Earlier today, I had a nice conversation with a potential customer who I've never spoken with before. He had a problem. He had an existing pipeline (not very old) and they had discovered that the "boot" they used to seal up the casing is now failing and they need to replace it with something. The original casing boot had been a stretchy, neoprene like material that was held in place by what were essentially clamps. The casing boot didn't last long and had experienced some drying, cracking and was no longer effectively sealing up the casing. Big problem right?
Why is it a big problem? Lots of reasons - here in Texas - all casing pipes have to be sealed with something. You absolutely do not want to shun the DOT requirements for anything pipeline related - it will hurt...badly. Casing pipe is put in place to protect the carrier pipe; kind of like an offensive lineman who's sole job it to protect the quarterback. There can be quite a lot of ground movement, vibration, soil stresses and other forces that are transferred to a pipeline that is operating underneath a road or highway. The casing pipe essentially takes the brunt of that by keeping the carrier pipe more or less suspended within it (forgive the incredibly simplistic explanation).
So as long as the casing pipe is intact, it is doing its job. But if that casing pipe corrodes away...the protection for the carrier goes away...and that is bad, bad, bad. If the casing pipe isn't properly sealed, it is very easy for water to get inside of it. This will literally destroy the casing pipe from the inside out until eventually, it crumbles. Water inside a casing pipe is a horrible, horrible recipe for corrosion. Once water has found its way in; more water is likely to find its way in. There will be plenty of oxygen to foster the corrosion, and the water can just sit on the steel, slowly chewing away at it.
It is actually the perfect application for our Caseal product. Caseal is a high expansion, fiber reinforced shrink sleeve with excellent sealing characteristics, penetration resistance and abrasion resistance. Caseals are tough. They wrap around the casing and shrink down to seal to the carrier. This is done with a propane torch.
In a case where the carrier pipe is an active pipeline, it makes it impossible to properly preheat the steel prior to installation, so we use the Covalence S1301M two part epoxy to act as the bonding agent between the casing seal and the carrier pipe. It works wonderfully.
Please, stop using those cold applied rubber boots to seal your casing pipe. They just don't last as along as a radiation crosslinked PE shrink sleeve (some of which have been in the ground 30+ years with no issue).
Had a recent correspondence with a gentleman abroad. He was having difficulty finding anyone locally who could answer his questions. Here was his situation: He was being encouraged to use shrink sleeves on a project, but he was concerned about some of the "potential issues" that might arise. As a result, he wanted me to address all of the above on a "what if" sort of basis. I told him that this was rather unusual, but I would be happy to give him honest answers and do my best to address his concerns.
In case you're new to this blog; here is my quick background. I've been with Joint Specialists for 14 years doing nothing but selling and supporting the heat shrink sleeve industry (Raychem/Tyco/Tyco Electronics/Berry/Covalence). In addition, I have had 14 years as student of one of the most knowledgeable shrink sleeve experts in the world - my father -Stan Simpson. Stan has been intimately involved with heat shrink dating back to the 1970's. He has served in R&D, tech service, sales and management for the last 40 years or so. He knows this product and market inside.
Please keep in mind, I'm responding to completely fictional installation issues here. These are not real problems. I'm having to answer very generically. If these were some kind of real issue, I'd be in my car or on a plane heading to a job site right now. If the job site was inaccessible to me (or if the material was not purchased from me) I'd be asking for photos so that I could determine exactly what was going on. Our products are proven. They've been installed successfully tens of thousands of times. I've never seen a true "failure" of our product. Installation errors? Occasionally. Incorrect product selection? Rarely, but yet. True failures? No.
It is always amazing what you can actually find when you get the chance to "see" a "failure" for yourself. The most memorable was a call that "the sleeves are falling right off the pipe." It made absolutely no sense, but it was a nice sized job, so there I was on a 4 hour flight to the coast. I felt like I was on CSI as I studied one of the sleeves that had "fallen off" the pipe....and right there visible to the naked eye were the knife marks and the plier marks where someone had pulled the shrink sleeve from the pipe using brute strength and a lot of sweat (quick side note - hey, thanks for the peel test...it was good to see that the shrink sleeve showed a cohesive failure, just like you'd like to see!). After the clear evidence of tampering was presented, we quickly learned that there was some kind of a union dispute occurring and as a result, the contractor was being barraged with phantom problems...but I digress.
