Overview
ISO 21013-4:2012 specifies requirements for pilot‑operated pressure‑relief valves and accessories for cryogenic service. It covers design, manufacture and testing for valves intended to operate with cryogenic fluids (and at temperatures from ambient down to the rated minimum temperature). The standard is limited to valves up to DN 300 and to devices relieving single‑phase vapours, gases or gas/vapour mixtures. ISO 21013-4 complements ISO 21013-3 (sizing and capacity) and takes precedence where it differs from ISO 4126-4.
Key topics and technical requirements
- Scope and definitions: Clear limits on fluid types (cryogenic fluids) and valve nominal sizes (DN ≤ 300).
- Design requirements (Clause 4):
- Operability across the full temperature range from the rated minimum to +65 °C.
- Disc guiding designed to resist freezing and moisture deposition.
- Use of inserts controlled to prevent cold flow and loss of shut‑off performance.
- Special provisions for sublimating fluids (e.g., CO2) to avoid solid deposition blocking operation.
- Electrical continuity requirement for flammable-service valves: ≤ 1 000 Ω at up to 28 V to prevent static build‑up.
- Set pressure must not exceed the valve’s rated pressure (PR); minimum shell thickness per recognized standards.
- Materials (Clause 4.3):
- Metallic materials must meet ISO 21028‑1/2 for toughness at cryogenic temperatures.
- Non‑metallics restricted mainly to seating/inserts and must be suitable for the rated minimum temperature.
- Gas–material compatibility: oxygen compatibility per ISO 21010; hydrogen considerations per ISO 11114; restrictions on copper content for acetylene mixtures.
- Qualification and testing (Clause 5):
- Type approval: inspection and testing of a valve from the first production batch; unique model numbering for approved configurations.
- Type tests include ambient condition operational and leakage/seat tightness testing; production testing requirements also specified.
- Marking, cleanliness, sealing, set‑pressure tolerances and re‑seating pressures are defined.
Applications and who uses it
ISO 21013-4 is used by:
- Valve manufacturers designing pilot‑operated pressure‑relief devices for cryogenic service
- Cryogenic vessel and system designers (LNG, industrial gases, lab cryogenics)
- Plant safety and process engineers specifying relief accessories for storage and distribution systems
- Certification bodies, inspectors and procurement teams ensuring compliance with cryogenic service requirements
Practical applications include safety relief systems on cryogenic storage tanks, transfer piping, vapor recovery systems and process plant relief arrangements for gases such as nitrogen, helium, oxygen, hydrogen and CO2.
Related standards
- ISO 4126‑4 (pilot operated safety valves)
- ISO 21013‑1/2/3 (other parts of cryogenic pressure‑relief accessories)
- ISO 21028‑1/2 (toughness at cryogenic temperatures); ISO 21010 (oxygen compatibility)
- ASME B16.34, ISO 15761, EN 12516 series (valve shell strength and construction)
Keywords: ISO 21013-4, cryogenic vessels, pilot operated pressure relief valves, pressure‑relief accessories, cryogenic service, DN 300, valve testing, materials compatibility.