Operating Manual

Preface

To verify the quality of a product, samples are taken for examination or a non-destructive

test (NDT) is carried out. In particular with fabricated (welded) assemblies, where a high

degree of constructional skill is needed, it is necessary that non-destructive testing is

carried out.

Most NDT systems are designed to reveal defects, after which a decision is made as to

whether the defect is significant from the point of view of operational safety and/or

reliability. Acceptance criteria for weld defects in new constructions have been specified

in standards.

However, NDT is also used for purposes such as the checking of assembled parts, the

development of manufacturing processes, the detection of corrosion or other forms of

deterioration during maintenance inspections of process installations and in research.

There are many methods of NDT, but only a few of these allow the full examination of a

component. Most only reveal surface-breaking defects.

One of the longest established and widely used NDT methods for volumetric examination

is radiography: the use of X-rays or gamma-rays to produce a radiographic image of an

object showing differences in thickness, defects (internal and surface), changes in

structure, assembly details etc. Presently, a wide range of industrial radiographic equip-

ment, image forming techniques and examination methods are available. Skill and expe-

rience are needed to select the most appropriate method for a particular application.

The ultimate choice will be based on various factors such as the location of the object to

be examined, the size and manoeuvrability of the NDT equipment, the existance of

standards and procedures, the image quality required, the time available for inspection

and last but not least financial considerations.

This book gives an overview to conventional industrial radiography, as well as digital

(computer-aided) techniques and indicates the factors which need to be considered for

selection of the most suitable system and procedures to be followed.

At the end of the book a chapter is added describing aspects of radiation safety.