Do Covalence Shrink Sleeves Have a Shelf Life?

Read HERE to find out.

But - I would add that our EPOXY does have an expiration date - typically 1-2 years (all epoxy kits are marked).  This would include our S1301M epoxy, the essentially obsoleted S1239 epoxy and the S1401 epoxy most often used with HTLP-PP and PPS120 products. 

For specific questions; email us or give us a call.

How Many Closures Per Sleeve?

Question:  I have a customer who is going to purchase master rolls of heat shrink sleeve material and cut their own shrink sleeves to length.  How many closures strips ("WPCPIV") will they need per shrink sleeve that they cut?

Answer:  First I would say that this is certainly an option.  Sometimes it makes sense for someone to purchase bulk master roll of WPCT (available in 11", 17",24" and 34" widths with the nomenclatures: WPCT 11x300-roll; WPCT 17x300-roll; WPCT 24x100-roll and WPCT 34x150-roll).  A customer might choose to do this because they have many different pipe sizes and configurations and they would rather custom cut their sleeves instead of order the cut pieces from us.

In any case; the answer for this one is simple.  Any wrap around shrink sleeve requires ONE and only ONE closure strip (sometimes also called a zipper; a WPCP or a patch).

This is a closure.  One is required for every wrap around shrink sleeve.  WPCPIV

Internal Field Joint Coatings

Question:  Does JSI currently have a product available that can be used to coat a field joint on the inside of a pipeline (internally) after the weld has been made?

Answer:  Unfortunately, no.  We do not carry (at the moment) and product designed for internally coating a pipeline; be that the field joint or the entire interior of the line.  As you might imagine, coating a pipe internally (particularly at the field joint; post weld) carries with it some complications that are not present when coating the exterior of a pipeline.

How Much Coating Repair Material Will I Need?

     Question:  I have a PE coated pipeline.  I've been told to have repair material on site.  How much polyethylene repair material will I need?

     Answer:  Unfortunately, it is almost impossible for me to know!  There are so many different ways that a pipeline can be damaged and so many varying degrees that I cannot ever predict how much you will have on your pipeline.  As a couple examples; here are some photos of damaged PE that I've seen:

Damage to the PE jacket outside of insulation caused by improper pipe storage

Damage to a PE outer jacket.  notice that the ROCS sleeve is untouched just a few inches away

Another area of PE damaged by a forklift

     In the real world, it is possible that PE coated pipe is loaded on a barge and every single joint of pipe is damaged to some degree.  It is also possible that a pipe is loaded without a single joint being damaged.  There is never any way for me (or the customer) to really know. 

     That is one reason that we keep so much PERP material in stock.  Very often, it isn't known how much damage a pipe has received during transit until the pipe is actually being strung up and welded.  In cases like that, it is very simple for us to throw a few rolls of PERP material - and the accompanying Perp Filler rolls onto a truck (or UPS) and have them at the job site in a day or two.

     You don't want to have to buy materials that you don't really need.  I don't want to sell you materials that you don't really need.  The fact that we keep this material in stock assures that we both get what we want. 

Shrink Sleeve Installation Tools

Shrink Sleeve Installation Tools

Question:  What tools are required for Covalence heat shrink sleeve installation?

Answer:  Ignoring the need to clean the pipe, Covalence heat shrink sleeves do not require

any special tools during installation.  Here is what is needed:

- A means of measuring preheat temperature.  This could range from something as 

sophisticated as a pyrometer with roller probe; to something

as simple as a temp stick.  

An example of temp sticks for different temperatures

 - A broad flamed torch (Covalence shrink sleeves cannot be shrunk

using an acetylene torch or a welding torch).  Our torches are sold as a kit

which includes a torch with a pilot lights; a regulator with a pressure guage

and a thirty foot long hose. 

A JS-2601 Torch Kit - available at JSI

- A long handled silicone roller.  This is used after installation to roll the overlap area

and can be used in the event that any air has become trapped (which could be

caused by poor application).  

A long handled roller; used during heat shrink sleeve installation

(Keep in mind that the contractor or end user will need to supply their own propane tanks for installation) 

Heat Shrink Sleeves: Most Dangerous Installation Error

  Question:  What is the most dangerous installation error when installing a heat shrinkable sleeve?

  Answer:  I'm going to overlook things like 'failing to clean the pipe' and 'failing to preheat the pipe'.  The most dangerous installation error is an installer who simply fails to care for the bottom of the pipe.

