Radiographic testing
Encyclopedia
Radiographic Testing or industrial radiography
, is a nondestructive testing
(NDT) method of inspecting materials for hidden flaws by using the ability of short wavelength
electromagnetic radiation
(high energy photon
s) to penetrate various materials.
Either an X-ray machine or a radioactive source (Ir-192, Co-60, or in rare cases Cs-137) can be used as a source of photons. Neutron radiographic testing (NR) is a variant of radiographic testing which uses neutron
s instead of photons to penetrate materials. This can see very different things from X-rays, because neutrons can pass with ease through lead and steel but are stopped by plastics, water and oils.
Since the amount of radiation emerging from the opposite side of the material can be detected and measured, variations in this amount (or intensity) of radiation are used to determine thickness or composition of material. Penetrating radiations are those restricted to that part of the electromagnetic spectrum of wavelength less than about 10 nanometre
s.
under examination for each exposure shall be such that the thickness of the material at the diagnostic extremities, measured in the direction of the incident beam, does not exceed the actual thickness at that point by more than 6%. The specimen to be inspected is placed between the source of radiation and the detecting device, usually the film in a light tight holder or cassette, and the radiation is allowed to penetrate the part for the required length of time to be adequately recorded.
The result is a two-dimensional projection of the part onto the film, producing a latent image of varying densities according to the amount of radiation
reaching each area. It is known as a radiograph, as distinct from a photograph produced by light. Because film is cumulative in its response (the exposure increasing as it absorbs more radiation), relatively weak radiation can be detected by prolonging the exposure until the film can record an image that will be visible after development. The radiograph is examined as a negative
, without printing as a positive as in photography. This is because, in printing, some of the detail is always lost and no useful purpose is served.
Before commencing a radiographic examination, it is always advisable to examine the component with one's own eyes, to eliminate any possible external defects. If the surface of a weld is too irregular, it may be desirable to grind it to obtain a smooth finish, but this is likely to be limited to those cases in which the surface irregularities (which will be visible on the radiograph) may make detecting internal defects difficult.
After this visual examination, the operator will have a clear idea of the possibilities of access to the two faces of the weld, which is important both for the setting up of the equipment and for the choice of the most appropriate technique.
Defects such as delamination
s and planar
cracks are difficult to detect using radiography, which is why penetrants are often used to enhance the contrast in the detection of such defects. Penetrants used include silver nitrate
, zinc iodide
, chloroform
and diiodomethane
. Choice of the penetrant is determined by the ease with which it can penetrate the cracks and also with which it can be removed. Diiodomethane has the advantages of high opacity
, ease of penetration
, and ease of removal because it evaporates relatively quickly. However, it can cause skin burns.
industry or within hospitals.
(ISO)
European Committee for Standardization
(CEN)
ASTM International
(ASTM)
American Society of Mechanical Engineers
(ASME)
American Petroleum Institute
(API)
Industrial radiography
Industrial Radiography is the use of ionizing radiation to view objects in a way that cannot be seen otherwise. It is not to be confused with the use of ionizing radiation to change or modify objects; radiography's purpose is strictly viewing. Industrial radiography has grown out of engineering,...
, is a nondestructive testing
Nondestructive testing
Nondestructive testing or Non-destructive testing is a wide group of analysis techniques used in science and industry to evaluate the properties of a material, component or system without causing damage....
(NDT) method of inspecting materials for hidden flaws by using the ability of short wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
(high energy photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s) to penetrate various materials.
Either an X-ray machine or a radioactive source (Ir-192, Co-60, or in rare cases Cs-137) can be used as a source of photons. Neutron radiographic testing (NR) is a variant of radiographic testing which uses neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s instead of photons to penetrate materials. This can see very different things from X-rays, because neutrons can pass with ease through lead and steel but are stopped by plastics, water and oils.
Since the amount of radiation emerging from the opposite side of the material can be detected and measured, variations in this amount (or intensity) of radiation are used to determine thickness or composition of material. Penetrating radiations are those restricted to that part of the electromagnetic spectrum of wavelength less than about 10 nanometre
Nanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...
s.
Inspection of welds
The beam of radiation must be directed to the middle of the section under examination and must be normal to the material surface at that point, except in special techniques where known defects are best revealed by a different alignment of the beam. The length of weldWeld
Weld most commonly refers to a joint formed by welding.Weld may also refer to:-People:* Weld family, an extended family of New England** Theodore Dwight Weld** Tuesday Weld* Weld-Blundell family* Cecil Weld-Forester, 1st Baron Forester...
under examination for each exposure shall be such that the thickness of the material at the diagnostic extremities, measured in the direction of the incident beam, does not exceed the actual thickness at that point by more than 6%. The specimen to be inspected is placed between the source of radiation and the detecting device, usually the film in a light tight holder or cassette, and the radiation is allowed to penetrate the part for the required length of time to be adequately recorded.
