Overview
ISO 21013-1:2021 - "Cryogenic vessels - Pressure‑relief accessories for cryogenic service - Part 1: Reclosable pressure‑relief valves" specifies requirements for the design, manufacture and testing of reclosable pressure‑relief valves used with cryogenic fluids (below −10 °C) and at ambient temperatures up to their rated minimum temperature through +65 °C. It applies to valves up to DN 150 intended to relieve single‑phase vapours or gases. Note: methods to determine relief valve capacity for a vessel are given separately in ISO 21013‑3.
Key topics and technical requirements
- Scope and applicability: Valves for cryogenic service, multiple gases and gas mixtures, size limit DN 150.
- Design requirements:
- Operation across the full cryogenic-to-ambient temperature range (rated minimum temperature to +65 °C).
- Drainage and stem guiding to prevent water accumulation and freezing‑related malfunctions.
- Special provisions for sublimating fluids (e.g., CO2) to avoid solid deposition inside the valve.
- Use of soft inserts designed to resist cold‑flow and maintain seat tightness.
- Electrical continuity requirement for oxidising/flammable services: maximum resistance 1 000 Ω with ≤28 V between ports to avoid static build‑up.
- Set pressure must not exceed the valve’s PS (maximum allowable pressure).
- Minimum shell thickness referenced to ISO 15761 or ASME B16.34 (or equivalent calculation methods).
- Materials and compatibility: Metallic and non‑metallic material selection per recognized standards and gas/material compatibility (see ISO 21010); consider corrosion, galling, oxygen compatibility.
- Qualification and testing:
- Type approval, ambient and cryogenic tests, alternate cryogenic tests and production testing.
- Tests include seat‑tightness and re‑seating pressure verification; determination of the certified discharge coefficient.
- Manufacturing controls: Cleanliness, marking, sealing and production inspection requirements are specified.
Applications and users
This standard is essential for:
- Valve manufacturers designing and certifying reclosable pressure‑relief valves for cryogenic service
- Cryogenic vessel designers and integrators selecting safety accessories
- Test laboratories performing ambient and cryogenic qualification tests
- Plant engineers, safety officers and procurement professionals in LNG, industrial gas, medical gas, and cryogenic storage/transport sectors
- Regulatory bodies and inspectors assessing compliance for pressure‑relief systems
Related standards
ISO 21013-1:2021 provides the practical framework to ensure safe, reliable, and compliant reclosable pressure‑relief valves for cryogenic applications.