Chapter #5 – Sheet Metal Spiral Machine
The spiral duct machine has the capacity depending on manufacture to make a range of sizes from 3” up to 98” round spiral duct.
Spiral ductwork is fabricated mostly from a 5.394” wide strip of sheet metal that comes from a coil and is sent through forming heads that shape the duct to the desired round size.
Forming heads range in size from 3” to 98” or 60 mm to 2500 mm. These spiral machines can do galvanized steel, stainless steel and aluminum material at various thicknesses.
The lengths can be as long as you want as the machine will keep running until it depletes the coil of sheet metal, creating one super long piece. Since this isn’t practical, standard lengths are usually stocked, but if you have your own shop you can specify the length for each piece per size.
Watch the video below to see how the metal is loaded on to the Spiral machine and the method by which spiral duct is made for the HVAC industry.
Spiral Machine Productivity
These spiral duct machines vary on their production speed, but one particular manufacture states that they can produce 2,460 feet (750m) of 4” spiral duct in one hour, and 236 feet (72m) of 64” spiral duct in an hour.
The spiral duct machines can handle galvanized, aluminum and stainless of various thicknesses. Some spiral duct manufactures limit the machine to 18 gauge material, the typical range being 26ga to 18ga. Some of these spiral machine run better with a minimum thickness of 26 gauge, even though SMACNA allows 28ga on spiral duct 14” and smaller for 2” static pressure.
The width of the coil material is 5.394” wide, and each coil can weight up to 2,000 pounds, that’s why a forklift or other type of lifting mechanism is required to mount the coil onto the spiral machine.
Spiral Duct Forming Heads
When you purchase a spiral duct machine, it will come with a range of forming head sizes, possibly from 3” up to 36”. If you want to make larger spiral ducts you would need to buy the corresponding forming head sizes for each size you wanted. Some manufactures have spiral machines that can produce up to 98” round spiral duct, any duct required larger than that you would custom make by rolling and welding the seam of the material.
Here is an additional video showing how the sheet metal coil is loaded onto the spiral machine.
Not as common as adjustable elbows or other types, but here you can see how spiral type 45-degree and 90-degree elbows are made.
Sheet Metal Spiral Pipe Cutter
There are sheet metal fabrication shops that have machines that will cut spiral pipe with a torch as shown in this video. This machine makes unique cuts for special duct configurations.
Now let’s look at chapter #6 to see how to make a sheet metal seam.
- Chapter #1 – Introduction to Sheet Shop Fabrication
- Chapter #2 – Sheet Metal Materials
- Chapter #3 – Sheet Metal Coil Line
- Chapter #4 – Plasma Cutting Table
- Chapter #5 – Spiral Machine
- Chapter #6 – Sheet Metal Seams
- Chapter #7 – Sheet Metal Joints
- Chapter #8 – Sheet Metal Casings and Plenums
- Chapter #9 – Sheet Metal Shop Fabrication Productivity