  Pipeline spreads are often NOT pretty.

A fairly typical (maybe even a 'good' pipeline spread.

 As you can see, there just isn't very much room underneath the pipe.  But still, the bottom half of the pipeline must still be cleaned and preheated.  In addition, the bottom of the sleeve must be shrunk and shrunk appropriately!  This same potential problem exists for any coating of course; working a liquid epoxy to prevent icicles can be even more challenging.

In any case, anytime an inspector asks me "what should I be looking for" one of the first things out of my mouth is that he's almost certainly going to need to get his knees dirty as he'll be crouching down under that pipeline to make sure the sleeve has been properly shrunk on the bottom of the pipe (and he/she needs to be familiar with this page!)

 

Installing Shrink Sleeves: How Important Is Pre-Heat?

     Another common question:  How Important is Pre-Heat?

     Short answer:  ABSOLUTELY CRUCIAL

     Long answer:  When installing a heat shrinkable sleeve as a field joint coating, you are doing so for one reason and one reason only.  You are protecting that field joint (girth weld) from corrosion.  Of course, the idea is, that if you can seal that field joint in a way that prevents water and oxygen from reaching the bare steel; then it will be impossible for corrosion to occur.


     We do this by installing a heat shrinkable sleeve that is coated with a sealant or adhesive of some kind.  If we can install that sleeve so that we get the best possible bond between sealant and bare steel (and factory applied coating) then we begin the life of that field joint from the very best possible position:  properly coated and protected.

     Of course the first step of installation is making sure we've achieved the proper cleanliness standard on the bare steel.  Different adhesives will have different requirements there and I won't discuss them here (but I did touch on surface prep for WPCT here).  The next step however is preheating the steel (and adjacent factory applied line coating) to the proper temperature.  Why is this necessary?

     Any hot melt adhesive or mastic coated shrink sleeve will have an optimum temperature at which the adhesive bonds to the substrate.  When we look at it very closely, we must create an environment where the bond-line reaches a temperature sufficient for ideal bonding.  The bond-line is that area where the hot melt adhesive of the mastic come into contact with the substrate (pipeline).  That interface is critical.

      Even though there is a significant amount of heat put into a heat shrink sleeve during the installation process; when you consider the heat insulation properties of the heat shrink sleeve and when you consider that the steel pipe will act as a heat sink (carrying temperature away from the girth weld as it acts to spread any elevated temperature through the steel in the immediate area) it isn't possible to actually achieve the necessary bond-line temperature exclusively using heat from the sleeve shrinking itself.

     As a result, the steel must be preheated.  This assures that the bond line temperature is met and that the adhesive/steel interface will be properly prepared for the bond to occur.  All Covalence heat shrink sleeves will be supplied with an installation sheet in each box.  No matter the product; there will be a 'minimum recommended preheat temperature' listed on that installation sheet.  It will certainly cause no problem to heat higher than that; with two exceptions.

- When installing a shrink sleeve system that utilizes a liquid epoxy (DIRAX, HTLP60, HTLP80, etc) it is important to keep the preheat temperature down below 200F.  Installing S1301M epoxy on a pipe that is heated above 200F will result in some smoke - and result in the epoxy more or less flash curing (which we want to avoid since we want the epoxy chemically bonding with the sleeve adhesive; and that can't happen in the epoxy cures "early")

- Most all shrink sleeves (all PE shrink sleeves anyway) shrink at ~267F.  We would not want to preheat (most of the time) to a higher temperature than that, as it could result in the sleeve shrinking before the installer is ready (as an example, before the closure has been secured). 

WPCT Surface Preparation

Question:  When installing WPCT shrink sleeves, how clean does the pipe have to be?

Answer:  We are always looking to get the recommended surface cleanliness ST 2 1/2 - 3.

     Sometimes this question is posed a little bit differently.  I recently had an email exchange where I was shown some photos of pipe that has been in a yard for some period of time (months).  The question was posed:  can I get these field joints to ST 2 1/2 with a wire brush after welding has been completed?

Surface corrosion from sitting unprotected for a few months.  In addition, there has been some FBE 'lifting'.

Another view of the surface rust on this pipe that has been sitting in a yard for a few months.

     Of course, it is impossible for me to tell, based on photos, how deep this rust goes and how clean the surface will be once a power wire brush has run over it; but I think this will probably still be 'ok'.  The final determination will (of course) have to be made once an effort has been made to clean it (even running the brush over it right there in the yard would be telling). 

