Failure analysis of a separator under various thermal loading: A numerical study

Abstract

In the present study, Computational Fluid Dynamics (CFD) simulations were carried out on a separator subjected to three different fire scenarios: pool fire, jet fire and fireballs. The empirical models applicable to such plants are not developed and conventional radiation models leads to an overestimation of the heat flux and safety distances. Therefore an alternative tool like CFD along with empirical models is used to model the potential scenarios mentioned above in a model oil and gas separator plant. The developed model were validated by comparing literature data on the flame length, maximum flame temperature and its location above pan surface in case of pool fire and comparing them with literature data. It is found that in case of flame length the deviation from literature data was about 10% and less than 5% for the maximum flame temperature. For jet fire the average surface temperature was 561 K while this value is 423 K in case of pool fire and 317 K for fireballs. When it comes to the radiative flux, an average value of 29 kW/m2 is found for jet fires while this value was only 14 kW/m2 for pool fire and 23 kW/m2 for fireballs. The thermal loads on the separator vessel due to above fire scenarios were also calculated. The obtained value of thermal stresses were around 285 MPa and 600 MPa for pool and jet fires respectively. Thus it can be concluded that from safety point of view jet fires are the most critical one. The results obtained form simulations were also compared with that of data from empirical models.