Road Bore Coating Post-Pull Analysis: DIRAX

DIRAX Post Pull Analysis

     We had a unique opportunity here recently.  On a large project utilizing some different two part liquid epoxies as their field joint coating, it was quickly determined that the epoxies were being damaged  beyond acceptable levels during the pull through.

     Now, I want to be clear - this was an extremely difficult pull.  There were large, razor sharp rocks sticking in the bore that were causing significant damage to anything that was being pulled through.  In my sixteen years of experience, I've never seen damage like this done on a lubricated directional drill pull through.  Never.  So I'm not saying there is or was a problem with the epoxies - I'm simply saying that they did not survive the incredibly challenging forces they were facing underground.

     The end user (after fully evaluating the system) decided that they would put a DIRAX shrink sleeve on the outside of the two part epoxy in order to add significant, added physical protection to that field joint coating.  Installations were done as normal when applying the two part epoxy - and then the DIRAX was installed directly on top of it (after the two part had cured).

     This introduced a 150+ mil layer of fiber reinforced polyolefin / polyamide material in the hopes that the DIRAX could act as a sacrificial coating preventing any damage from getting to the two part epoxy.  Fortunately, the DIRAX that was on the leading end of the pull through was pulled all the way through the bore so that it could be inspected.  The DIRAX was then cleaned off with a rag and a bottle of water.  Here was the result:

DIRAX after being pulled through a large directional drilling bore hole.

     Clearly there was a small amount of mud and dirt still left on the DIRAX sleeve, but all in all its performance was outstanding.  No tears in the sleeve; no holes in the sleeve, no wrinkles in the sleeve.  The DIRAX came through several hundred feet of being dragged through a hole and looks exactly as it looked just moments after installation.  DIRAX is an absolutely incredible product. 

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).  

JSI Coatings - Master Distributor for Covalence / Seal for Life Products

     Joint Specialists was established in 1995 by Stan Simpson and Sam Damico.  They had been working directly for Raychem Corp for ~20 years by that point in R&D, technical support, field service and sales.   Their unique expertise translated easily into distribution and JSI was born.  Even today, many years later, JSI still prides itself upon its technical knowledge and ability to engineer solutions for nearly any customer need.

     We also recognize the need for fast turnarounds on orders within the oil, gas and water pipeline industries.  We keep our 20,000 square feet warehouse full of the most commonly sold pipeline coatings.  90% of orders placed with us ship same day (most of the rest ship next day).  Whether your pipeline is ambient temperature or elevated temperature; whether you require a 3 layer or a 2 layer coating solution; whether your application is subsea, involved in a road bore or simple to seal up a casing; you can count on the fact that we've got you covered.