Valve Standard Reference
ISO 5208
InternationalIndustrial Valves — Pressure Testing of Metallic Valves
ISO 5208 is the international standard for pressure testing of metallic valves.
Overview — ISO 5208
ISO 5208 is the international standard for pressure testing of metallic valves. It defines test procedures, pressures, durations, and permissible leakage rates for shell (body) tests and seat leakage tests. ISO 5208 is commonly specified alongside API 598 for export and international projects where ISO rather than API standards are preferred. The two standards are largely equivalent but differ in leakage rate definitions and acceptance criteria labelling.
Scope
Applies to metallic industrial valves including gate, globe, check, ball, butterfly, plug, needle, diaphragm, and pinch valves. Covers both hydrostatic (liquid) and pneumatic (gas) shell and seat tests. Defines leakage rates A through F where A = zero leakage and F = relaxed leakage.
Applicable Valve Types
All metallic industrial valve types
Gate, Globe, Ball, Butterfly, Check, Plug, Needle valves
Applicable Pressure Classes
Key Requirements — ISO 5208
Shell test pressure: 1.5× maximum allowable pressure at 38°C (100°F)
Shell test duration: minimum 15 seconds for DN ≤ 50; 60 seconds for DN > 50 to DN 300; 120 seconds for DN > 300
Seat test pressure: 1.1× maximum allowable pressure OR 6 bar minimum
Leakage Rate A (zero leakage): no measurable leakage — required for gas and toxic fluids
Leakage Rate D: standard for most industrial valves
Pneumatic test alternative: 6 bar (87 psi) for gas valves where liquid test not practical
Test medium: water (with corrosion inhibitor) for shell test; water or air/nitrogen for seat test
Testing Requirements — ISO 5208
Shell test: 1.5× rated pressure, per duration table
Seat test: 1.1× rated pressure, per leakage rate
Pneumatic test option: 6 bar air or nitrogen for gas valves
Documentation Required for ISO 5208 Compliance
ISO 5208 test certificate
Leakage rate classification (A through F) specified on certificate
Test medium and temperature recorded
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