The result is a two-dimensional projection of the part onto the film, producing a latent image of varying densities according to the amount of radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
reaching each area. It is known as a radiograph, as distinct from a photograph produced by light. Because film is cumulative in its response (the exposure increasing as it absorbs more radiation), relatively weak radiation can be detected by prolonging the exposure until the film can record an image that will be visible after development. The radiograph is examined as a negative
Negative (photography)
In photography, a negative may refer to three different things, although they are all related.-A negative:Film for 35 mm cameras comes in long narrow strips of chemical-coated plastic or cellulose acetate. As each image is captured by the camera onto the film strip, the film strip advances so that...
, without printing as a positive as in photography. This is because, in printing, some of the detail is always lost and no useful purpose is served.
Before commencing a radiographic examination, it is always advisable to examine the component with one's own eyes, to eliminate any possible external defects. If the surface of a weld is too irregular, it may be desirable to grind it to obtain a smooth finish, but this is likely to be limited to those cases in which the surface irregularities (which will be visible on the radiograph) may make detecting internal defects difficult.
After this visual examination, the operator will have a clear idea of the possibilities of access to the two faces of the weld, which is important both for the setting up of the equipment and for the choice of the most appropriate technique.
Defects such as delamination
Delamination
Delamination is a mode of failure for composite materials. Modes of failure are also known as 'failure mechanisms'. In laminated materials, repeated cyclic stresses, impact, and so on can cause layers to separate, forming a mica-like structure of separate layers, with significant loss of mechanical...
s and planar
Planar
In computer graphics, planar is the method of representing pixel colours with several bitplanes of RAM. Each bit in a bitplane is related to one pixel on the screen...
cracks are difficult to detect using radiography, which is why penetrants are often used to enhance the contrast in the detection of such defects. Penetrants used include silver nitrate
Silver nitrate
Silver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...
, zinc iodide
Zinc iodide
Zinc iodide is a chemical compound of zinc and iodine, ZnI2. The anhydrous form is white and readily absorbs water from the atmosphere. It can be prepared by the direct reaction of zinc and iodine in refluxing ether...
, chloroform
Chloroform
Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...
and diiodomethane
Diiodomethane
Diiodomethane or methylene iodide, commonly abbreviated "MI", is a liquid organoiodine compound. It is insoluble in water, but soluble in ether and alcohol. It has a relatively high refractive index of 1.741, and a surface tension of 0.0508 N·m−1...
. Choice of the penetrant is determined by the ease with which it can penetrate the cracks and also with which it can be removed. Diiodomethane has the advantages of high opacity
Opacity (optics)
Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc...
, ease of penetration
Penetration
Penetration may refer to:* Penetration depth of light or any electromagnetic radiation.* Penetrating trauma* Sexual penetration, a term which may mean**sexual intercourse in general or,...
, and ease of removal because it evaporates relatively quickly. However, it can cause skin burns.
Safety
Industrial radiography appears to have one of the worst safety profiles of the radiation professions, possibly because there are many operators using strong gamma sources (> 2 Ci) in remote sites with little supervision when compared with workers within the nuclearNuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...
industry or within hospitals.
Standards
International Organization for StandardizationInternational Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
(ISO)
- ISO 4993, Steel and iron castings - Radiographic inspection
- ISO 5579, Non-destructive testing - Radiographic examination of metallic materials by X- and gamma-rays - Basic rules
- ISO 10675-1, Non-destructive testing of welds - Acceptance levels for radiographic testing - Part 1: Steel, nickel, titanium and their alloys
- ISO 11699-1, Non-destructive testing - Industrial radiographic films - Part 1: Classification of film systems for industrial radiography
- ISO 11699-2, Non-destructive testing - Industrial radiographic films - Part 2: Control of film processing by means of reference values
- ISO 14096-1, Non-destructive testing - Qualification of radiographic film digitisation systems - Part 1: Definitions, quantitative measurements of image quality parameters, standard reference film and qualitative control
- ISO 14096-2, Non-destructive testing - Qualification of radiographic film digitisation systems - Part 2: Minimum requirements
- ISO 17636, Non-destructive testing of welds - Radiographic testing of fusion-welded joints
- ISO 19232, Non-destructive testing - Image quality of radiographs
European Committee for Standardization
European Committee for Standardization
The European Committee for Standardization or Comité Européen de Normalisation , is a non-profit organisation whose mission is to foster the European economy in global trading, the welfare of European citizens and the environment by providing an efficient infrastructure to interested parties for...
