TWDB for High Velocity Industrial Duct Systems

 Theremofit Wrap Around Duct Work for High Velocity Industrial Duct Work

Example of a Duct Joint sealed by TWDB

     Raychem (now called Covalence) make a product for sealing the joints on high velocity, industrial duct work.  It is called TWDB which is short for thermofit wraparound duct bands.  TWDB is a heat shrinkable tape for sealing duct joing on air conditioning and heating systems.  

     TWDB Duct Sealing Tape is a two layer system.  The first layer is a copolymer adhesive that bonds very well to metal duct work.  The second outer layer is a thick walled, radiation crosslinked, high density polytheylene.  TWDB is a hot applied duct sealing tape composed of a heat shrinkable backing with a heat resistant pressure sensitive, non-drip adhesive and a closure patch.  TWDB is superior to any cold applied options out there and dramatically easier to install (and less messy) than the paste options out there in the world today.

     Installed using propane torches or industrial heat guns, TWDB is very easy to install.  The ducts are assembled and raised into position.  The TWDB tape is wrapped around the ducts where joined and a closure is then applied, allowing the tape to essentially form a tube or band around the joint.  When heated to a temperature of 267F, the tape shrinks tightly around the substrate of the joint area.  During recovery, the adhesive softens and flows to form a tenacious bond with the substrate and to fill any irregularities such as the interlocking seams of the duct work.  The bond builds up during cool down and is fully retained after completion of the job.  Mechanically strong, pressure tight seals are created by the TWDB.

    Features of TWDB thermofit wrap around duct bands:

• No primer is required - leading to no dry time and a simple install.
• Low preheat sensitivity and proven functionality.  TWDB allows easy installation combined with high functional performance levels. 
• High mechanical resistance backing.  TWDB resists vibration in high velocity systems operating at up to 158F.
• Minimal inventory costs.  TWDB's cut to length packaging system eliminates the need for multiple sizes (all rolls are 165 feet long; you can choose 3" or 4" widths).
• Specialty formulated sealant ensures a reliable protection with high peel and shear values after installation.
• No special equipment or training required.
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TWDB Thermofit Cut Lengths

Cut Lengths for TWDB Thermofit Wraparound Duct Bands

     Ok, everything I will share here is printed on the actual TWDB boxes themselves (whether 3" wide or 4" wide).  No need to take notes.  When your TWDB arrives you will have all of this data and info right at your fingertips (literally).

TWDB Installation Instructions:
Materials and Equipment required:
- TWDB
- High temperature closure tape (included in the TWDB package)
- JS2601 torch or equal
- Propane tank
- Heat resistant work gloves

1: Join duct sections using internal couplers or crimped end male female type connection.  Apply sheet metal screws.  2 screws 180 degrees apart are usually sufficient.
2: Wipe joint area to remove foreign materials.  Preheat joint to remove moisture and burn off surface oil that may be present.
3: Cut TWDB to appropriate length (see sizing chart).  Center TWDB and wrap around duct joint.  Using the supplied closure tape, secure the loose TWDB end by taping in place across the width of the overlap.
4: Adjust torch to provide soft billowy flame.  Heat TWDB uniformly.  As heat is applied, the TWDB will chrink and bond to the duct to form a pressure tight seal.
5: With gloved hand pat down overlap area to ensure proper adhesion.
6: Recovering is complete when the TWDB is in 360 degree contact with duct and the molten adhesive is visible at both ends. 

The following chart is organized:  Duct Size / TWDB Cut Length
2" / 9"
3"/ 12"
4"/ 15"
5"/ 18"
6"/ 21"
7"/ 24"
8"/ 28"
9"/ 31"
10"/ 34"
11"/ 37"
12"/ 40"
14"/ 46"
16"/ 53"
18"/ 59"
20"/ 65"
22"/ 72"
24"/ 78"
26"/ 84"
28"/ 90"
30"/ 97"
32"/ 103"
34"/ 109"
36"/ 115"
38"/ 122"
40"/ 128"
42"/ 134"
44"/ 141"
46"/ 147"
48"/ 153"
50"/ 160"
52"/ 166"
54"/ 172"
56"/ 178"
58"/ 185"
60"/ 191"
62"/ 197"
64"/ 204"