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Monday, April 17, 2017

WPCT Shrink Temperature

At What Temp do Shrink Sleeves Shrink?

     As you might expect, this is actually not a simple question.  Shrink sleeve backing can be made from many different material types.  Each of those material types have their own chemical make up - and as a result; can often have different crystalline melt points.  The crystalline melt point is the temperature at which the structure of the backing begins to melt.  If the backing has been crosslinked it doesn't melt, it instead shrinks back to its original dimension (pre-stretch). 

     With most of our Covalence (formerly Raychem) heat shrinkable sleeves (products like WPCT, TPS, WPC100M, HTLP60, DIRAX, etc) that backing is comprised of a modified polyethylene (a polyolefin).  Speaking generally, the crystalline melt point of those product is ~267F.  That means that the backing temperature must reach 267F (minimum) before the sleeve will begin to shrink.  This could certainly be done in an oven or some other situation - but what we see most is the heating taking place with a propane torch (propane torch with a broad bushy flame). 

     Most of the time, we see our shrink sleeves installed on a steel pipeline, overlapping onto some form of a factory applied corrosion coating (FBE / Powercrete / TLPE / etc).  In those cases, that installation temperature is not a big deal.  Most of those coatings (FBE and TLPE at least) are often seeing temperaturese greater to or equal to that during the original application time.  In some cases though, there are cases where someone wants to install a shrink sleeve on something else - perhaps a PE line; or some sort of flexible composite material. 

     In cases like that, it is always critical to speak to the manufacturer of your non-steel pipeline to find out what temperature range those materials are able to withstand without sacrificing their integrity or performance.  I couldn't possibly be an expert in every type of specialty tubing, so please rely on the folks you purchased the pipe from to determine what is acceptable if you're using something significantly different than standard steel pipeline tubing. 

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