What is Covalence WPCPIV

 What is Covalence WPCPIV Used For?

     WPCPIV is a Covalence part number (started as a Raychem part number of course).  Every single wrap around shrink sleeve will use a WPCPIV closure strip.  The purpose of the closure strip is simple:  it holds the sleeve in the shape of a tube during the shrink process.  Without a closure, the shrink sleeve that was wrapped around a pipe would slowly fall away from the pipe and eventually be dangling off of the pipe or laying in the dirt. Once the sleeve is fully installed and cooled however; the closure strip no longer serves any purpose.  There would really be no point in removing it; but after the installation the WPCPIV has no corrosion prevention responsibility or contribution.  

     You want the WPCPIV closure strip to be as wide (or slightly wider) than the shrink sleeve material you are working with.  Historically, standard shrink sleeve widths are:  11.25", 17.75", 23.50" and 34.25" (customs always available on request).  In terms of the other dimension, WPCPIV closure strips can be 3", 4", 6", 8" or any custom size requested.  

     Picture this:  a 25" long shrink sleeve is wrapped around a 6" pipe with a circumference of just under 21".  You start by putting one end of the sleeve on the pipe (that has been cleaned and preheated) and the sleeve is then wrapped all the way around the pipe and overlaps onto itself by at least 2" (leaving a slight "bag" or some slack in the sleeve.  The closure (if you're installing a two piece sleeve) would then be half on one side of the sleeve --- and half on the other.  The closure is then heated with a propane torch, causing the adhesive so get soft and aggressive.  The WPCP closure is then patted down (or rolled) to make sure that it has good contact with both side of the sleeve (so the sleeve can't slip off of the pipe).  A bit more heat is added to the closure and the smooth black of the closure will begin to show signs of the reinforced mesh material that is laminated within it.  Then you know the closure has been properly heated.  

    

Here is the adhesive side of the WPCPIV closure strip.  You can also see the checkered pattern of the laminated reinforcement.  That reinforcement insures that the closure doesn't stretch during the shrink process.

Here is a close up of the adhesive (clear) and the fiber mesh behind it.

Here is the smooth black backing of the WPCPIV closure.  This should be on the OUTSIDE (yes, I've seen people try to install them the wrong way).