The Fundamentals of Industrial Radiography PDF
The Fundamentals of Industrial Radiography PDF
The Fundamentals of Industrial Radiography PDF
To meet the changing needs of modern industry, the FUJIFILM Corporation has
always striven to furnish excellent industrial radiographic materials. Research
and development in search of new testing materials and automatic processors
continues in order to keep abreast of new techniques in radiography. This
handbook has been prepared to furnish personnel thus engaged, with
information on the fundamentals of industrial radiography. Included are
properties of industrial X-ray films and up-to-date processing techniques. The
time invested in becoming familiar with the contents of this handbook will
result in rationalization and simplification.
NOTICE
CONTENTS
beams and cosmic rays emitted in nuclear reactions are
also derived from radioactivity.
I. MATERIALS AND Of these radioactive sources X-rays and gamma rays are
EQUIPMENT REQUIRED in general practice used in industrial radiography. Gamma
FOR MAKING rays have greater penetrating power than X-rays. X-rays
have a smoothly spread, continuous spectrum, while
RADIOGRAPHS gamma rays have a discrete spectrum characteristic to
the particular radioactive element involved.
1. X-ray and Gamma Ray Sources When high voltage direct current is applied between the
1.1 X-rays and Gamma Rays cathode and the anode, electrons are emitted by the
cathode which flow toward the anode with X-rays being
X-rays were discovered by W.C. Rntgen. Tradition has generated when the anode is struck. The voltage applied
it that Rntgen discovered them by chance when he between the two electrodes is called the X-ray tube
noticed that a screen painted with barium platinocyanide voltage, and the surface area of the anode which is struck
fluoresced when placed in close proximity to a cathode- by electrons is called the target.
ray tube.
In his report Rntgen called the newly discovered rays As electron emission is facilitated by heating, a filament
X-rays to indicate that their nature was unknown. The is incorporated in the cathode that is similar to that in a
rays were also later called Rntgen rays in honor of the tungsten filament lamp. A focusing cup is used to direct
distinguished achevement. the stream of electrons so as to obtain a focus on the
target. When electrons strike the anode, heat is generated
In 1912 M. von Laue and other investigators identified X- raising the temperature of the anode. Since the target and
rays as electromagnetic waves similar in nature to visible other parts, are heated to extremely high temperatures,
light, though invisible. the target is made of high melting point tungsten which
X-rays have far greater penetrating power than either also facilitates the generation of X-rays.
visible light or ultraviolet rays. Their nature is such that
the shorter the wavelength, the greater the penetrating The number of electrons emitted from the cathode and,
power. therefore, the dose of X-rays generated off the target
of the anode can be adjusted by changing the filament
Radium emits alpha(), beta(), and gamma() rays voltage of the X-ray tube. When the X-ray tube voltage is
which are penetrating in the same manner as X-rays. In
1898 Marie Curie termed the emanations of this element
radioactivity. Besides radium many radioactive elements Figure 2 Schematic Diagram of an X-ray Tube
have since been discovered. At present not only the rays
Target (Tungsten)
emitted by such radioactive sources but corpuscular Glass Envelope
Filament
Anode Cathode
7AVELENGTH CM
(6
8
RAYS
2ADIO 7AVES 5SED IN Focusing Cup
#OMMUNICATION !PPLICATIONS
5LTRAVIOLET 2AYS
)NFRARED 2AYS Electron Beam
X-rays
-ICROWAVES 'AMMA 2AYS
LV. . . . . T his terminal is connected to a low-voltage source for filament
heating.
&REQUENCY HV. . . . . This terminal is connected to a high-voltage source for electron
6ISIBLE ,IGHT emission from the cathode.
changed, the speed at which electrons strike the target 2.1 Lead Screens
changes causing a change in the nature of the X-rays (X-
Certain materials emit electrons when struck by high-
ray energy distribution in relation to spectrum). X-rays
energy X-rays or gamma rays. These electrons are called
which have relatively short wavelengths are called hard
secondary electrons and photographic film is sensitive not
X-rays, and those which have relatively long wavelengths
only to light, X-rays and gamma rays but also to secondary
soft X-rays.
electrons. This phenomenon is utilized in the lead screen.
Thin lead foil that readily emits electrons when struck by
In an X-ray generator, the line voltage is boosted by a
X-rays or gamma rays is bonded to a support so as not to
step-up transformer and rectified. As a result, a pulsating
affect penetration. The lead foil is usually 0.03 to 1.0 mm
voltage is applied to the X-ray tube. In radiography the
thick and the thickness generally needs to be increased
pulsating voltage that is applied to the X-ray tube is
with increasing radiation energy. In X-ray radiography,
expressed in peak values and the unit symbol kVp is
however, secondary electrons that have the capacity to
used.
affect the film are not generated below 100 kVp. Quite
to the contary the speed of the film is reduced, as X-rays
The kilovoltage which is used to cause the emission of
are absorbed by the lead coating of the screens. In X-ray
electrons in the way described above cannot be increased
radiography generally the front lead foil is 0.03 mm thick
beyond 400 kVp because of the inadequate dielectric
and the back lead foil 0.03 to 0.1 mm thick. In gamma ray
strength of presently available insulators. For faster
radiography the front and back lead foils used are from
acceleration of electrons X-ray generators use resonant
0.1 to 0.3 mm thick. The intensification factor of these lead
transformers, static electricity generators, betatrons or
screens varies from 2 to 3.
linear accelerators.
&IGURE 8
RAYS
3. Penetrameters or Image Quality
3TRUCTURAL AND &UNCTIONAL $IAGRAM
FOR THE ,EAD 3CREEN 3UPPORT Indicators
A test piece which is referred to as a penetrameter or
8
RAYS image quality indicator is used to obtain radiographs
,EAD &OIL which better serve the purpose of product testing.
