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:
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|
- 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.
|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:
WPCT - minimum 140F
TPS - minimum 140F
WPC65M - minimum 160F
WPC100M - minimum 212F
Is it possible to preheat TOO MUCH? Yes. What is the Maximum Preheat Temperature at which I can approve an installation?
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.
|Permanent Change Indicator|
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.
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
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.