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Thursday, November 7, 2013

Heat Shrink Sleeves on Large OD Pipe?

     A "big" pipeline job has been floating around lately.  I don't mean "big" in the sense that it is a project that will ultimately end up as a nice sale -- I mean "big" as in "WOW that is big pipe!"  Honestly, the entire project would be fewer than ten shrink sleeves; so kind of unusual in its small-ness.  But the pipe that is needing a coating here is greater than 160" in inside diameter!  At 13.33 feet, just about any of you could actually drive your car through this pipe if you chose to!  You could hang a basketball goal in this pipe (and have shooting practice as long as you're firing flat shots).  The only people who could jump in that pipe and touch the top would be very tall world class athletes (I'm not even sure that Lebron James could touch the top!).

    In any case, when considering the question "can I use a shrink sleeve here" at the initial step, we are doing nothing more than simple mathematics.  A master roll of WPCT material (say 17" wide) comes to us in a 300 foot length.  If we turned that 300 feet roll of WPCT into a single shrink sleeve - it could wrap around a substrate that is:  (a 300 foot roll = 3600 inches) - 3600" / 3.14 = 1146.  Save some room (say 12" of room for the WPCT shrink sleeve to overlap onto itself and you would see that the shrink sleeve is actually large enough to wrap around a substrate that is 1146" (or) 95.5 feet OD!  That would be a big sleeve! 

     A pipe that large would raise a lot more questions than I have time to discuss here.  During the specification phase of the project we'd have to consider:  what is the weight of a pipe that large?  what sort of soil stresses would a pipe that large have associated with it?  what sort of pipe movement could we expect?  can the shrink sleeve backing handle that kind of weight without elongating?  is the mastic thickness of the shrink sleeve going to be displaced by that kind of weight?  etc, etc.  So - I'm not saying (please read that again) that WPCT would be an approved product on a 1140" OD pipeline - I'm simply saying that in some cases, the upper limits of a wrap around shrink sleeve is determined by the length of the master roll. 

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