Heat-shrinkable sleeve

The technology used to make sleeves has advanced significantly since then, with new methods of cross-linking the polyolefin backings and new-generation adhesives that are formulated to provide performance under more-demanding pipeline conditions.

A heat-shrinkable sleeve starts out with a thick extruded poly olefin sheet (polyethylene or polypropylene) that is formulated to be cross-linkable.

This improves the molecular structure such that the polyolefin will work as part of a heat-shrinkable sleeve and provide the required level of mechanical protection while in-service.

The adhesive has many functions; it adheres the installed sleeve to the steel at the coating cutback and mainline coating, it resists shear forces imparted by soil pressure after the pipeline is buried and provides long term corrosion protection to the steel.

As an example, for small diameter flow lines operating at ambient temperatures, a soft mastic-based adhesive may be chosen, while on large diameter pipelines operating at higher temperatures, a hard, semi-crystalline hot-melt adhesive is used.

The backing provides mechanical protection against abrasion and soil stress forces after the pipeline is buried.