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Wednesday, August 12, 2015

Heat Shrink Sleeve Cut Lengths

Cut Lengths for Heat Shrink Sleeves

     So, how long does a heat shrinkable sleeve need to be?  What are the proper dimensions?  How much wiggle room is there?  Well we are going to cover that for you here.  But first a little basic math.

     Most of the time in the pipeline world, we are looking at one of several standard outside diameters of a pipeline (ID does not generally matter in my world).  In addition, most of the time we are looking at a factory applied coating that is some kind of a thin coat - be that FBE or a relatively thin PE coating (something less than a 1/4").  So in almost every case, we are able to consider the pipe OD as the true OD of the line without needing to consider coating thicknesses.

     So step 1 (if we were figuring things out by hand rather than relying on tried and true specifications for shrink sleeve dimensions):  determine the circumference of the pipeline.  How do we determine the circumference?  Pipe OD x 3.14 = circumference.  So here are a few standard circumferences (which do NOT equal cut lengths so don't get carried away here!).

 4.5" OD Pipe = 14.13" circumference
6.625" OD Pipe = 20.8" circumference
10.75" OD Pipe = 33.76" circumference
40" OD Pipe = 125.6" circumference

      In this case, the circumference of the pipe or substrate gives us our base dimension but not our actual dimension.  To use this base dimension would result in a massive failure of the product.  It simply would not work no matter what.
     In order to find our final number, we have to be aware the a shrink sleeve must be long enough to wrap around the pipe surface (and any pertinent coating) and then must overlap ONTO ITSELF by at least a few inches (generally 3+ but that generally grows for larger pipe sizes).  If the shrink sleeve does not wrap around the pipe and overlap onto itself, the sleeve will absolutely NOT work.
     So taking that overlap requirement into account - I would end up with the following actual cut lengths:
4.5" = 18" cut length
6.622" = 25" cut length
10.75" = 38" cut length
40" = 134" cut length

     Now for some bonus info:  let's touch quickly on product width which also comes up often.  The width of a shrink sleeve (coverage along the pipe) must be wide enough to coat all bare steel and overlap onto the adjacent factory applied coating by at least 2 inches per side.  So if you have 4" of bare steel, you would require at least 8" of shrink sleeve (4+2+2).  Our nearest standard is 11", so the 11" wide product would be sufficient and cost effective (other options would be 17" wide, 24" wide, 34" wide).  

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