Overview
EN ISO 8659:2020 - Thermoplastics valves - Fatigue strength - Test method specifies an endurance (fatigue) test for hand‑operated thermoplastics (plastic) valves to confirm their ability to withstand prolonged cyclic operation (repeated opening and closing). Adopted by CEN as EN ISO 8659:2020, this standard defines the test apparatus, cycle procedure, parameter values and required test reporting. It does not cover resistance to chemically aggressive media, extreme velocities or cavitation (see ISO/TR 10358 for chemical aggression classification).
Keywords: thermoplastics valves, fatigue strength, endurance test, ISO 8659:2020, valve fatigue testing, hand-operated plastics valves.
Key topics and technical requirements
- Scope & limits: Applies to fatigue (endurance) testing of hand‑operated thermoplastic valves; adverse chemical or hydraulic aggression excluded.
- Apparatus: Equipment must test the complete valve assembly without imposing axial forces on end connections or radial forces on the stem; include means to pause cycles during pressurization and to maintain closed pressure. Instrument accuracies: pressure gauges ±1% FS, temperature sensors ±2 °C.
- Procedure (endurance cycle):
- Open valve: multiple‑turn valves - hand‑wheel speed 40 r/min ±10 r/min (≤ DN50) or 20 r/min ±10 r/min (> DN50); quarter‑turn valves - opening time ≥2 s (≤ DN50) and ≥4 s (> DN50). Valve held open 5–20 s.
- Close valve: multiple‑turn at 40 r/min ±10 r/min; quarter‑turn closing time ≥1 s. Closing performed using torque specified in relevant product standard.
- Apply internal pressure in closed position for 5–20 s.
- Repeat cycles as required by the applicable product standard.
- Test media & conditions: Water, air or gas at temperatures, pressures and velocities specified in product standards.
- Test report requirements: Reference to ISO 8659 and product standard; valve identification (type - ball, butterfly, diaphragm, gate, globe - material, DN, PN, manufacturer), opening/closing torques, test conditions, number of specimens, pass/fail and failure mode.
Applications and users
- Who uses it: valve manufacturers, independent test laboratories, product designers, quality/production engineers, certification and compliance bodies, procurement and specification writers.
- Practical uses:
- Validate durability and operational life of thermoplastic valves used in industrial and fluid transport systems.
- Provide objective endurance data for design verification, product standards compliance and buyer specifications.
- Support failure analysis by recording opening/closing torque changes and leakage/fracture outcomes.
Related standards
This standard is essential when specifying or testing the fatigue strength and operational endurance of thermoplastic valves in non‑aggressive service conditions.
