The integrity verification on pressure equipment is a combination of the results of a visual inspection conducted externally and, where possible, internally to the frame, supplemented by Ultrasonic thickness measurements.
These non-destructive tests, aimed essentially at detecting surface discontinuities of the membrane produced by the combined action of mechanical and thermal stresses and the corrosive action generated by the contained fluid and the surrounding environment, for other explicitly prescribed (in Italy is the art. 12 of the D.M. n. 329/2004), are considered mandatory and preparatory to any other type of diagnostic verification for the purposes of integrity verification.
Although elementary, the visual and spessimetric controls combine characteristics of effectiveness, speed and economy.
The principles of thickness measurement for direct contact of metallic and non-metallic materials based on the detection of the flight time of ultrasonic pulses are defined in ISO16809: 2012 - "Non-Destructive Testing - Ultrasonic thickness measurement".