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 should be used in the assessment of nozzle loads on the header box design. Subsequently, the designer must rely either on empirical guidelines or Finite Element Analysis (FEA) in line with the requirements of ASME Section VIII U-2(g). The aim of this project therefore was to develop an analytical design methodology that accounts for the effects of these nozzle loads on the header box. A new mechanical model was derived by extending the existing ASME Section VIII rigid frame theory model and the result was tested against an FEA case study to determine whether the model was useable. It was found that the new model makes some useful qualitative statements but cannot be used for accurate stress analysis of the stresses near the base of the nozzle on the header box. The case study was also used to examine the effectiveness of a commonly used empirical guideline.

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