 MM
33MM
ALUMINIUM
63.5 MM
-
STEEL
STEEL
ISO-R1106 (WELDS)
10MM
38MM
DIN 5411 (WELDS)
40-100 MM
70-120 MM
34
FIGURE
35
36
LIMITATIONS OF RADIOGRAPHY
A KNOWLEDGE OF THE FACTRS THAT DETERMINE THE
QUALITY OF A RADIOGRAPH ENEBLES US TO PREDICT FAIRLY
ACCURATELY WHERE RADIOGRAPHY IS USEFUL AND WHERE
IT CANNOT BE USED TO ANY GREAT ADVANTAGE.
(a) THE FIRST OBVIOUS LIMITATION IS THICKNESS
OF THE PART BEING RADIOGRAPED.
(b) THE SECOND LIMITATION IS THE CONFIGURATION
OF THE PART, WHICH MAY NOT PERMIT CLOSE
POSITIONING OF THE FILM TO THE PART. A
COMPLEX SHAPE MAY PRODUCE AN EXCESSIVE
AMOUNT OF SCATTERED RADIATION.
37
(c) RADIOGRAPHY CANNOT NORMALLLY DEDECT CRACKLIKE DISCONTINUITIES UNLESS THE PLACE OF THE
CRACK PARALLELS THE RADIATION BEAM AS SHOWN
IN FIG.4-16. CRACK ‘a’ WILL SHOW ON THE FILM BUT
CRACK ‘b’ WILL NOT BECAUSE THE BEAM TRAVERSES
ONLY ITS THICKNESS THAT IS THAN THE LIMIT OF
SENSITIVITY NORMALLY ATTAINED BY RADIOGRAPHY,
i.e., APPROXIMATELY 1%. CRACK ‘c’ WILL SHOW AS A
BROAD, SLIGHTLY DARKER IMAGE ON THE FILM AND
MAY BE VERY DIFFICULT TO DEFECT.
38
CODES & STANDARDS:
1.
CODE:
* A SET OF RULES OF GOOD PRACTICE . EX: ASME,
DIN, JIS Etc.
* COMPREHENSIVE DOCUMENT RELATING TOALL
ASPECTS OF DESIGN, MATL., FABN.,
CONSTRUCTION ERECTION, QC & TESTING Etc.
* CODES REFER AND ADAPT STANDARDS.
2. STANDARDS:
- DOCUMENTS GIVING DETAILS OF HOW A
PARTICULAR OPERATION TO BE CARRIED OUT.
- RECENT ADVANCES INTO ACCOUNT.
- PREPARED BY PROFESSIONAL BODIES.
EX: ASTM, ISO, IS Etc.
39
3. SPECIFICATIONS:
DOCUMENT WHICH PRESCRIBES IN DETAIL
THE REQTS. OF APRODUCT OR SERVICE TO
COMPLY.
EX: RAW MATL., INSTALLATION, INSPN.
SPEC.
4. PROCEDURE:
* LAST LEVEL OF DOCUM. FOR ANY
PROCESS FOR SHOP FLOOR.
* NO CHANGES ALLOWED UNLESS
APPROVED JBY THE COMPETANT
AUTHORITY.
40
MAIN INTERNATIONAL AND NATIONAL CODES
APPLICABLE FOR RADIOGRAPHY:
(I)ASTM.
(II) ASME
(III) ISO.
(IV) BIS.
(V) B.S.
(VI) JIS.
(VII) DIN/API ETC.
41
2004 ASME
BOILER AND PRESSURE VESSEL CODE
SECTIONS
I
RULES FOR CONSTRUCTION OF POWER BOILERS
II
MATERIALS
PART A- FERROUS MATERIAL SPECIFICATIONS
PART B – NONFERROUS MATERIAL SPECIFICATIONS
PART C – SPECIFICATIONS FOR WELDING RODS,
ELECTRODES, AND FILLER METALS
PART D – PROPERTIES
III
SUBSECTION NCA – GENERAL REQUIREMENTS FOR
42
DEVISION 1 AND DIVISION 2
III
DIVISION 1
SUBSECTION NB – CLASS 1 COMPONENTS
SUBSECTION NC – CLASS 2 COMPONENTS
SUBSECTION ND – CLASS 3 COMPONENTS
SUBSECTION NE – CLASS MC COMPONENTS
SUBSECTION NF - SUPPORTS
SUBSECTION NG – CORE SUPPORT STRUCTURE
III
DIVISION 2 – CODE FOR CONCREATE REACTOR
VESSELS AND CONTAINMENTS
IV
RULES FOR CONSTRUCTION OF HEATING
BOILERS
V
NONDESTRUCTIVE EXAMINATION
43
VI
RECOMMENDED RULES FOR THE CARE AND
OPERATION OF HEAING BOILERS
VII
RECOMMENDED GUIDELINES FOR THE CARE OF
POWER
BOILERS
VIII
RULES FOR CONSTRUCTION OF PRESSURE VESSELS
DIVISION 1
DIVISION 2 – ALTERNATIVE RULES
IX
WELDING AND BRAZING QUALIFICATIONS
X
FIBER-REINFORCED PLASTIC PRESSURE VESSELS
XI
RULES FOR INSERVICE INSPECTION OF NUCLEAR
POWER PLANT COMPONENTS.
