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Friday, December 6, 2013

Pipeline Coating Supply and Technical Help

Pipe coatings are critical to the health of any steel pipeline.  In the United States, the dominant mainline factory applied coating is fusion bond epoxy.  In other parts of the world, three layer polyethylene coatings (which generally include a layer of fusion bond epoxy as one of the three coating layers) are more dominant.  The question any pipeline corrosion engineer has to answer is: "what type of coating am I going to use for the field joints?"

A field joint is the area of bare steel where two pipes are welded together.  In the plant, a pipe can't be coated from end to end, since that would result in that coating be damaged during the welding process.  Instead a pre-determined space at each end of the pipe is left bare (called a cutback).  In the field, as the pipeline is constructed, the contractor is left with somewhere in the neighborhood of 2% of the pipeline to coat (~12" or less of every 40 feet).  Of course, that contractor will be working from a specification which will let them know what coatings are acceptable in the end users eyes for coating those sections.  Sometimes, the contractor has their choice from a number of different pipeline coating technologies.  Other times, that contractor can choose from a single technology.  Sometimes the contractor is directed to use a specific product, from a specific manufacturer, from a specific technology.

If it sounds like it can sometimes be confusing; it can be.  With multiple technologies,  multiple manufacturers and a wide range of product quality, it is very difficult to find valuable, accurate, honest information.  The field joint coating (as mentioned above) represents only 2% of the pipeline coating.  Beyond that, the pipeline coating is only half (more or less, depending on who you talk to) of the corrosion prevention system (cathodic protection being the other).  Now add in things like backfill, rockshield, soil condition analysis and other factors and it quickly becomes clear.  Field joint coating is incredibly critical and important...but also a very small factor when considering the entire scope of building a pipeline.  If YOU are familiar with all of the intricacies of all of the different technologies and manufacturers; then you are a rare bird indeed!
Too often, decisions are ultimately made based purely on material cost.  I certainly understand that costs must be analyzed; business exist to make a profit after all.  But, you need someone on your side that can give an idea of installed costs rather than just material costs.  A look at the whole picture is often much, much more beneficial than a simple look at one single cost factor.

As a general rule, there are 4 current, commonly accepted field joint coating technologies (and in some cases components are mingled to create a multi-technology coating system. 

These technologies are:
- Fusion Bond Epoxy (FBE).  Generally accepted in the USA as the premier mainline coating, it can also be put on field joints.  Requires induction heating coils and flocking equipment.
- Heat Shrink Sleeves - More than 30 years of successful use history.  Many different products designed for specific pipeline operating conditions and applications.
- Two Part Epoxies - These stand alone epoxies mimic (in some ways) a fusion bonded epoxy.  Mixed and generally hand applied in the field.
- Cold Applied Tapes - Not as commonly used as they once were, this technology certainly still has a place in the market under certain conditions (if you're using the right manufacturer's product).

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