     If a quick power brush does not get the pipe clean; the contractor will have a couple of options.  They can put in a little bit more labor with the wire brush to get the desired cleanliness or they could skip the wire brush altogether and simply sand blast the surface clean (post weld of course). 

     But to sum up; when you're dealing with a product like Covalence's WPCT which utilizes an incredibly aggressive mastic sealant, the fact that this pipe has sat for a few months probably won't mean a darn thing.

Wrap Around Shrink Sleeve

Wrap Around Shrink Sleeve

     A wrap around shrink sleeve is one of two heat shrink sleeve configurations that are available (the other being a tubular sleeve).  A wrap around generally has two components; the sleeve material itself and the closure strip.  To make matters much more complicated than they truly need to be; each component (sleeve and closure) is a multi-layer material.  I'll break each down below.

     First we will look at the shrink sleeve itself.  In this particular case we are looking at the WPCT product, currently manufactured by Covalence Heat Shrinkable Products, underneath the Seal for Life umbrella of corrosion prevention products (WPCT was originally created under the Raychem name).  WPCT is a two layer shrink sleeve, with the outer layer being a radiation crosslinked, high density polyolefin and the inner layer consisting of a mastic sealant (WPCT is supplied with a release paper, but I am ignoring it for the sake of this discussion because it will be discarded during installation).

Here we see the WPCT backing.  Notice the dimples which will fade away as this product is properly installed

Here we see that once the release paper is peeled back, the stick mastic material is exposed.

     You can't tell from the photo (of course) but the WPCT is coated with an extremely aggressive mastic sealant.  In the Texas summer, this material will stick aggressively to anything it touches.  The beautiful thing is that it retains that same aggressive nature for many years (we know because we have seen pipelines with this product installed many decades after their original installation.

     Next we will take a closer look at the closure strip (internal name 'WPCPIV').  It is typically supplied in the same standard widths as the shrink sleeves are and is available in 3", 4" and 6" widths.  Selecting a width depends primarily on sleeve material type; pipe OD, etc.  The WPCPIV is technically a three layer product; incorporating a radiation crosslinked, HDPE backing; a fiber mesh to give the closure superior integrity and a high shear hot melt adhesive to make sure there is no slipping that occurs during installation (if slipping were to occur, the shrink sleeve might begin to work its way off of the pipe during installation).  

The closure backing.  This is the side which will be visible after complete sleeve installation.

This is the high shear adhesive side (with the fiber mesh visible through it).

     In the picture immediately above this sentence; that checkered pattern is the fiber mesh of the closure and also the side of the closure strip that will no longer be seen once the shrink sleeve is installed (it will be fully pressed and bonded to the PE backing of the shrink sleeve).  

     In our shop, we don't ever sell the closures and shrink sleeves separately; they are always attached to one another to make life easier on the contractors.  The truth is that it makes life easier on us as well as we experience dramatically fewer calls for field service, missing components or field problems.  

     There you have it; all you ever wanted to know about wrap around shrink sleeves!

Benefits of Cross Linking

What is the benefit of crosslinking a polyethylene?

 Shape memory!  

Crosslinking gives a heat shrink sleeve a memory (and a desire) to return to its original shape.  This is how a 2" tube shrinks to a 1"; how a 30" sheet shrinks to a 22" or how a molded part shrinks to its original shape (read more about crosslinking here).  In the pipeline coatings world or the electrical splicing world; without shape memory; we would not have a product to sell.

 Abrasion resistance.  

Crosslinking makes the PE (or polyolefin) backing tougher and more abrasion resistant.  This is important for buried and subsea pipelines; for high voltage wire insulation and for splicing.  In addition, because the PE is more abrasion resistant; a thinner PE jacket can sometimes be used which translates to dramatically less weight on airplanes, automobiles, etc.   

Better performance at higher temperatures.  

Since the PE no longer melts, it isn't subject to dramatic weakening at higher temperatures (within reason, of course).  

Improved chemical resistance.  

The crosslinked PE is less susceptible to different chemicals and solvents. 

Reduction in gas permeation.  

In corrosion prevention, reducing the water vapor transmission is VERY important.

Improved mechanical properties. 

Properties like tensile strength, penetration resistance, hot water immersion and others. 

Closures: Must I use them when Installing Shrink Sleeves?

