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!

Give me a call (936/321-3333) or shoot me an email for pricing (steve@jsicoatings.com)

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.  

TWDB - Joint Specialists

TWDB Themofit Wraparound Duct Bands

     Thermofit Wraparound Duct Bands are heat shrinkable tapes, made of cross linked polyolefin, precoated with a hotmelt adhesive.  The band is cut to length on on the jobsite, wrapped around the duct joint and fixed at the overlap with a pressure sensitive adhesive patch.  TWDB is black in color in terms of the backing and also black in color with regard to the adhesive.  This is a product that shrinks at 125C which can be achieved with an open flame or with an industrial hot air gun.

     The typical application for this product is as a pressure sealing joint on round or flat oval ducts in air conditioning or heating systems.  TWDB can be used at up to 70C and pressures up to 50 kPa at 25C.  It is highly recommended for spiral ducting in high velocity air conditioning. 

     TWDB is available in standard widths of 3" and 4".  All rolls are 165 feet long and shipped within boxes can aid with measuring as each TWDB strip is cut.  The backing wall thickness is a nominal .5mm.  The adhesive coating thickness is a nominal .7mm.  This product is manufactured to shrink 15% which is significantly less than most of our heat shrinkable pipeline coatings which can range anywhere from 25% to 66%.

     Each TWDB roll is packed in a unique box, containing TWDB and a roll of positioning patches.  Installation instructions and recommended cut lengths are printed on the box.  Generally, the 3" wide TWDB will include 35 of the pressure sensitive closing patches.  The 4" wide will generally include 20 of the closing tape patches. 

     For the most part, the 3" TWDB is recommended for duct sizes of 400-800mm.  The 4" TWDB is recommended for duct sizes larger than that.  There really is no limit though.  The 4" TWDB could be used on any size duct offering even more overlap onto the adjacent ductwork.

     Feel free to contact us today for price and delivery information on your TWDB needs.  We can be reached Monday thru Friday at 936/321-3333 -- or around the clock (within reason) at steve@jsicoatings.com