Problem
High temperature pressure vessels use refractory to ensure that shell temperatures are uniform and low enough to avoid material creep. Refractory can sometimes become compromised due to wear, damage or gas tracking exposing localised regions of the shell to high temperatures. The shell material can lose its strength at higher temperatures and thermal gradients can cause thermal stresses and failure of the shell. The consequences of a failure can be significant and so there is motivation to understand and document the risk associated with such events.

Solution
Finite element stress analysis (FEA) allows the calculation of stresses and displacements under thermal and pressure loads. Stress calculations can be used in a ASME FFS-1 / API 579 Fitness for service assessment (FFS) to ensure that the vessel will be protected against plastic collapse, local failure, failure from cyclic loading and buckling. At higher temperatures a creep analysis is also required to understand the likelihood of time dependent creep buckling and rupture of the shell.

Result
FEA modelling in conjunction with an approved code of practice ensures that vessel will be safer for workers and the general public.