Fans are installed to provide exhaust, intake or circulation. A common application for angle rings and other curved steel sections is in fan housings. The metal rings serve as structural supports as well as mating flanges to connect to round ductwork.
Metal angle rings can be supplied in both standard sizes (with standard diameters, bolt circles, number of holes and hole diameter) and special sizes (with any variety of diameters and punched hole specifications as well as angle sizes). Angle rings can be welded on the outside only, on the inside only, all around, or not welded at all (OBJ, open butt joint). The welds can also be ground smooth.
Standard angle rings are often carried in stock or, if not, can be produced within a day or two. Same day delivery is often an option. Custom rings can be made in a day or two.
Metal rings for fan housings can be made of virtually every steel section: angles, bars, beams, channels, pipe and tube. The rings can be made of stainless steel, mild steel, aluminum or other alloys. In addition to full rings, ring segments can be provided. Rings can be galvanized, plated or painted.
Fans with metal rings are commonly part of a system that includes ductwork. Round ductwork can be made from lock seam pipe or welded pipe and is often connected by angle flanges.
More information on fans including fan ratings can be found at the Air Movement and Control Association International (AMCA).