     I'm often asked, "Do I have to use these closures?  Can I install this shrink sleeve without it?"  You see, not every manufacturer out there sells /UNI sleeves (where the closure is pre-attached to the sleeve as explained here).  Often times, someone gets a big box of shrink sleeves and the closure strips come in a separate box.  Other times, the closure strips are all buried at the bottom of the box which can make it difficult to get to them.  Sometimes, all of the closures get dropped in a mud puddle and are essentially ruined!
 

Please only expose your shrink sleeves to an environment like this AFTER installation!

      Since every single sleeve we at Joint Specialists sell goes out as a /UNI sleeve, we don't get this question too often, but it is always shocking how often we get phone calls asking for technical support about our competitors products!

     In any case, the answer is YES.  Every wrap around shrink sleeve MUST have a closure strip to be properly installed.  Without the closure strip, the sleeve will simply fall to the ground during installation making a rather large mess.  The closure strip holds the sleeve in the shape of a tube (pressed to the pipe) during installation.  After the sleeve has cooled, the closure strip has essentially served its purpose (but we always recommend you go ahead and leave it in place anyway!). 

     There are tubular products that do not require a closure.  A few examples of those would be TPS, WCSM, MWTM and CPSM (there are others).  Don't get yourself into a position where you're having to call me with this question.  Make sure you're buying /UNI sleeves and it will never come up!

DIRAX Kit - Explained

     Question:  What is included in a DIRAX kit?

     Answer:  This is one of the most commonly asked questions.  Given the fact that ordering a WPCT sleeve is very simple and straightforward - I completely understand why the DIRAX Kit is harder to understand.

A DIRAX kit includes three components as seen below:

A DIRAX Sleeve

     This (above) is the DIRAX shrink sleeve.  It is (as discussed elsewhere in this blog) a fiber reinforced, high shear shrink sleeve specifically designed to withstand the tremendous forces that a pipe coating experiences during a road bore (or directional drilling) application.  As standards, it is available in widths of 12", 17" and 24" (the sleeve in the picture is a 12" wide sleeve).

Leader Strip or Wear Cone

     This (above) is the Wear Cone or Leader Strip.  It is a 3" wide shrink sleeve; made from the same exact material as the DIRAX sleeve.  It is installed on the leading edge of the sleeve to give it added protection.  

An S1301M Epoxy Primer Kit

     This (above) is an S1301M Primer 15 Kit.  It includes the "A" component; the "B" component; an applicator pad; two gloves and a mixing stick.  This acts as the primary corrosion coating for DIRAX shrink sleeves.  One thing that can be confusing to new customers is that one epoxy kit (as pictured) contains enough epoxy for more than one field joint (most of the time) depending on the outside diameter of the pipe and the width of the sleeve (since epoxy is applied everywhere the sleeve will contact the pipe on FBE and ARO coated pipe).  

Below is the ratio of Epoxy Primer Kits to Shrink Sleeve dependent on sleeve and pipe sizes.  Where it says 5:1; this means 5 DIRAX road bore kits can be installed using 1 epoxy kit (assuming the contractor has properly welded, and cleaned those 5 joints ahead of time).  It also means 1 epoxy kit will be supplied; as part of the kit; for every 5 DIRAX sleeve kits purchased.

