The primary difference lies in flange design, defined by EN 10279:
UPE (Parallel Flange): Flange edges are parallel, with uniform thickness across the flange width. This simplifies bolted connections, as the parallel edges ensure consistent contact with brackets. Example: UPE 100 has 55 mm parallel flanges, 5 mm web thickness.
UPN (Normal Flange): Flanges have a slight taper (typically 1:10) from the web to the edge, increasing load-bearing capacity by distributing stress more evenly. Example: UPN 100 has 56 mm tapered flanges, 5.5 mm web thickness.Other dimensions (height, web thickness) are similar for equivalent sizes, but UPN flanges are often thicker than UPE for the same height, making UPN suitable for heavier loads.