Sizing rupture disk vent line systems for high-velocity gas flows

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 installed in a vent-line. Proper sizing of rupture disk vent-line system involves fluid dynamic coupling of the rupture disk device and the entire vent-line with all its fittings. Pressure drop and dischargeable mass flow rate through a safety device must be determined. This should be done with correct consideration of the fittings relieving area and the fitting's loss coefficient, which depend on flow conditions upstream of rupture disk device. Sizing of rupture disk relief systems should also consider flow contraction caused by the rupture disk device as this contraction limits flow through the device.This work presents a scientific method to calculate the pressure profile in a vent-line system with a rupture disk installed with the rupture disk zero-velocity minor loss coefficient, KRD,0. This proposed characteristic number is determined experimentally and taken to be constant for a rupture disk type, and nominal pipe size. The rupture disk losses are enhanced to factor compressibility fully. The pressure drop across a rupture disk and the pressure profile in a rupture disk relief line are predicted seamlessly for low-to high-velocity gas flows and validated experimentally. A new test-section equipped with state-of-the-art instrumentation is used to deliver precise experimental data. Experiments show that this method predicts the pressure profile along a vent-line with a rupture disk installed with less uncertainty as compared to classic methods. The method is applicable for both low-velocity and high-velocity compressible gas flow as is typically the case during pressure relief in a complex rupture disk relief line.