Overview
EN ISO 4126-1:2013/A1:2016 is Amendment 1 to the European adoption of ISO 4126‑1:2013, titled Safety devices for protection against excessive pressure - Part 1: Safety valves. Published and approved by CEN in 2016, this amendment updates testing and performance tolerances for safety valves used as pressure‑relief devices. It forms part of the EN ISO 4126 series and supports essential requirements of relevant EU directives for pressure equipment.
Key topics and technical requirements
This amendment replaces Clause 7.2.1 and defines revised testing, tolerances, and verification rules for safety valves:
- Set pressure testing: Tests shall be conducted at the minimum and maximum set pressures for which the spring is designed.
- Test media:
- Valves for gas service: test with air or another gas of known characteristics, or superheated steam (≥10 °C superheat).
- Valves for steam service: test on steam, air or another known gas.
- Valves for liquid service: test on water or other liquids of known characteristics.
- Allowable tolerances / limits:
- Set pressure: ±3% of set pressure or ±0.1 bar, whichever is greater.
- Lift at overpressure: not less than manufacturer‑stated values.
- Overpressure: manufacturer‑stated value but not exceeding 10% of set pressure or 0.1 bar, whichever is greater.
- Blowdown: must not exceed manufacturer‑stated value and shall fall within specified limits:
- Compressible fluids: min 2.0% (not applicable to valves with proportional opening), max 15% or 0.3 bar, whichever is greater.
- Incompressible fluids: min 2.5% (not applicable to valves with proportional opening), max 20% or 0.6 bar, whichever is greater.
- Restricted lift valves: overpressure and blowdown tolerances same as unrestricted lift valves.
- Proportional opening valves: overpressure and blowdown must be verified as stable across lifts between manufacturer’s minimum and maximum; a lift vs overpressure curve is required.
Applications and users
This amendment is directly relevant to the specification, testing and certification of safety valves and pressure‑relief devices across industries that require protection against excessive pressure, including:
- Power generation (boilers, steam systems)
- Oil & gas and petrochemical plants
- Chemical manufacturing and process plants
- Compressed air and gas systems
- Pressure vessel and pipeline manufacturers
- HVAC, marine and industrial equipment
Primary users: safety valve manufacturers, test laboratories, design and mechanical engineers, safety managers, conformity assessors, inspection bodies and regulators.
Related standards
- EN ISO 4126‑1:2013 (base document) - see amendment A1 for updated test and tolerance rules.
- Other parts of the ISO 4126 series and national pressure equipment standards may be relevant for full compliance and system design.
Keywords: safety valves, EN ISO 4126‑1 amendment, excessive pressure protection, set pressure tolerance, overpressure, blowdown, proportional opening, restricted lift, pressure relief devices.