Radiography in Modern Industry - Kodak

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DensityLog Relative ExposureDifference of Log RelativeExposure1.0 1.57 + 0.221.5 1.79 02.0 1.92 - 0.133.0 2.10 - 0.31The values in column 3 are the differences between the logarithm of relative exposure required toproduce the density for which the chart was originally drawn (in this case 1.5) and the logarithm ofexposure required for the desired density. They represent the log E intervals that the "exposure"grid of the exposure chart must be shifted up or down to give exposures that will result in thelower or higher densities. Plus signs indicate that the added marks on the margin should beabove that printed on the chart; minus signs, that the added marks are to be below. Figure 59shows the chart with the transparent overlay positioned to directly read exposures required togive a density of 2.0.Figure 59: Overlay positioned so as to make the exposure chart and the nomogram applyto a density of 2.0, rather than 1.5. See No. 5, "Film density".Estimating Exposures For Multithickness SpecimensA minimum acceptable density for radiographs is often specified, not because of any virtue in theparticular density, but because the slope of the characteristic curve (and hence the film contrast)below a certain point is too low for adequate rendition of detail. Similarly, a maximum acceptabledensity is often designated because either the film contrast is lower at high densities or detailcannot be seen on the available illuminators if the density is above a certain value.Radiography in Modern Industry 82
The problem of radiographing a part having several thicknesses is one of using the availabledensity range most efficiently. In other words, the kilovoltage and exposure should be adjusted sothat the image of the thinnest part has the maximum acceptable density, and the thickest has theminimum. Exposure charts alone, although adequate for the radiography of uniform plates, canserve only as rough guides for articles having considerable variation in thickness. Previousexperience is a guide, but even when a usable radiograph has been obtained, the questionremains as to whether or not it is the best that could be achieved.A quantitative method for finding such exposures combines information derived from theexposure chart and the characteristic curve of the film used. The procedure is outlined below:Assume that 1.0 is the lowest acceptable density on Film X (See Figure 47) and that 3.5 is thehighest. As shown in the figure below, this density interval corresponds to a certain log exposureinterval, in this case 0.63.Figure 60: Characteristic curve of Film X. Dotted lines show how the log E intervalcorresponding to a certain density interval (in this case 1.0 to 3.5) can be found.The antilog of 0.63 is 4.3, which means that 4.3 times more exposure is required to produce adensity of 3.5 than of 1.0. It is therefore desired that the thinnest portion of the object to beradiographed transmit exactly 4.3 times more radiation than the thickest part, so that with theproper adjustment of radiographic exposure, all parts of the object will be rendered within thedensity range 1.0 to 3.5. The ratios of x-ray intensities transmitted by different portions of theobject will depend on kilovoltage; examination of the exposure chart of the x-ray machine revealsthe proper choice of kilovoltage. For example, in the chart shown in the figure below, the 180 kVline shows that a thickness range of about 7/8 to about 11/4 inches of steel corresponds to anexposure ratio of 35 mA-min to 8 mA-min, or 4.3, which is the ratio required. The next problem isto determine the radiographic exposure needed. The chart shown below gives the exposure toproduce a density of 1.0 on Film X. Since it is desired to produce a density 1.0 under the thicksection (11/4 inches), the exposure time would be 35 mA-min.Radiography in Modern Industry 83
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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
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 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: Figure 58: Overlay positioned so as
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
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
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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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