Penetrameters are used as an aid in interpreting the
radiographs when the internal conditions of a specimen
&ILM
are to be examined in precise detail. Customarily, test
exposures are made under varied conditions so as to be
3ECTIONAL 6IEW OF ,EAD &OIL
able to plot an exposure chart. Specimens are exposed
#ASSETTE under the conditions derived from the exposure chart.
The penetrameter images on the resultant radiographs
8
RAYS
3UPPORT are checked to evaluate the exposure. The procedures
Secondary for judgment of penetrameter images are standardized in
Electrons
some countries of the world. Typical penetrameters, wire
and plaque types, are shown in Figures 6 and 7.
&IGURE 8
RAYS
3TRUCTURAL AND &UNCTIONAL $IAGRAM
FOR THE &LUORESCENT 3CREEN Figure 6 Typical Penetrameter of the Wire Type (JIS, Japan)
3UPPORT
5NIT MM
0HOSPHOR ,AYER &
8
RAYS
0ROTECTIVE ,AYER
&ILM
0ROTECTIVE ,AYER
3ECTIONAL 6IEW OF
#ASSETTE
8
RAYS 0HOSPHOR ,AYER
Fluorescent
Light
3UPPORT Figure 7 Typical Penetrameter of the Plaque Type (ASME, USA)
4 DIAM
4 DIAM
&IGURE 8
RAYS
4 DIAM
3TRUCTURAL AND &UNCTIONAL $IAGRAM
FOR THE &LUOREMETALLIC 3CREEN 3UPPORT v
,EAD &OIL
v v
v
4
0HOSPHOR ,AYER
8
RAYS v
0ROTECTIVE ,AYER ) v
&ILM
4. Industrial X-ray Films
0ROTECTIVE ,AYER In order to meet the various requirements of industrial
3ECTIONAL 6IEW OF
radiography Fuji Industrial X-ray Film is available in
#ASSETTE several types offering distinct advantages such as high
0HOSPHOR ,AYER
speed, high contrast, excellent definition, and fine grain.
8
RAYS
Radiographs of an excellent quality can be obtained
Fluorescent ,EAD &OIL
Light by making an appropriate choice among these films
Secondary relative to the purposes and kinds of specimens to be
Electrons 3UPPORT
radiographed.
4.1 Structure of Industrial X-ray Film 5.1 Developer
X-ray films for industrial radiography consist of an When photographic film is exposed to light or radioactive
emulsion and a bluetinted base of polyester 175 thick. rays, an invisible image (called a latent image) is formed
The emulsion is coated on both sides of the base in in the emulsion layer of the film. The process of converting
layers and protected on both sides with thin outer the latent image to a visible image is called development,
protective layers. The emulsion consists of silver halides and a developer solution is used in this process.
as the photosensitive material, additives and gelatin. The
Developer Composition
silver halides form an image when influenced by X-rays,
Chemically, development refers to the reducing action of
gamma rays, secondary electrons or fluorescent light.
a chemical. For the exposed film, it is necessary to reduce
In films for general photography the emulsion is coated
only the silver compound deposited in the latent image
only on one side of the base, whereas it is coated on
during exposure to metallic silver to form a visible image.
both sides for industrial radiography. The absorption of
The chemical which is chosen to reduce the exposed
highly-penetrative X-rays or gamma rays is increased by
silver compound to metallic silver is called a developing
using two emulsion layers so that the photosensitive silver
agent. The developing agent is not used alone but in
compound is utilized more effectively for the absorption
combination with other ingredients which perform special
of radiation and electrons. Furthermore, the two emulsion
functions. They include: the accelerator which activates
layers also help to increase the contrast and image
the developing agent; the preservative which reduces
density of the radiographs.
the aerial oxidation of the developer; the restrainer which
prevents development fog by restraining the action of the
Figure 8 Industrial X-ray Film Structure
developer on the unexposed silver compound; and other
additives.
0ROTECTIVE ,AYER
Developer
%MULSION ,AYER TO
Developing Agent
[Monol] (equivalent of Metol), hydroquinone,
0OLYESTER "ASE
Pyrazon] (equivalent of Phenidone), etc.]
Other Ingredients
%MULSION ,AYER TO
Accelerator
0ROTECTIVE ,AYER
[Sodium carbonate, sodium hydroxide, etc.]
Preservative
[Sodium sulfite, sodium bisulfite, etc.]
Restrainer
[Potassium bromide, etc.]
Additives
[Gelatin hardener, water softener, etc.]
4.2 Features of the Various Types of Fuji ]
Trademarks of the FUJIFILM Corporation
Industrial X-ray Films
Many developers are kept alkaline by the accelerator. The
X-ray films are generally classified according to the
more alkaline the developer or the greater the quantity of
various use purposes involved as shown in Table 1. The
accelerator added to the developer, the stronger the action
types of industrial X-ray films which are available from
of the developer. The developer for X-ray film contains
FUJIFILM Corporation are indicated in the table under the
more ingredients than the developers for conventional
subheading Industrial X-ray Films.
black-and-white films, because a larger quantity of silver
The features, speed and contrast of the five types of Fuji
halide is used in X-ray film.
Industrial X-ray Films are compared in Table 2.
Table 1 Classification of X-ray Films
.ON
SCREEN TYPES
)NDUSTRIAL 8
RAY &ILMS $IRECT EXPOSURE
3CREEN TYPE
.ON
SCREEN TYPES
$IRECT EXPOSURE
8
RAY 3CREEN TYPES
-EDICAL 8
RAY &ILMS
&ILMS
)NDIRECT EXPOSURE PHOTOFLUOROGRAPHY
3OFTEX 3OFT 8
RAY RADIOGRAPHY
8
RAY MOTION PICTURE
/THER APPLICATIONS 2ADIATION MONITORING
2ADIOGRAPH DUPLICATION
!UTORADIOGRAPHY
stop bath. In radiography a 3% solution of acetic acid is 5.5 Wetting Agent
used. If the stop bath is not used, the developer carried
When the washed film is dried the processing is completed.
