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Dry air-cooled heat exchangers (ACHE) form an integral part of refinery cooling systems of which the header boxes form an important component. It is commonly designed as an ASME Section VIII Division 1 pressure vessel, but unfortunately neither ASME nor the American Petroleum Institute (API) provide guidance regarding to the methodology which shoul...

## Contexts in source publication

**Context 1**

... header boxes are rectangular pressure vessels and are commonly designed according to ASME Section VIII Division 1 Appendix 13 [2] and API 661 [3]. Figure 2 shows the current Appendix 13 [2] model used for the design of unpartitioned, plug-type header boxes. API 661 Section 7.1.10 ...

**Context 2**

... frame theory is an extension of standard beam theory where several beams are rigidly connected together, i.e. there is moment transfer from one beam to another. The model present in Division 1 Appendix 13 [2], Fig. 2, is identical to that in Division 2 Part 4.12 [7] and both work on a unit length basis. This implies that the vessel is assumed to be infinitely long and then a unit section is taken as the basis of the analysis. The effect of this is that the end plates are neglected and only the four side walls remain. This results in a classic rigid ...

**Context 3**

... in cross-section, as in Fig. 4. Only two of the forces in Fig. 3., F x and F y , and one of the moments, M z , exist in the cross-section and will be considered. The other nozzle loads will be neglected. Since the loading is asymmetric the stress distribution will no longer be symmetric. This means that instead of a single corner point, Q in Fig. 2, and two mid- side points, M and N in Fig. 2, as in the Appendix 13 [2] analysis, each corner and mid-side point will have a unique equation. The loads F x , F y and M z were then applied by distributing them over the entire nozzle width, N w , in Fig. 4. Bending moment and membrane force equations, Annex A, were then derived using ...

**Context 4**

... of the forces in Fig. 3., F x and F y , and one of the moments, M z , exist in the cross-section and will be considered. The other nozzle loads will be neglected. Since the loading is asymmetric the stress distribution will no longer be symmetric. This means that instead of a single corner point, Q in Fig. 2, and two mid- side points, M and N in Fig. 2, as in the Appendix 13 [2] analysis, each corner and mid-side point will have a unique equation. The loads F x , F y and M z were then applied by distributing them over the entire nozzle width, N w , in Fig. 4. Bending moment and membrane force equations, Annex A, were then derived using Kleinlogel [13], a classic text on rigid frames. ...

**Context 5**

... containing the maximum internal stress. Figure 6 shows an enlarged section of corner A for a case where the maximum tensile stress occurs at the sharp corner and the maximum compressive stress occurs a small distance away, at the red line. It is thought that this effect can be attributed to a difference between the way the 2D FEA model, as per Fig. 2 and Fig. 5, and the extended rigid frame model handle the corner joint. Since rigid frame theory is essentially beam theory, the walls are modelled as their mid-planes, which creates an overlap region and a region with no material, while the 2D FEA models the corner completely. This difference in modelling is shown in Fig. 7. The results of the ...

## Citations

... A centering mandrel is introduced into the tube and the welding is performed. Studies can be found about this kind of heat exchanger in [25][26][27][28], but they are related to the design and analysis of the header box, especially the nozzle joints. ...

The rear wall of the header box serves as a tubesheet in heat exchangers of double plate header box. Tube-to-tubesheet welding must be performed using orbital Gas Tungsten Arc Welding (GTAW) with a head extension, which is passed through the corresponding hole in the front wall (plugsheet) of the header box, where the welding machine is supported. In this project, the effect of parallelism deviations between the plugsheet and the tubesheet of carbon steel header box is analyzed to evaluate its influence on the quality of the tube-to-tubesheet welding. Welded tube (SA-210 Gr. A1) to tubesheet (SA-516 Gr. 70) coupons are manufactured simulating the parallelism deviations previously analyzed in two double plate header boxes of air-cooled heat exchangers using two different preheating temperatures. Macrographic analysis is performed in order to evaluate the weld penetration (minimum leak path) and length of the weld leg in tube-to-tubesheet joints. The results obtained show important variations in those parameters when the parallelism deviations are equal to or greater than −1 mm over the theoretical distance as well as when the distance approaches +1 mm or more. Finally, the incorporation of dimensional controls prior to the welding process is discussed and the implementation of improvements in orbital GTAW equipment is recommended as an optimal solution for this kind of heat exchangers.