So, how about those issues listed above? Here are my thoughts and experiences.
Shrink Sleeve Wrinkling
I've seen a lot of shrink sleeves installed and I've shrunk a lot of shrink sleeves. If I've seen any form of wrinkling at all it has been because of 2 things (or possibly 4 things, depending on how you break these down).
2. I have also occasionally seen minor wrinkling when a shrink sleeve is dramatically overheated. Sometimes this overheating can be caused by the use of a non-approved torch (say a welding torch, rose bud, or extremely high output torch in the hands of an inexperienced crew member).
The truth is that I have rarely seen sleeve wrinkling. It just doesn't happen very often.
Shrink Sleeve Air Entrapment
When installing a shrink sleeve there are a number of small things that are critically important. Addressing only those things that could possibly lead to air entrapment underneath the shrink sleeve...here are three:
1. For pipe sizes 12" and larger, we recommend two installers be working together - one on each side of the pipe - in order to shrink the sleeve together, working in tandem.
2. An installer working on a horizontal pipeline should always be moving his torch up and down while shrinking the sleeve circumferentially. An installer cannot have a shotgun blast approach to his shrinking - his movements need to be calculated and logical (common sense).
3. There are two options for sleeve shrink: start in the middle then shrink your way (up and down) to one side - then back to the middle and out to the other side.....or.....starting shrinking on one end and shrink with the wind; up and down; all the way across the sleeve. This way any air is pushed out ahead of you.
Picture this for a moment (I've never seen this). Picture an installer who wraps the shrink sleeve loosely around the pipe leaving a 'two finger' bag in the bottom (this would be an old-school install technique that is still alive in some corners of the world). Now picture the installer shrinking one edge of the sleeve. Then the installer comes back and shrinks just the other edge of the sleeve. He will have created a ziplock bag! It wouldn't make any sense and I've never seen it done.
Now, even with the best installers and the best intentions, it is possible that a small air pocket get trapped under the sleeve. Have no fear! That is what the silicone roller is for that you've purchased for your crew. While the sleeve is hot; that air pocket can be carefully pushed to the side and spit out the edge of the sleeve. If you were to see an air pocket later after the sleeve has cooled; no problem - get your torch and reheat the sleeve in that area and use the roller to push the air out.
2. A sleeve was being installed on a VERY dusty PE coated line. As the adhesive was pushed out a bit due to the force of the sleeve shrinking; the adhesive was coming into contact with the dusty, dirty PE surface. Of course, nothing will bond through a thick layer of dirt - so it is impossible for the adhesive to bond to the substrate. Picture putting a bumper sticker on your incredibly dirty car! It won't stick -- but it isn't the bumper stickers fault; it is the fault of the dirt.
Shrink Sleeve Tenting
The only time I've seen this; I absolutely knew it was going to happen (it was expected). I've never seen this happen "by accident." Shrink sleeves are designed to shrink tightly to 'rounded' surfaces. Rounded is in quotes because it is a bit of a misnomer. A shrink sleeve will work great on a square, a rectangle, a circle, an oval, a triangle and a myriad of other shapes.
But picture a circle with a 'pie piece' cut out (so it looks like pac-man). What will happen if you install a shrink sleeve on that circle? It will bridge pac-man's mouth. It will not flow and fill down into the mouth. Similarly, take a large square and place it on a circle. Shrink around that whole contraption and the sleeve will bridge from the top of the square out to the edge of the circle.
In other words, the only upsets that a shrink sleeve can truly fill and seal to are upsets whose dimension is at or less than the thickness of the adhesive layer of the shrink sleeve. That is why when you consider (on a micro level) the 'upset' of the weld bead - or the 'upset- of the step down from factory applied coating to bare steel of the girth weld - those are filled very nicely.
