Radiography in Modern Industry - Kodak

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Figure 74: Water should flow over the tops of the hangers in the washing compartment.This avoids streaking due to contamination of the developer when hangers are used overagain.Efficient washing of the film depends both on a sufficient flow of water to carry the fixer awayrapidly and on adequate time to allow the fixer to diffuse from the film. Washing time at 60 to 80°F (15.5 to 26.5° C) with a rate of water flow of four renewals per hour is 30 minutes.The films should be placed in the wash tank near the outlet end. Thus, the films most heavilyladen with fixer are first washed in water that is somewhat contaminated with fixer from the filmspreviously put in the wash tank. As more films are put in the wash tank, those already partiallywashed are moved toward the inlet, so that the final part of the washing of each film is done infresh, uncontaminated water.The tank should be large enough to wash films as rapidly as they can be passed through theother solutions. Any excess capacity is wasteful of water or, with the same flow as in a smallertank, diminishes the effectiveness with which fixer is removed from the film emulsion. Insufficientcapacity, on the other hand, encourages insufficient washing, leading to later discoloration orfading of the image.The "cascade method" of washing is the most economical of water and results in better washingin the same length of time. In this method, the washing compartment is divided into two sections.The films are taken from the fixer solution and first placed in Section A. (See Figure 75) Afterthey have been partially washed, they are moved to Section B, leaving Section A ready to receivemore films from the fixer. Thus, films heavily laden with fixer are washed in somewhatcontaminated water, and washing of the partially washed films is completed in fresh water.Figure 75: Schematic diagram of a cascade washing unit.Washing efficiency decreases rapidly as temperature decreases and is very low at temperaturesbelow 60°F (15.5°C). On the other hand, in warm weather, it is especially important to removefilms from the tank as soon as washing is completed, because gelatin has a natural tendency toRadiography in Modern Industry 112
soften considerably with prolonged washing in water above 68°F (20°C). Therefore, if possiblethe temperature of the wash water should be maintained between 65 and 70°F or 18 and 21°C).Formation of a cloud of minute bubbles on the surfaces of the film in the wash tank sometimesoccurs. These bubbles interfere with washing the areas of emulsion beneath them, and cansubsequently cause a discoloration or a mottled appearance of the radiograph. When this troubleis encountered, the films should be removed from the wash water and the emulsion surfaceswiped with a soft cellulose sponge at least twice during the washing period to remove thebubbles. Vigorous tapping of the top bar of the hanger against the top of the tank rarely issufficient to remove the bubbles.Prevention of Water SpotsWhen films are removed from the wash tanks, small drops of water cling to the surfaces of theemulsions. If the films are dried rapidly, the areas under the drops dry more slowly than thesurrounding areas. This uneven drying causes distortion of the gelatin, changing the density ofthe silver image, and results in spots that are frequently visible and troublesome in the finishedradiograph.Such "water spots" can be largely prevented by immersing the washed films for 1 or 2 minutes ina wetting agent, then allowing the bulk of the water to drain off before the films are placed in thedrying cabinet. This solution causes the surplus water to drain off the film more evenly, reducingthe number of clinging drops. This reduces the drying time and lessens the number of water spotsoccurring on the finished radiographs.DryingConvenient racks are available commercially for holding hangers during drying when only a smallnumber of films are processed daily. When the racks are placed high on the wall, the films can besuspended by inserting the crossbars of the processing hangers in the holes provided. Thisobviates the danger of striking the radiographs while they are wet, or spattering water on thedrying surfaces, which would cause spots on them. Radiographs dry best in warm, dry air that ischanging constantly.When a considerable number of films are to be processed, suitable driers with built-in fans, filters,and heaters or desiccants are commercially available.Marks in RadiographsDefects, spots, and marks of many kinds may occur if the preceding general rules for manualprocessing are not carefully followed. Perhaps the most common processing defect is streakinessand mottle in areas that receive a uniform exposure. This unevenness may be a result of:• Failure to agitate the films sufficiently during development or the presence of toomany hangers in the tank, resulting in inadequate space between neighboring films.• Insufficient rinsing in water or failure to agitate the films sufficiently before fixation.• The use of an exhausted stop bath or failure to agitate the film properly in the stopbath.• In the absence of satisfactory rinsing--insufficient agitation of the films on firstimmersing them in the fixing bath.Other characteristic marks are dark spots caused by the spattering of developer solution, staticelectric discharges, and finger marks; and dark streaks occurring when the developer-saturatedfilm is inspected for a prolonged time before a safelight lamp. If possible, films should never beexamined at length until they are dry.A further trouble is fog - that is, development of silver halide grains other than those affected byradiation during exposure. It is a great source of annoyance and may be caused by accidentalexposure to light, x-rays, or radioactive substances; contaminated developer solution;Radiography in Modern Industry 113
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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
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 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: When development is complete, the f
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 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
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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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