Directional Drilling Field Joint CoatingPipeline coating selections are always incredibly important. Millions of dollars invested in an asset means that smart choices have to be made in order to protect that asset. This selection process can be challenging enough when dealing specifically with field joint coatings, but it gets even more challenging when selecting field joint coatings on pipe that will be involved in a road bore or directional drill.
Why? Because the pipeline is going to be seeing immense stresses on those coatings and will never be visually inspected again. I've seen cases where (in a product evaluation) a cold applied tape was applied to the field joints of a pipeline that was pulled through a bore hole (a short bore hole at ~80 feet) and when the pipe came out the other end of the hole, the cold applied tape was completely gone. Those joints were buried with no coating of any kind. I sure hope the CP system was a good one.
In other cases you might have a coating that is specifically in danger during a pull through. Did you use a two part epoxy with sub optimal installation? Are there icicles hanging down from the pipe? What is going to happen when those icicles break off? What is going to happen if the pipe strikes a rock along the way? Will you be putting a pipeline into service that already has damaged areas and bare steel showing? I sure hope your CP system is a good one.
That bring us to one of the unique things about the DIRAX coating system. DIRAX utilizes a two part epoxy as the primary corrosion coating on the field joints. As we all know, two part epoxies do have a number of strengths and two of those are cathodic disbondment resistance and excellent adhesion (as long as surface prep is properly done). The DIRAX coating system then offers significant physical protection of that pipeline for the life of the pipeline. During that boring process, your field joint is protected by several layers of different polyamide materials.