So when someone talks about tenting, the first place I am looking is to see what is under that shrink sleeve that is causing this tenting phenomenon. Rest assured - it is something. Is the weld bead profile too high? Weld spatter leave a 'tent pole' so to speak? Is there a very thick factory applied coating that was not bevelled? Was the first part of the shrink sleeve set on the pipe folded over to cause an abnormality? Did someone leave a hunk of duct tape or a weld rod in there? I've never seen any of these happen; but as we all know - anything is possible on a pipeline spread!
Shrink Sleeve Bubbles
Well, I left this one for last because I've never heard of it! I hate to close this article without an answer for every question, but I just don't know what someone might mean by 'bubbles'. If you'd like to explain - please drop me a note at steve@jsicoatings.com - or better yet - send me a photo!
You may remember that I wrote a little about Raychem's transcendent success on the Great Alaskan Pipeline previously. There I talk about the tremendous impact that Raychem had on that pipeline - and on the tremendous impact that pipeline had on Raychem...launching it to Fortune 500 status (in time).
We have recently been compiling and sorting through the assorted pieces of Raychem history that we have here at our facility. With a relationship with Raychem dating back to the 1970's, there really is quite a bit! Not quite enough for a full museum, but definitely more than enough for a few interesting displays.
One bit of history that has been removed from mothballs is the actual outfit, purchased by Stan Simpson in the 1970's directly from the Ayeska store. At that time, this coat alone cost more than $600.00! According to www.dollartimes.com, $600.00 in 1973 is the equivalent to $3290.00 in 2014! Some of that is inflation, some of that is the insulation quality of the coat; some of it is the Disneyland type prices they were probably charging that group of captive, freezing cold workers!
So, without further ado: the coat and pants worn during installation of product on the Great Trans Alaskan Pipeline. It is really too small to see; but over the left shoulder of the coat you can see a photo of both Stan and Sam Damico on the job site wielding their torches!
Cold weather coat and pants worn in sub-freezing temps on a pipeline spread in Alaska
Heat Shrink Sleeve Short Course for Pipeline Inspectors Mastic Shrink Sleeves
I've been asked to put together a short course in heat shrink sleeve inspection and make it available on line here for no cost. I'm happy to do that! Following, I will give you a brief overview of what you should be looking for when inspecting Covalence shrink sleeve installations on a pipeline spread. Please note: some tips here might also be useful if you are working with a shrink sleeve manufacturer other than Covalence - but you should really be speaking with their manufacturer's representatives because there may be significant differences.
Here, I will try to give a step by step overview and include answers (links) to common questions that might arise. Keep in mind, we have a number of different material types, not all of them will be covered here. I will attempt to get short courses written for our other products as time allows in the weeks ahead.
Products covered in this Mastic Shrink Sleeves short course are
WPCT, TPS, WPC65M and WPC100M
So, without further ado:
presents....
Proper Inspection Checklist
for overseeing installation of WPCT, TPS, WPC100M and WPC65M heat shrink sleeves installed on girth welds of pipelines
Included in this short course:
I. Before a sleeve is even removed from the box
II. Surface Preparation
III. Pipe Preheat
IV. Sleeve Install
V. Post Install Inspection
Section I: Before a sleeve is even removed from the box
Sleeve Selection - many times, shrink sleeves are purchased without being properly researched. As you might imagine, this can causes tremendous problems months, years and decades down the line. Like any coating or product ever made - using a shrink sleeve on an application for which it was not designed will absolutely lead to problems. It must be avoided at all costs!
When you look at the box which houses your shrink sleeve, you should see a label that tells you the contents of the box. This label will give you the basic information with which to determine if the shrink sleeves in that box are compatible with the conditions of your pipeline. The first thing to do is to double check that the right shrink sleeves have been purchased (you may be laughing or you may be crying...but trust me - this is important).
If the sleeves have come from us, you will see something like this in front of you:
So you are definitely starting way ahead of the game. You've got my phone number right there. Don't hesitate to call. In the upper right hand corner, you've got a description of what is inside of this box: 30 each WPCT 8625-11/UNI. The first letters (sometimes numbers are included there as well; but not in this short course) indicate the material type and sleeve configuration.
