Protection Sleeve for Welded Field Joints of Steel Pipelines with Thin-Film Internal Linings

Thermally sensitive internal linings such as epoxy or polyurethane are often used to protect the interior of steel water pipelines from corrosion. Welded joints are usually required for higher pressure pipelines and to provide axial restraint. When welded joints and thermally sensitive linings are specified, the heat from welding would degrade or destroy any thermally sensitive lining in the vicinity of the weld. Therefore, the industry standard is to hold back the lining in the heat-affected area of the pipe ends to be welded and to patch the lining in this area after the girth welds have been completed. Field-patching of epoxy or polyurethane linings is prone to present the quality issues common with field-applied coatings. Adverse environmental conditions and the difficulty of inspecting coating quality in the confined space inside of a pipeline have commonly led to patch failures. Furthermore, the process of patching the weld zone after welding significantly slows down construction, increasing its cost. This paper reviews the use of an internal joint protection sleeve that is installed during new construction to protect the bare steel pipe at the weld zone from corrosion. The keys to the internal sleeve functionality are to prevent water from reaching the weld zone, withstand welding heat, and to be easily installed. Shop test results, third-party qualifications, and field installations are presented.