8/16/2019 Determination of Thickness by RT http://slidepdf.com/reader/full/determination-of-thickness-by-rt 1/25 AS 2452.1—2004Australian Standard ™ Non-destructive testing—Determination of thickness Part 1: Determination of wall thickness of pipe by the use of radiography A S 2 4 5 2 . 1 — 2 0 0 4 A c c e s s e d b y B U R E A U V E R I T A S A U S T R A L I A P T Y L T D o n 2 7 M a r 2 0 1 3 ( D o c u m e n t c u r r e n c y n o t g u a r a n t e e d w h e n p r i n t e d )
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This Australian Standard was prepared by Committee MT-007, Non-DestructiveTesting of Metals and Materials. It was approved on behalf of the Council ofStandards Australia on 15 October 2004.This Standard was published on 1 November 2004.
The following are represented on Committee MT-007:
ANSTO
Australian Aerospace Non-Destructive Testing Committee
Australian Industry Group
Australian Institute for Non-Destructive Testing
Australian Pipeline Industry Association
Australian Railway Association
Bureau of Steel Manufacturers of AustraliaInstitution of Engineers Australia
National Association of Testing Authorit ies Australia
TestSafe Australia
Victoria Workcover Authority
Welding Technology Institute of Australia
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This Standard was issued in draft form for comment as DR 03553.
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This Standard was prepared by the Joint Standards Australia/Standards New Zealand
Committee MT-007, Non-Destructive Testing of Metals and Materials, at the request ofindustry. This Standard supersedes AS 2452.1 1982, Non-destructive testing
Determination of thickness, Part 1: Determination of wall thickness of pipe by the use of
radiography.
This Standard was prepared by the Australian members of the Joint Standards
Australia/Standards New Zealand Committee MT-007. After consultation with shareholders
in both countries, Standards Australia and Standards New Zealand decided to develop this
Standard as an Australian Standard rather than an Australian/New Zealand Standard.
The objective of this Standard is to specify methods for film radiography to determine wall
thickness of pipes and small fabricated vessels.
The objective of this revision is to expand the technology for the equipment and accessoriesused for radiography in determining wall thickness.
The methods in this Standard provide suitable bases for the testing of round pipe or other
small pressure vessels, including gas cylinders. The methods rely on the use of a source of
radiation, X-rays or gamma-rays, and require testing personnel to be experienced in the
handling and use of radiation equipment and materials.
This Standard is Part 1 of a series of Standards covering the radiography of ferrous
castings.
The series comprises the following parts:
AS
2452 Non-destructive testing
Determination of thickness2452.1 Part 1: Determination of the wall thickness of pipe by the use of radiography
2452.3 Part 3: Use of ultrasonic testing
The term ‘normative’ has been used in this Standard to define the application of the
appendix to which it applies. A ‘normative’ appendix is an integral part of a Standard.
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Non-destructive testing—Determination of thickness
Part 1: Determination of wall thickness of pipe by the use of radiography
1 SCOPE
This Standard specifies the methods for the determination of the wall thickness of pipes and
small fabricated vessels using X-ray or gamma-ray radiography.
NOTES:
1 Under a given set of radiographic conditions, the accuracy of the methods specified herein is
reduced with decreasing wall thickness and with increasing pipe or vessel diameter.
2 The methods specified herein are more accurate when a pipe is empty.
2 REFERENCED DOCUMENTS
The following documents are referred to in this standard:
AS
1929 Non-destructive testing — Glossary of terms
2243 Safety in laboratories
2243.4 Part 4: Ionizing radiations
3998 Non-destructive testing — Qualification and certification of personnelCode of Practice for the Control and Safe Handling of Sealed Radioactive Sources Used in
Industrial Radiography*
NH and MRC Radiation Health Series No. 31, Code of Practice for the safe use of
Industrial Radiography Equipment
3 SAFETY PRECAUTIONS
Exposure of any part of the human body to ionizing radiation may be injurious. It is
therefore essential that when X-ray equipment or radioactive sources are being used
adequate precautions be taken to protect testing personnel and any other persons in the
vicinity. NOTE: The use of radioactive substances and irradiating apparatus is controlled by various
statutory regulations. Reference should also be made AS 2243.4, the ‘Code of Practice for the
Control and Safe Handling of Sealed Radioactive Sources used in Industrial Radiography’ and
NH and MRC Radiation Health Series No.31 ‘Code of Practice for the safe use of Industrial
Radiography Equipment’.
