Three Layer Field Joint Coating

TLPE Field Joints

     Worldwide, two and three layer polyethylene factory applied coatings are very common.  In the USA, the decision is generally made to use only one layer PE coatings (FBE).  This is a little bit ironic because a normal TLPE factory applied coating is going to use FBE as the primary corrosion coating, then add a layer of an adhesive and then an outer layer of a PE to improve many technical aspects of that coating.  So in a sense, the USA is often using FBE only as a coating, while other parts of the world use FBE + +.   Whatever is decided though, it is always necessary to be aware of the critical nature of the field joints on a pipeline project.  Field conditions are not factory conditions; there is a lot that can go wrong there.  When considering a three layer field joint coating for a field joint (whether that will be used with TLPE factory applied coating or simple FBE coating), HTLP60 is an ideal product for field joint protection of oil and gas pipelines.

Installed HTLP60 shrink sleeve

           So how does this go in the field?  What is the installation like? 

1. Pipe of course has to be clean.  Any coating is only as strong as its weakest bond; the bond of mud to steel is not a strong one...
2. Preheat the steel and adjacent line coating.  The goal here is to get all of it to something in the 140-160F range.  Read this article about our S1301M to find out why this is important.
3. Mix and apply the S1301M Epoxy.  What is included the S1301M Primer 15 Kit?  A can, B can, mix stick, gloves, applicator pad.
4. Wrap the sleeve around the still wet epoxy.  No force curing here. 
5. Secure the closure strip.  The closure forms the sleeve into the shape of a tube during the shrink process.
6. Shrink the HTLP60 sleeve, using a broad, bushy flamed torch.  You want to shrink circumferentially, around the pipe (two installers for 12" pipe and larger).  
7. Check for signs of proper install:  no cold spots or dimples; weld profile and factory coating step down visible; adhesive flow at both edges.

     There you have it, fairly simple and a truly superior coating when compared to most of the other options out there.  

Epoxies and PE (Part 2)

Do Epoxies Bond Well to PE?

     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.

HTLP60 vs HTLP80 - What is the Difference?

HTLP60 vs HTLP80

     I get a lot of technical questions emailed to me via this blog...and via our website (www.heatshrinksleeves.com).  These questions come from all over the world. Here is a recent questions I've received from India:

Sir,
What is the difference between HTLP60 and HTLP80?  I am writing the specification for a 6" pipeline and I need to know which product you would recommend and why.

     Obviously, not a lot of information there!  Now, I know that if this project will never become an order for me.  I don't sell material into India and to the best of my knowledge (somewhat limited); Covalence has excellent coverage in terms of sales effort and distribution in India.  But, I am still thrilled that I get to be a part of the process here by sharing my product knowledge and information.  Our business is shrink sleeves.  I've been selling and studying nothing shrink sleeves for 13 years.  My father has been selling and studying shrink sleeves for 30+ years.  In a sense, I've been around "shrink sleeves" either as a profession...or as a witness to household discussions...or tagging along with my Dad to a job site when a vacation was disrupted...or working in production (cutting, bonding and processing shrink sleeves) as a high school student - for almost my entire life (my Dad went to work for Raychem when I was ~4 years old and I'm 42 now).

     When you're sharing knowledge about a product that you believe in; it is fun.  When you're helping to answer a simple question that someone has been trying to track down an answer to for weeks (which happens a lot - phone calls unanswered - referrals to disconnected phone numbers - referrals to people with no product knowledge - etc - etc) - the relief in their voice when they can finally get the answer to a simple technical question is very rewarding.  It is nice to be needed!

     In any case, all of that to say:  I'm thrilled when I get to answer technical questions and offer technical assistance - even when there is no chance of me personally getting any business.  I believe in this Covalence product line (formerly Raychem).

     So here is my answer to the question "what is the difference between HTLP60 and HTLP80?":

Dear Sir,
Thank you for the inquiry.  The basic difference between HTLP60 and HTLP80 is very simple:
HTLP60 utilizes an adhesive that is designed to withstand a continuous pipeline operating temperature of 60C or below.
HTLP80 utilizes an adhesive that is designed to withstand a continuous pipeline operating temperature of 80C or below.

Both are components of a three layer field joint coating system that utilizes a two part epoxy as one of the components of the system.  It is important that the epoxy used be a Covalence(formerly Raychem) epoxy that has been specifically designed to work in conjunction with the HTLP adhesives (generally the S1301M epoxy can be used with either as it is rated to 80C -- the S1239 can be used only with the HTLP60 as it is rated only to 60C).

There are some (what I would consider fairly minor) technical differences in the product performance as can be seen at our website (www.heatshrinksleeves.com).  Both products have a long successful use history.  Both products are proven. 

I'm happy to help you determine the specific part number that I would recommend for this project - but I would need to know:

- pipeline operating temperature once it is in service (design temp)

- what is the factory applied mainline coating?

- what are the cutbacks on the mainline coating?

- will this be a buried line?

- what is the quantity of field joints that will be needed? (important as some products have a minimum order quantity)

If you can answer some of those questions - I am happy to continue the dialogue!