DIRAX Epoxy Supplied Chart

DIRAX 2375-12 - 5:1

DIRAX 2375-17 - 5:1

DIRAX 2375-24 - 5:1

DIRAX 2875-12 - 5:1

DIRAX 2875-17 - 5:1

DIRAX 2875-24 - 5:1

DIRAX 3500-12 - 5:1

DIRAX 3500-17 - 5:1

DIRAX 3500-24 - 5:1

DIRAX 4500-12 - 5:1

DIRAX 4500-17 - 5:1

DIRAX 4500-24 - 4:1

DIRAX 6625-12 - 5:1

DIRAX 6625-17 - 4:1

DIRAX 6625-24 - 3:1

DIRAX 8625-12 - 5:1

DIRAX 8625-17 - 3:1

DIRAX 8625-24 - 2:1

DIRAX 10750-12 - 4:1

DIRAX 10750-17 - 3:1

DIRAX 10750-24 - 2:1

DIRAX 12750-12 - 3:1

DIRAX 12750-17 - 2:1

DIRAX 12750-24 - 2:1

DIRAX 14000-12 - 3:1
DIRAX 14000-17 - 2:1
DIRAX 14000-24 - 3:2

DIRAX 16000-12 - 3:1
DIRAX 16000-17 - 2:1
DIRAX 16000-24 - 3:2

DIRAX 18000-12 - 3:1
DIRAX 18000-17 - 2:1
DIRAX 18000-24 - 3:2

DIRAX 20000-12 - 2:1
DIRAX 20000-17 - 3:2
DIRAX 20000-24 - 1:1

DIRAX 22000-12 - 2:1

DIRAX 22000-12 - 3:2

DIRAX 22000-12 - 1:1

DIRAX 24000-12 - 2:1
DIRAX 24000-17 - 3:2
DIRAX 24000-24 - 1:1

DIRAX 26000-12 - 2:1
DIRAX 26000-17 - 3:2
DIRAX 26000-24 - 1:1

DIRAX 28000-12 - 3:2
DIRAX 28000-17 - 1:1
DIRAX 28000-24 - 1:1

DIRAX 30000-12 - 3:2
DIRAX 30000-17 - 1:1
DIRAX 30000-24 - 2:3

DIRAX 32000-12 - 3:2
DIRAX 32000-17 - 1:1
DIRAX 32000-24 - 2:3

DIRAX 34000-12 - 3:2
DIRAX 34000-17 - 1:1
DIRAX 34000-24 - 2:3

DIRAX 36000-12 - 3:2
DIRAX 36000-17 - 1:1
DIRAX 36000-24 - 2:3

 

DIRAX 38000-12 - 3:2
DIRAX 38000-17 - 1:1
DIRAX 38000-24 - 2:3

 

DIRAX 40000-12 - 1:1
DIRAX 40000-17 - 1:1
DIRAX 40000-24 - 1:2

 

DIRAX 42000-12 - 1:1
DIRAX 42000-17 - 3:2
DIRAX 42000-24 - 1:2

 

DIRAX 44000-12 - 1:1
DIRAX 44000-17 - 2:3
DIRAX 44000-24 - 1:2

 

DIRAX 46000-12 - 1:1
DIRAX 46000-17 - 2:3
DIRAX 46000-24 - 1:2

 

DIRAX 48000-12 - 1:1
DIRAX 48000-17 - 2:3
DIRAX 48000-24 - 1:2

 

How Many Field Joints in a Mile?

Question:  How many field joints are in a mile?

or

Question:  How do I know how many shrink sleeves I'm going to need for my project?

Answer:  They don't get very much simpler than this!  In our world; pipe is almost always sold in lengths very close to 40 feet.  Based on that, all we need is a calculator, pen and paper, or my favorite - and abacus to figure it out.

So, you've got 5 miles of pipe.

1 mile equals 5,280 feet.

Every 40 feet is a field joint.

You will have 132 field joints per mile of pipe.

5 x 132 = 660 sleeves will be needed

(this does not include any overage allowance).

Or, you've got a 1200 foot directional drill.

1200 / 40 = 30 DIRAX sleeves will be needed.

Or, you've got 57 miles of 24" pipe

57 x 132 = 7,524 sleeves will be needed.

Simple!

How Long After Install Can the Shrink Sleeve Hit the Stinger?

Question:  How long do I have to wait on an offshore pipeline installation (S-Lay) before the shrink sleeve can contact the stinger?

Answer:  The only real stipulation is that the sleeve must be cooled to ambient temperatures.  Many times an sea water quenching system is put in place to cool the sleeve within seconds. 

How Long After Installing Dirax Can I Start the Bore?

Question:  The DIRAX sleeve has been installed.  How long do I have to wait until I can begin my road bore, lake bore, directional drill or beach pull?

Answer:  As a quick reminder, DIRAX is a three + layer sleeve system with the first layer being a two part liquid epoxy called S1301M.  Anytime a liquid epoxy is involved, there is always going to be the question of CURE TIME.  Of course, there are many factors when determining cure time for any epoxy; including ambient temperatures, humidity levels, etc.  This can be complicated. 
 
     Anytime before an epoxy cures, it is susceptible to flying grass and dirt, to being bumped into, to bugs and to many other field conditions.  In addition, at some colder temperatures, it is impossible to use a stand alone epoxy without erecting a heating tent of some kind because epoxy just won't cure if it's too cold.

