Overview
EN ISO 4126-5:2013/A1:2016 is Amendment 1 to Part 5 of the ISO 4126 series, titled Safety devices for protection against excessive pressure - Part 5: Controlled safety pressure relief systems (CSPRS). Published/approved by CEN in 2016, this document updates testing and performance requirements for CSPRS used to protect vessels, piping and systems from overpressure. It forms part of the EN/ISO framework for pressure-relief device safety and supports relevant EU Directive requirements.
Key topics and technical requirements
The amendment revises Clause 7.2.1 (General requirements) and defines testing media and allowable tolerances for operating characteristics:
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Test media by service
- CSPRS for air or other gas: test with air, another gas of known characteristics, or superheated steam with at least 10 °C superheat.
- CSPRS for steam service: may be tested on steam, air or other gas of known characteristics.
- CSPRS for liquid service: test on water or other liquids of known characteristics.
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Allowable tolerances / limits
- Set pressure: ±3% of set pressure or ±0.1 bar, whichever is greater.
- Overpressure: value declared by the manufacturer but not exceeding 10% of set pressure or 0.1 bar, whichever is greater.
- Lift of main valve at overpressure: must be at least the value stated by the manufacturer.
- Closing sensing pressure: must be no less than 93% of set pressure.
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Additional items: the amendment is endorsed by CEN without modification and notes possible patent-rights considerations and applicability across national standards bodies.
Applications and who uses it
This standard is directly relevant to:
- Valve and safety device manufacturers designing and certifying CSPRS.
- Pressure equipment designers and plant engineers selecting pressure-relief solutions for gas, steam or liquid services.
- Inspection, testing and certification bodies performing type and routine testing.
- Asset owners and operators in process industries (chemical, petrochemical, power generation, utilities) implementing compliant overpressure protection.
Use of EN ISO 4126-5:2013/A1:2016 helps ensure predictable performance, compliance with regulatory safety requirements, and consistent testing procedures for controlled safety pressure relief systems.
Related standards
- ISO 4126 series (other parts) covering different types of pressure-relief devices and general requirements.
- Relevant national adoptions of the EN ISO text and accompanying informative Annex ZA for EU Directive relationships.
Keywords: EN ISO 4126-5:2013/A1:2016, CSPRS, controlled safety pressure relief systems, safety devices for excessive pressure, set pressure tolerance, overpressure, industrial valves, pressure-relief testing.