over with the film not only increases the exhaustion of the
After the wash step, water adheres to the film in streaks
fixer but may become the cause of a lack of processing
and drops. If the film is dried in this condition, not only
uniformity or stain formation in the radiograph.
will the drying time be extended but water marks will be
5.3 Fixer left on the radiograph. To reduce drying time and prevent
After development and stop bath neutralization the water marks, The FUJIFILM Corporation has developed a
emulsion still contains unreduced silver halide which is wetting agent called Driwel.
not necessary for the image. Such material is detrimental, 5.6 Other Processing Chemicals
especially to the radiograph as viewed by transmitted
In addition to the processing chemicals discussed above,
light. The fixer is used to remove the unreduced silver
certain other chemicals may also be used. When the
halide.
density of the silver image is too high, a chemical solution
called a reducer is used to reduce it. When the density of
The commonest fixing baths are solutions of sodium
the silver image is too low, a chemical solution called an
thiosulfate. Ammonium thiosulfate is also used when quick
intensifier is used to increase it.
fixation is required. These chemicals possess activity
that converts silver halides to soluble compounds. The 5.7 Chemicals for Automatic Processing
emulsion which is softened by the developer is hardened
Some of the processing chemicals which have been
by the fixer. Acid hardening baths which stop the action
discussed above are also used in automatic processing
of the developer carried with the film and harden the
of X-ray film, but the developer and fixer for use in
emulsion are used in all fields of photography, let alone
automatic processing are specially formulated for the
radiography. Almost all fixers in common use are of this
following reasons. (For information on the automatic
acid hardening type.
processors refer to Section 6 Processors and Chapter
Fixer Composition IV AUTOMATIC PROCESSING.)
The fixer contains a solvent for silver halide and other
A. Developer
ingredients, as shown below.
In the roller transport type automatic processors (like the
Fixer Fuji FIP 7000) for industrial X-ray films, processing solutions
Silver Halide Solvent are used at higher temperatures (about 30C/86F) than
[Sodium and ammonium thiosulfates] in manual processing in order to speed things up. Many
Other Ingredients transport rollers are used to squeegee the film and
Preservative remove the exhausted solutions from the film surfaces.
[Sodium sulfite, etc.] Developers for use in automatic processors are specially
Acid formulated. Fuji Superdol l, for instance, is formulated
[Acetic acid, etc.]
to be suitable for processing at high temperatures and
Hardener
includes special chemicals which adjust the contrast and
[Potassium alum, etc.]
fog and a hardener which hardens the emulsion in order
Buffer
[Nabox] (equivalent to Kodalk mild alkali), etc.] to give sufficient resistance to forced roller squeegeeing.
]
Trademark of the FUJIFILM Corporation B. Fixer
The fixer for use in roller transport type automatic
To save users the trouble of weighing the ingredients of processors is specially formulated (as in the Fuji Super
the fixer, the FUJIFILM Corporation has made available FI) so as to produce a greater emulsion-hardening effect
ready-mixed fixers Hi-Renfix I (concentrated liquid) than with the fixer used in manual hand processing.
which are formulated to give good fixation results. Developer tank transport rollers reduce the amount of
5.4 Wash Accelerator (Quick Washing Agent) developer carry-over to the fixer. This extends the life of
the fixer, although the primary function of the rollers is to
The film removed from the fixing bath retains not only the
move the film through the processor.
fixer ingredients but other compounds which were formed
in dissoving the silver halides. To remove these, the film Notes:
is washed in running water for 20 minutes or more. To Stop Bath
reduce the washing time the FUJIFILM Corporation has The stop bath is not used in roller transport type
developed a wash accelerator called Fuji QW. This Fuji automatic processors, because the rollers adequately
QW can reduce the washing time to one-third or one-fifth remove developer solution from the surfaces of the
of that required without its use. film. This prolongs the life of the fixer to a far greater
extent than in manual processing.
Wash Accelerator
In roller transport type automatic processors the II. Photographic
fixer tank rollers effectively remove fixer from the film
surfaces and wash tank rollers provide for continual
characteristics of
turnover of fresh water on the film surface so that the X-ray films
necessity of a wash accelerator has not been voiced
to date.
Wetting Agent
In roller transport type automatic processors the
rollers effectively remove the wash water clinging to
the surfaces of the film so that the wetting agent is not
needed.
1. Photographic Density
The degree of blackening of the photographic image is
referred to as photographic density, and there are two
6. P
hotographic Processing kinds of density. One kind is transmission density and the
Equipment other reflection density. The first kind of density is used
Photographic processing involves two basic orientations to express the density of a photographic image in film.
those being manual processing and automatic The transmission density of a photographic image is
processing. In the case of manual processing, the expressed as the logarithm of its opacity. Let the intensity
processing chemicals are placed in a tray and into this of the light falling on a film surface (incident light) be I0
the film is introduced while the tray is tilted back and and the intensity of the light after it passes through the film
forth in a repeated pattern to induce the reaction, or the be I, and the following equations will hold.
processing chemicals are placed into a tank and the film Transparency = I/I0
is suspended with a hanger in the solution so that it can Opacity = I0/I
be moved over and over again in the solution. With this Density = Log I0/I
kind of manual processing things such as the tray, the
solution tank, the hanger and the like are needed by way Figure 9 Density
of equipment. In these types of situations the equipment
used comes into direct contact with the chemicals and
must therefore be made of materials that are not corroded
)
by this contact. In addition to these items there is the
necessity for equipment to control the processing solution
temperatures. In this category certain kinds of equipment
are placed directly into the processing solutions such as $ENSITY
the heater and in other cases the use of a thermostatic
bath is central.