WPCT - Covalence's Wraparound Pipe Coating with Thermal Indicator (WPCT) is designed to be used on buried or subsea pipelines where the operating temperature will not exceed 108F. If you've got WPCT and a HOT line - call me. If anything else seems inconsistent - call me. If you have a question - call me. Get it? We have a fool proof method here. If you are unsure about something - call me.
TPS - Covalences Tubular Pipe Sleeve (TPS) is essentially identical to WPCT but supplied in the form (shape) of a tube; so it must be slipped on to the pipe before the weld has been made. It is also approved for use on pipelines operating at up to 108F; when the line is going to be buried or subsea.
WPC65M - A wrap around shrink sleeve rated for use on pipelines operating at up to 65C (149F). Can be buried or subsea.
WPC100M - A wrap around shrink sleeve rated for use on pipelines operating at up to 80C (176F) or 100C (212F) when used offshore.
Next we will look at the first set of numbers. In this case: 8625. These numbers indicate the outside diameter of the pipe for which these shrink sleeves were designed in mils. So 8625 is what would normally be called "an 8" pipe." 12750 would indicate a 12" pipe (since the true OD of a 12" pipe is 12.75").
Next we see the 11 in the nomenclature above. This indicates the width of the shrink sleeve that is in the box. Standards would be 11", 17", 24" and 34". This is IMPORTANT! Please stop for a moment and read this article explaining "How Wide of a Shrink Sleeve do I Need?"
Finally, you see the /UNI. This means that the closure strip is pre-attached to the shrink sleeve here in our shop. This makes life in the field much simpler; reduces field problems and avoids a dozen or more potential problems with contamination, loss and installation difficulty. There is no extra cost for getting a /UNI sleeve - and the benefits are nearly limitless...so if you're not getting /UNI sleeves; you are honestly making a large mistake.
This is a /UNI Sleeve - the closure is attached to the sleeve material
So, by this point you have confirmed that the shrink sleeves you have on site are:
- the proper material type based on application and operating temperature
- the proper size based on pipe OD
- the proper width based on End User Specification and factory applied coating cut backs
- and - you've called me if you have any questions.
Now you are cleared to open the box (wow, it really took a long time to get here!). Open the box and right inside you should see an installation guideline for this very product. No, don't crumple it up and throw it down in the ditch (yes, that is where most wind up!). Read it!!! You hold in your hand the keys to properly installing this product. Treasure it. Caress it. Love it.
Section II: Surface Preparation
Proper surface preparation is one of the most important factors in determining bond strengths. Just like almost everything else in life; the simple truth is: The cleaner the surface; the better the bond. In the case of all four of these products, the installation guideline says "Clean exposed steel and adjacent pipe coating to be covered by this shrink sleeve with a hand or power wire brush, to remove loose and foreign materials. Wiping may be necessary to remove particles."
Sounds simple doesn't it? I wish it were as simple as it sounds. If you're dealing with pipe that has been fairly recently delivered from the coating plant, you very likely have pipe that is VERY clean with some minimal amount of surface rust on it that was gathered during transit. That pipe will very easily clean up nicely.
Please be aware: Many end users require that field joints be grit blasted prior to coating. They do not care that the manufacturer of this product (Covalence) allows a wire brush. They want the joints grit blasting because they understand that the cleaner the surface; the better the bond. They are willing to spend a little more money in labor and time in order to install they coating the best way they know how. That is a good thing. Remember: when in doubt: the field joint coating specification always wins.
Section III: Pipeline Preheat
Preheating the bare steel and adjacent factory applied coating is the next ESSENTIAL step of the installation process. In many ways, the key to a good bond lies not only in the surface preparation - but also in the bond line temperature. The bond line temperature is that place where the mastic sealant of the shrink sleeve meets the steel/factory applied coating of the pipe. Reach the proper bond line temperature (assuming the surface prep was done) and you'll have a great bond. Fail to reach the bond line temperature and you might not achieve a great bond. There is no reason to risk it -- make sure that proper preheat is being performed.
