Overview
EN ISO 21028-2:2018 - "Cryogenic vessels - Toughness requirements for materials at cryogenic temperature - Part 2: Temperatures between −80 °C and −20 °C" - defines toughness requirements for metallic materials intended for cryogenic vessels and related pressure equipment operating in the −20 °C to −80 °C range. The standard ensures materials and welds have adequate fracture toughness at low temperatures and supports conformity with the EU Pressure Equipment Directive (2014/68/EU).
Key topics and technical requirements
- Scope and materials: Applies to fine-grain and low-alloy steels (specified yield strength ≤ 460 N/mm²), aluminium and aluminium alloys, copper and copper alloys, and austenitic stainless steels.
- Design reference temperature (TR): TR is calculated as the minimum metal temperature (TM) plus a temperature adjustment term (TS) to account for pressure-induced stresses (TR = TM + TS). TR determines the required impact test temperature.
- Impact testing: Specifies use of Charpy V-notch impact tests (referenced ISO 148) and guidance on test specimen selection, including sub-sized specimens and cases where full-size specimens cannot be extracted.
- Welds: Contains provisions for toughness assessment of welds and related testing requirements.
- Normative references: Includes ISO 148 (Charpy tests) and ISO 9016 (weld impact test specimen location and notch orientation).
- Annexes: Informative Annex A gives technical justification for the temperature adjustment term; Annex B provides an example calculation of the lowest authorized operating temperature.
- Updates: This edition supersedes EN 1252-2:2001 and is the second ISO edition (revising the 2004 edition).
Practical applications and users
EN ISO 21028-2:2018 is used to:
- Select and qualify base materials and weld procedures for cryogenic vessels, storage tanks, and piping operating between −20 °C and −80 °C.
- Define acceptance criteria for Charpy V-notch impact testing for manufacturers, material suppliers, and testing laboratories.
- Provide design input for pressure-vessel and cryogenic equipment engineers, inspectors, welding engineers, and certification bodies seeking compliance with the Pressure Equipment Directive (PED).
- Support risk assessment for brittle fracture and inform material specification in industries such as LNG, cryogenic storage, industrial gas production, and hydrogen technologies.
Related standards
- EN ISO 21028 series (other parts for different temperature ranges)
- ISO 148 (Charpy pendulum impact test)
- ISO 9016 (weld impact testing)
- EN 13445-2 and EN 13480-2 (alternative brittle fracture prevention methods applicable for certain steels)
EN ISO 21028-2:2018 is essential for ensuring material toughness and safe operation of cryogenic pressure equipment in the −80 °C to −20 °C range.