)
Automatic dry-to-dry machine processing is coming
into wider acceptance because of the increased )
stability afforded to the photographic processing
itself not to mention the increase in processing speed
and abbreviation in processing steps. Most of these $ENSITY
processors incorporate mutually or simultaniously driven
rollers. The processing steps employed in these types
of processors are development, fix, wash and dry being )
composed of four procedures and in all there are many
roller units therein arranged. All of these rollers are driven )
at the very same speed and thus turn together so that
while the film is being transported between them it is also
being processed. Normally there are also included in the $ENSITY
automatic processor such devices as the temperature
control units for the processing solutions, the dryer
heater and fan and the automatic solution replenishment )
devices. For more detailed information see Chapter IV
AUTOMATIC PROCESSING.
2. The Characteristic Curve Unexposed Portion:
A density which is just noticeable appears in the
The properties of X-ray film can be expressed in several
unexposed areas of processed film and this density is
ways. The most widely used is the characteristic curve.
called fog.
By the characteristic curve of an X-ray film is meant the
Toe Region:
curve that results on a graph from plotting the correlation
Underexposed films generally have a density in the range
between image density and X-ray or gamma ray exposure
indicated by this section.
that is derived from processing, as illustrated in Fig. 10.
Straight-line Portion:
This characteristic curve furnishes information on the
Properly exposed films generally have a density in the
speed, contrast (average gradient) and fog of X-ray film.
range indicated mainly by the straight-line section and
As it is difficult to measure the absolute strength of X-rays
toe. Contrast is most closely related to the straight-line
and gamma rays, relative exposure is determined, and its
section.
logarithm expressed as Log Relative Exposure is plotted
Shoulder Region:
along the horizontal axis of the graph against the density
Overexposed film generally has a density in the range
which is laid off along the vertical axis at intervals equal to
indicated mainly by the shoulder and straight-line
those on the horizontal axis. The shape of the characteristic
portion.
curve and its position on the graph differs from one type
Solarization Portion:
of film or radiation source to the other. Further, variations
The density may even fall again upon increasing exposure
in the curve are seen with varying processing conditions
above that indicated by the shoulder. This portion is
and relative to the presence or absence of intensifying
not included in exposures used for the formation of
screens.
photographic images.
Customarily, the characteristic curve is divided into five
sections, as shown in Figure 10: (1) the unexposed
Figure 11 Characteristic Curve of a Non-screen Type Film
position; (2) the toe; (3) the straight-line portion; (4) the
shoulder; and (5) the solarization portion.
Note: The term sensitometry refers to the science
of establishing accurate numerical values
for exposure-density relationships and the
determination of film speed, contrast, fog and other
parameters as derived from the characteristic
curve.
$ENSITY
3TRAIGHT
LINE
0ORTION=
$
,OG 2ELATIVE %XPOSURE
#
3OLARIZATION
0ORTION
Figure 12 Characteristic Curve of a Screen Type Film
$ENSITY
3HOULDER
2EGION=
4OE 2EGION=
5NEXPOSED
0ORTION
"
&OG $ENSITY=
$ENSITY
!
,OG 2ELATIVE %XPOSURE=
]
1 Fog Density
The fog density may or may not include the base density. In many
instances it is not indicated whether base fog is included or not.
]
2 Toe, Straight-line and Shoulder Portions
These designations indicated fairly well-defined portions of the
characteristic curve, but do not have such distinct points as B and C in
Figure 10.
]
3 The logarithm of the relative exposure when the film is exposed to X-rays ,OG 2ELATIVE %XPOSURE
or gamma rays.
3. Speed Figure 13 Characteristic Curves for Four Types of Film
$ENSITY
the relative speed.
Note: The speed scale is so arranged that the speed
decreases with increasing exposure and increases with
decreasing exposure. The speed is therefore expressed by
the reciprocal of the exposure for ease of understanding.
Table 3 Relative Speeds
4. Average Gradient
The contrast for industrial X-ray film is expressed by the
average gradient (G)]. The certain range of all densities
which form a photographic image significantly influences
Point A = Fog-plus-base density + 3.5
its contrast. The slope of a straight line joining the points
Point B = Fog-plus-base density + 1.5
of the highest and lowest densities of this range on the
D = b
characteristic curve is defined as the average gradient. b
The slope (tan = a ) of the straight line joining points A
]
G is read Gee bar.
and B in relation to the horizontal axis is called the average
The density range (D) for industrial X-ray films is defined
gradient (G).
as follows:
D = (fog-plus-base density + 3.5)
(fog-plus-base density + 1.5)
The density range on a characteristic curve is shown in
Fig. 15.
10
5. Fog 7. Graininess
Film may have a slight density without being exposed to The photographic image produced after development
visible light, X-rays or gamma rays. This density is produced consists of silver particles a few microns in diameter which
when the silver halide in the emulsion of the film is in part are irregularly distributed. That is why raidographs usually
reduced and is called fog. As fog that exceeds a certain have a grainy appearance, when viewed by the naked
limit produces a detrimental effect on the photographic eye. This appearance is called graininess. It is clumps of
image, it must be inhibited as far as possible. developed silver grains rather than single grains which
impart the grainy appearance. Graininess is a subjective
Fog has many causes which include film storage impression, and its objective aspect is referred to as
conditions, composition of the developer, development granularity. The former is subjectively determined by the
conditions, and handling conditions. Undersirable naked eye, using either constant sample illumination or
densities which are caused by light and pressure are constant field brightness. The method of determination
also called fog. Unwanted density caused by excessive is selected relative to the purpose for which the film is
exposure to a safelight (even though a light color which intended, but the constant sample illumination method is
does not affect the sensitive material is used within best suited to X-ray films.
reasonable limits of time as the safelight) is called safelight
fog. The unwanted density which is produced when a On the other hand granularity is physical and refers to
high pressure is exerted on the film is called pressure fog. the structure of the light sensitive emulsion which is
All these kinds of fog which are produced by undesired objectively determined by physical methods. Granularity
external factors adversely affect the photographic image is superior in reproducibility and objectivity to graininess
and must therefore always be prevented. as a scientific measure of the variation in the distribution
of silver deposits. Granularity is determined through the
use of Selwyns method fo Fourier analysis.