How can you determine that proper preheat temperatures are being reached if neither you or the crew have a means with which to check the temperature?? Obviously, you can't. Do you trust the welder when he says the weld is good? No - you x-ray the weld. Do you trust the trucking company that they've delivered all of your pipe? NO - you sign for each and every shipment so that you know with 100% certainty that all of your pipe has been delivered. Why would you trust a shrink sleeve installer to gauge (using nothing more than his intuition) whether or not the 12" schedule 40 pipe he is heating with the propane torch has achieved a uniform 212F temperature at every circumferential pipe point (12 o'clock, 9 o'clock, 6 o'clock and 3 o'clock) AND that he has properly heated the adjacent factory applied coating?? That would be INSANE wouldn't it? Yes it would, but it happens every single day.
A digital pyrometer
You must have a means with which to check pipeline preheat temperatures. Digital pyrometers are inexpensive. Contact pyrometers can be a little bit more costly; but are also more accurate and they can last (if cared for) for years. Imagine that you're responsible for cooking the turkey at Thanksgiving. If the thermometer on your oven were broken, would you be satisfied to stick your hand in there and say "ya, this feels like about 350F"? Of course not! Your Thanksgiving dinner would almost certainly turn out badly. You would be embarrassed. Your family might disown you. You'd end up living on the streets talking to yourself about the fact that in 2014 there was a "incident" with a turkey that has ruined your life. Well, when talking about the corrosion coating on a multi-million dollar pipeline, we should care about the pre-heat temperature on each and every joint just as much as we care about our Thanksgiving turkey.
As for specific preheat temperatures for the bare steel and adjacent factory applied coating, they are as follows:
Section IV: Sleeve Install
So you've gone through the other steps; the pipe is cleaned properly...and the pipe has been preheated properly. First we should take a quick step back. What tools do you need in order to properly install the sleeve?
- Means of temperature measurement - we covered this above
- A propane torch; preferably with an adjustable flame, regulator, pilot light and long hose (like the JS-2601 Torch Kit seen here). This is critical. I've seen people try to use rosebuds; welding torches and torches that run purely off bottle pressure. Those don't work well and will likely destroy the coating.
- A Silicone Roller (as seen in this photo series of shrink sleeve installation tools).
Have those? Great. Your pipe is clean. Your pipe is hot. Remove a shrink sleeve from the box (unless you are installing TPS in which case you slid it onto the pipe before the weld was even made). Remove the white release paper, exposing the aggressive, black, sticky mastic (you might think it is silly to mention this -- I assure you it is not).
Center the sleeve around the weld and place the non-closure side down on the pipe first. Right now, you should be double checking that your shrink sleeves are wide enough. They should cover all bare steel and overlap onto the adjacent pipe coating by at least 2" per side (more if the end user requires it).
Wrap the sleeve around the pipe - and make sure it OVERLAPS BACK ONTO ITSELF by at least a couple of inches. DO NOT butt the sleeve ends up against each other. To be clear, you will have a small section where the shrink sleeve is now doubly thick (or more considering the closure strip will be there as well). To say it another way: wrap the shrink sleeve snugly around the pipe and it should be properly set up (no tension needed).
The next step is to secure the closure strip. Using the torch on low (but bushy/yellow flame) heat, apply heat to the closure strip and pat it down with a gloved hand. As the closure is properly heated - you will see a cross hatch pattern appear in the closure. That is the fiber reinforcement showing through (this is a good thing). Pat / press / push / smooth down the closure with your gloved hand while the closure is hot. Continue heating as needed. Keep in mind, if you were to get a small wrinkle or a small bubble in the closure as it is smoothing down - that can be fixed. If it can't be fixed, please keep in mind; the sole purpose of the closure is to hold the tube in the shape of a tube during the heat shrink process. The closure itself serves no actual "coating" responsibility.
Now your closure is fully secured and you are ready to shrink. There are a couple of schools of thought on what is the best method for shrinking the sleeve. Here they are:
1. The way I like best. Make sure your torch is set to have a broad, bushy, yellow flame. Begin shrinking the sleeve right in the middle; over the weld in an up and down motion moving circumferentially around the pipe (if you're my age - picture the Karate Kid learning to paint the fence). If the pipe is larger than 12", we recommend an installer on each side of the pipeline; working together in unison; each keeping their torch always moving; always up and down. Do not forget the bottom of the pipe - that is a critical area that is often overlooked.
