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Wednesday, January 22, 2014

Shrink Sleeves: Tubes vs Wraps on Large OD Pipe

Tube Shrink Sleeves vs Wrap Shrink Sleeves

 Question:  I have a 30" Pipeline and I'm writing the specification.  Could you walk me through what the advantages of using tubular shrink sleeves versus wrap around shrink sleeves would be?

Answer:   I do not personally believe there is any advantage to using a single piece tubular sleeve versus a single piece wrap around sleeve.  Here are the reasons I believe that:

For starters, there are two ways that tubes are manufactured.
- They can be extruded - in which case they truly are seamless tubes when they are manufactured.  This presents some challenges for the manufacturer as the size of extruding equipment is going to determine the maximum size that an extruded tube can be.  Most extruded tubes are small (8" and lower).  I am not aware of any manufacturer that is able to extrude seamless tubular shrink sleeves.
- They are manufactured from sheet material and bonded into the shape of a tube using a peroxide (or other) bonder.  This would be the exact same sheet material as would be used in a wrap around shrink sleeve.  The difference is - a strip of mastic is laid over the internal seem in order to give it an extra adhesive thickness -- and in a sense "hide" the seam.  The seam is still there - it just isn't visible. 
To be clear - when I talk about "seam" we are not talking about a place where a shrink sleeve "butts up" to itself - we are talking about the area where one end of the shrink sleeve overlaps the other end of the shrink sleeve (by at least a few inches) creating an area at the pipe surface) where the thickness of the shrink sleeve steps down from a double thickness to a single thickness.  All shrink sleeves - be they tubes bonded from wrap around material - or wrap around shrink sleeve - are designed to "flow and fill" enough to fill that area (factors would be adhesive thickness, shrink force of the PE, viscosity of the adhesive) - of course we do recommend that all installations utilize a silicone roller as the final step of the installation process on all sleeves is to roll the sleeve; including a focus on the overlap area. 

So particularly in your case, with a pretty large substrate, I really don't see that you have any option other than a wrap around shrink sleeve.  If it is any consolation - wrap around shrink sleeves have been generally accepted for many years.  If the seam were causing corrosion problems, we would have heard about it long before now.  In my world - we see wrap around shrink sleeves used ten times more than tubular sleeves. 

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