Radiography in Modern Industry - Kodak

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greater length later. Although an image may be formed by light and other forms of radiation, aswell as by gamma rays or x-rays, the properties of the latter two are of a distinct character, and,for this reason, the sensitive emulsion must be different from those used in other types ofphotography.Figure 69: Cross section showing the distribution of the developed grains in an x-ray filmemulsion exposed to give a moderate density.Selection Of Films For Industrial RadiographyIndustrial radiography now has many widely diverse applications. There are many considerationsin obtaining the best radiographic results, for example:• the composition, shape, and size of the part being examined--and, in some cases, itsweight and location as well• the type of radiation used--whether x-rays from an x-ray machine or gamma raysfrom a radioactive material• the kilovoltages available with the x-ray equipment• the intensity of the gamma radiation• the kind of information sought--whether it is simply an overall inspection or the criticalexamination of some especially important portion, characteristic, or feature• the resulting relative emphasis on definition, contrast, density, and the time requiredfor proper exposureAll of these considerations are important in the determination of the most effective combination ofradiographic technique and x-ray film.The selection of a film for the radiography of any particular part depends on the thickness andmaterial of the specimen and on the voltage range of the available x-ray machine. In addition, thechoice is affected by the relative importance of high radiographic quality or short exposure time.Thus, an attempt must be made to balance these two opposing factors. As a consequence, it isnot possible to present definite rules on the selection of a film. If high quality is the decidingfactor, a slower and hence finer grained film should be substituted for a faster one--for instance,for the radiography of steel up to 1/4-inch thick at 120-150 kV. Film Y (See Figure 47) might besubstituted for Film X. If short exposure times are essential, a faster film (or film-screencombination) can be used. For example, 11/2-inch steel might be radiographed at 200 kV usingfluorescent screens and a film particularly sensitive to blue light, rather than a direct exposure filmwith lead screens.Radiography in Modern Industry 96
Figure 70 indicates the direction that these substitutions take. The "direct exposure" films may beused with or without lead screens, depending on the kilovoltage and on the thickness and shapeof the specimen. (See "Radiographic Screens".)Figure 70: Change in choice of film, depending on relative emphasis on high speed orhigh radiographic quality.Fluorescent intensifying screens must be used in radiography requiring the highest possiblephotographic speed (see "Fluorescent Screens"). The light emitted by the screens has a muchgreater photographic action than the x-rays either alone or combined with the emission from leadscreens. To secure adequate exposure within a reasonable time, screen-type x-ray filmssandwiched between fluorescent intensifying screens are often used in radiography of steel inthicknesses greater than about 2 inches at 250 kV and more than about 3 inches at 400 kV.Film PackagingIndustrial x-ray films are available in a number of different types of packaging, each one ideallysuited to particular classes of radiography.Sheet FilmsFormerly, x-ray films were available only in individual sheets, and this form is still the mostpopular packaging. Each sheet of film may be enclosed in an individual paper folder (interleaved).The choice between the interleaved and non-interleaved films is a matter of the user'spreference. When no-screen techniques are used, the interleaving paper can be left on the filmduring exposure, providing additional protection to the film against accidental fogging by light ormarking by moist fingertips. In addition, many users find the interleaving folders useful in filing thefinished radiographs, protecting them against scratches and dirt during handling, and providing aconvenient place for notes and comments about the radiograph.Envelope PackingIndustrial x-ray films are also available in a form in which each sheet is enclosed in a folder ofinterleaving paper sealed in a light tight envelope. The film can be exposed from either sidewithout removing it from the envelope. A rip strip makes it easy to remove the film in thedarkroom for processing. This form of packaging has the advantage that the time-consumingprocess of darkroom loading of cassettes and film holders is eliminated. The film is completelyprotected from finger marks and dirt until the time the film is removed from the envelope forprocessing.Envelope Packing with Integral Lead Oxide ScreensThe main feature of this type of packaging is that the sheet of film is an envelope is enclosedbetween two lead oxide screens which are in direct contact with the film. This form of packagingaffords great convenience in material handling in an industrial x-ray department. As pointed out in"Lead Oxide Screens", it provides the advantage of cleanliness. This is particularly importantwhere heavy inclusions in the specimen are significant. The use of film in this packaging preventsthe images of such inclusions from being confused with artifacts caused by dust, cigarette ash,Radiography in Modern Industry 97
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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
Page 45 and 46: lead foil screens ran be retained w
Page 47 and 48: Figure 33: The sharpness of the rad
Page 49 and 50: Figure 34: Low density (right) is a
Page 51 and 52: such as a wall or floor, on the fil
Page 53 and 54: from this source. Since scatter als
Page 55 and 56: 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: Chapter 9: Industrial X-ray FilmsMo
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
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Figure 89: Demonstration of the eff
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Figure 90: The amount of gamma radi
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The radiograph exposed in the right
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To illustrate, let us assume that t
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Figure 95: High-speed x-ray picture
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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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