Non-destructive testing - Radiographic inspection of corrosion and deposits in pipes by X - and gamma rays - Part 1: Tangential radiographic inspection (ISO 20769-1:2018)
This document specifies fundamental techniques of film and digital radiography with the object of enabling satisfactory and repeatable results to be obtained economically. The techniques are based on generally recognized practice and fundamental theory of the subject.
This document applies to the radiographic examination of steel pipes for service induced flaws such as corrosion pitting, generalized corrosion and erosion. Besides its conventional meaning, "pipe" as used in this document is understood to cover other cylindrical bodies such as tubes, penstocks, boiler drums and pressure vessels.
Weld inspection for typical welding process induced flaws is not covered, but weld inspection is included for corrosion/erosion type flaws.
The pipes can be insulated or not, and can be assessed where loss of material due, for example, to corrosion or erosion is suspected either internally or externally.
This document covers the tangential inspection technique for detection and through-wall sizing of wall loss, including with the source:
a) on the pipe centre line; and
b) offset from pipe centre line by the pipe radius.
ISO 20769-2 covers double wall radiography, and note that the double wall double image technique is often combined with tangential radiography with the source on the pipe centre line.
This document applies to tangential radiographic inspection using industrial radiographic film techniques, computed radiography (CR) and digital detector arrays (DDA).