4 DEFINITIONS
For the purposes of this Standard, the terms and definitions given in AS 1929 apply.
* Issued by the National Health and Medical Research Council, Canberra. A c c e s s e d b
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An image of the tangential section of a pipe produced on a radiographic film positioned
with its plane approximately normal to the path of the beam of radiation on the opposite
side. The wall thickness of the pipe at the point which is tangential to the beam is
determined from the resultant film images by the use of appropriate equations.
6 EQUIPMENT AND ACCESSORIES
6.1 General
The radiographic testing system shall be capable of delineating boundaries and contours,
determining wall thickness of pipes of small fabricated vessels, and of producing
satisfactory image quality in a radiograph.
6.2 X-ray equipment
X-ray equipment up to 450 kV shall be used. The exposure shall be carried out at the lowest
voltage consistent with a reasonable time.
6.3 Gamma-ray sources
Gamma-ray sources given in Table 6.1 may be used for penetrating the approximate
thickness of steel specifications.
NOTE: Methods using gamma-rays are usually less sensitive than methods using X-rays.
TABLE 6.1
GAMMA-RAY SOURCE FOR THE TESTING OF STEEL
Approximate thickness of steel*
mmGamma-ray source
min. max.
Cobalt 60 (Co60) 50 200
Iridium 192 (Ir192) 10 90
Ytterbium 169 (Yb169) 6 20
* Values of thickness are generally regarded as those values above which exposure times
will be unreasonably long and below which the required quality may not be readily
achieved.
6.4 Intensifying screens
Metal intensifying screens emit electrons under irradiation and the action of these electrons
on the film contributes to producing a chosen density of radiograph with a shorter exposuretime. Screens are used to minimize scatter radiation. The following recommendations apply
to screens:
(a) Screens shall be handled carefully to avoid dents, creases, scratches and
contamination by dirt and grease.
(b) Any damaged screens which produce a spurious image in the section under test on the
radiographic film shall not be used.
(c) Foreign material such as grease or lint shall be removed with care from the surface of
the screen.
6.5 Cassettes
Irrespective of the type of cassette used, adequate precautions shall be taken to ensure good
film-to-screen contact. Rigid cassettes may be necessary to maintain a fixed position in
relation to the beam, especially where it is difficult to obtain film/screen contact. A c c e s s e d b
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All radiographs shall be free from mechanical, chemical, or other blemishes to the extent
that they cannot mask or be confused with the image of any wall thickness changes in the
test area.
7 PROCEDURE
7.1 General
7.1.1 Arrangement
The radiation source, the area of interest and the radiographic film shall be arranged in
accordance with the method chosen (see Figures 1 to 6).
NOTE: Vibration may effect the sharpness of the image.
7.1.2 Source-to-object distance
The distance of the radiation source to the edge of the area of interest shall be not less than
5 times the distance of the tangent point to the plane of the film. NOTE: This ratio should be increased proportionately with sources larger than 2 mm.
7.1.3 Exposure for steel
Exposure shall be selected to produce a film image of the area of interest which may be
satisfactorily measured. Consequently it is not necessary to achieve the radiographic density
levels used for the detection of discontinuities in normal radiography.
Dimensions of chord lengths for typical pipe sizes are given in Appendix A.
NOTE: Exposure charts (see Figures 7 and 8) are provided for steel using the following sources
of radiation:
(a) Ir192
.
(b) Co60.
These charts give exposures which have been found by experience for the various chord lengths
of a range of sizes of steel pipe. An alternative procedure involves the use of conventional
exposure charts (pipe thickness vs exposure) prepared for the type of radiation source it is
proposed to use.
7.1.4 Radiographic equivalence factors
Exposures for materials other than steel may be calculated by multiplying the section
thickness by the Radiographic Equivalence Factor (Table 7.1) and referring to the
appropriate exposure curve for steel.
7.1.5 Film processing
Normal film processing shall be carried out in accordance with the instructions of the film
manufacturer.
7.2 Method No.1
7.2.1 Application
This method is suitable for use on unlagged piping up to 300 mm in diameter where the
pipe axis can be aligned with the source.
7.2.2 Procedure
The procedure shall be as follows:
(a) Estimate minimum film size required from pipe diameter and source-to-film distance.
(b) Position the cassette so that axis of the beam of radiation is normal to the plane of the
cassette through the centre of the pipe (see Figure 1). A c c e s s e d b
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