By "Non-destructive tests or NDT" we mean all those methods of analysis that allow us to obtain information on the state of the art or integrity of a product, without having to alter its structure.
NDT are applied to various sectors of activity, including civil, industrial, energy production, research, art and geology. In the industrial sector they are applied in two specic areas:

• In the production phase (acceptance of parts based on the presence of defects);
• During in-service inspection (integrity monitoring and search for damage typical of the degradation immediately suffered by the equipment under operating conditions);

Non-destructive tests are based on different physical principles: consequently, for each advantage and disadvantage, diagnostic capabilities and limits. The peculiarities of each method must be taken into consideration when choosing the most suitable method to search for a specic type of damage.