The effects of severe thermal and pressure transients on the survival of internally coated tubes

The effects of severe thermal and pressure transient pulses on the interior of coated tubes have been analyzed using finite-element methods. For the modeling, an axisymmetric mesh was developed and used to assess the transient, thermal-and stress-states and the propensity for fracture related damage. For all calculations, temperature dependent thermophysical and elastic properties were used during the analysis. The model also utilized uniform heating and pressure across the ID surface imposed via convective coefficients and a piece-wise linear pressure function over time. Results for the strictly elastic analysis indicated that both had a significant influence on the maximum circumferential (hoop) stresses and temperatures and that the compressive thermal-stresses help to offset any tensile components generated by the internal pressure on the ID. Preliminary calculations also investigated the influence of these factors when a crack was introduced at the interface of the coating and substrate.