Hairpin units have always occupied a difficult position in the world of mechanical design because they do not follow the geometry of conventional shell-and-tube equipment. While many engineers expect a single pressure vessel design software platform to model the entire assembly directly, the reality is far more complicated. The tubular shell itself may be straightforward because it is essentially a pipe section, but the rear closure arrangement introduces a completely different design philosophy involving rectangular flanges, custom end caps, transition details, and non-standard reinforcement areas.
Unlike conventional equipment with standardized configurations, hairpin assemblies are often approached as a collection of individual components rather than as one unified model. Designers typically separate the shell, channel, flanges, covers, and transition regions into isolated calculations. In practice, many engineers rely on dedicated spreadsheets for each part of the assembly because every region follows different mechanical behavior and different code considerations.
The geometric complexity becomes especially evident at the return end. Circular shells suddenly connect to rectangular or highly customized flange arrangements that do not fit traditional assumptions. Standard automated routines struggle to interpret these transitions correctly because the load paths are not as predictable as those found in ordinary cylindrical layouts. As a result, many commercially available solutions force designers into workarounds, approximations, or manual verification methods.
Another important aspect is structural stability. Hairpin assemblies are usually lightweight compared to larger process equipment, which often leads engineers to simplify or even omit stability evaluations altogether. Although this approach may reduce calculation effort, it can leave important local effects insufficiently examined, particularly around discontinuities and non-circular closures.
This is where VCLAVIS introduces a more practical methodology through its “Collections mode.” Instead of forcing the engineer into a rigid predefined template, the platform allows every component to be treated independently, almost as if each section were being verified through its own engineering spreadsheet. Pipe shells, rectangular flanges, covers, and specialized transition regions can therefore be evaluated individually while still remaining part of the same project workflow.
The advantage of this methodology is flexibility. Engineers can apply the correct mechanical rules to each component without compromising accuracy or struggling against software limitations. By supporting specialized calculation methodologies, including approaches for rectangular flange arrangements, the platform simplifies the mechanical design of hairpin equipment and transforms what has traditionally been a difficult and fragmented task into a far more manageable engineering process.