Double jointing is a process in which two singular pipes are welded together to form up to an 80’ length. This process takes place prior to any coating application, meaning that the joint is coated at the full 80’ length.

There are several benefits to Double Jointing during the coating process:

• Double Jointing eliminates the need for Field Joint coating, a process in which the pipe weld joints must be coated after welding in the field or at sea before being laid. This is a more expensive and less protective process.
• Welding joints together prior to transporting them to the field means cutting on-site welding in half and reducing the amount of time required for such an installation.

Field Joint Coating

Field Joints are required for every coated pipe, and as their name states, they are applied in the field, both onshore and offshore. Since joints must be welded together in the field, this process is used to cover weld seams that exist post-installation and provide protective coating to all portions of the pipeline. In most cases, shrink sleeves of polyolefin product are heated to coat the weld seams.

FBE coated pipe joints are relatively simple to coat. However, Three and Five Layer Field Joint Coating applications are more complex. For Three Layer, a method known as Flame Spray can be administered where the coating is sprayed onto the weld joint to fuse the original coating over the seam. For Five Layer, sleeves made from Solid Polypropylene or Polyurethane are used to cover and protect all weld seams. This can also be established by injecting Solid Polypropylene into a mold covering the weld joint.