Industrial rupture disk vent line areas for two-phase flow are currently overestimated. As a consequence, the dischargeable mass flow rate is partially much higher than necessary often leading to malfunctions in downstream retention systems and increased environmental loads. For two-phase gas/liquid flow there is no standardized sizing procedure available. Hence, the homogeneous non-equilibrium model HNE-DS is transferred from sizing safety valves to a procedure for sizing rupture disk vent lines. Thermodynamic non-equilibrium effects like boiling delay are considered. The extend method is called HNE-CSE method. Characteristic numbers of rupture disk vent lines like the resistance coefficient K-g are typically measured under laboratory, subcritical conditions with incompressible fluids, i.e. liquids or gases at very low velocities. In contrast, the flow typically encountered in an industrial rupture disk vent line is a compressible gas or two-phase gas/liquid flow under critical flow conditions. The sizing of a rupture disk vent line based on characteristics for incompressible fluids is therefore a challenge. An appropriate test section for compressible fluids as an extension of ASME PTC25 is recommended. In addition the definition of the resistance coefficient is extended to compressible fluid flows. (C) 2015 Elsevier Ltd. All rights reserved.