Radiography in Modern Industry - Kodak

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a radiographic sensitivity level of 2-2T. The first symbol (2) indicates that the penetrameter shallbe 2 percent of the thickness of the specimen; the second (2T) indicates that the hole having adiameter twice the penetrameter thickness shall be visible on the finished radiograph. The qualitylevel 2-2T is probably the one most commonly specified for routine radiography. However, criticalcomponents may require more rigid standards, and a level of 1-2T or 1-1T may be required. Onthe other hand, the radiography of less critical specimens may be satisfactory if a quality level of2-4T or 4-4T is achieved. The more critical the radiographic examination--that is, the higher thelevel of radiographic sensitivity required--the lower the numerical designation for the quality level.Some sections of the ASME (American Society of Mechanical Engineers) Boiler and PressureVessel Code require a penetrameter similar in general to the ASTM penetrameter. It containsthree holes, one of which is 2T in diameter, where T is the penetrameter thickness. Customarily,the other two holes are 3T and 4T in diameter, but other sizes may be used. Minimum hole size is1/6 inch. Penetrameters 0.010 inch, and less, in thickness also contain a slit 0.010-inch wide and1/4 inch long. Each is identified by a lead number designating the thickness in thousandths of aninch.Equivalent Penetrameter SensitivityIdeally, the penetrameter should be made of the same material as the specimen. However, this issometimes impossible because of practical or economic difficulties. In such cases, thepenetrameter may be made of a radiographically similar material--that is, a material having thesame radiographic absorption as the specimen, but one of which it is easier to makepenetrameters. Tables of radiographically equivalent materials have been published whereinmaterials having similar radiographic absorptions are arranged in groups. In addition, apenetrameter made of a particular material may be used in the radiography of materials havinggreater radiographic absorption. In such a case, there is a certain penalty on the radiographictesters, because they are setting for themselves more rigid radiographic quality standards thanare actually required. The penalty is often outweighed, however, by avoidance of the problems ofobtaining penetrameters of an unusual material or one of which it is difficult to makepenetrameters.In some cases, the materials involved do not appear in published tabulations. Under thesecircumstances the comparative radiographic absorption of two materials may be determinedexperimentally. A block of the material under test and a block of the material proposed forpenetrameters, equal in thickness to the part being examined, can be radiographed side by sideon the same film with the technique to be used in practice. If the density under the proposedpenetrameter materials is equal to or greater than the density under the specimen material, thatproposed material is suitable for fabrication of penetrameters.In practically all cases, the penetrameter is placed on the source side of the specimen--that is, inthe least advantageous geometric position. In some instances, however, this location for thepenetrameter is not feasible. An example would be the radiography of a circumferential weld in along tubular structure, using a source positioned within the tube and film on the outer surface. Insuch a case a "film-side" penetrameter must be used. Some codes specify the film-sidepenetrameter that is equivalent to the source-side penetrameter normally required. When such aspecification is not made, the required film-side penetrameter may be found experimentally. In theexample above, a short section of tube of the same dimensions and materials as the item undertest would be used to demonstrate the technique. The required penetrameter would be used onthe source side, and a range of penetrameters on the film side. If the penetrameter on the sourceside indicated that the required radiographic sensitivity was being achieved, the image of thesmallest visible penetrameter hole in the film-side penetrameters would be used to determine thepenetrameter and the hole size to be used on the production radiograph.Sometimes the shape of the part being examined precludes placing the penetrameter on the part.When this occurs, the penetrameter may be placed on a block of radiographically similar materialRadiography in Modern Industry 92
of the same thickness as the specimen. The block and the penetrameter should be placed asclose as possible to the specimen.Wire PenetrametersA number of other penetrameter designs are also in use. The German DIN (Deutsche Industrie-Norm) penetrameter (See Figure 66) is one that is widely used. It consists of a number of wires,of various diameters, sealed in a plastic envelope that carries the necessary identificationsymbols. The thinnest wire visible on the radiograph indicates the image quality. The system issuch that only three penetrameters, each containing seven wires, can cover a very wide range ofspecimen thicknesses. Sets of DIN penetrameters are available in aluminum, copper, and steel.Thus a total of nine penetrameters is sufficient for the radiography of a wide range of materialsand thicknesses.Figure 66: DIN (German) penetrameter (German Standard DIN 54109).Comparison of Penetrameter DesignThe hole type of penetrameter (ASTM, ASME) is, in a sense, a "go no-go" gauge; that is, itindicates whether or not a specified quality level has been attained but, in most cases, does notindicate whether the requirements have been exceeded, or by how much. The DIN penetrameteron the other hand is a series of seven penetrameters in a single unit. As such, it has theadvantage that the radiographic quality level achieved can often be read directly from theprocessed radiograph.On the other hand, the hole penetrameter can be made of any desired material but the wirepenetrameter is made from only a few materials. Therefore, using the hole penetrameter, aquality level of 2-2T may be specified for the radiography of, for example, commercially purealuminum and 2024 aluminum alloy, even though these have appreciably different compositionsand radiation absorptions. The penetrameter would, in each case, be made of the appropriatematerial. The wire penetrameters, however, are available in aluminum but not in 2024 alloy. Toachieve the same quality of radiographic inspection of equal thicknesses of these two materials, itwould be necessary to specify different wire diameters--that for 2024 alloy would probably have tobe determined by experiment.Special PenetrametersSpecial penetrameters have been designed for certain classes of radiographic inspection. Anexample is the radiography of small electronic components wherein some of the significantfactors are the continuity of fine wires or the presence of tiny balls of solder. Special image qualityindicators have been designed consisting of fine wires and small metallic spheres within a plasticblock, the whole covered on top and the bottom with steel approximately as thick as the case ofthe electronic component.Radiography in Modern Industry 93
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RadiographyinModernIndustry
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RadiographyinModernIndustryFOURTH E
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ContentsIntroduction...............
