Radiography in Modern Industry - Kodak

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and of higher or lower density on the finished radiograph. By the same token, the mandrelshould rotate uniformly. Uneven rotation will cause a series of longitudinal density variations inthe final record.Figure 86: Plan of a setup for rotary radiography of annular specimens.The lead shield should be comparatively thick. Any radiation transmitted by the shield will havethe same effect on radiographic quality as additional scattered radiation in the same amount. Arule of thumb is that the shield should transmit, during the entire exposure, no more than a fewpercent of the amount of radiation received by a particular area of the film during thecomparatively short time it is receiving an imaging exposure.This form of radiography, like that described in the previous section, is also largely or entirelyconfined to x-radiation. With the average gamma-ray sources, exposure times would be long; theshield required would be very thick, requiring careful alignment of source and slit.The motion unsharpness U m to be expected can be calculated from the formula:where w here is the width of the slit in the shield.The required peripheral velocity V p of the mandrel can be calculated from the exposure time T fora "still" radiograph from this formula:The same caution about units should be observed as described earlier.Scanning Methods--Orthogonal ProjectionSometimes it is desirable to use scanning methods even with specimens small enough to beradiographed in their entirety in a single exposure. This is true when critical measurements ofdimensions or clearances must be made from radiographs.Radiography in Modern Industry 144
When radiation passes through a specimen at an angle, as shown in Figure 87 (left), spatialrelationships are distorted and measurements of clearances can be significantly falsified. If, onthe other hand, the whole radiograph is made with a thin "sheet" of perpendicularly directedradiation, dimensions can be measured on the radiograph with considerable accuracy (SeeFigure 87, right).Figure 87: Left: Spatial relationships can be distorted in a conventional radiograph (seealso Figure 12). Right: Spatial relationships are preserved by moving the specimen andfilm through a thin "sheet" of vertically directed radiation. (For the sake of illustrativeclarity, the source-film distance is unrealistically short in relation to the specimenthickness.)This is often most easily accomplished by moving the film and specimen beneath a narrow slit,with the x-ray tube rigidly mounted above the slit. The carriage carrying the film and specimenmust move smoothly to avoid striations in the radiograph. Occasionally it is advantageous tomove slit and tube over the stationary specimen and film. In general, however, this requiresmoving a greater weight and bulk of equipment, with the resulting increase in power required andin difficulties encountered in achieving smooth, even motion. Weight can be minimized by locatingthe slit near the focal spot, rather than close to the specimen. The disadvantage to this, however,is that the slit must be exceedingly narrow, very carefully machined, and precisely aligned withthe central ray.It should be recognized that this technique corrects for the errors of distance measurementshown in the figure above in only one direction--that parallel to the direction of movement of thespecimen (or of tube and slit). Fortunately, most specimens to which this technique is applied arequite small, or quite long in relation to their width. If, however, the specimen is so large thatmeasurements must be made in directions parallel to the slit (that is, at right angles to the motion)and remote from the center line, it may be necessary to scan the specimen twice in directions atright angles to one another. In a few cases, the specimen can provide its own slit. An examplewould be the measurement of end-to-end spacing of cylindrical uranium fuel pellets in a thinmetal container. In this application, little radiation could reach the film unless it passed betweenthe pellets almost exactly parallel to the faces of the adjacent cylinders. In such a case the slitshown in Figure 87 (right) can be comparatively wide.TomographyTomography--in medical radiography, often termed "body-section radiography"--is a techniquethat provides a relatively distinct image of a selected plane in a specimen while the images ofRadiography in Modern Industry 145
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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
Page 93 and 94: of the same thickness as the specim
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
Page 143: narrow angle would be very thick, e
Page 147 and 148: Figure 89: Demonstration of the eff
Page 149 and 150: Figure 90: The amount of gamma radi
Page 151 and 152: The radiograph exposed in the right
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
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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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Radiography in Modern Industry - Kodak

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