6. Definition or Sharpness
Definition or sharpness are the photographic terms which Figure 15 Sound Frequency Response Characteristics
are used to indicate the distinctness of the boundary
between differing densities and the clearness of the fine
detail in a image. 2ESPONSE
A frequency response curve as shown in Figure 16 can
thus be obtained.
if the high-pitched sounds are not faithfully reproduced, Figure 17 RMS Granularity
the response in the high frequency range is small. This
frequency response curve is very useful when evaluating
the quality of a reproduced sound. In photography, on
the other hand, the frequency response curve is drawn &ILM "
by plotting the number of black-and-white lines per mm
(which is called spatial frequency after the analogy of
2-3
&ILM !
audio frequency) against the input-output ratio, this is,
the response of the reproduced image to the visible light
or radioactive rays as an input (Figure 16). This plot is
referred to in photography as the response function or
modulation transfer function.
$ENSITY
)NCREASING
11
Selwyn granularity G is expressed as a product of the
square root of an area a of a microdensitometer measuring
aperture and standard deviation D for a given average
III. Making of radiographs
density D. Selwyn granularity: G = Da However, this
formula does not result in constant value for G when the
area of certain individual silver grains is larger than the
area a of the measuring aperture. Today granularity is
expressed by the value of D alone more often than by
Selwyns constant, and is referred to as RMS granularity
(root-mean-square granularity). The smaller the RMS
value, the better the granularity. In Figure 17, for instance,
film A has better granularity than film B.
1. Radiographic Exposure
1.1 Precautionary Concerns in Set-up
It is important to comply with the standards established for
industrial X-ray films and consider the effect of geometric
factors (e.g., specimen-to-film distance) on the image
quality when determining the arrangement of the X-ray
or gamma-radiation source, the cassette, the specimen
and the penetrameter. It is also necessary to make an
appropriate prior choice of exposure method according to
the material and the shape or the portion of the specimen
to be examined. For instance, when examining a welded
pipe, the most appropriate choice should be made from
among the single radiography method, the stereoscopic
radiography method and the double-exposure (parallax)
method.
12
The X-ray equipment needs a warm-up period as density. In the case shown in Figure 18 the kilovoltage is
prescribed by the manufacturer, and in the case of a determined from the thickness of the specimen and the
gamma radiation source it is necessary to ascertain its exposure is made under conditions (mAmin.) determined
Ci value. When X-rays are used, a radiograph of high by the kilovoltage. In the case shown in Figure 19 the
definition can be obtained by using low kilovoltage with intensifying screen is chosen relative to the thickness
long exposure time. An exposure chart is generally used of the specimen and the exposure made at kilovoltages
as a guide for determining exposure conditions (e.g., suited to the type of screen chosen.
kilovoltage, X-ray tube current, and exposure time).
Ordinary exposure charts are plotted by laying off the
thickness of the specimen along the horizontal axis and
1.3 Care in Film Handling
the exposure (mAmin. or mAsec.) or kilovoltage (kVp) When removing the X-ray film from the interleaved paper
along the vertical axis of a graph. folder, no more pressure than necessary should be
However, it is recommended that appropriate exposure exerted on the interleaving paper, or scratches and static
charts be plotted according to exposure conditions for electricity marks may be left on the X-ray film. Also leave
each case, as the results of exposures vary with the the interleaving paper on the X-ray film when it is placed
variable characteristics of the X-ray source, the focus-to- on the work bench before exposure, as it protects the
film distance, the specimen material and desired image film from dirt, iron powder, moisture, chemicals and other
undersirable matter.
Figure 18 An Exposure Chart Example Good, uniform contact between the screens and the film
Milliamperage and Peak Kilovoltage is very important. If they are in poor contact, the image
definition sharpness will be adversely affected. Particular
care should be used to obtain good contact between the
screens and the film, when the casettes are of the flexible
type. When removing the film from a vacuum cassette,
K6P take out the film with the screens and remove the film
by opening the screens so as to avoid friction between
M! q MIN
EN
XPOS
CRE
3-
,EA
N
IV.
$IRE
E
CRE
3
K6P
IC
L
TAL
2.1 Development
ME
ORO
4HICKNESS OF 3PECIMEN
)NCREASING
13
Developer Temperature and Development Time development time needs to be extended so as to increase
The image density and contrast of a radiograph are speed and contrast, a maximum limit of 8 minutes should
remarkably influenced by the development temperature not be exceeded at a developer temperature of 20C
and time. It is necessary to keep the developer at a (68F). Figure 21 is an expression of the relationships
specified temperature (usually 20C/68F for manual between development time and photographic properties
processing) and carry out development during a for X-ray film.
specified time. When the temperature of the developer is
higher than normal, much the same results are had as Developer Agitation
obtained by extending the development time, and vice During development, the developer solution or the hanger
versa. In either case, however, it is most desirable that loaded with exposed film is agitated at frequent intervals in
the temperature of the developer be kept within a range order to keep the emulsion in contact with a fresh solution
of from 18 to 23C (64.4 to 73.4F). As the development at all times, thus accomplishing even development. If the
time may vary with each brand of developer, be sure to film is not agitated during development, the solution in
observe the instructions given by the manufacturer. The contact with high-density areas of the film will be locally
time and temperature specifications for Fuji Hi rendol I exhausted so that development of those areas stops,
developer are 5 minutes and 20C (68F). while the solution in contact with low-density areas is
exhaust to a lesser extent so that development proceeds.
Time Related Development Properties As a result, such a radiograph will show low contrast. The
The photographic properties of X-ray film change when locally exhausted solution affects the rate and evenness
the development time is changed while maintaining of development by moving from one area of the film to the
other conditions of development, such as temperature other during development. Thorough and even agitation
and agitation, constant. Speed and contrast increase of the film during development is very important. When
to a certain extent with increasing development time tray processing is used, care should be taken to assure
but contrast may fall due to fog or other causes and that radiographs do not cling to one another, and the
the graininess may become coarser when a certain tray should be rocked to provide continual mixing and
development time limit is exceeded. Even when the redistribution of the solution.
