Originally Posted by
Michael W. Clark
I don't doubt that you still see a lot of spiral in the places you reference, but I promise you the clamped duct is not just being used by hobbyists and small commercial. There are at least (3) companies that supply a similar product, KB Duct (our company's brand), Nordfab, and US Duct. A lot of this gets sold through distributers that are also reps for equipment (woodworking, dust collection equipment, etc) so the ducting gets incorporated as a package with the equipment a lot of times.
I think Nordfab may be part of Nederman and I know they do a lot of commercial/industrial systems with their equipment brands. Donaldson who is probably the largest player in the market for cartridge dust collectors pairs this type ducting with their systems and so do their reps when it is appropriate. I'm not sure what percentage of sales of this ducting goes into woodworking applications, but I know it is significant. Donaldson and Nederman are not seen that often in hobby shops.
The brand I work for (Fisher-Klosterman), we supply equipment (cyclones and scrubbers) into wood processing facilities such as for sawmills, planer mills for construction lumber, plywood, OSB, MDF, wood pellet, wood drying, etc. Most all the ducting connected to our equipment is welded and flanged. They do use some clamped duct on smaller branches now sometimes, but welded is still more the norm for new, but occasionally see some sprial there on old systems. Often these systems are large due to the airflows required so the DC equipment is large and heavy too. These systems can be over 100,000 ACFM, but doesn't compare to steel mills where those systems can be well over 1M ACFM!
I'm not saying spiral isn't used or isn't suitable, we have installed on some applications too, but it is not used near as often as welded or clamped from what we see on a normal basis. Perhaps we are not as involved as heavily in some of these other industries. I know they use a lot of open collectors and Dantherm, Agget, and others do a lot in this market.
IMO, spiral would be considered for light industrial applications where there is no concern with abrasion, corrosion, or excess humidity (like from a dryer). This would fit a lot of furniture and woodworking applications just fine. Clamp together would be a step up for the advantages already discussed, then welded would be the next step up for many industrial applications since you have so much flexibility in gauge and materials and go much larger for the bigger airflows.