Once the middle of the sleeve is shrunk properly, you will see a bit of a bowtie effect. In addition, you will have now seen one of the features that makes Covalence shrink sleeves the best in the world; you have now witnessed the permanent change indicator in action!
Permanent Change Indicator
The left side of the picture (cross hatch pattern) shows the sleeve backing as supplied. The right hand side has been shrunk properly and is now smooth. Simple, easy, wonderful.
Continue moving the torch up and down circumferentially around the pipe from the middle, out toward one edge. Complete that - then back to the middle and out to the other end.
Or
2. Begin shrinking on one end of the sleeve, shrinking in such a way that your flame is going "with the wind". Keep your torch always moving as described above; slowly working your way from one end of the sleeve to the other. You will be finished when the sleeve backing has all faded to black.
In both of those cases; upon completion of the shrink; reheat the entire surface of the shrink sleeve. At this point; you will have visually seen that there are no air pockets trapped beneath the surface of the sleeve and you are just reheating to make sure you are getting full and complete mastic flow and getting the sleeve into full recovery mode; exerting pressure on the flowing adhesive and forcing it to fill all areas underneath the shrink sleeve. Finally - roll the overlap area and the closure area (and anywhere else you'd like to roll) with the silicone roller. This absolutely ensures proper mastic flow at the overlap area.
Section V: Sleeve Inspection
What do you look for immediately after installation to know if the shrink sleeve was installed properly?
1. The sleeve should be fully conformed to the pipe surface. You should be able to see the profile of the weld bead - and the step down area from the factory applied coating to the bare steel.
2. You can tough the sleeve with a gloved hand to ensure you've had mastic flow (do so without intentionally displacing large amounts of mastic or disfiguring the sleeve.
3. You should see adhesive flow on both edges of the shrink sleeve (which will be over the factory applied coating). There should be a clear line of adhesive there which indicates that the adhesive flowed, filled and was pushed out by the shrink force of the sleeve.
4. Visually inspect to be certain that there are no cold spots and that all of the cross hatch pattern has disappeared.
Congratulations! If you have questions about any of those sections; please call me. In the mean time, any questions might be answered by watching these short installation videos:
WPCT Installation Video
WPC100M
TPS Installation Video
If you are interested in earning a certificate for having spent some time going through this short course; please contact me for an open book evaluation of what you've learned here. Answer the questions correctly and I will gladly bestow upon you a Certificate of Completion - Covalence Mastic Shrink Sleeve Short Course.
I was asked this question on Friday (and honestly have probably heard it once or twice a year for the last 14 years). Like most questions that I write about here (and like most questions that I am asked, to be honest), the answer is never quite as simple as it seems...so, will heat shrink sleeves bond to concrete?
The sample answer is: some will. Many of our shrink sleeve material types that utilize a mastic sealant are designed to be very, very aggressive. It is only with this aggressive mastic material that our shrink sleeves are able to bond to a wide variety of commonly applied factory pipeline coatings (including FBE, CTE, PE, TLPE, PP, etc). These aggressive mastics have been proven effective time and time again over the years.
So why is this question complicated? They either stick...or they don't! They either stay in place, or they don't! Why does everything have to be so complicated?
First we have to back up. More important than "will it stick" is "will it do what I want it to do." Believe it or not - those are dramatically different questions. Here are some of the reasons why I need to know what you want to do with it:
- Potential Problem #1 - as you probably already know (if you're working with, selling, or specifying for concrete pipe) is that concrete is porous. You don't have to look very far beyond your own driveway during a rain storm to see that. If I slap a shrink sleeve onto one section of a concrete pipe; it will do almost nothing. The first time that pipe gets wet; the area underneath the shrink sleeve will be wet as well! (not the bond line so much as the inner pipe). So in terms of actually creating a seal of some kinds - very difficult on concrete.