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Chapter 1: The Radiographic Process
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Intensifying ScreensX-ray and other
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makes it a very suitable material f
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Figure 6: Typical voltage waveforms
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Table I - Typical X-ray Machines an
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The wavelengths (or energies of rad
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Table III - Industrial Gamma-Ray So
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1. The source of light should be sm
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B and H in the Figure 13 show the e
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Figure 14: Geometric construction f
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Figure 17: Pinhole pictures of the
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The kilovoltage applied to the x-ra
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Figure 21: Schematic diagram of som
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kind of material radiographed, the
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instance, the kilovoltage may be fi
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The technique need not be limited t
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Chapter 5: Radiographic ScreensWhen
Page 41 and 42: Contact between the film and the le
Page 43 and 44: Figure 29: The number of electrons
Page 45 and 46: lead foil screens ran be retained w
Page 47 and 48: Figure 33: The sharpness of the rad
Page 49 and 50: Figure 34: Low density (right) is a
Page 51 and 52: such as a wall or floor, on the fil
Page 53 and 54: from this source. Since scatter als
Page 55 and 56: A filter reduces excessive subject
Page 57 and 58: Definite rules as to filter thickne
Page 59 and 60: 0.010-inch front screen of value be
Page 61 and 62: Example: Suppose that with a given
Page 63 and 64: If the milliamperage remains consta
Page 65 and 66: espectively. In other words, a cons
Page 67 and 68: Any given exposure chart applies to
Page 69 and 70: Figure 46: Typical gamma-ray exposu
Page 71 and 72: where the slope of the characterist
Page 73 and 74: Figure 49: Characteristic curves of
Page 75 and 76: Figure 51: Characteristic curve of
Page 77 and 78: Nomogram MethodsIn Figure 54, the s
Page 79 and 80: Figure 56: Transparent overlay posi
Page 81 and 82: Figure 58: Overlay positioned so as
Page 83 and 84: The problem of radiographing a part
Page 85 and 86: Figure 62: System of lines drawn on
Page 87 and 88: Chapter 8: Radiographic Image Quali
Page 89 and 90: Film contrast refers to the slope (
Page 91: Hole Type PenetrametersThe common p
Page 95 and 96: Chapter 9: Industrial X-ray FilmsMo
Page 97 and 98: Figure 70 indicates the direction t
Page 99 and 100: the lead letters on a radiation-abs
Page 101 and 102: Therefore, protection requirements
Page 103 and 104: 5. Avoid pressure damage caused by
Page 105 and 106: Paddles or plunger-type agitators a
Page 107 and 108: slow, and the development time reco
Page 109 and 110: ubbles make their way to the surfac
Page 111 and 112: When development is complete, the f
Page 113 and 114: soften considerably with prolonged
Page 115 and 116: Figure 77: The roller transport sys
Page 117 and 118: Rapid Access to Processed Radiograp
Page 119 and 120: Figure 78: Film-feeding procedures
Page 121 and 122: Chapter 11: Process ControlUsers of
Page 123 and 124: 3. Age of the developer replenisher
Page 125 and 126: Figure 80: Control chart below for
Page 127 and 128: DiscussionDensitometric data and pr
Page 129 and 130: Figure 82: Plan of a manual x-ray p
Page 131 and 132: Figure 83: A schematic diagram of a
Page 133 and 134: loading-bench activities are carrie
Page 135 and 136: KODAK Quinone-Thiosulfate Intensifi
Page 137 and 138: Methylene-Blue MethodTwo variations
Page 139 and 140: KODAK Hypo Test Solution HT-2Avoird
Page 141 and 142: In summary, use of the test papers
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narrow angle would be very thick, e
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When radiation passes through a spe
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Figure 89: Demonstration of the eff
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Figure 90: The amount of gamma radi
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The radiograph exposed in the right
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To illustrate, let us assume that t
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Figure 95: High-speed x-ray picture
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Figure 97: Two methods of neutron r
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Duplicating RadiographsSimultaneous
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Sometimes, as when sets of referenc
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PhotofluorographyIn photofluorograp
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discontinuities or of segregation i
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from the camera or by reaching down
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Figure 106: Schematic diagram of th
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valuable technique, for instance, i
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The position of the spots is determ
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Powder Diffraction File, Internatio
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Processing TechniquesRadiographs on
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Since this formula applies only to
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such that it does not distort the i
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Figure 113: A: Representation of a
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Figure 115: Characteristic curve of
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film fairly well. If high densities
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Density = 1.5 Density = 2.5Film Rel
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In most industrial radiography, the
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e noted here. Although the average
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Chapter 17: Film Graininess; Signal
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The ratio of signal to noise has a
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Chapter 18: The Photographic Latent
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Thus, the change that makes an expo
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Figure 130: Stages in the developme
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electrons by successive Compton int
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Development is essentially a chemic
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Chapter 19: ProtectionOne of the mo
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duct is brought into the x-ray room
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