Issuing body
IEC
Latest edition
Various parts
Region
Global
Equipment items
2
Scope
International control valve series — sizing, terminology, noise, testing.
Key requirements (8)
- Industrial process control valves — sizing and characteristics.
- Cv / Kv calculation: Q = N·Cv·√(ΔP/ρ) for liquid (with corrections for choked flow).
- Choked flow: ΔP_choke = FL²·(P1 – Ff·Pv) for cavitation.
- Compressible flow: choked when P2/P1 ≤ critical pressure ratio (~0.55 for air).
- Noise prediction: aerodynamic (Part 8-3) and hydrodynamic (8-4) — 85 dBA limit typical.
- Inherent flow characteristics: linear, equal-percentage (most common), quick-opening.
- Rangeability: typical 30:1 (globe), 50:1+ (rotary segmented ball).
- Leakage classes: I (no test), II (0.5% Cv), III (0.1% Cv), IV (0.01% Cv) standard, V (very tight), VI (resilient seat / soft-seated).