44
RADIATION AND HUMAN BODY
• Radiation is present in our natural environment
- Cosmic radiation (radiation from space)
- Radioactive materials existing below
the earth
• Ionizing radn, when exceeds a certain level,
can damage human body tissue.
• Ionization is the process by which an e is
knocked out of the orbit of its parent atom.
45
• Exposure of persons / materials to γ radiation
does not cause them to become radioactive.
• Excessive radiation can damage the human
body. But this damage does not cause the body
to become radioactive and emit radiation.
• Can a person who has received radiation
damage spread radiation damage to others?
46
RADIATION MEASUREMENT UNITS
• Coulomb / Kg (Old unit: Roentgen) – unit to express
EXPOSURE to γ radiation.
• Measurement made in AIR
• Coulomb / Kg (Old unit: Roentgen) is a measure of γ
radn EXPOSURE in AIR
Which of the following statements is true?
• Coulomb / Kg is a direct measure of radiation
quantity absorbed by human tissue?...
• Coulomb / Kg is a measure of exposure a person
could receive in radiation area?.....1B
47
• α, β, γ and X- rays can cause ionizing radn.
• Other waves such as infrared , visible light,
radio-waves etc are non-ionizing radiations,
• As Coulomb / Kg unit is based on ionizing
effect of radiation in Air, it applies for
measurement of exposure to γ rays only.
• Is roentgen unit applicable for measuring
exposure to X rays?
48
Of course
• Units used to relate to biological effects of
radiation caused to human tissue – Gray,
Sievert, Radiation Weighting Factor, Tissue
Weighting Factor.
• Rad - old unit for Radiation Absorbed Dose in
tissue/mtls of α, β and γ radiation.
• SI unit for radiation absorbed dose is Gray.
1Gy = 100 rad
• Which applies to all types of radiation …
Coulomb / Kg or Gray ?
49
RADIATION EFFECTS
• The degree to which the different body cells are
sensitive to radiation.
• Partial list of cells in the order of decreasing radio
sensitivity
- white blood cells
- Immature red blood cells
- cells lining the gastro intestinal canal
- Cells of the reproductive organ
- skin cells
- Cells of the blood vessels
- Cells of tissue, bone, muscle, and nerves
• Which is the first to get affected by radn?
50
6A
Whole body dose
recd. Within 24
Effect
hours (mSv)
0-250
-
250-500
Slight temporary blood changes;
reduction in white blood cells
1000
Nausea, Fatigue
2000-2500
Hospitalisation mandatory; First death
5000
Half die Median Lethal Dose
Are the above effects are somatic or genetic?
51
•
•
•
•
RADIATION MEASURING DEVICES
- Survey meters
- Personnel monitoring devices
Survey meters are portable instruments used to
monitor radn areas
Which of the following does the survey meter
indicate
Radiation exposure rate
Cumulative radiation exposure
52
• All
• With pocket dosimeter, cum. exposure (since it
was last charged) can be directly read
instantaneously.
• Normal range 0 – 200mR
• Before use (everyday), it should be re-charged
to zero.
• In your opinion, what do you think is the
advantage of pocket dosimeter
- instantaneous reading ……..8A
- accurate measurement ……..8B
53
recording devices
SURVEY METERS
• Portable instruments used to monitor radiation areas
• Indicates exposure rate (or radn rate or dose rate) –
mR/hr
• Types of survey meters
- Ionization chamber meters: can read upto
50R/hr
- Geiger Muller Counters: typical range
0-50 mR/hr
• Which counter is more accurate for measuring low
levels of radiation?.
54
• 20 mSv per year. (With a sp. Provision that the
above value can exceed to 30 mSv in any
particular year, provided that the average in 5
years shall not exceed 20 mSv ).
• For general public, max. permissible limit is
… / yr.
55
56
THANK YOU !
57