Radiography in Modern Industry - Kodak

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Capacity of Solutions. Don't overwork chemical solutions. Observe the manufacturer'srecommendations in regard to capacity and renewal of solutions. Discard solutions--1. When 150 square feet of radiographic paper has been processed2. After 1 week regardless of the amount of paper processed3. When a processed radiograph shows noticeable degradation4. Dry Processing Trays. Check before loading them with chemicals. Some stabilizationsolutions are not compatible with water.Avoid contamination of the activator with the stabilizer. This results in chemical fog on theradio- graphs. The smell of ammonia is an indication of contamination.Do not wash stabilized radiographs unless they have been fixed in an ordinary fixing bath.Washing without fixing makes a stabilized radiograph sensitive to light.Because stabilized radiographs are impregnated with chemicals, do not file them in contact withprocessed x-ray films or other valuable material. Stabilized radiographs that are to be kept for anextended period of time must be fixed and washed (post-stabilization processing).Automated ProcessingSome radiographic papers can be processed in specially modified automated film processors.However, papers designed for stabilization processing are not usually processible in filmprocessors. Check the paper manufacturer's recommendations for specific processinginformation.Radiographic paper cannot be intermixed with x-ray film for processing. Replenishment rates forpaper are much lower than for film. Consequently, if film is intermixed with paper, the film willreceive improper processing.Manual ProcessingMost radiographic papers can be processed manually. Check the manufacturer'srecommendations for the specific processing chemicals, times, and temperatures required.Viewing Paper RadiographsA correctly exposed, properly processed radiograph on paper is only part of the story. To beuseful in providing information, the radiograph must be viewed, and viewing radiographs on lightreflectingpaper is entirely different from viewing radiographs on light-transmitting film. It is almostimmediately apparent that some of the familiar methods of measurement and interpretationapplicable to film are not relevant to the interpretation of paper radiographs.Density--Transmission vs ReflectionWhen electromagnetic radiation--in the form of light, x-rays, or gamma rays--reacts with thesensitive emulsion of x-ray film or radiographic paper, the emulsion will show a blackening after ithas been processed. The degree of blackening is defined as density. Up to this point,radiographic paper acts identically like film, but beyond this point, differences appear.Density--MeasurementThe density on transparent-based film is known as transmission density. D T and is defined as thelogarithm of the ratio of the incident light intensity, I O (from the illuminator), on the radiograph, tothe light intensity transmitted through the radiograph, I T . The formula is:Radiography in Modern Industry 178
Since this formula applies only to light-transmitting images, it cannot be applied to an opaquebasedimaging material such as radiographic paper. Therefore, a slightly different means ofmeasuring density is necessary, and this is called reflection density, D R . Reflection density isdefined as the logarithm of the ratio of incident light intensity, I O , to the reflected light intensity, I Rfrom the image area. This formula is:So, although the formula appears to be quite similar to that of transmission density, in practicalapplication, reflection density measures the light reflected from the radiograph, not that whichpasses through. For example, reflection densities are measured by a reflection densitometer, andthe familiar densitometer for measuring transmitted densities cannot be used.To carry the discussion one step further, exposure is defined as the product of the quantity ofradiation--measured in roentgens or other units--and time. In this respect, the exposure toradiographic paper is measured exactly the same as it is for x-ray film, although the order ofmagnitude of the exposure may be different. Reflection characteristic curves can be generated forradiographic paper. The difference between these curves and those for film is that transmissiondensity values are used for x-ray film, while reflection densities are used for radiographic paper.Characteristic curves (which are also known as H & D curves) for paper have a shorter range ofdensities and usually a shorter log exposure scale.Comparable Densities--Paper and FilmInterpreters could easily be led astray at this point by becoming involved in the purely objectiverelationship between reflection density and transmission density. They may theorize, for example,that under a given set of viewing conditions, reflection density of 0.7 appears to them to be similarto a transmission density of 2.0. In reality, the transmission density to reflection densityrelationship has no bearing upon where the same radiographic information is recorded on thefilm's transmission density scale as related to the paper's reflection density scale. The questionreally is--which densities contain the same information if x-ray film and radiographic paper areused to record the same image?Given the correct intensity of illumination, it is universally believed that the most usefulinformation is recorded on the essentially straight line portion of the characteristic curve. In fact, itis rather generally accepted that in industrial radiography the higher the density of a filmradiograph, the better the visibility of tiny discontinuities limited mainly by the available intensity ofthe illuminator. Because of the essentially opaque base of paper radiographs and the shouldereffect of the H & D curve of paper, this concept cannot be applied to reflection densities.A radiographic image on paper of the same image area of a subject will contain the sameimportant image details as a radiograph on film. These details will be modified in density (andpossibly in contrast) because the response is fundamentally different.It must also be recognized, of course, that the total range of information capable of beingrecorded will be less on a paper radiograph because the reflection density scale is shorter than itsx-ray film counterpart. For example, a reflection density of 2.0 on a paper radiograph is so blackthat detail is completely obscured.In addition, because of the opaque nature of the paper base, the method of viewing reflecteddensities of images on paper is fundamentally different from the method for viewing transmittedRadiography in Modern Industry 179
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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
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kind of material radiographed, the
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instance, the kilovoltage may be fi
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The technique need not be limited t
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Chapter 5: Radiographic ScreensWhen
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Contact between the film and the le
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Figure 29: The number of electrons
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lead foil screens ran be retained w
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Figure 33: The sharpness of the rad
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Figure 34: Low density (right) is a
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such as a wall or floor, on the fil
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from this source. Since scatter als
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A filter reduces excessive subject
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Definite rules as to filter thickne
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0.010-inch front screen of value be
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Example: Suppose that with a given
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If the milliamperage remains consta
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espectively. In other words, a cons
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Any given exposure chart applies to
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Figure 46: Typical gamma-ray exposu
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where the slope of the characterist
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Figure 49: Characteristic curves of
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Figure 51: Characteristic curve of
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Nomogram MethodsIn Figure 54, the s
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Figure 56: Transparent overlay posi
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Figure 58: Overlay positioned so as
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The problem of radiographing a part
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Figure 62: System of lines drawn on
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Chapter 8: Radiographic Image Quali
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Film contrast refers to the slope (
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Hole Type PenetrametersThe common p
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of the same thickness as the specim
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Chapter 9: Industrial X-ray FilmsMo
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Figure 70 indicates the direction t
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the lead letters on a radiation-abs
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Therefore, protection requirements
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5. Avoid pressure damage caused by
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Paddles or plunger-type agitators a
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slow, and the development time reco
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ubbles make their way to the surfac
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When development is complete, the f
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soften considerably with prolonged
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Figure 77: The roller transport sys
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Rapid Access to Processed Radiograp
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Figure 78: Film-feeding procedures
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Chapter 11: Process ControlUsers of
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3. Age of the developer replenisher
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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: Processing TechniquesRadiographs on
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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