TWDB Application Guidelines

 TWDB Installation Guidelines

     TWDB is a Covalence (formerly Raychem) product that has been around for many years.   TWDB stands for Thermofit Wraparound Duct Bands and these would be used to seal up the joints on high velocity industrial duct work to eradicate air leaks at those joints.  Available in 3" and 4" widths, TWDB is sold in rolls that are 165 feet long.  Installers would cut their own strips of material from those rolls (cut lengths are explained on the box) and the installation is simple, easy -- and maybe most importantly:  NOT MESSY!

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Join duct sections that you will be sealing with TWDB using internal couplers or crimped end male/female type connections.  Apply sheet metal screws.  Two screws 180 degrees apart are usually sufficient.

Wipe the joint area to remove foreign materials.  Preheat joint to remove moisture and burn off any surface oil that may be present.  

Cut the TWDB (thermofit wraparound duct band) to the appropriate length.  Center the TWDB and wrap it around the duct joint (TWDB was once called TDAB)

Using the included supplied high temperature sealing tape (which holds the duct band in place during the shrink process), secure the loose TWDB end by taping in place.  TWDB should overlap onto itself. 

Using a standard propane torch, heat TWDB on all sides until it has shrunk uniformly and adhesive is showing at each end.  

Smooth down the overlap area with a gloved hand to ensure proper contact to the duct.  

Duct Band Heat Shrink

Heat Shrink for Duct Bands

     Thermofit Wraparound Duct Bands (TWDB) is Raychem's (now called Covalence) product fpr solving the problem of costly joint leaks in air conditioning duct systems.

     This duct sealing band, made of cross linked polyolefin heat shrinkable material, is precoated with a hot melt adhesive.  When heated in excess of 250F, TWDB shrinks and the adhesive melts, forcing it into all surface irregularities.  Mechanically strong, pressure tight seals are provided. 

     Ducts can be assembled on the floor and raised into position shortly after installation.  TWDB's cut to length system keeps inventory cost minimal by eliminating the need for multiple sizes.  Its wrap around design makes it suitable for flat oval and rectangular duct as well. 

     Used in high velocity systems operating up to 158F, TWDB is non toxic and resistant to solvents and vibration.  Shelf life is unlimited.  This product offers an efficient, neat and permanent method for sealing duct joints, all at a low installed cost. 

     As you see here, the installation procedure is quite simple. 
1:  Cut TWDB to appropriate length.  Recommended overlap is 2 inches onto itself.
2:  Using a heat resistant tape (supplied) secure the TWDB end by taping it in place to form the TWDB into a circle (or rectangle).
3:  Using a standard propane torch, heat TWDB on all sides until it has shrunk uniformly and adhesive is showing at each end.  

Thermo Fit Wrap Around Duct Band

Thermofit Wraparound Duct Band

 

     Duct work, is by its very nature, riddled with leaks and air paths.  Every joint where one bit of duct work connects with another allows a loss of pressure, air flow, temperature, gasses, etc.  Imagine trying to set up a sprinkler system in your yard, but for all of the PVC pipe, you don't bother using connectors, glue, epoxy or couplings...you just kind of slide one bit of PVC into another...and assume that will be good.

 

     Well that is exactly what happens with duct work in commercial and residential buildings all over the USA. Leaks, leaks and more leaks are leading to less energy efficient HVAC systems, less effective chemical hoods and more and more wasted dollars on lost heated or cooled air flow. 

 

     So what is the answer?  Using a product like our TWDB heat shrinkable tape for sealing joints on duct work.  TWDB is installed using a propane torch or an industrial heat gun.  The TWDB covers the seam at the joint of the duct work and overlaps onto the adjacent duct.  It forms an air tight seal preventing any air current leakage.  You are paying to get a certain amount of air from point A to point B.  Why are you allowing 20+% of that air to escape along the path??

 

     TWDB is also used to seal the vent work on chemical fume hoods.  It makes sure any vapors or gasses get exactly where you want them to go without allowing them to escape where they shouldn't go.  Sounds smart huh?  So, get your HVAC situation under control.  Improve the efficiency of your HVAC system.  Reduce your energy bills!  Stop heating or cooling the attics and ceilings of your buildings!