&OG
3TANDARD
2-3 'RANULARITY
)NCREASING
3TANDARD
3TANDARD
4IME $EVELOPMENT 4IME
)NCREASING )NCREASING
14
Developer Exhaustion and Replenishment The replenisher should be added in small quantities
If the water volume is not accurately measured in and at frequent intervals in order to reduce variations
the preparation of developer solutions, the resulting in developer solution activity for the sake of uniform
properties will be divergent from the original specifications radiographic results.
and fog may result. Accurate measurement of water is
therefore important. However, it should be remembered
that the development capacity of even an accurately
2.2 Stop Bath
prepared developer solution decreases, as it is used. It is As the function of the stop bath is to nullify the action of
necessary to check the developer solution for exhaustion the developer through the action of the acetic acid, care
by maintaining records of the sizes and quantities of X-ray should be taken to assure that the action of the developer
films processed and the number of days the developer is nullified over the entire surface of the film. Care should
has been used. also be used to prevent a rapid change in the extent of
To obtain uniform radiographic results over a period of swelling in the emulsion layer. To meet these requirements
time, it is necessary to check the use condition of the the stop bath should be maintained at a constant
developer solution and add developer replenisher in temperature close to that of the developer solution. If the
proportion to the quantity of film processed or at regular temperature of the developing solution is 20C (68F), the
intervals. Figure 22 shows a graph in which the effects of temperature of the stop bath should be maintained within
the developer replenisher on the photographic properties a range of from 15 to 20C (59 to 68F).
of X-ray films are demonstrated. The rate of replenishment
varies with the size and quantity of films and the average For about 15 seconds after the film passes into the stop
density. The developing power of the developer decreases bath, it must be continuously agitated so as to prevent
with increasing density or film size, and vice versa. The development unevenness. Care should be used to assure
relative areas of various size films as determined by that films do not cling to one another, and films should be
assigning the value 1 to the reference size 25.4 x 30.5 cm immersed in the stop bath for about 30 seconds.
(10 x 12 in.), are shown below.
The stop bath is checked for exhaustion with a pH meter.
When the pH of the stop bath exceeds 6.0, its neutralizing
Film Size Relative Area
power has decreased to such an extent that it no longer
35.6 x 43.2 cm (14 x 17 in.) 2 is able to perform its proper function. Make it a rule to
25.4 x 30.5 cm (10 x 12 in.) 1 replace the stop bath when its pH value is close to the
11.4 x 43.2 cm (4-1/2 x 17 in.) 0.6 critical level of 5.5. If a stop bath cannot be prepared for
8.5 x 30.5 cm (3-1/3 x 12 in.) 0.3 one reason or another, a fresh running water rinse may be
used in place of an acetic acid stop bath.
2.3 Fixing
Figure 22 Effects of the Developer Replenisher on the
Properties of X-ray Films
A permanent image cannot be retained in the exposed
and developed X-ray film unless it is treated with the
fixer. As the fixing conditions greatly influence the degree
of radiographic permanency, sufficient care should
2ELATIVE 3PEED
)NCREASING
1UANTITY OF &ILMS 0ROCESSED
)NCREASING
2EPLENISHMENT
15
Figure 23 Fixer Temperature-Time Curve Fixing Capacity
Customarily, the fixer solution is not replenished and as
such used until exhausted beyond use. As it is used, its
fixing capacity decreases to a point at which the time
required for the film to clear is increased by twice the time
required with fresh fixer solution. When this critical state
has been reached, the fixer solution should be replaced.
#LEARING 4IME
Fixer Agitation
When the film is first transferred from the stop bath into
&RESH 3OLUTION )NCREASING
the fixing bath, it should be agitated continuously for 10 1UANTITY OF &ILMS 0ROCESSED
seconds and then thereafter occasional agitation is to be
employed. Care should be exercised to insure that films As film after film carries the processing solution of the
do not cling to one another. If the stop bath is unavoidably preceding step into the fixing bath, the fixer solution is
skipped (the skipping of the stop bath should be avoided exhausted in time. The amount of processing solution
by all means as such practice will become the cause of carried on the film exerts a significant effect on the
uneven development), and the film is directly transferred strength of the fixer solution. The smaller the carry-over
from the developer solution into the fixing bath, or if the film the less the fixer solution will be degraded. If film is to
is rinsed after development and transferred into the fixing be drained thoroughly, it must be held out of solution for
bath, it must be agitated vigorously in the fixer for about a long time and such exposure to air brings with it the
30 seconds. If agitation is not vigorous enough, uneven risk of discoloration. Films wet with any of the processing
fixation may result and even dichroic fog and stains may solutions should not be allowed to remain in contact with
occur when the fixer solution is exhausted. the air for longer than 10 seconds.
16
When films are transferred time and again directly from Figure 25 Washing Time and Residual Thiosulfate
the developer solution into the fixing bath, or rinsed and
7ATER 7ASH
transferred into the fixing bath without using the stop bath,
the hardening capacity of the fixer solution decreases
rapidly so that films are easily scratched or longer
than normal drying times are required after washing.
Furthermore, under these conditions development may
2ESIDUAL 4HIOSULFATE
proceed even in the fixing bath, leading to dichroic fog]
and uneven fixation.
In such cases it is necessary to replace the fixer solution
&UJI 17 "ATH
/RDINARY 7ATER 7ASH
even before complete exhaustion has taken place.
]
Dichroic Fog
,ARGER
This kind of fog is liable to result from the presence of traces of
developer in the fixing bath. When viewed by transmitted light, film 7ATER 7ASH AFTER
with dichroic fog has yellowish to brownish stains. The stains are )MMERSSION IN &UJI 17
of a bluish, greenish or yellowish metallic luster when viewed by
reflected light. 7ASHING 4IME
)NCREASING
17
Table 5 Examples of Temperature Adjustments for Processing Solutions
DEVEL-
STOP BATH FIXER WASH WATER
OPER
20C 22 to 25C 25 to 28C 30C
Summer
(68F) (71.6 to 77.0F) (77.0 to 82.4F) (86F)
18
3.3 Density b. As industrial X-ray films are quite sensitive to heat and
moisture, a cool, dry place should be chosen for storage.
