I forgot which net friend needed BS ISO 4126-10:2010,whose title is Safety devices for protection against excessive pressure — Part 10: Sizing of safety valves for gas/liquid two-phase flow.He said he couldn’t find this standard.Now i will share it and hope this pdf file can help you.
Part of the document is as follows:
BS ISO 4126-10:2010 includes a widely usable engineering tool for the sizing of the most typical safety valves in fluid services encountered in various industrial fields. It is based on the omega parameter method, which is extended by a thermodynamic non-equilibrium parameter. Without this extension for considering non-equilibrium, the proposed method is in accordance with API RP 520. A balance is attempted between the accuracy of the method and the unavoidable uncertainties in the input and property data under the actual sizing conditions. There are other sizing methods available, which are referred to in this part of ISO 4126.
BS ISO 4126-10:2010 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.