Radiography in Modern Industry - Kodak

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Figure 91: Schematic diagram of slit method for radiography of radioactive specimens.Neutron RadiographyNeutron radiography is probably one of the most effective methods for radiography of radioactivespecimens. Its applications, however, are limited by the relative scarcity of suitable neutronsources and by the small cross-sectional areas of the available neutron beams. For a greatdiscussion of the techniques of neutron radiography, see "Neutron Radiography".Depth Localization Of DefectsTwo general methods are available for determining the location in depth of a flaw within aspecimen--stereoradiography and the parallax method. The chief value of stereoradiography liesin giving a vivid three-dimensional view of the subject, although with the aid of auxiliaryprocedures it can be used for the actual measurement of depth. The more convenient scheme fordepth measurement is the parallax method in which from two exposures made with differentpositions of the x-ray tube, the depth of a flaw is computed from the shift of the shadow of theflaw. Although stereoradiography and the parallax method are essentially alike in principle, theyare performed differently. It is therefore necessary to discuss them separately.StereoradiographyObjects viewed with a normal pair of eyes appear in their true perspective and in their correctspatial relation to each other, largely because of man's natural stereoscopic vision; each eyereceives a slightly different view, and the two images are combined by the mental processesinvolved in seeing to give the impression of three dimensions.Because a single radiographic image does not possess perspective, it cannot give the impressionof depth or indicate clearly the relative positions of various parts of the object along the directionof vision. Stereoradiography, designed to overcome this deficiency of a single radiograph,requires two radiographs made from two positions of the x-ray tube, separated by the normalinterpupillary distance. They are viewed in a stereoscope, a device that, by an arrangement ofprisms or mirrors, permits each eye to see but a single one of the pair of stereoradiographs. As inordinary vision, the brain fuses the two images into one in which the various parts stand out instriking relief in true perspective and in their correct spatial relation.Radiography in Modern Industry 150
The radiograph exposed in the right-shift position of the x-ray tube is viewed by the right eye, andthe one exposed in the left-shift position is viewed by the left eye. In fact, the conditions ofviewing the radiographs should be exactly analogous to the conditions under which they wereexposed; the two eyes take the place of the two positions of the focal spot of the x-ray tube, andthe radiographs, as viewed in the prisms or mirrors, occupy the same position with respect to theeyes as did the films with respect to the tube during the exposures. The eyes see the x-rayrepresentation of the part just as the x-ray tube "saw" the actual part (See Figure 92).Figure 92: Above: Schematic diagram showing method of making stereoscopicradiographs. Below: Diagram of a stereoscopic viewer (Wheatstone type).The stereoscopic impression is much more distinct if the specimen has a well-defined structureextending throughout its volume. If such a structure does not exist as, for example, in a flat plateof homogeneous material, it is necessary to provide such a structure upon one or more surfacesof the specimen. A widely spaced array of wires mounted on both front and rear surfaces of thespecimen will generally suffice, or a similar pattern can be applied in the form of cross lines oflead paint. In stereoscopic radiographs, these added structures not only help to securesatisfactory register of the two films but also serve as a reference marking for the location of anydetails shown stereoscopically within the specimen.The stereoscopic method is not often utilized in industrial radiography, but occasionally it can beof some value in localizing defects or in visualizing the spatial arrangement of hidden structures.Double-Exposure (Parallax) MethodThe figure below gives the details of this method. Lead markers (M 1 ) and (M 2 ) are fastened to thefront and back, respectively, of the specimen. Two exposures are made, the tube being moved aknown distance (a) from F 1 to F 2 between them. The position of the images of the marker (M 2 ) willchange very little, perhaps imperceptibly, as a result of this tube shift, but the shadows of the flawand marker (M 1 ) will change position by a larger amount.Radiography in Modern Industry 151
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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
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Contact between the film and the le
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Figure 29: The number of electrons
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lead foil screens ran be retained w
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Figure 33: The sharpness of the rad
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Figure 34: Low density (right) is a
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such as a wall or floor, on the fil
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from this source. Since scatter als
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A filter reduces excessive subject
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Definite rules as to filter thickne
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0.010-inch front screen of value be
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Example: Suppose that with a given
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If the milliamperage remains consta
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espectively. In other words, a cons
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Any given exposure chart applies to
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Figure 46: Typical gamma-ray exposu
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where the slope of the characterist
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Figure 49: Characteristic curves of
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Figure 51: Characteristic curve of
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Nomogram MethodsIn Figure 54, the s
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Figure 56: Transparent overlay posi
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Figure 58: Overlay positioned so as
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The problem of radiographing a part
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Figure 62: System of lines drawn on
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Chapter 8: Radiographic Image Quali
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Film contrast refers to the slope (
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Hole Type PenetrametersThe common p
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of the same thickness as the specim
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Chapter 9: Industrial X-ray FilmsMo
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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
Page 143 and 144: narrow angle would be very thick, e
Page 145 and 146: When radiation passes through a spe
Page 147 and 148: Figure 89: Demonstration of the eff
Page 149: Figure 90: The amount of gamma radi
Page 153 and 154: To illustrate, let us assume that t
Page 155 and 156: Figure 95: High-speed x-ray picture
Page 157 and 158: Figure 97: Two methods of neutron r
Page 159 and 160: Duplicating RadiographsSimultaneous
Page 161 and 162: Sometimes, as when sets of referenc
Page 163 and 164: PhotofluorographyIn photofluorograp
Page 165 and 166: discontinuities or of segregation i
Page 167 and 168: from the camera or by reaching down
Page 169 and 170: Figure 106: Schematic diagram of th
Page 171 and 172: valuable technique, for instance, i
Page 173 and 174: The position of the spots is determ
Page 175 and 176: Powder Diffraction File, Internatio
Page 177 and 178: Processing TechniquesRadiographs on
Page 179 and 180: Since this formula applies only to
Page 181 and 182: such that it does not distort the i
Page 183 and 184: Figure 113: A: Representation of a
Page 185 and 186: Figure 115: Characteristic curve of
Page 187 and 188: film fairly well. If high densities
Page 189 and 190: Density = 1.5 Density = 2.5Film Rel
Page 191 and 192: In most industrial radiography, the
Page 193 and 194: e noted here. Although the average
Page 195 and 196: Chapter 17: Film Graininess; Signal
Page 197 and 198: The ratio of signal to noise has a
Page 199 and 200: 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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