EN ISO 21013-3:2016 PDF

Overview

EN ISO 21013-3:2016 - "Cryogenic vessels - Pressure-relief accessories for cryogenic service - Part 3: Sizing and capacity determination" provides standardized calculation methods for determining the required mass flow to be relieved from cryogenic vessels under a range of operating and upset conditions. The standard is the CEN-endorsed version of ISO 21013-3:2016 and supersedes EN 13648-3:2002. It also includes informative recommendations for cryostats (Annex A) and supports conformity with the EU Pressure Equipment Directive (2014/68/EU).

Key topics and requirements

• Specified relief scenarios - Separate calculation methods are provided for:
  • Vacuum‑insulated vessels with intact insulation under normal vacuum (outer jacket at ambient, inner vessel at liquid temperature).
  • Same as above with a pressure‑build up regulator functioning at full potential.
  • Vacuum or non‑vacuum insulated vessels with loss of vacuum (insulation remaining) and fire engulfment scenarios.
  • Vessels containing fluids with saturation temperature below 75 K at 1 bar with loss of vacuum involving air or nitrogen, with and without fire.
  • Vessels with insulation system totally lost under fire engulfment.
• Heat transfer calculations - Procedures to compute total heat transfer per unit time from outer jacket to inner vessel for normal, loss‑of‑vacuum and fire conditions.
• Mass flow determination - Methods to convert heat input to the mass flow that pressure‑relief devices must handle.
• Relief device sizing - Guidance for sizing pressure relief valves and bursting discs, including:
  • Determination of critical vs. subcritical flow regimes.
  • Discharge capacity calculations.
  • Consideration of piping pressure drops, back pressure, and heat transfer in relief lines.
• Supporting content - Symbols, worked examples, calculation steps and normative references to support engineering application.
• Good engineering practice - Where the standard does not cover a specific condition, established physical science and engineering judgment are required.

Practical applications and users

EN ISO 21013-3:2016 is intended for professionals involved with cryogenic systems safety and compliance:

• Design engineers sizing pressure‑relief accessories for liquid oxygen, nitrogen, hydrogen, LNG and other cryogenic storage vessels.
• Safety and loss‑prevention engineers evaluating relief capacity for fire, vacuum loss or regulator failure scenarios.
• Manufacturers and suppliers of pressure relief valves, bursting discs and cryostats who need to demonstrate device capacity.
• Inspectors and notified bodies assessing conformity with safety regulations, including the Pressure Equipment Directive.
• Facility operators preparing safety cases and emergency relief system documentation.

Related standards and compliance

• Supersedes EN 13648-3:2002.
• Supports conformity with EU Directive 2014/68/EU (Pressure Equipment Directive) - see Annex ZA.
• Part of the ISO 21013 family (other parts address different aspects of cryogenic vessel safety and accessories).

Keywords: EN ISO 21013-3:2016, cryogenic vessels, pressure‑relief accessories, sizing, capacity determination, pressure relief valve, bursting disc, loss of vacuum, fire engulfment, cryostats.