On the Adequacy of API 521 Relief-Valve Sizing Method for Gas-Filled Pressure Vessels Exposed to Fire

Abstract

Abstract:In this paper, the adequacy of the legacy API 521 guidance on pressure relief valve (PRV) sizing for gas-filled vessels subjected to external fire is investigated. Multiple studies show that in many cases, the installation of a PRV offers little or no protection-therefore provides an unfounded sense of security. Often the vessel wall will be weakened by high temperatures, before the PRV relieving pressure is reached. In this article, a multiparameter study has been performed taking into consideration various vessel sizes, design pressures (implicitly vessel wall thickness), vessel operating pressure, fire type (pool fire or jet fire) by applying the methodology presented in the Scandpower guideline. A transient thermomechanical response analysis has been carried out to accurately determine vessel rupture times. It is demonstrated that only vessels with relatively thick walls, as a result of high design pressures, benefit from the presence of a PRV, while for most cases no appreciable increase in the vessel survival time beyond the onset of relief is observed. For most of the cases studied, vessel rupture will occur before the relieving pressure of the PRV is reached.

HydDown: A Python package for calculation of hydrogen (or other gas) pressure vessel filling and discharge

“…The author is also thankful for enlightning discussions with colleague Jacob Gram Iskov Eriksen (Ramboll Energy, Denmark) and former Ramboll Energy colleague Carsten Stegelmann (ORS Consulting) in relation to vessel depressurisation, nozzle flow and heat transfer considerations. This work has also benefitted significantly from the understanding of thermo-mechanical pressure vessel behaviour obtained in previous works (Andreasen et al, 2018;Bjerre et al, 2017;Eriksen & Bjerre, 2015). Furthermore, this project relies on high quality open source Python packages: NumPy (Harris et al, 2020;Walt et al, 2011), SciPy (Virtanen et al, 2020), matplotlib (Hunter, 2007), pandas (McKinney, 2010), PyYaml, cerberus, Streamlit, tqdm (Costa-Luis et al, 2021 and pytest (Krekel et al, 2004).…”

Fire Protection of Steel Structures with Epoxy Coatings under Cryogenic Exposure

“…An LNG spill can cause a high-pressure heat load fire. There are two common types of fire that can happen in hydrocarbon processing facilities: pool fire, which occurs when a flammable liquid leaks from a vessel or pipeline, forming a "pool" of liquid that ignites, and jet fire, which is a potentially more dangerous type of fire that can result from the rupture of a pressurized vessel and/or pipeline (Figure 1) [21]. The risks of exposure to cryogenic liquids must be considered when designing steel structures for oil and gas facilities.…”

Revealing hidden debottlenecking potential in flare systems on offshore facilities using dynamic simulations – A preliminary investigation

“…The initial rate is used as input to a steady-state flare network simulation. Even individual relief loads from various relief scenarios are analyzed using dynamic simulations (Singh et al, 2007;Firth, 2016;Bjerre et al, 2017;Andreasen et al, 2018). On the other hand, the analysis of the flare system as a whole is typically not subjected to dynamic analysis (Chen et al, 1992).…”