- Potential Problem #2 - As has been discussed here before, a bond is only as strong as its weakest link. Slap a shrink sleeve on the outside of a concrete pipe and you've created a very strong bond between the aggressive mastic of the shrink sleeve and the outermost surface of the concrete. But, how strong is that concrete? Over time, it is possible that the outermost layer of the concrete becomes brittle, gets damaged or cracked, is eroded by a water source of some kind (beyond the shrink sleeve), etc. The bond between the shrink sleeve and the concrete is only as strong as the concretes bond with itself on the outermost microns of the pipe. How strong is that bond? I'm afraid I couldn't hazard a guess - you'd need to talk to the pipe manufacturer.
That is why we need to know precisely what it is you are wanting our shrink sleeves to do. There are dozens of possible applications here, so please give me a call so we can discuss your specific project!
I had this question today and it really was a great, great example of how sometimes in this world of pipeline coating....what seems perfectly logical actually turns out to be exactly wrong. The question is: when working with HTLP60 or HTLP80, what preheat temperature should I be achieving specifically at the overlap area (the area where the shrink sleeve wraps around onto itself)?
The more I've thought about it - WHAT A GREAT QUESTION! This is the type of question that a person who is really THINKING asks! Why is it great?
Well, the overlap area of a shrink sleeve (where it overlaps itself) is a complicated part of the coating. For starters, you've got an area there that is doubly thick. In addition, you've got the closure strip that; while thin; does block/absorb temperature from the torch. Finally, that area where the sleeve is doubly thick is also the area where the sleeve goes from 2 layers to 1 layer - there is a natural step down (small - and the sleeve adhesive fills that area thanks to the shrink force of the backing....but I digress). That is a pretty critical area as you absolutely do not want that step down to become some kind of leak path (which is one of the main reasons that you should be using a silicone roller to roll the overlap area of every single shrink sleeve that you install!).
So, this man's thinking process must be: double thick shrink sleeve...closure strip...step down area....I know! I will give extra preheat to that area and that will insure that my bond line temperature is properly achieved and then I will be able to sleep comfortably at night knowing that I installed that shrink sleeve as well as a shrink sleeve has ever been applied, and as a result - that sleeve will be a fantastic coating for one hundred years!
Makes perfect sense on every level right? Yes....except it is wrong.
Look back at the first paragraph. This man is using HTLP60 or HTLP80. That is the Covalence three layer field joint coating. The first of those three layers is a two part epoxy. Covalence (formerly Raychem) specially formulated their epoxies and their adhesives to bond both physically and chemically as the epoxy cures and the adhesive cools. In order for that to happen, the sleeve must be installed over the still wet (not cured) epoxy layer. See the problem yet?
Epoxy cure time is directly related to temperature (and other factors, but ambient temperature has a tremendous impact on cure time). If you put the S1301M Epoxy (one of the Covalence epoxies) onto a pipe operating at 50F, it will cure very slowly (likely take hours). If you put it on a pipe that is 140 degrees F it will cure MUCH faster, but still give you time to shrink the sleeve in place. If you put it on a pipe that is 220 degrees F the epoxy will likely 'flash cure'. Flash cure - as in essentially cure instantly. Why is that a problem?
If the epoxy flash cures - then you will be installing your HTLP60 shrink sleeve on top of cured epoxy. If you are installing on cured epoxy; the coating system will not achieve the chemical bond it was supposed to get (and whether it gets the proper physical bond or not is open to debate). So, by OVER heating the overlap area (thinking that would improve our coating); we've actually drastically reduced our coatings performance.
It seemed like we were doing something smart and good and productive....but we weren't. So, was I right? Was that a great question or what??
Every box of Covalence shrink sleeves should include an instruction sheet to guide you step by step through the application process. Please, please, please - follow it.
I received a comment from yesterdays post (do epoxies bond well to PE) and I realized that I'd failed to address one very important aspect of that discussion. Here was the message I received:
"If epoxies don't bond well to polyethylenes, how do you properly coat field joints on
three layer PE coated pipelines??"
Oops! In my mind, yesterday's article was all about stand alone epoxies being used with PE coated lines (in my mind, I was picturing epoxy with a two layer PE; or with a solid film PE backed tape).
