Radiography in Modern Industry - Kodak

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used to set up the exposing unit (if an exposure error is indicated), or poor densitometry. If anabnormal process is indicated, process another set of control strips. (It is for this purpose thatmore than the minimum of two strips for each processor is advisable.)When an out-of-control condition does exist that is the result of a film processing variation and notan obvious testing error, the process should be restarted with fresh solutions. Adding chemicalsto the developer is frequently unsuccessful, is more time consuming, and is more expensive inthe end than restarting the process. Contamination of the developer (1 mL of fixer in a gallon ofdeveloper can be detected in film densities) and underreplenishment of the developer areexamples of conditions that indicate the process should be restarted with fresh solutions.TechniqueExposure of Control FilmLoad the cassette with a sheet of control film. (If the control film has been refrigerated, be sure toallow enough time for the film to reach room temperature before handling.) If lead intensifyingscreens are used in the normal production operation, use the set reserved for process control.Carefully set up the x-ray exposure unit for the exposure technique. The cassette and thestepped wedge must be positioned identically each time control film is exposed.Cut the exposed film into a minimum of twice the number of processors in the control system. Ifpossible, cut more than the minimum, but do not make duplicate exposures and assume they areidentical. Each exposure of control film must be considered a complete control.Identify the strips as to date and exposing unit.Place half or the exposed control strips in an airtight, light tight, and moisture proof wrapper andstore them in the refrigerator. Remove the moisture proof package of control strips exposed in thesame unit the previous day. When these latent-image control strips are at room temperature, theycan be handled and processed.Processing of Control StripsProcess the freshly exposed control strips and the strips exposed in the same unit the previousday in the corresponding processor (or processors).If the strips are less than 21/2 inches wide, tape them to a leader. If a leader is not used, processa cleanup sheet before processing the control strips.Always process a fresh control strip exposed in a designated unit with a control strip exposed inthat same unit the previous day.Record in the log the temperature of the developer at the time the strips are in the processor.Record in the log any other information pertinent to process control.DensitometryCheck the accuracy and the precision of the densitometer each time before it is used to obtainthe numerical density values from the control strips.Determine the density value of each of the two steps selected for measuring density on thefreshly exposed and processed control strip and the density of the two corresponding steps onthe latent-image control strip. (Once these steps have been selected, the density of the samearea on each of the steps is used every time control strips are measured.)Record the densitometric readings and plot them on the process control charts.Radiography in Modern Industry 126
DiscussionDensitometric data and process control charts for one exposing unit and one processor arepresented as Figures 79 to 80. The process density aim (the mean density) and the upper andlower control limits on the charts (the table immediately above and the one below) werecomputed from the densitometric data for the 10-day period shown in Figure 79. As stated earlier,the control limits on both charts are wider than would be the case if either the exposing unit or theprocessor were monitored individually. Although two control charts are illustrated, they can becombined into one for convenience.Exposure and Processing VariationsVariations in both exposure and processing are reflected on the process control chart reproducedas Figure 80. All the high-density readings are plotted, but only the readings from control stripsexposed at the same time are connected. The lines represent the day-to-day repeatability of filmprocessing, the difference between the point plots on a given day represents the repeatability ofexposure.Figure 81: Control chart for one exposing unit and one processor indicating changes incontrast. Plot the difference between the high-density reading and the low-density readingof the fresh-image control strips, and connect the plots. A decrease in density differencefrom the process density aim, or the mean density, indicates lower contrast; an increaseindicates higher density.Process Control Chart--Changes in Film ContrastMon. Tues. Wed. Thurs. Fri. Sat. Sun. Mon. Tues. Wed. Thurs. Fri.UppercontrollimitProcessdensityaimLowercontrollimit1.301.100.90There will be a slight density loss of the latent image on the control strips processed one to threedays after exposure even though they are refrigerated. However, this small difference in densityis no cause for concern with the type of control chart shown in Figure 80. If the density of therefrigerated control strip is always slightly lower (0.03 to 0.04) than that of its corresponding freshcontrol strip, the process is repeating identically.Contrast VariationsVariations in film contrast are reflected on the control chart reproduced as Figure 81. Thedifference between the high-density reading and the low-density reading of the fresh-imagecontrol strips is plotted on this chart. (Latent-image control strips serve equally well fordetermining density difference.) A decrease in density difference from the mean density, or theprocess density aim, indicates lower contrast, an increase in density difference indicates highercontrast.Radiography in Modern Industry 127
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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
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 and 92: 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: Figure 80: Control chart below for
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 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
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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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