Radiography in Modern Industry - Kodak

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of the specimen and the kilovoltage. When these conditions exist, the exposure chart may take asimplified form as shown in Figure 45, which allows the kilovoltage for any particular specimenthickness to be chosen readily. Such a chart will probably be particularly useful when uniformsections must be radiographed in large numbers by relatively untrained persons. This type ofexposure chart may be derived from a chart similar to Figure 44 by following the horizontal linecorresponding to the chosen milliampere-minute value and noting the thickness corresponding tothis exposure for each kilovoltage. These thicknesses are then plotted against kilovoltage.Figure 45: Typical exposure chart for use when exposure and distance are held constantand kilovoltage is varied to conform to specimen thickness. Film X (Figure 47 forexample), exposed with lead foil screens to a density of 1.5. Source-film distance, 40inches; exposure, 50 mA-min.Gamma-Ray Exposure ChartsThe figure below shows a typical gamma-ray exposure chart. It is somewhat similar to the next toFigure 46.However, with gamma rays, there is no variable factor corresponding to the kilovoltage.Therefore, a gamma-ray exposure chart contains one line, or several parallel lines, each of whichcorresponds to a particular film type, film density, or source-film distance. Gamma-ray exposureguides are also available in the form of linear or circular slide rules. These contain scales onwhich can be set the various factors of specimen thickness, source strength and source-filmdistance, and from which exposure time can be read directly.Sliding scales can also be applied to gamma-ray exposure charts of the type in the figure belowto simplify some exposure determinations. For the preparation and use of such scales, see"Sliding Scales For Exposure Charts".Radiography in Modern Industry 68
Figure 46: Typical gamma-ray exposure chart for iridium 192, based on the use of Film X(Figure 47 for example).The Characteristic CurveThe characteristic curve, sometimes referred to as the sensitometric curve or the H and D curve(after Hurter and Driffield who, in 1890, first used it), expresses the relation between the exposureapplied to a photographic material and the resulting photographic density. The characteristiccurves of three typical films, exposed between lead foil screens to x-rays, are given in Figure 47.Such curves are obtained by giving a film a series of known exposures, determining the densitiesproduced by these exposures, and then plotting density against the logarithm of relativeexposure.Relative exposure is used because there are no convenient units, suitable to all kilovoltages andscattering conditions, in which to express radiographic exposures. Hence, the exposures given afilm are expressed in terms of some particular exposure, giving a relative scale. In practicalradiography, this lack of units for x-ray intensity or quantity is no hindrance. The use of thelogarithm of the relative exposure, rather than the relative exposure itself, has a number ofadvantages. It compresses an otherwise long scale. Furthermore, in radiography, ratios ofexposures or intensities are usually more significant than the exposures or the intensitiesthemselves. Pairs of exposures having the same ratio will be separated by the same interval onthe log relative exposure scale, no matter what their absolute value may be. Consider thefollowing pairs of exposures.Radiography in Modern Industry 69
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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
Page 17 and 18: The wavelengths (or energies of rad
Page 19 and 20: Table III - Industrial Gamma-Ray So
Page 21 and 22: 1. The source of light should be sm
Page 23 and 24: B and H in the Figure 13 show the e
Page 25 and 26: Figure 14: Geometric construction f
Page 27 and 28: Figure 17: Pinhole pictures of the
Page 29 and 30: The kilovoltage applied to the x-ra
Page 31 and 32: Figure 21: Schematic diagram of som
Page 33 and 34: kind of material radiographed, the
Page 35 and 36: instance, the kilovoltage may be fi
Page 37 and 38: The technique need not be limited t
Page 39 and 40: Chapter 5: Radiographic ScreensWhen
Page 41 and 42: Contact between the film and the le
Page 43 and 44: 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: Any given exposure chart applies to
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 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
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Figure 78: Film-feeding procedures
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Chapter 11: Process ControlUsers of
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3. Age of the developer replenisher
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Figure 80: Control chart below for
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DiscussionDensitometric data and pr
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Figure 82: Plan of a manual x-ray p
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Figure 83: A schematic diagram of a
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loading-bench activities are carrie
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KODAK Quinone-Thiosulfate Intensifi
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Methylene-Blue MethodTwo variations
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KODAK Hypo Test Solution HT-2Avoird
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In summary, use of the test papers
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narrow angle would be very thick, e
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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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