Overview - EN ISO 4126-4:2013 (Pilot‑operated safety valves)
EN ISO 4126-4:2013, adopted by CEN, is the international product standard for pilot‑operated safety valves used as safety devices for protection against excessive pressure. It specifies general requirements for pilot‑operated safety valves irrespective of the fluid handled. The standard applies to valves with a valve flow diameter ≥ 4 mm and set pressures ≥ 0.1 bar gauge and places no limitation on temperature. Note: this is a product standard - it defines valve design, testing and marking requirements, but it is not a standard for specific system applications.
Key topics and technical requirements
- Scope and definitions: clear terminology for main valve, pilot, flowing/non‑flowing pilot and ON/OFF action.
- Design requirements: materials, valve end connections, minimum spring requirements and general construction principles for pilot‑operated safety valves.
- Testing regimes:
- Production testing: hydrostatic and pneumatic tests, seat leakage tests, pressure seals and set/differential adjustment checks.
- Type testing: tests to determine operating characteristics, flow characteristics and the coefficient of discharge; certification procedures for discharge coefficient.
- Performance, sizing and selection: procedures to determine valve performance and guidance for sizing pilot‑operated safety valves (see Clauses 8–9).
- Marking and sealing: mandatory marking and sealing information for traceability and compliance.
- Normative references: references to common data and related parts of ISO 4126 (Part 7 is normative for common data).
- Regulatory linkage: Annex ZA maps the standard to EU Directive 97/23/EC (PED) showing which clauses support presumption of conformity for pressure equipment.
Practical applications and users
This standard is essential for:
- Valve manufacturers designing and testing pilot‑operated safety valves to meet international product requirements.
- Quality and compliance engineers who must verify production and type tests, marking and certification.
- Safety and pressure systems engineers specifying valves for pressure relief systems (for correct selection and sizing, noting this standard is for the product itself, not system application).
- Notified bodies and testing laboratories conducting conformity assessments and coefficient of discharge certification.
Typical applications include industrial pressure protection on vessels, piping, compressors and pump systems where pilot control provides higher capacity, tighter set accuracy or special operating characteristics compared with direct‑acting safety valves.
Related standards
- ISO 4126 series (other parts): Part 1 (safety valves), Part 2 (bursting discs), Part 3 (combinations), Part 5 (CSPRS), Part 7 (common data), Part 9, Part 10, Part 11.
- EN adoption by CEN ensures alignment with European regulatory requirements (PED).
