Field Joint Coating Specification Assistance
So, you've been tasked with assisting in the writing of a field joint coating specification and maybe you're not sure where you should start. Have no fear, I can be of assistance. Any major project (and most smaller projects) will require a field joint coating specification. This is essentially the guideline that the contractor will use to determine what he is able, required or encouraged to use. Sometimes the field joint coating specification will be very broad, allowing just about any technology to be used. Other times, a field joint coating specification calls for a single product, made by a single manufacturer, in a specific size, width and temperature rating. As they say, different strokes for different folks. What are you leaning toward at the moment?
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| An example of the cover page of a specification. I probably see fifty or more per year. |
Pipeline Design Temperature: When selecting an external pipeline coating (no matter the technology) it is critical to know the pipeline design temperature. This is the temperature at which the pipeline is expected to operate. As you would imagine, take a few miles of steel and run something through it that is hot enough to boil water. What will happen? Well the pipeline itself (including the exterior coating) is going to get pretty stinking hot. What if you run something cold in through it? The pipeline will very likely be cold. You will want to be certain you are selecting / specifying a coating that is designed to behave properly when your pipeline is in service. As a further example, a shrink sleeve designed to be used on a pipeline operating at 100F will be very soft if installed on a pipeline operating at 250F. It would be a rookie mistake to select a coating without knowing the operating design temperature of the pipeline.
Factory Applied Coating: In the world today, there are a number of widely used and accepted factory applied pipeline coatings. In the United States, fusion bond epoxy is by far the most commonly used. In other parts of the world multi layer polyethylenes and polypropylenes are the dominant coatings up choice. Why does this matter when selecting a field joint coating? Because not all field joint coating technologies are compatible with all factory applied coating materials. As a few examples: generally two part epoxies are not compatible with polyethylenes or polypropylenes. Shrink sleeves which use a hot melt adhesive as the sealant are generally not compatible with polypropylenes. You can search the internet and quickly find stories related to lawsuits in which the wrong coating technology was selected and installed on a pipeline where it shouldn't have been...and shortly thereafter, chaos ensued as field joint after field joint coating failed.
Knowing the factory applied coating is also important because it generally gives us a very good idea what your cutbacks will be. Knowing the cutbacks is important because that way we will know how much bare steel you will have at the girth weld. This is important because it helps us determine how wide of a field joint coating you are going to require. All field joint coatings must overlap onto adjacent factory applied coatings by at least two inches per side.
Pipeline Conditions: I could probably write pages and pages about just this bullet point, so I will try to be brief. Special pipeline conditions generally require a special pipeline coating. Is a section of your pipeline going to be involved in a road bore or directional drill (including a bundled road bore)? Then you need to use a special product there (DIRAX). Is your pipeline going to be travelling through some particularly harsh soil conditions? Heavy wet/dry cycles? Heavy, sticky clay? Salt water flats? J-Lay offshore? S-Lay offshore? Above ground sections? Conditions that require high shear? Construction conditions that require a special fast install, small right of way, etc? All of those can matter. All of those are potential pitfalls if you haven't selected the proper pipeline coating for your field joints.
Technical Requirements: I've been doing this 14 years. Our company has been in business for for 19 years. Before that, our owner was a direct Raychem employee for more than 20 years. I share all of that, only to demonstrate that our experience with the pipeline coatings world dates back to the mid 1970's. Just about 40 years. In that time, one of the only things I've seen that is consistent....is that (looking at them as a whole) engineers are very inconsistent. One engineer might hold the opinion that cathodic disbondment testing results are the single most critical data point when analyzing a field joint coating. Another believes that peel strength is the single most important piece of information when selecting a field joint coating. Still another believes that cost is the single most important factor. Another thinks penetration resistance. Another thinks shear is the most important. Another thinks water vapor transmission, another electrical resistivity, another shrink force, another elongation, another thickness, another shore D.....do you get the picture? We have seen it all. To quote Forest Gump: Engineers are like a box of chocolates...... - you probably know the rest.
Availability: I know it sounds kind of silly, but this one is more important than you might think. We have seen dozens and dozens of times that the field joint coating is very often the red headed stepchild of a pipeline project. In order to build a pipeline, you've got to assemble hundreds of people and probably close to a thousand different materials before the job has even begun! What very often happens is that the pipeline project is underway, the pipe is being welded up and someone looks around and says "We forgot to order the field joint coating!!" I know it sounds silly, but it happens all the time. In those cases, we often run into big, big problems when a specification that is in place calls for a product that is literally never sold....and as a result - it is never in stock and available anywhere. No, not anywhere in the entire world. In those cases, I can hear the panic in someone's response when I tell them "current lead time on that product is 6-8 weeks." They say "you don't understand! I have pipe strung up already!!" At that point, our only option is to quickly work through the process of offering a product as a substitute (which isn't normally a problem, but always does add some stress to the project). So, make sure that the product you are specifying is one that will be generally available when you need it!
I think I'll stop there. Just a taste - but a very good starting point. If you have answers and thoughts about all of these points - you are likely on your way to being able to narrow this decision down to a final selection. If I can help at all - please give me a call. 936/321-3333
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