The aim of this research is to understand the reason of failure in a fire-tube heater-treater using finite element method (FEM). The fire tube, made of ASTM A516 G70 steel, failed after 15 years in service under continues operation. A crack in the fire tube at U-turn section started on the outer diameter (OD) surface of the heat-affected zone (HAZ) and consequently led to leakage. In this investigation, the results obtained from the experimental analysis were summarized, and finite element (FE) models were employed to predict thermal stress during continues service operation. It was observed that increasing the thickness of the scale layer, increased the temperature gradient in the fire tube and therefore caused severe thermal stress concentration at the U-turn section. The fractographic studies showed that Manganese sulfide (MnS) inclusion played an important role in the crack formation.

这项研究的目的是通过有限元方法（FEM）了解火管加热器的故障原因。由ASTM A516 G70钢制成的火管在继续运行15年后失效。U形转弯处的火管破裂始于热影响区（HAZ）的外径（OD）表面，从而导致泄漏。在这项调查中，总结了从实验分析中获得的结果，并采用了有限元（FE）模型来预测继续服务期间的热应力。观察到，增加氧化皮层的厚度，增加了火管中的温度梯度，因此在U形转弯处引起了严重的热应力集中。