     DIRAX is a bit different.  Since it is a part of a heat shrinkable sleeve system, the pipe is preheated and then the heat shrink sleeve is torch shrunk.  As a general rule, all of our shrink sleeves shrink when their backing temperature reaches 267F.  The combination of the pre-heated pipe and the heat applied during installation inevitably leads to the epoxy of the DIRAX system being cured at the same time installation is completed (as a general rule, we always recommend the epoxy be applied at least one inch wider than the shrink sleeve so this can be double checked in the field). 

     As a result, after installation the DIRAX sleeve is ready to see action as soon as it cools to ambient temperatures.  It is acceptable to cool the sleeve with water if the contractor needs to move the pipe immediately.

How Long Do I Have to Wait Before Backfilling a Heat Shrinkable Sleeve?

Question:  How long after sleeve installation do I have to wait before I can backfill? 

Answer:  Assuming we are talking about WPCT, WPC100M, WPC120, TPS or any number of our other two layer heat shrinkable sleeve systems; the answer is simple.  You must wait until the sleeve has cooled to ambient temperatures.  If necessary, you can even quench the sleeve (after installation) with water to cool it faster.

That is one of the great things about shrink sleeves.  After it is installed and inspected, you don't have to worry about it anymore.  No chance of anything happening to it (unless someone drives their truck into the pipeline and their bumper scrapes a hole in the sleeve....which I have seen before!)

How Important Is Surface Preparation?

Question:  How important is surface preparation when installing a shrink sleeve?

Answer: It is VERY important!  The simple fact is that when considering the cleanliness of the bare steel field joint (and the adjacent factory applied coating), the cleaner it is; the better your bond will be (generally speaking).  When considering the strength of a bond between a coating of some type and a substrate of some type; we can illustrate this point simply using real world examples.

How well will a bumper sticker stick to this car?

     Imagine slapping a bumper sticker on this car.  How long do you think it would stay put?  My guess is that it would fall off just about the second your hand stopped holding it up!  In any bond scenario; a bond is only as strong as its weakest link.  In a case like this (pictured above) no matter what you put on the outside of the dirt; the weakest bond will always be the bond between the dirt and the car.  How strong it that bond?  So weak that you can destroy it with something as weak as a wet finger or a squirt gun.

     Another factor in determining surface preparation requirements is the specific adhesive type involved in the coating.  In general, an aggressive mastic will require minimal surface prep (though it will still need to be free of dust, dirt, grease, etc).  The higher performance the adhesive, the higher the required surface prep is likely to be.  

     Keep in mind when considering minimum surface preparation requirement, these are the cleanliness levels that have been determined to meet or exceed the data as reported on data sheets or manufacturing specifications. 

 

How Do I Coat a Long Length of Pipe or a Bend with a Shrink Sleeve

     It is fairly common that someone in the field needs to coat a length of pipe; or needs to coat an uncoated bend.  In such a case, we typically recommend that they lobster back the shrink sleeves down the length of the pipe.  This is a fairly simple application.  After the pipe has been cleaned (to whatever standard is required based on the sleeve material selected); the pipe is preheated (again; per manufacturers suggested installation methods) and then the first sleeve is installed; overlapping the existing factory applied coating by at least 3" (possibly 2" depending on end user specification).

     Next; the adjacent uncoated pipe is preheated; a new sleeve is wrapped (overlapping the previous sleeve by at least 3") and shrunk.  Shrink; preheat and repeat.  It's quite simple.  I've seen lengths of pipe as long as 600 feet coated in this manner and it was all done quickly and easily.  Sleeves are generally available in 11", 17", 24" and 34" widths and some combination of these can be used to coat most long radius bend and any length of uncoated pipe.

     Installation video:

Shrink Sleeve Overheating: What is the Effect?

Question:  My crews have overheated a shrink sleeve.  What do I do now?

Answer:  I wish the answer were a little simpler!  There are many different levels and degrees of overheating.  I will try to address three below.

    First of all; as seen here - a shrink sleeve is supplied with a cross hatch pattern in the backing.  As the sleeve is properly heated (the backing temperature must reach 267F in order for the cross linked PE to reach its crystalline melt point and revert back to its original size), those cross hatches disappear and are replaced by a smooth PE backing. 

    For the purposes of this discussion, I will limit the possible extent of overheating to three different groups:  surface crazing; crazing with smoke and/or flame; and splitting.