It is necessary to maintain at fixed levels the densities
Storage temperatures should remain at around 10 to
of radiographs for use in nondestructive testing. The
15C (50 to 59F). Fuji Industrial X-ray Films are enclosed
definition in non-screen type films increases with
in interleaving paper folders and sealed in light tight,
increasing density.
moisture proof envelopes so that they are relatively safe
3.4 Image Magnification and Distortion from moisture before being removed from these envelopes.
However, once the film is removed from the envelope, the
The image in a radiograph may be magnified and distorted
emulsion will absorb moisture until it attains equilibrium
depending on geometrical arrangements relative to the
with the moisture content of the surrounding air. Relative
positions of the radiation source, the specimen and the
humidity for industrial X-ray film handling should be from
film. The causes of image magnification and distortion are
60 to 70%. On the other hand, excessive dryness is not
listed in Table 8.
suitable to the storage of industrial X-ray films, because
in such locations films may become charged with static
4. Film Storage and The Darkroom electricity resulting in marks on the radiographs. X-ray
films removed from their envelopes should be wrapped
4.1 Storage and Care of X-ray Films in air tight vinyl sheeting and kept under refrigeration,
Unexposed X-ray films are readily and adversely affected to be removed several hours before use and allowed to
by chemicals, heat, moisture, mechanical pressure, stand until equilibrium with room temperature is attained.
visible light and radiations such as X-rays and gamma If such films do not have the same temperature as that of
rays requiring that utmost care must be taken in the the ambient room air, moisture may condense on the film
storage and handling of such films and in the selection of surfaces.
storage locations.
c. Industrial X-ray films may develop fog, when exposed
a. Industrial X-ray films are generally stored near the to polished metal surfaces, painted surfaces, thinner,
radiation source in readiness to serve the purposes hydrogen peroxide, coal gas, hydrogen sulfide, ammonia
for which they are intended but in this regard are more gas, mercury vapor, formalin, engine exhaust gases,
sensitive to radioactive rays than other types of sensitive acetylene and terpene. Provision should be made to
materials. What matters most in the storage of unexposed prevent the occurrence of this kind of fog which is referred
industrial X-ray films is the provision for adequate protection to as a false photographic effect.
against radiation. Lead-Lined containers should be used
d. The emulsion layer is scratched when strongly rubbed,
when unexposed films and loaded cassettes are to be
so that black streaks appear in the processed radiograph.
kept in the X-ray room. The darkroom must be separated
A shadow looking like a crescent, generally called a kink
from the X-ray or radiation source room by a partition wall
mark, is seen in the radiograph when the film is folded.
which can completely shut out radiation.
Generally, the crease made in a film before exposure
seems to have a lower density than the surrounding area,
while the crease made after exposure seems to have a
higher density than the surrounding area. Mechanical
pressure also influences the film likewise. Marks resulting
from contact with fingers that are contaminated with
processing chemicals can be avoided by wearing thin,
soft cotton gloves. The use of gloves made of synthetic
fibers or gloves of synthetic fibers blended with cotton
should be avoided, as they may cause static marks to
appear on the radiographs.
19
4.2 Darkroom Design Processing Darkroom (Wet Area)
The processing tanks, washing tanks, hanger racks
The space for the darkroom should be determined by the
and work benches should be arranged to facilitate film
volume of work to be done there, but generally speaking,
processing. Forced ventilation is necessary since the air
high efficiency of operation can be achieved when it is
is readily contaminated in a hot and humid processing
spacious enough to allow two to three persons to work
darkroom. An air-conditioner may also be necessary to
in it together at the same time. The darkroom must be
keep the air dry.
completely protected against Radiations. The inner
surfaces of the darkroom should be treated with a material
which is resistant to processing chemicals and can be 4.3 Safelight
washed with water in the area where water is used. The Light having spectral qualities that are outside the region
walls should be painted in a light color which best reflects in which sensitive materials are affected is to be used
light from the safelight. The walls of the labyrinth should for safelight illumination. The Fuji Safelight Filter SLG 8U
be painted matt-black to absorbe any reflected light, and (colored dark reddish orange) is recommended as such
a white line should be painted at about eye-level to assist for use in the darkroom. The relationship between the
entry and exit. A ventilator is also necessary to keep the spectral sensitivity of Fuji Industrial X-ray Film and the
air moving from the dry side to the wet side of the room spectral transmission factors for the Fuji Filter SLG 8U
and out. The darkroom should have an antechamber or a safelight is shown in Figure 27. Industrial X-ray films should
labyrinth that makes an efficient light trap. be handled at a distance of at least 1 meter from the Fuji
Preferably there should be a film loading darkroom and a Filter SLG 8U safelight in which a 100-volt, 15- or 20-watt
processing darkroom. If film loading and unloading and lamp is incorporated. The safelight may be turned on
processing are to be carried out in the same darkroom, under normal conditions for 10 to 15 minutes without any
the wet area should be in a position opposite to that of the detrimental effect on X-ray film.
dry area. The following precautions should be observed,
when the darkroom area is large enough for a loading The safety of the safelight in use can be tested in the
darkroom and a processing darkroom. following way. A sheet of industrial X-ray film is placed
in its normal handling position and covered with a sheet
Loading Darkroom (Dry Area) of black paper. The black paper is moved at 5-minute
The loading darkroom is to be provided with film containers, intervals to expose the X-ray film to the safelight in step
cassette and film holder storage, and a loading bench. fashion, and an unexposed portion is left. When the test
The loading darkroom should always be kept clean, and X-ray film is processed under standard conditions, it
free of water and chemicals. can be discerned from the processed film how long the
safelight should be allowed to remain on without causing
Figure 26 Light Traps for the Darkroom
fog in the film.
