Radiography in Modern Industry - Kodak

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It is essential to secure uniformity of development over the whole area of the film. This isachieved by agitating the film during the course of development.If a radiographic film is placed in a developer solution and allowed to develop without anymovement, there is a tendency for each area of the film to affect the development of the areasimmediately below it. This is because the reaction products of development have a higher specificgravity than the developer and, as these products diffuse out of the emulsion layer, they flowdownward over the film surface and retard the development of the areas over which they pass.The greater the film density from which the reaction products flow, the greater is the restrainingaction on the development of the lower portions of the film. Thus, large lateral variations in filmdensity will cause uneven development in the areas below, and this may show up in the form ofstreaks. Figure 72 illustrates the phenomena that occur when a film having small areas whosedensities are widely different from their surroundings is developed without agitation of film ordeveloper.Figure 72: An example of streaking that can result when a film has been allowed to remainin the solution without agitation during the entire development period.Agitation of the film during development brings fresh developer to the surface of the film andprevents uneven development. In small installations, where few films are processed, agitation ismost easily done by hand. Immediately after the hangers are lowered smoothly and carefully intothe developer, the upper bars of the hangers should be tapped sharply two or three times on theupper edge of the tank to dislodge any bubbles clinging to the emulsion. Thereafter, films shouldbe agitated periodically throughout the development.Acceptable agitation results if the films are shaken vertically and horizontally and moved fromside to side in the tank for a few seconds every minute during the course of the development.More satisfactory renewal of developer at the surface of the film is obtained by lifting the film clearof the developer, allowing it to drain from one corner for 2 or 3 seconds, reinserting it into thedeveloper, and then repeating the procedure, with drainage from the other lower corner. Thewhole cycle should be repeated once a minute during the development time.Another form of agitation suitable for manual processing of sheet films is known as "gaseousburst agitation." It is reasonably economical to install and operate and, because it is automatic,does not require the full-time attention of the processing room operator. Nitrogen, because of itsinert chemical nature and low cost, is the best gas to use.Gaseous burst agitation consists of releasing bursts of gas at controlled intervals through manysmall holes in a distributor at the bottom of the processing tank. When first released, the burstsimpart a sharp displacement pulse, or piston action, to the entire volume of the solution. As theRadiography in Modern Industry 108
ubbles make their way to the surface, they provide localized agitation around each small bubble.The great number of bubbles, and the random character of their paths to the surface, provideeffective agitation at the surfaces of films hanging in the solution (See Figure 73)Figure 73: Distribution manifold for gaseous burst agitation.If the gas were released continuously, rather than in bursts, constant flow patterns would be setup from the bottom to the top of the tank and cause uneven development. These flow patternsare not encountered, however, when the gas is introduced in short bursts, with an intervalbetween bursts to allow the solution to settle down.Note that the standard sizes of x-ray developing tanks will probably not be suitable for gaseousburst agitation. Not only does the distributor at the bottom of the tank occupy some space, butalso the tank must extend considerably above the surface of the still developer to contain thefroth that results when a burst of bubbles reaches the surface. It is therefore probable that specialtanks will have to be provided if the system is adopted.Agitation of the developer by means of stirrers or circulating pumps should be discouraged. Inany tank containing loaded film hangers, it is almost impossible to prevent the uniform flow ofdeveloper along certain paths. Such steady flow conditions may sometimes cause more unevendevelopment than no agitation at all.Activity of Developer SolutionsAs a developer is used, its developing power decreases, partly because of the consumption ofthe developing agent in changing the exposed silver bromide to metallic silver, and also becauseof the restraining effect of the accumulated reaction products of the development. The extent ofthis decrease in activity will depend on the number of films processed and their average density.Even when the developer is not used, the activity may decrease slowly because of aerialoxidation of the developing agent.Some compensation must be made for the decrease in developing power if uniform radiographicresults are to be obtained over a period of time. The best way to do this is to use the replenishersystem, in which the activity of the solution is not allowed to diminish but rather is maintained bysuitable chemical replenishment.In reference to the replenisher method or replenishment, the following should be understood. Asused here, replenishment means the addition of a stronger-than-original solution, to revive orrestore the developer to its approximate original strength. Thus, the replenisher performs thedouble function of maintaining both the liquid level in the developing tank and the activity of thesolution. Merely adding original-strength developer would not produce the desired regeneratingeffect; development time would have to be progressively increased to achieve a constant degreeof development.Radiography in Modern Industry 109
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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
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 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: slow, and the development time reco
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 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
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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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Radiography in Modern Industry - Kodak

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