EN ISO 20769-2:2018 PDF

Overview

EN ISO 20769-2:2018 - “Non-destructive testing - Radiographic inspection of corrosion and deposits in pipes by X- and gamma rays - Part 2: Double wall radiographic inspection” (CEN adoption of ISO 20769-2:2018) specifies fundamental film and digital radiography techniques for economical, repeatable detection of in-service wall loss in metallic cylindrical bodies. The scope covers pipes, tubes, penstocks, boiler drums and pressure vessels - insulated or exposed - where corrosion, pitting, generalized corrosion or erosion is suspected. Weld flaws from welding processes are excluded, except where they are related to corrosion/erosion.

Key topics and technical requirements

• Double wall techniques: Double wall single image (DWSI) and double wall double image (DWDI), including their recommended test arrangements and beam/film alignment.
• Radiation sources: Guidance on selection of X-ray and gamma-ray sources appropriate for double-wall inspection.
• Image media: Use of industrial radiographic film, computed radiography (CR) imaging plates and digital detector arrays (DDA).
• Image quality indicators (IQI): Requirements for single-wire and duplex-wire IQIs (including digital-specific duplex IQIs) and minimum image quality values (see normative Annex A).
• Measurement methods: Principles and procedures for measuring differences in penetrated thickness from image grey levels and attenuation coefficients (Annex B).
• Scatter control and geometry: Reduction of scattered radiation (filters, collimation, shielding), source-to-detector distance, axial and circumferential coverage, and overlap rules.
• Digital workflow: Scan/read-out, DDA calibration, bad-pixel handling, image processing, storage and monitor viewing conditions.
• Quality assurance and reporting: Personnel qualification, radiation protection, identification/marking of radiographs, film processing/viewing conditions and test report content.
• Normative annexes: Minimum image quality values, penetrated thickness measurement procedures, and basic spatial resolution determination.

Practical applications

• In-service inspection programs to detect and quantify internal or external wall loss in pipelines, process piping, boilers and cylindrical pressure equipment.
• Condition-monitoring surveys where access is restricted to the outside surface or where double-wall geometry prevents single-wall imaging.
• Combination with tangential radiography (ISO 20769-1) when enhanced defect characterization is required.

Who should use this standard

• NDT engineers and radiography specialists conducting pipeline and pressure-equipment inspections.
• Asset integrity and corrosion engineers, inspection contractors, regulatory bodies and plant owners implementing in-service inspection procedures.
• NDT training organizations and certification bodies for establishing procedures, acceptance criteria and reporting formats.

Related standards

• ISO 20769-1 (tangential radiographic inspection techniques) - often combined with DWDI
• Supersedes EN 16407-2:2014 (previous European edition)

Keywords: EN ISO 20769-2:2018, double wall radiographic inspection, radiographic inspection of pipes, corrosion inspection, computed radiography, digital detector arrays, X‑ray, gamma ray, NDT, image quality indicator.