ISO 20421-1:2019

Overview

ISO 20421-1:2019 - "Cryogenic vessels - Large transportable vacuum-insulated vessels - Part 1: Design, fabrication, inspection and testing" specifies requirements for the safe design, fabrication, inspection and testing of large transportable vacuum-insulated cryogenic vessels. It applies to vessels with a volume greater than 450 L that are either permanently attached (fixed tanks) or not permanently attached (demountable and portable tanks) to a means of transport and intended for one or more transport modes. The standard excludes vessels for toxic fluids and does not cover general vehicle systems (running gear, brakes, lighting). It also excludes refillable liquid-hydrogen and LNG fuel tanks dedicated to vehicle propulsion (see ISO 13985).

Key topics and technical requirements

ISO 20421-1:2019 covers the full product lifecycle from concept to operation, including:

• Design principles and options - design by calculation, pressure strengthening, and experimental methods; design loads; fatigue and corrosion allowance.
• Materials and selection - guidance on suitable materials (including specific annexes for materials such as 9 % Ni and austenitic stainless steels), material inspection and documentation.
• Mechanical, chemical and thermal requirements - mechanical load cases, pressure conditions, thermal behavior and chemical compatibility for specified cryogenic fluids.
• Fabrication practices - cutting, forming, welding qualifications, non-welded joints and manufacturing tolerances.
• Inspection and testing - quality plans, production control test plates, non‑destructive testing (NDT), pressure testing, rectification and final acceptance tests.
• Safety features and components - pressure relief devices, valves, insulation systems, inspection openings and electrical continuity.
• Documentation and marking - mandatory records, periodic inspection schedules and labelling requirements.
• Normative and informative annexes - detailed calculation methods, specific material requirements, weld details, outer-jacket relief devices and examples.

Practical applications and users

This standard is intended for organizations involved in the design, manufacture, testing and operation of large transportable cryogenic tanks, including:

• Design engineers and structural analysts developing vacuum‑insulated cryogenic vessels.
• Fabricators and welders implementing material, forming and welding provisions.
• Quality, inspection and testing personnel performing NDT and pressure tests.
• Transport operators and fleet managers ensuring periodic inspection and compliance.
• Regulators and certification bodies assessing conformity with design and safety requirements.

Use cases include transportable storage of industrial gases, cryogenic bulk distribution, and intermodal transport systems for refrigerated liquefied gases (non-toxic).

Related standards

• ISO 13985 - referenced for requirements on refillable liquid-hydrogen fuel tanks used in vehicles.
• Consult applicable transport and vehicle regulations for running-gear, braking and lighting requirements (these are outside the scope of ISO 20421-1:2019).

Keywords: ISO 20421-1:2019, cryogenic vessels, large transportable vacuum-insulated vessels, design fabrication inspection testing, cryogenic tank standards, pressure testing, non-destructive testing.