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Engineering Specialties Used:
Boiling Heat Transfer
Finite Element

A boiler was opened during a recent turnaround for inspection and minor repairs. What was found was a significant failure of the refractory used to protect the integral tube sheet from hot process gases. When the tube sheet material is exposed to high temperature, metallurgical deterioration occurs which significantly reduces its strength. The boiler was a critical path item for the turnaround. Therefore, the facility

Finite Element Model of the
Waste Heat Boiler Area of Interest

did not want to replace the integral tube sheet due to cost and schedule. If the temperature profile through the tube sheet thickness could be determined, we would know whether to replace the part or leave it in service.

A three-dimensional thermal finite element model (FEM) was built for a portion of the tube sheet with several tubes. Convection boundary conditions for both gas heating and boiling water cooling were calculated and applied to the model. We found that most of the tube sheet thickness was below the critical temperature. Because the potential for metallurgical deterioration of the tube sheet was predicted by the FEM to be so shallow, we decided to confirm this by drilling into the tube sheet a short distance at several locations. The results of this procedure confirmed the analysis findings and the tube sheet remained in service.

As Found Condition at the Beginning
of the Turnaround

Our rapid analysis of an existing part enabled on-time completion of the plant turnaround. Argos Engineers is ready to partner with your turnaround team to evaluate unexpected findings. Let us provide the analysis input needed for quality decisions. Make safe choices, but avoid costly ones that are overly conservative.

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