This document discusses and compares film and filmless techniques for non-destructive testing using radiography. With film techniques, radiation is captured on film plates which are then chemically processed to make the image visible. Filmless techniques use radiation-sensitive digital detectors to directly create digital images. While film techniques have better image quality for thick-walled objects, filmless methods have advantages like real-time imaging, lower operating costs, and easier archiving. Both techniques have advantages and disadvantages depending on the application and material properties being examined.

1. M.KARTHIKEYAN
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEERING & TECHNOLOGY, SIVAKASI
karthikeyan@aaacet.ac.in
ME8097 NON DESTRUCTIVE
TESTING AND EVALUATION

2. UNIT V RADIOGRAPHY (RT)
1. Principle, interaction of X-Ray with matter,
2. imaging, film and film less techniques,
3. types and use of filters and screens,
4. geometric factors, Inverse square, law,
5. characteristics of films - graininess, density, speed, contrast,
6. characteristic curves, Penetrameters,
7. Exposure charts, Radiographic equivalence.
8. Fluoroscopy- Xero-Radiography,
9. Computed Radiography, Computed Tomography

3. FILM TECHNIQUES
 Industrial X-ray testing techniques can generally be divided into
conventional and digital methods.
 With film techniques, the image information is captured by a
film that is radiation sensitive on both sides.
 After the exposure the film is processed by a chemical
treatment, either manually or fully automated by a film
processing machine.
 Film viewing and evaluation is done by using special
illuminators.
 The optical density of any point of the film can be measured by
densitometers.
 Areas that represent too thick walls to show the minimum
required optical densities cannot be evaluated initially.

4.  The same applies to areas with too high densities representing
too thin walls.
 These areas require additional films with suitable densities. This
can be achieved by using several films with different
sensitivities in one light protective bag (multi film technique).
 This increases the so called covered thickness range, which is
the maximum wall thickness difference that can be captured
with one exposure.
 Usually, films are put between two metal screens (mostly lead),
in order to reduce the disturbing influence of scattered
radiation and to intensify the image building radiation.
 The evaluation of visible discontinuities is -especially for
castings- done by comparison with reference radiographs. The
discontinuities are classified by their types and sizes.

5.  Radiographic testing with film is characterized by a complex
work of standards that have been under development for
decades.
 These standards define rules for the execution of tests,
qualification of personnel, properties and verifications of used
tools and devices and the evaluation of films.
 In most cases European standards (e.g. EN 17636 for weld
inspection or EN 12681-1 for inspection of castings) or US
standards according to the ASME Code are postulated.

6. ADVANTAGES
 The advantages of the film technique are a much larger range of
applications and lower investment costs.
 X-ray films can be cut to the required sizes, are flexible,
lightweight and easy to place.
 The image quality of thick-walled objects is much better than
with digital methods.
 X-ray films can be digitized.
 This offers an easy alternative for archiving and copying.

7. DISADVANTAGES
 The disadvantages of film radiography are the high material
costs because of film and chemistry consumption as well as the
missing real-time imaging.
 The result of an exposure cannot be discovered before film
processing.

8. FILM LESS TECHNIQUES
 With digital techniques the image information is captured by a
radiation sensitive detector.
 There is a distinction between detectors that are directly read
out (e.g. rigit flat panels) and detectors that are read out by
scanners, so called CR systems (computed radiography systems)
with flexible storage imaging plates.
 Signals of detectors with direct read-out are converted to gray
value images that can be displayed on monitors.
 Storage imaging plates have to be read out by special scanners
before a digital image is produced.

9.  The sensitivity of digital detectors is much higher for low
energy radiation (e.g. scattered radiation) than for the image
building high energy radiation.
 As a result, the (low energy) scattered radiation produced in the
test object causes high counting rates that decrease contrast
and image quality.
 This effect is much lower with film techniques.
 As primary energies for the inspection of thin-walled or lighter
objects are lower, the detectability of discontinuities is
comparable between film and digital techniques.
 But the thicker the walls and the denser the material, the
higher is the required radiation energy, which means, that the
achievable image quality is more and more reduced with digital
techniques in comparison to film techniques.

10. THE ADVANTAGES OF DIGITAL TECHNIQUES ARE
 The operating costs are low because there are no consumables
necessary.
 Digital detectors are characterized by a high dynamic range,
thus large differences in radiation intensity and wall
thicknesses can be captured at the same time.
 The evaluation of X-ray images can be supported by
computerized image enhancement.
 Many digital systems are real-time capable. Therefore test areas
can be moved in the live image by manipulators.
 Image archiving is easier and more comfortable.

11. THE DISADVANTAGE OF DIGITAL TECHNIQUES
 High investment costs
 For both flat panel detectors and storage imaging plates the
necessary effort for the preparation of exposures to reduce
scattered radiation is higher than in film radiography. This
applies particularly, if the detector is not completely covered by
the test object (Example: ellipse technique for welds or
inspection of small castings).
 For complex shaped objects with large differences in wall
thickness it is often not possible to reduce the scattered
radiation generated inside the object sufficiently, in order to
produce an image that can be evaluated.