Abstract
In the chemical and petrochemical industry, vessels and pipes are protected against overpressure using safety relief devices, usually rupture disks (also called a bursting disc) or safety valves. In contrast to a safety valve, the opening of a bursting disk is a stochastic process leading to a certain range of flow areas, depending on the manufacturing process of the disc. In general, this area cannot be predicted to the last percent. It determines dominantly the overall pressure loss and, in case of critical flow, the mass flow rate to be discharged through a bursting disk vent line system. To date, tests to determine the rupture disk flow resistance factor are typically performed with low velocity, subcritical, almost incompressible flow with air, nitrogen and water. Test conditions are stationary flow despite the fact that the flow regime during emergency relief varies from liquid only, gas only, gas/liquid two-phase flow or even flashing liquids. Even though a rupture disk is used as a primary relief device, the rupture disk flow resistance coefficients are not precisely applicable for compressible gas, vapor liquid or multiphase service (Friedel & Kißner, 1988). For two-phase flow, there is neither a standardized test section, nor any reliable test results available. Consequently, there is also no precise model to size a rupture disk device in these cases (Schmidt & Claramunt, 2014). Additionally, for typical industrial rupture disk vent-line systems, significant errors can be made by applying current sizing methods (Schmidt, 2015). Over-dimensioning the rupture disk vent line system leads to unnecessary financial costs and may cause malfunction of the collecting systems downstream when the fluids discharged are more than the design limits. Under-dimensioning may lead to hazardous incidents with loss of human life and equipment. There is a strong need for experimental data and a reliably validated sizing method that is valid for single-phase compressible gas as well as for flashing and non-flashing two-phase flow.
