Radiography in Modern Industry - Kodak

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Figure 37: The combined use of metallic shot and a lead mask for lessening scatteredradiation is conducive to good radiographic quality. If several round bars are to beradiographed, they may be separated with lead strips held on edge on a wooden frame andthe voids filled with fine shot.Lead Foil ScreensLead screens, mounted in contact with the film, diminish the effect on the film of scatteredradiation from all sources. They are beyond doubt the least expensive, most convenient, andmost universally applicable means of combating the effects of scattered radiation. Lead screenslessen the scatter reaching the films regardless of whether the screens permit a decrease ornecessitate an increase in the radiographic exposure. The nature of the action of lead screens isdiscussed more fully in "Radiographic Screens".Many x-ray exposure holders incorporate a sheet of lead foil in the back for the specific purposeof protecting the film from backscatter. This lead will not serve as an intensifying screen, first,because it usually has a paper facing, and second because it often is not lead of "radiographicquality". If intensifying screens are used with such holders, definite means must be provided toinsure good contact.X-ray film cassettes also are usually fitted with a sheet of lead foil in the back for protectionagainst backscatter. Using such a cassette or film holder with gamma rays or with million-volt x-rays, the film should always be enclosed between double lead screens; otherwise, the secondaryradiation from the lead backing is sufficient to penetrate the intervening felt or paper and cast ashadow of the structure of this material on the film, giving a granular or mottled appearance. Thiseffect can also occur at voltages as low as 200 kV unless the film is enclosed between lead foil orfluorescent intensifying screens. (See Figure 26.)Masks and DiaphragmsScattered radiation originating in matter outside the specimen is most serious for specimens thathave high absorption for x-rays, because the scattering from external sources may be largecompared to the primary image-forming radiation that reaches the film through the specimen.Often, the most satisfactory method of lessening this scatter is to use cutout diaphragms or someother form of mask mounted over or around the object radiographed. If many specimens of thesame article are to be radiographed, it may be worthwhile to cut an opening of the same shape,but slightly smaller, in a sheet of lead and place this on the object. The lead serves to reduce theexposure in surrounding areas to a negligible value and therefore to eliminate scattered radiationRadiography in Modern Industry 52
from this source. Since scatter also arises from the specimen itself, it is good practice whereverpossible, to limit the cross an x-ray beam to cover only the area of the specimen that is of interestin the examination.For occasional pieces of work where a cutout diaphragm would not be economical, barium claypacked around the specimen will serve the same purpose. The clay should be thick enough sothat the film density under the clay is somewhat less than that under the specimen. Otherwise,the clay itself contributes appreciable scattered radiation.It may be advantageous to place the object in aluminum or thin iron pans and to use a liquidabsorber, provided the liquid chosen will not damage the specimen. A combined saturatedsolution of lead acetate and lead nitrate is satisfactory.WARNING! Harmful if swallowed. Harmful if inhaled. Wash thoroughly after handling. Use onlywith adequate ventilation.To prepare this solution, dissolve approximately 31/2 pounds of lead acetate in 1 gallon of hotwater. When the lead acetate is in solution, add approximately 3 pounds of lead nitrate.Because of its high lead content this solution is a strong absorber of x-rays. In masking withliquids, be sure to eliminate bubbles that may be clinging to the surface of the specimen.One of the most satisfactory arrangements, combining effectiveness and convenience, is tosurround the object with copper or steel shot having a diameter of about 0.01 inch or less (SeeFigure 37). This material "flows" without running badly. It is also very effective for filling cavities inirregular objects, such as castings, where a normal exposure for thick parts would result in anoverexposure for thinner parts. Of course, it is preferable to make separate exposures for thickand thin parts, but this is not always practical.In some cases, a lead diaphragm or lead cone on the tube head may be a convenient way to limitthe area covered by the x-ray beam. Such lead diaphragms are particularly useful where thedesired cross section of the beam is a simple geometric figure, such as a circle, square, orrectangle.FiltersIn general, the use of filters is limited to radiography with x-rays. A simple metallic filter mountedin the x-ray beam near the x-ray tube (See Figure 38) may adequately serve the purpose ofeliminating overexposure in the thin regions of the specimen and in the area surrounding the part.Such a filter is particularly useful to reduce scatter undercut in cases where a mask around thespecimen is impractical, or where the specimen would be injured by chemicals or shot. Of course,an increase in exposure or kilovoltage will be required to compensate for the additionalabsorption; but, in cases where the filter method is applicable, this is not serious unless the limitof the x-ray machine has been reached.The underlying principle of the method is that the addition of the filter material causes a muchgreater change in the amount of radiation passing through the thin parts than through the thickerparts. Suppose the shape of a certain steel specimen is as shown in Figure 38 and that thethicknesses are 1/4 inch, 1/2 inch, and 1 inch. This specimen is radiographed first with no filter,and then with a filter near the tube.Radiography in Modern Industry 53
Page 1 and 2: RadiographyinModernIndustry
Page 3 and 4: RadiographyinModernIndustryFOURTH E
Page 5 and 6: ContentsIntroduction...............
Page 7 and 8: Chapter 1: The Radiographic Process
Page 9 and 10: Intensifying ScreensX-ray and other
Page 11 and 12: makes it a very suitable material f
Page 13 and 14: Figure 6: Typical voltage waveforms
Page 15 and 16: 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: such as a wall or floor, on the fil
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 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
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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
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Figure 77: The roller transport sys
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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
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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
Page 141 and 142:
In summary, use of the test papers
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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
Page 167 and 168:
from the camera or by reaching down
Page 169 and 170:
Figure 106: Schematic diagram of th
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valuable technique, for instance, i
Page 173 and 174:
The position of the spots is determ
Page 175 and 176:
Powder Diffraction File, Internatio
Page 177 and 178:
Processing TechniquesRadiographs on
Page 179 and 180:
Since this formula applies only to
Page 181 and 182:
such that it does not distort the i
Page 183 and 184:
Figure 113: A: Representation of a
Page 185 and 186:
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
Page 193 and 194:
e noted here. Although the average
Page 195 and 196:
Chapter 17: Film Graininess; Signal
Page 197 and 198:
The ratio of signal to noise has a
Page 199 and 200:
Chapter 18: The Photographic Latent
Page 201 and 202:
Thus, the change that makes an expo
Page 203 and 204:
Figure 130: Stages in the developme
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electrons by successive Compton int
Page 207 and 208:
Development is essentially a chemic
Page 209 and 210:
Chapter 19: ProtectionOne of the mo
Page 211 and 212:
duct is brought into the x-ray room
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