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In practice vessel design engineers often struggle with the design of pressure vessels in early stages of a project, when the piping loads exerted on the nozzle by the connected piping are yet unknown.

The prevailing assumption is that external loads require by definition additional reinforcement of the nozzle.

In the article cited in this blog Walther Stikvoort poses the argument that extra reinforcement rarely proves necessary as the recognized design code or standard will already provide for a reasonable amount of piping imposed loading ability because of the inherent amount of reinforcement.

The original calculations of the stresses in a horizontal vessel on saddle supports by L.P. Zick in 1951 made no distinction between vessels lying loose on the saddle and vessels lying on a wear or reinforcement plate, welded or not. However, this has a significant influence on the magnitude of the circumferential combined compression stresses at the horn of the saddle. In this blog derived methods are discussed that do take this into account. Furthermore the conditions are discussed under which each of these methods may be used.

Flange rigidity approaches intend to limit flange rotation in order to prevent leakage. Recently, Walther Stikvoort has published an article in which he evaluates various flange rigidity approaches for large-diameter body flanges. He concludes that the k-factor approach excessively compensates when compared to the index J approach which leads to a larger flange thickness and a less economical flange design.

Recently, a comparative study was carried out by Walther Stikvoort into the load capacity of saddle-supported horizontal pressure vessels. He compared the L.P.Zick method with the limit load-based method. One of the tools used in this study is the VES software developed by P3 Engineering.

Dimensioning a custom heat exchanger flange can be done quite quickly using a number of simple rules. Starting with the internal diameter B the flange dimensions can be determined step by step. The end result is a feasible flange with dimensions that can be used to do a stress analysis with, for example, the P3 Engineering VES-software.

This blog is a condensed version of the full paper that is available here.