Radiography in Modern Industry
Table of Contents
Introduction
The Radiographic Process
X-ray and Gamma-ray Sources
Geometric Principles
Factors Governing Exposure
Radiographic Screens
Scattered Radiation
Arithmetic of Exposure
Radiographic Image Quality and Detail Visibility
Industrial X-ray Films
Fundamentals of Processing
Process Control
The Processing Room
Special Processing Techniques
Special Radiographic Techniques
Paper Radiography
Sensitometric Characteristics of X-ray Films
Film Graininess; Signal-to-Noise Ratio in Radiographs
The Photographic Latent Image
Protection
Introduction
Many of the spectacular scientific and engineering achievements of the past
few years can be traced to nondestructive testing methods, which--by
determining internal soundness without destroying product usefulness--
assure the satisfactory performance for which the product was intended.
Radiography today is one of the most important, most versatile, of all the
nondestructive test methods used by modern industry. Employing highly
penetrating x-rays, gamma rays, and other forms of radiation that do not
damage the part itself, radiography provides a permanent visible film record
of internal conditions, containing the basic information by which soundness
can be determined. In the past decade alone, the evidence from millions of
film records, or radiographs, has enabled industry to assure product
reliability; has provided the informational means of preventing accidents and
saving lives; and has been beneficial for the user.
Since economic justification is a major criterion for any testing method, the
value of radiography lies to some extent in its ability to make a profit for its
user. This value is apparent in machining operations where only pieces
known to be sound are permitted on the production lines. It is equally
apparent in cost reductions when less expensive materials or fabricating
methods can be employed instead of costlier ones in which soundness is only
an estimated quality. The information gained from the use of radiography
also assists the engineer in designing better products and protects the
company by maintaining a uniform, high level of quality in its products. In
total, these advantages can help to provide customer satisfaction and
promote the manufacturers reputation for excellence.
Industrial radiography is tremendously versatile. Objects radiographed range
in size from micro-miniature electronic parts to mammoth missile
components; in product composition through virtually every known material;
and in manufactured form over an enormously wide variety of castings,
weldments, and assemblies. Radiographic examination has been applied to
organic and inorganic materials, and to solids, liquids, and even gases. An
industry's production of radiographs may vary from the occasional
examination of one or several pieces to the examination of hundreds of
specimens per hour. This wide range of applications has resulted in the
establishment of independent, professional x-ray laboratories as well as of
radiographic departments within manufacturing plants themselves. The
radiographic inspection performed by industry is frequently monitored for
quality by its customers -- other manufacturers or governmental agencies --
who use, for the basis of monitoring, applicable specifications or codes,
mutually agreed to by contract, and provided by several technical societies or
other regulatory groups.
To meet the growing and changing demands of industry, research and
development in the field of radiography are continually producing new
sources of radiation such as neutron generators and radioactive isotopes;
lighter, more powerful, more portable x-ray equipment as well as
multimillion-volt x-ray machines designed to produce highly penetrating
radiation; new and improved x-ray films and automatic film processors; and
improved or specialized radiographic techniques. These factors, plus the
activities of many dedicated people, extend radiography's usefulness to
industry.
It is not surprising then, that radiography, the first of the modern
sophisticated methods of non-destructive testing (dating back to 1895), has
led hundreds of industries to put great confidence in the information that it
supplies. The list is growing year after year as industry's management,
designers, engineers, production men, inspectors, and everyone concerned
with sound practices, dependable products, high yields, and reasonable
profits discover the value of radiography in modern industry.
