Radiography in Modern Industry - Kodak

More documents

Recommendations

Info

Maximum contrast of screen-type films is at a density of about 2.0. Therefore, other things beingequal, the greatest radiographic sensitivity will be obtained when the exposure is adjusted to givethis density.Film Graininess, Screen Mottle(See also "Film Graininess; Signal-to-Noise Ratio in Radiographs".)The image on an x-ray film is formed by countless minute silver grains, the individual particlesbeing so small that they are visible only under a microscope. However, these small particles aregrouped together in relatively large masses, which are visible to the naked eye or with amagnification of only a few diameters. These masses result in the visual impression calledgraininess.All films exhibit graininess to a greater or lesser degree. In general, the slower films have lowergraininess than the faster. Thus, Film Y (Figure 47) would have a lower graininess than Film X.The graininess of all films increases as the penetration of the radiation increases, although therate of increase may be different for different films. The graininess of the images produced at highkilovoltages makes the slow, inherently fine-grain films especially useful in the million- andmultimillion-volt range. When sufficient exposure can be given, they are also useful with gammarays.The use of lead screens has no significant effect on film graininess. However, graininess isaffected by processing conditions, being directly related to the degree of development. Forinstance, if development time is increased for the purpose of increasing film speed, the graininessof the resulting image is likewise increased. Conversely, a developer or developing technique thatresults in an appreciable decrease in graininess will also cause an appreciable loss in film speed.However, adjustments made in development technique to compensate for changes intemperature or activity of a developer will have little effect on graininess. Such adjustments aremade to achieve the same degree of development as would be obtained in the fresh developer ata standard processing temperature, and therefore the graininess of the film will be essentiallyunaffected.Another source of the irregular density in uniformly exposed areas is the screen mottleencountered in radiography with the fluorescent screens. The screen mottle increases markedlyas hardness of the radiation increases. This is one of the factors that limits the use of fluorescentscreens at high voltage and with gamma rays.PenetrametersA standard test piece is usually included in every radiograph as a check on the adequacy of theradiographic technique. The test piece is commonly referred to as a penetrameter in NorthAmerica and an Image Quality Indicator (IQl) in Europe. The penetrameter (or lQI) is made of thesame material, or a similar material, as the specimen being radiographed, and is of a simplegeometric form. It contains some small structures (holes, wires, etc), the dimensions of whichbear some numerical relation to the thickness of the part being tested. The image of thepenetrameter on the radiograph is permanent evidence that the radiographic examination wasconducted under proper conditions.Codes or agreements between customer and vendor may specify the type of penetrameter, itsdimensions, and how it is to be employed. Even if penetrameters are not specified, their use isadvisable, because they provide an effective check of the overall quality of the radiographicinspection.Radiography in Modern Industry 90
Hole Type PenetrametersThe common penetrameter consists of a small rectangular piece of metal, containing several(usually three) holes, the diameters of which are related to the thickness of the penetrameter(See Figure 65).Figure 65: American Society for Testing and Materials (ASTM) penetrameter (ASTM E 142-68).The ASTM (American Society for Testing and Materials) penetrameter contains three holes ofdiameters T, 2T, and 4T, where T is the thickness of the penetrameter. Because of the practicaldifficulties in drilling minute holes in thin materials, the minimum diameters of these three holesare 0.010, 0.020, and 0.040 inches, respectively. These penetrameters may also have a slitsimilar to the ASME penetrameter described below. Thick penetrameters of the hole type wouldbe very large, because of the diameter of the 4T hole. Therefore, penetrameters more than 0.180inch thick are in the form of discs, the diameters of which are 4 times the thickness (4T) andwhich contain two holes of diameters T and 2T. Each penetrameter is identified by a lead numbershowing the thickness in thousandths of an inch.The ASTM penetrameter permits the specification of a number of levels of radiographicsensitivity, depending on the requirements of the job. For example, the specifications may call forRadiography in Modern Industry 91
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 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: Film contrast refers to the slope (
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
show all

Radiography in Modern Industry - Kodak

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?