(CEN)
- EN 444, Non-destructive testing; general principles for the radiographic examination of metallic materials using X-rays and gamma-rays
- EN 462-2, Non-destructive testing - image quality of radiographs - Part 2: image quality indicators (step/hole type) - determination of image quality value
- EN 462-3, Non-destructive testing - Image quality of radiogrammes - Part 3: Image quality classes for ferrous metals
- EN 462-4, Non-destructive testing - Image quality of radiographs - Part 4: Experimental evaluation of image quality values and image quality tables
- EN 462-5, Non-destructive testing - Image quality of radiographs - Part 5: Image quality of indicators (duplex wire type), determination of image unsharpness value
- EN 584-1, Non-destructive testing - Industrial radiographic film - Part 1: Classification of film systems for industrial radiography
- EN 584-2, Non-destructive testing - Industrial radiographic film - Part 2: Control of film processing by means of reference values
- EN 1330-3, Non-destructive testing - Terminology - Part 3: Terms used in industrial radiographic testing
- EN 1435, Non-destructive testing of welds - Radiographic testing of welded joints
- EN 2002-21, Aerospace series - Metallic materials; test methods - Part 21: Radiographic testing of castings
- EN 10246-10, Non-destructive testing of steel tubes - Part 10: Radiographic testing of the weld seam of automatic fusion arc welded steel tubes for the detection of imperfections
- EN 12517-1, Non-destructive testing of welds - Part 1: Evaluation of welded joints in steel, nickel, titanium and their alloys by radiography - Acceptance levels
- EN 12517-2, Non-destructive testing of welds - Part 2: Evaluation of welded joints in aluminium and its alloys by radiography - Acceptance levels
- EN 12679, Non-destructive testing - Determination of the size of industrial radiographic sources - Radiographic method
- EN 12681, Founding - Radiographic examination
- EN 13068, Non-destructive testing - Radioscopic testing
- EN 14096, Non-destructive testing - Qualification of radiographic film digitisation systems
- EN 14784-1, Non-destructive testing - Industrial computed radiography with storage phosphor imaging plates - Part 1: Classification of systems
- EN 14584-2, Non-destructive testing - Industrial computed radiography with storage phosphor imaging plates - Part 2: General principles for testing of metallic materials using X-rays and gamma rays
ASTM International
ASTM International
ASTM International, known until 2001 as the American Society for Testing and Materials , is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services...
(ASTM)
- ASTM E 94, Standard Guide for Radiographic Examination
- ASTM E 155, Standard Reference Radiographs for Inspection of Aluminum and Magnesium Castings
- ASTM E 592, Standard Guide to Obtainable ASTM Equivalent Penetrameter Sensitivity for Radiography of Steel Plates 1/4 to 2 in. [6 to 51 mm] Thick with X Rays and 1 to 6 in. [25 to 152 mm] Thick with Cobalt-60
- ASTM E 747, Standard Practice for Design, Manufacture and Material Grouping Classification of Wire Image Quality Indicators (IQI) Used for Radiology
- ASTM E 801, Standard Practice for Controlling Quality of Radiological Examination of Electronic Devices
- ASTM E 1030, Standard Test Method for Radiographic Examination of Metallic Castings
- ASTM E 1032, Standard Test Method for Radiographic Examination of Weldments
- ASTM 1161, Standard Practice for Radiologic Examination of Semiconductors and Electronic Components
- ASTM E 1648, Standard Reference Radiographs for Examination of Aluminum Fusion Welds
- ASTM E 1735, Standard Test Method for Determining Relative Image Quality of Industrial Radiographic Film Exposed to X-Radiation from 4 to 25 MeV
- ASTM E 1815, Standard Test Method for Classification of Film Systems for Industrial Radiography
- ASTM E 1817, Standard Practice for Controlling Quality of Radiological Examination by Using Representative Quality Indicators (RQIs)
- ASTM E 2104, Standard Practice for Radiographic Examination of Advanced Aero and Turbine Materials and Components
American Society of Mechanical Engineers
American Society of Mechanical Engineers
The American Society of Mechanical Engineers is a professional body, specifically an engineering society, focused on mechanical engineering....
(ASME)
- BPVCASME Boiler and Pressure Vessel Code (BPVC)The ASME Boiler and Pressure Vessel Code is an American Society of Mechanical Engineers standard that provides rules for the design, fabrication, and inspection of boilers and pressure vessels...
Section V, Nondestructive Examination: Article 2 Radiographic Examination
American Petroleum Institute
American Petroleum Institute
The American Petroleum Institute, commonly referred to as API, is the largest U.S trade association for the oil and natural gas industry...
(API)
- API 1104, Welding of Pipelines and Related Facilities: 11.1 Radiographic Test Methods