Can a Series 21 (Permalock Seam) Centrifugal fan be welded?
In 1994, Greenheck developed the Series 21 and 41 scroll housing centrifugal fans. Series 21 fans were designed to meet more commercial applications. Series 41 fans are intended for both commercial and industrial applications. Physically, the only difference between a Series 21 and 41 fan is the method of fastening the side plates of the housing to the scroll wrap. Series 21 construction uses a Permalock design which crimp locks the two pieces together and Series 41 fans have side plates and scroll wraps which are welded together. When a Series 21 fan has gone through the Permalock process, it is possible to have it welded, but it is more economical to simply choose a Series 41 fan.
