In this study, using the American Society of Mechanical Engineers - ASME VIII Div.1 and the German AD - MERKBLÄTTER 2000 (that is a code of practice for pressure vessels and other pressure equipment, it was drawn up by the German Pressure Vessel Association which includes many German associations and institutions specialized in boilers and pressure vessels). This pressure vessel had its geometry generated from the Inventor software, which has equipment specification for industrial applications. The validation of two types of horizontal cylindrical vessels was performed: one without and one with four nozzles (A, B, C, D). For this, two common parameters between both standards were considered: the minimum required thickness in millimeters (of the cylindrical shell, elliptical head, and nozzles A, B, C, and D), as well as the maximum membrane stress (in the presence and absence of nozzles). The percentage differences between both standards, considering the membrane stress of the vessel without nozzles, was not significant. However, regarding the vessel with nozzles, the percentage differences between nozzles B and D (18.26% and 13.64%, respectively) are considerable. Finally, for the case of the minimum required thickness, the percentage differences for each of the components (shell, head, nozzle A, nozzle B, nozzle C, and nozzle D) show high disparity (99.2%, 79.7%, 180.5%, 159.2%, 180.5%, 189.5%, respectively). Based on these percentage differences, comments and conclusions are drawn regarding the applicability of both standards in real-world pressure vessel validation contexts. For numerical simulations, Ansys Workbench software [15] was used, as well as DIMy, from the company TÜV NORD.