4RANSMITTANCE OF &ILTER
2ELATIVE 3ENSITIVITY OF &ILM
#ORRIDOR
$ARKROOM
7AVELENGTH MM
20
4.4 Processing Tanks
The processing solutions are either alkaline or acidic so IV. Automatic processing
that the processing tanks must be alkali or acid resistant.
Suitable materials include stainless steel, plastics and
enamelware.
21
1.1 Rapid Access to Finished Radiographs Figure 28 Sectional View of Fuji FIP 7000 Processor
%.4%2
%8)4
-/$% 2%0, ,)'(4 !,!2-
/&&
22
1.3 Care in Automatic Processing
In automatic processing it is indispensable that certain avoid variations in solution temperatures, replenishment
processing conditions be fulfilled and kept constant as rates and wash water flow rates. The essential checks
indicated in Table 10. Processing control should be rigidly which should be made in the operation of the Fuji FIP 7000
practiced by making periodic measurements so as to Processor are indicated in Table 11.
Table 10 Processing Conditions Established for the Fuji FIP 7000 Processor
PROCESSING CONDITION
FACTOR
(5 min. Processing) (11 min. Processing)
Developer Superdol I
(25 ml per liter of Superdol SI starter)
Developer temperature 30C/86F, 23C/73F
DEVELOPMENT
Development time 1 min., 2 min.
Developer tank capacity 30 lit.
Replenishment rate 65 ml/4 sheets of 8.5 x 30.5 cm film
Fixer Super FI
Fixer temperature 31C/88F
FIXING Fixing time 1 min. 05 sec., 2 min. 10 sec.
Fixer tank capacity 24 lit.
Replenishment rate 200 ml/4 sheets of 8.5 x 30.5 cm film
23
2. Requisites to X-ray Films for Rapid Reaction and Activity Recovery
In automatic processing both development and fixing
Automatic Processing
are to be completed respectively within the brief span
Industrial X-ray films designed for automatic processing of about 1 minute and 30 seconds. Processing solutions
must meet the following requirements. must provide for quick recovery of working strength, when
replenished at rates proportionate to the quantity of film
Increased Adaptability to Rapid Processing processed, so as to give constant results.
In spite of satisfactory development the image in a
radiograph may discolor and fade with time, if fixing, Suitability for High Temperature Processing
washing and/or drying are not adequate. Films which are As processing solutions are maintained at high
processed in automatic processors, must therefore meet temperatures, they must be formulated so that performance
special requirements that conventional industrial X-ray will not be adversely affected by high temperatures.
films need not comply with. For instance, the emulsion
layer must be thinner and the emulsion must react with Extended Performance Maintenance
processing chemicals more rapidly. Processing solutions are generally used in automatic
processors over a long period of time without being
Increased Strength of the Emulsion Layer replaced. Throughout this period the processing solutions
Rapid processing will serve no purpose if resulting quality must show consistent performance, without soiling the
is inferior to that of hand processing. When solution tanks, racks and films.
temperatures are increased, softening and swelling of
the emulsion layer is also increased subjecting the film
to much severer physical conditions and roller pressure. 3.1 Control of Processing Solutions
The emulsion layer of industrial X-ray film for automatic It is indeed rare when chemicals manufactured under
processing must therefore be strong enough to withstand exactly the same conditions possess precisely the same
such severe processing conditions. properties. In actuality, there are differences that exist to
a greater of lesser extent. Accordingly it is unavoidable
Adoption of a Polyester Base that X-ray films processed in automatic processors show
More than ten years has elapsed since inflammable some degree of variation in quality. Radiographic quality
cellulose nitrate as a film base was replaced with is affected by the following factors, making it necessary
noninflammable cellulose acetate. Later polyester base to minimuze such variations in the control of processing
materials have come into commercial use following upon solutions.
progress in the plastics industry and the advent of automatic
processors. Polyester base materials are advantageous
in several ways. Such materials provide for flatness and
great strength. Little expansion and contraction take
place and the material is not hygroscopic. These salient
features of polyester as the film base are indispensable to
rapid processing in automatic processors.
24
3.2 Developer Control corrective action is taken to bring the developer solution
into control. In practice, the characteristics obtained from
As in hand processing the activity level of the developer
the fresh developer are used as the standard and a control
solution used in automatic processing is kept constant
strip is processed after processing a certain number of
by the addition of replenisher. The degree of exhaustion
films or at the beginning of each work shift (at the time that
of the active components may differ from case to case
processing conditions are stabilized following processor
depending on the type of processor, the average density
preparation). The results obtained with control strips are
of the radiographs, and the water quality even if the
compared with the standard thus derived so as to bring
quantities of films processed remain constant.
the developer solution into control if there are seen shifts
from the standard.
Even when the same replenishment rates are continued
in use in different laboratories, there is little wonder that
Densitometric Method
the activity of the developer solutions differ over time from
The densitometric method also uses control strips as in
one situation to the other. The developer solution should
sensitometric control. The density of a specific step of
therefore be controlled in a manner suited to the specific
relatively high density is used to plot a control chart. The
conditions of the particular laboratory. The developer
control film is processed at the same specified times as
solution is controlled in several ways, but in radiography
indicated for the sensitometric control method.
the sensitometric and densitometric methods are in general
use as control procedures of high practical value.
3.3 Fixer Control
Sensitometric Method An exhausted fixer solution will produce adverse effects
This method provides the highest control accuracy. A relative to the permanency of radiographs. It is necessary
control strip which is exposed to visible light or X-rays in step to check the fixer solution for exhaustion at regular
fashion is developed under predetermined conditions and intervals and replenish it with fresh solution as required
a characteristic curve is derived from this control strip. The for constant chemical activity.
characteristic values (of speed, contrast and fog) obtained
from the characteristic curve are graphically represented.
If characteristics of the control strip deviate from normal,
02/#%33).'