Thank you my friend for asking this question! When coating the girth weld of pipe with a plant applied three layer coating -- of course you are going to utilize an epoxy as the primary corrosion protection on that field joint. Anytime an end user has spent the money to put a high performance coating like TLPE on their pipeline; it makes absolutely sense to recreate a similar three layer PE coating on the field joints (a la` HTLP60 and HTLP80). So please understand, there is a difference here between an epoxy being used as one component of a three layer system; and an epoxy being used as a stand along coating where it is expected to bond/seal to a polyethylene directly.
In many cases, on three layer PE coated pipe, there are two cutbacks to consider (three if this is an offshore pipeline as there will likely be a concrete cutback as well); the FBE cutback and the PE cutback. In many cases, the TLPE line will have a "toe" of FBE sticking out. This is perfect as liquid epoxies generally bond quite well to FBE. This also allows the field joint to be coated bonding epoxy to epoxy; shrink sleeve adhesive to PE and shrink sleeve adhesive to epoxy. All proven; all reliable, all cohesively bonded.
Please note - nothing I've written here says that epoxies will bond to PE. So please be aware that there is a world of difference between the two scenarios presented here in the last 24 hours.
This question comes up an awful lot...and I'm always surprised. Much like the mythical white whale, there is plenty of heresay, plenty of speculation and plenty of anecdotal "evidence" on all sides of the issue. Will epoxies bond to polyethylenes in a fashion that will be sufficient for coating buried steel pipelines? Let me cut to the chase and possibly save you some time here: in my opinion: NO. Don't do it. Find another solution. Don't risk it. There are other better options out there, use one of them.
Was that clear enough? Now, there are all kinds of stories out there. Somebody was told that Manufacturer A says their epoxy gets a great bond with PE. Strangely, I don't see that listed on any data sheets anywhere and I don't see it in writing anywhere.
Other stories are "Yes, Manufacturer B has an epoxy developed specifically for bonding to PE" - again, I don't see any actual evidence of this.
I'm not going to name names, but there was a case of a manufacturer assuring an end user that their epoxy would bond well to a PE coated pipe. The job was somewhere in Europe - and for all I know, the outcome is still being determined by the courts. It was a big problem though....a big, big problem.
So let's just look at this from a practical point of view. When coating a field joint, you have a few critical, critical areas (I would argue that it is ALL important - but some areas are clearly more crucial).
- How the coating coats and bonds with the weld is critical.
- How the coating fills, flexes and interacts at the junction with the factory applied coating is critical.
- How the coating bonds to the adjacent factory applied coating is critical.
Of course this list could be almost infinite - how does it react to soil stress? CD? Peel (I happen to believe Peel is kind of a useless property...but I'll leave that for another article)? Electrical resistivity (believe it or not, electrical resistivity is actually a GOOD thing to have in a coating...don't believe the hype), Shear, Penetration resistance, Shore D Hardness, Hot water immersion, UV resistance, etc, etc, etc.
When considering this specific question (epoxies and PE), I'm really going to focus only on the middle one up there. How does the epoxy (generally talking about 2 part epoxies here) fill, flex and interact at the junction between the field joint coating (epoxy) and the factory applied coating (PE in this case).
In the shrink sleeve world, one of our goals when coating a field joint is to create a SEAL. To create this seal, we install a shrink sleeve wide enough to coat all bare steel and overlap onto the adjacent factory applied coating. This creates a seal on that factory applied coating...at least 3" away from the section of pipe that was not factory coated. This essentially 'moves' the critical 'seal' location a few inches (or more) away from the field joint.
In a case where a stand alone epoxy is installed on a field joint coating, that critical interface is right there at the edge of the field joint. That critical area is directly on top of bare steel (in many cases). That interface isn't really even protected. Why? Well you've got two different material types with dramatically different qualities and characteristics meeting right there over your steel. It would be like meeting a blind date at your house. No one does that! You meet somewhere else - you meet on neutral ground - you meet at a restaurant or a bar. That way if things are going well - if the two of you don't mesh...you can quietly sneak out the back and disappear back into anonymity (not that I've ever done that!).
In addition, you've got two different material types with different bending and flexing characteristics. That isn't going to work very well. When a hard material is up against a more flexible material...what happens? The hard material will tend to crack over time as any kind of movement occurs. That isn't good!
