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Monday, November 16, 2015

Heat Shrink Sleeve Maximum Operating Temperature

Temperature Limitations for Heat Shrinkable Sleeves

     I am often asked about the upper range for temperature limitations on heat shrinkable sleeves.  The most recent cases have been a few different companies inquiring after a coating that is easy to install and able to withstand potential continuous operating temperatures in the 350 to 400F range.  This is a challenge.

     In the world of heat shrinkables, you must really break this question down into two different categories.  Spoiler alert:  in spite of the in depth analysis here - let me offer you an early peak ahead:  there is no shrink sleeve solution for temperatures that high.  I'm sorry!  I wish I had something to offer you.

     So breaking this down into two categories, we must look at the heat shrinkable backing -- and we must look at the adhesive sealant.

     First the Heat Shrinkable Backing:  The backing of our most commonly sold heat shrink sleeves for pipeline coatings are all made from a modified polyethylene (a polyolefin).  The chemistry of that compound by its very nature generally has a crystalline melt point of ~267F.  Now, this means that if the backing had not been radiation crosslinked -- then that backing would essentially melt at 267F.  Because the backing has been radiation crosslinked, however - it does not melt.  But, being crosslinked and then exceeding that 267F temperature rating means that the backing will be 'in a state of shrink' at that temp.  The backing would be soft and malleable; attempting to return to its original shape and size (that is how a shrink sleeve works).  As a result, at or above that 267F temperature, the backing does not have the strength to physically protect the field joint as it is supposed to.  As a result, it can't do what it is supposed to do at that temperature.  As a result, our shrink sleeves would not be recommended for use at or above 267F (or actually even lower; our highest temperature rated heat shrink sleeve is rated for use at up to 251F). 

     The second factor that determined maximum operating temperature of heat shrinkable sleeves is the temperature at which the adhesive is rated with approval.  This means that at 'that' certain temperature, the adhesive behaves as it is supposed to; resulting in the desired and expected physical properties including peel strength, penetration resistance, ring and ball softening point, etc.  There are many characteristics that a pipeline coating is supposed to meet in order to properly offer a protective and corrosion resistant coating to a pipeline or substrate.  Covalence / Seal for Life (formerly Raychem) has patented any number of proprietary adhesives designed for different specific pipeline coating applications.  I'm sorry to say though - that none exceed the 251F mentioned above. 

     I'm afraid that a pipeline operating at 350F quite simply, exceeds the chemical potential of PE based components of a heat shrinkable backing. 

Monday, November 9, 2015

Shrink Sleeves on top of Powercrete

Powercrete with a Shrink Sleeve on top

     We've all seen him....that old man walking around who is wearing a belt around his waist and also wearing suspenders.  Is it a fashion statement?  Did he forget he had the belt on when he put the suspenders?  Were they both gifts from his grandkids and he just wants to remember them and honor their gift?  Does he get frustrated with himself every time he goes to the bathroom?  I think like many things, the obvious answer is the correct one:  he really, really, really doesn't want his pants to fall down!  I don't blame him!  I think we've all had those kind of dreams/nightmares and those are not fun.  So a DIRAX shrink sleeve installed on top of Powercrete?  I've seen it done many times and I can say from direct conversations I've had with the people doing it:  they really want to make sure that their field joints are properly protected on those directional drilling applications!

     Most everyone in the industry understands the strengths of the Powercrete plant applied abrasion resistant overcoat.  Installed on top of the fusion bonded epoxy, plant applied Powercrete has many years of successful pull throughs where FBE has emerged unscathed in spite of whatever it encountered underground.

     In addition, most in the industry are aware of many of the strengths of two part epoxies as field joint coatings on road bore applications.  With excellent Shore D hardness; abrasion resistance and cathodic disbondment resistance - there is a lot to offer there (which are many of the same reasons that our DIRAX is installed on top of a two part epoxy of some kind in ever situation - most commonly our S1301M epoxy).

     I think many would also agree that DIRAX also has some tremendous characteristics that are perfectly suited to road bore applications.  Just a few of these are:  electrical resistivity; penetration resistance, abrasion resistance, peel resistance and shear resistance.  It also has a proven track record that goes back for decades.

     So why use both?  First of all, I have to say...hundreds of thousands of installations have proven that using Powercrete underneath a DIRAX sleeve is not necessary.  DIRAX has an excellent track record all on its own; using the Covalence S1301M epoxy primer as the bonding agent there.  But; using the DIRAX on top does actually improve the performance of the Powercrete --- or at least the installation.
     Worried about getting the proper coating thickness?  Toss a DIRAX on top of the Powercrete and you'll now exceed any coating requirement.  Worried about the amount of labor required to continue to work that Powercrete to achieve uniform thickness and avoid icicles?  Throw a DIRAX on there and let the DIRAX do that work for you.  Worried about micro corrosion at a microscopic level where maybe the peaks and valleys of the anchor pattern aren't quite being filled?  Throw a DIRAX on there - no water / no oxygen - means that even if you have a holiday show up through a fish eye late during the installation; the DIRAX is going to be there to cover your back. 

Monday, November 2, 2015

WPCT for Road Bores?

Standard Shrink Sleeves on Road Bore Applications

     The world of pipeline coatings is much like the world of tools. Different tools are designed for different functions.  Brooms are great, and very effective when sweeping up dirt....but they are going to be pretty much useless if you're trying to cut down a tree.  Likewise an axe is great for cutting down a tree, but is not going to be particularly effective for tightening a bolt.  A wrench can tighten a bolt great, but it isn't going to be very effective if you're trying to dig a deep hole.  Likewise; standard shrink sleeves are great for basic, drop the pipe in a ditch and backfill it types of applications; but they are quite simply:  not designed for use in road bore applications. 

     WPCT is our most commonly sold ambient temperature, wrap around, heat shrink sleeve for corrosion prevention.  It is a fantastic product.  It has successfully prevented corrosion for decades on literally millions of field joints over the last decade.  It is easy to install.  It is reliable.  It essentially inspects itself.  But WPCT is not approved or recommended for use on road bore applications.  That simply isn't what it is designed for. 

     The product that is specifically designed for road bore service is our DIRAX product.  Incredible peel and shear resistance.  Unparalleled abrasion resistance and penetration resistance.  This sleeve is three times thicker than the WPCT product (on the leading edge of the coating).  DIRAX uses a two part epoxy as the primary corrosion coating.  That two part epoxy brings with it excellent cathodic disbondment resistance and improves the physical characteristics of the system (better peel / shear).  The DIRAX sleeve is then installed over the wet epoxy.  DIRAX is comprised of a three layer backing system and a high shear polyamide adhesive; which is designed to physically and chemically bond to the two part epoxy; forging a contiguous, bonded, thick field joint coating system that will easily withstand any forces it is put through during the boring process. 

     To sum up:
DIRAX for directional drilling:  GOOD
WPCT for directional drilling:  Not Good
     Now, there are folks out in the world who will tell you that "WPCT will do just fine on a road bore."  Please, do not believe those folks.  They are just looking to make a quick and easy sale.  They aren't evil people, they are simply uneducated.  They want things quick and easy rather than spending the time to learn the ins and the outs of the Covalence heat shrinkable products product line.