     Surface crazing can occur when an area of the shrink sleeve gets too hot.  This is most often caused by the installer failing to keep his torch continually moving in a circumferential motion.  Keep in mind, a propane torch might operate at several thousand degrees.  In order to shrink a shrink sleeve, we are trying to get the temperature of the backing up to 267F.  Installers MUST keep their torches moving!  In a case where a sleeve has cooled, and there is an area with light surface crazing (often accompanied by a dull area lacking in shine) this is not a problem.  Crazing does not effect the integrity of the sleeves (in fact some studies would actually indicate the crazing increases the fracture toughness of a polymer! That doesn't mean we recommend intentionally creating crazing in your shrink sleeve).  In a case where crazing has or is occurring; simply STOP heating that area and move on to the other sections of the shrink sleeve; always moving the torch in a circumferential motion. 

      Sometimes, this surface crazing can be accompanied by smoke or even flame.  The fact that the PE backing of our shrink sleeves have been cross linked means that the backing will no longer melt as a typical PE will.  The backing can still burn, however, and will burn if the installer is not continually keeping his torch moving.  In a case where a sleeve begins to smoke; the installer should simply stop heating that section of the sleeve!  In a case where a sleeve begins to flame; the installer should immediately put the fire out (this can be done by simply removing the torch and quickly patting the flame out with a gloved hand).  As long as this has been caught soon enough; again - this causes no serious damage to the shrink sleeve and no repair needs to take place.

     Finally, there are times that an installer seriously, seriously overheats a shrink sleeve.  I have seen hundreds of shrink sleeves installed and I've never actually seen this happen in person.  To actually burn completely through one of our shrink sleeves; an installer would have to be incredibly distracted by something; leaving his torch open full bore while concentrating the flame on a small portion of the sleeve.  Even then; the sleeve itself would give him many warnings as it crazed; smoked; caught fire; and ultimately burned through.  Once the backing has been compromised, it will be obvious as the mastic material will begin to flow freely through the backing and the backing will continue to split wide open.  This is the kind of thing that could not possibly escape the attention of even the most inexperienced inspector.  In a case like this; there would absolutely have to be repairs made.  Repairs are discussed in depth here.  

     One other thing I would mention.  Every wrap around shrink sleeve requires a closure strip to hold the sleeve in the shape of a tube during the installation process.  That is the closures only job; it has no corrosion prevention or sealing duties.  At times, particularly when it is dog eared; or slightly raised; the closure strip can flame up when overheated.  In such a case, the torch would simply be moved away; the installer would 'pat out' the flame (patting down the closure in the process) and then installation would resume.  This would not be a problem at all and would require no repair.  

     As always, we are available for consultation.  Any time someone might have a question about overheating; my first bit of advice would be to take some photos and email them right away to steve@jsicoatings.com - I will get back to you quickly. 

How Do I Repair A Damaged Shrink Sleeve or PE Line Coating?

Question:  How do I repair damage to a PE factory applied coating?

Answer:  We have several options; all are dependent upon the size and scope of the damage.  I will break it down as follows:

Pin Hole / Very Minor Damage

Perp Melt Stick in action, repairing minor damage

     For very minor damage, we offer what we call a Perp Melt Stick.  This is a stick of hot melt adhesive supplied in the form of a cylinder, 1" diameter by 12" long.  Using a propane torch, the melt stick is heated and the adhesive flows down to fill and cover the area of minor damage.  This is very similar to (but larger than) the commonly used FBE repair sticks that most people are familiar with.  This product is sold by the stick and is always in stock and ready to ship at Joint Specialists.

Minor to Moderate Damage

In the center of the pipe, we see the installed Perp patch.

     Perp, which stands for Poly Ethylene Repair Patch is a cross-linked, but not expanded product.  This means that it doesn't shrink.  Perp is sold as a roll of material and patches are cut in the field for specific sizes of damage.  As an example, if you have a 2" square damaged area; you would cut a piece of Perp at least 6" x 6" in order to have 2" of overlap on all sides for the proper seal to be made.

     In addition, Perp Filler is sold as a roll of mastic material and is used to rebuild the damaged area so that there is a flat surface to bond the Perp patch to.  This also helps avoid any entrapped air in the repair.

     For three layer repair requirements, a layer of S1301M epoxy primer can always be used as the initial coating (prior to applying Perp Filler and Perp Patch). 

Major Damage

      Lastly, for major damage, it is best to install a full encirclement shrink sleeve; chosen based upon the specific requirements of the pipeline (click HERE for more info).  In such a case, we are essentially treating the major damage as another field joint; coating, sealing and encapsulating the area with a shrink sleeve (after proper cleaning, etc of course).