Radiography in Modern Industry - Kodak

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Figure 61: Abridged form of the exposure chart derived from a previous figure, butshowing exposures at 180 kV to produce a density of 1.0 on Film X. Dotted lines indicatethe metal thickness corresponding to the log E interval of the figure above. If theseparation of lines ABC and DEF is maintained, they can be moved up and down the chart.They will then mark off a large number of thickness ranges on the various kilovoltagelines, all of which will completely fill the density range which has been assumed to beuseful.A simple means for applying this method to routine work is as follows:Parallel lines are drawn on a transparent plastic sheet, such as a fixed-out x-ray film, in themanner shown in the figure below. The spacing between the base line and the line immediatelyabove is the log relative exposure interval for Film X between D = 1.0 and D = 3.5. It is laid off tothe same scale as the ordinate (vertical) scale of the exposure chart. Similarly, the distance fromthe baseline to any other line parallel to it can be made to correspond to the log relative exposureinterval for other density limits and films. This transparent guide is moved up and down on theexposure chart with its lines parallel to the thickness axis. The two guidelines being used form arectangle with the two vertical lines of the exposure chart that mark the thickness limits of thespecimen. The correct kilovoltage is the one whose graph intersects diagonally opposite comersof the rectangle. If the film type used is the one for which the chart was prepared, the correctexposure is indicated at the intersection of the upper guide line with the exposure scale (Point CFigure 1). If a different film is used, a suitable correction factor obtained either from tables ofrelative speeds or by the method described in Example 2 in "Overlay Methods" and "NomogramMethods", must be applied to the exposure as determined from the chart.Radiography in Modern Industry 84
Figure 62: System of lines drawn on a transparent sheet to be used in connection with anexposure chart for estimating radiographic exposures for multithickness specimens.If there is only one graph on a gamma-ray exposure chart, this procedure will indicate limitingthicknesses of material that can be radiographed within the prescribed density limits.On a chart of the type Figure 46, which has lines for various densities, the thickness range thatcan be radiographed in a single exposure can be read directly. For example, the same exposure(exposure factor = 0.7) will give a density of 1.5 through 2 inches of steel and a density of 2.5through about 11/2 inches of steel.Use Of Multiple FilmsIf the chart shows that the thickness range is too great for a single exposure under any condition,it may be used to select two different exposures to cover the range. Another technique is to loadthe cassette with two films of different speed and expose them simultaneously, in which case thechart may be used to select the exposure. The log relative exposure range for two films ofdifferent speed, when used together in this manner, is the difference in log exposure between thevalue at the low-density end of the faster film curve and the high-density end of the slower filmcurve. Figure 47 shows that when Films X and Y are used, the difference is 1.22, which is thedifference between 1.57 and 2.79. It is necessary that the films be close enough together inspeed so that their curves will have some "overlap" on the log E axis.Limitations Of Exposure ChartsAlthough exposure charts are useful industrial radiographic tools, they must be used with somecaution. They will, in most cases, be adequate for routine practice, but they will not always showthe precise exposure required to radiograph a given thickness to a particular density.Several factors have a direct influence on the accuracy with which exposures can be predicted.Exposure charts are ordinarily prepared by radiographing a stepped wedge. Since the proportionof scattered radiation depends on the thickness of material and, therefore, on the distribution ofthe material in a given specimen, there is no assurance that the scattered radiation underdifferent parts will correspond to the amount under the same thickness of the wedge. In fact, it isunreasonable to expect exact correspondence between scattering conditions under two objectsthe thicknesses of which are the same but in which the distribution of material is quite different.The more closely the distribution of metal in the wedge resembles that in the specimen the moreaccurately the exposure chart will serve its purpose. For example, a narrow wedge wouldapproximate the scattering conditions for specimens containing narrow bars.Radiography in Modern Industry 85
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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
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 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: The problem of radiographing a part
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 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
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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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