Radiography in Modern Industry - Kodak

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increase in kilovoltage or exposure, or both, to produce the same photographic result. However,the atomic elements in a specimen usually exert a far greater effect on x-ray absorption thaneither the thickness or the density. For example, lead is about 1.5 times as dense as ordinarysteel, but at 220 kV, 0.1 inch of lead absorbs as much as 1.2 inches of steel. Brass is only about1.1 times as dense as steel, yet, at 150 kV, the same exposure is required for 0.25 inch of brassas for 0.35 inch of steel. Table IV gives approximate radiographic equivalence factors. It shouldbe emphasized that this table is only approximate and is intended merely as a guide, since it isbased on a compilation of data from many sources. In a particular instance, the exact value of theradiographic equivalence factor will depend an the quality of the x-radiation and the thickness ofthe specimen. It will be noted from this table that the relative absorptions of the different materialsare not constant but change with kilovoltage, and that as the kilovoltage increases, thedifferences between all materials tend to become less. In other words, as kilovoltage is increased,the radiographic absorption of a material is less and less dependent on the atomic numbers of itsconstituents.Table IV: Approximate Radiographic Equivalence FactorsX-raysGamma RaysMaterial 50 kV 100 kV 150 kV 220 kV 400 kV 1000 kV 2000 kV4 to25 MeVIr 192 Cs 137 Co 60RadiumMagnesium 0.6 0.6 0.5 0.08Aluminum 1.0 1.0 0.12 0.18 0.35 0.35 0.35 0.402024 (aluminum) alloy 2.2 1.6 0.16 0.22 0.35 0.35 0.35Titanium 0.45 0.35Steel 12. 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.018-8 (steel) alloy 12. 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0Copper 18. 1.6 1.4 1.4 1.3 1.1 1.1 1.1 1.1Zinc 1.4 1.3 1.3 1.2 1.1 1.0 1.0 1.0Brass * 1.4 * 1.3 * 1.3 * 1.2 * 1.2 * 1.2 * 1.1 * 1.1 * 1.1 * 1.1 *Inconel X alloy 16. 1.4 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3Zirconium 2.3 2.0 1.0Lead 14. 12. 5.0 2.5 3.0 4.0 3.2 2.3 2.0Uranium 25. 3.9 12.6 5.6 3.4Aluminum is taken as the standard metal at 50 kV and 100 kV and steel at the higher voltages and gamma rays. The thickness of another metal is multipliedby the corresponding factor to obtain the approximate equivalent thicknes of the standard metal. The exposrue applying to this thickness of the standard metalis used.Example: To radiograph 0.5 inch of copper at 220 kV, multiply 0.5 inch by the factor 1.4, obtaining an equivalent thickness of 0.7 inch of steel. Therefore, givethe exposure required for 0.7 inch of steel.* Tin or lead alloyed in the brass will increase these factors.For x-rays generated at voltages upward of 1000 kV and for materials not differing too greatly inatomic number (steel and copper, for example), the radiographic absorption for a given thicknessof material is roughly proportional to the density of the material. However, even at high voltagesor with penetrating gamma rays, the effect of composition upon absorption cannot be ignoredwhen dealing with materials that differ widely in atomic number. For instance, the absorption oflead for 1000 kV x-rays is about five times that of an equal thickness of steel, although its densityis but 11/2 times as great.The kilovoltage governs the penetrating power of an x-ray beam and hence governs the intensityof the radiation passing through the specimen. It is not possible, however, to specify a simplerelation between kilovoltage and x-ray intensity because such factors as the thickness and theRadiography in Modern Industry 32
kind of material radiographed, the characteristics of the x-ray generating apparatus, and whetherthe film is used alone or with intensifying screens exert a considerable influence on this relation.The following example illustrates this point:Data from a given exposure chart indicate that radiographs of equal density can be made of 1/4-inch steel with either of the following sets of exposure conditions:80 kilovolts, 35 milliampere-minutes120 kilovolt, 15 milliampere-minutesThus, in this case, a 50 percent increase in kilovoltage results in a 23-fold increase inphotographically effective x-ray intensity.Two-inch aluminum can also be radiographed at these two kilovoltages. Equal densities will resultwith the following exposure relations:80 kilovolts, 17 milliampere-minutes120 kilovolts, 2.4 milliampere-minutesIn this case, the same increase in kilovoltage results in an increase of photographically effectivex-ray intensity passing through the specimen of only seven times. Many other examples can befound to illustrate the extreme variability of the effect of kilovoltage on x-ray intensity.Gamma-ray EquivalencyEssentially the same considerations apply to gamma-ray absorption, since the radiations are ofsimilar nature. It is true that some radioactive materials used in industrial radiography emitradiation that is monoenergetic, or almost so (for example, cobalt 60 and cesium 137). However,even with these sources, scattering is dependent on the size, shape, and composition of thespecimen, which prevents the laws of absorption from being stated exactly. For those gamma-rayemitters (for example, indium 192) that give off a number of discrete gamma-ray wavelengthsextending over a wide energy range, the resemblance to the absorption of x-rays is even greater.The gamma-ray absorption of a specimen depends on its thickness, density, and composition, asdoes its x-ray absorption. However, the most commonly used gamma-ray sources emit fairlypenetrating radiations corresponding in their properties to high-voltage x-radiation. The tableabove shows that the absorptions of the various materials for penetrating gamma rays are similarto their absorptions for high-voltage x-rays--that is, the absorptions of materials fairly closetogether in atomic number are roughly proportional to their densities. As with high-voltage x-rays,this is not true of materials, such as steel and lead, that differ widely in atomic number.Radiographic ScreensAnother factor governing the photographic density of the radiograph is the intensifying action ofthe screens used. Intensifying screens and lead screens are fully discussed in "RadiographicScreens". It will suffice to state here that x-rays and gamma rays cause fluorescent intensifyingscreens to emit light that may materially lessen the exposure necessary to produce a givendensity. Lead screens emit electrons under the action of x-rays and gamma rays. Thephotographic effect of these electrons may permit a shorter exposure than would be requiredwithout lead screens.Radiography in Modern Industry 33
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: Figure 21: Schematic diagram of som
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 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
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
Page 147 and 148:
Figure 89: Demonstration of the eff
Page 149 and 150:
Figure 90: The amount of gamma radi
Page 151 and 152:
The radiograph exposed in the right
Page 153 and 154:
To illustrate, let us assume that t
Page 155 and 156:
Figure 95: High-speed x-ray picture
Page 157 and 158:
Figure 97: Two methods of neutron r
Page 159 and 160:
Duplicating RadiographsSimultaneous
Page 161 and 162:
Sometimes, as when sets of referenc
Page 163 and 164:
PhotofluorographyIn photofluorograp
Page 165 and 166:
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
Page 171 and 172:
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
Page 187 and 188:
film fairly well. If high densities
Page 189 and 190:
Density = 1.5 Density = 2.5Film Rel
Page 191 and 192:
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
Page 205 and 206:
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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