BS ISO 4126-10:2010 - Page 2

Safety devices for protection against excessive pressure. Sizing of safety valves for gas/liquid two-phase flow | Status: Superseded, Withdrawn

1 Scope This part of ISO 4126 specifies the sizing of safety valves for gas/liquid two-phase flow in pressurized systems such as reactors, storage tanks, columns, heat exchangers, piping systems or transportation tanks/containers. The possible fluid states at the safety valve inlet that can result in two-phase flow are given in Table 1.

NOTE The expression “safety valve” is a synonym for valves as described in ISO 4126‑1, ISO 4126‑4 and ISO 4126‑5.

Table 1 — Possible fluid state at the inlet of the safety valve that can result in two-phase flow Fluid state at valve inlet Cases Examples liquid subcooled (possibly flashing in the safety valve) saturated with dissolved gas cold water boiling water CO2/water gas/vapour near saturated vapour (possibly condensing in the safety valve) steam gas/liquid vapour/liquid non-evaporating liquid and non-condensable gas (constant quality) gas/liquid mixture, when gas is desorbed or produced steam/water air/water