Horizontal directional drilling (HDD) is an efficient and ecologically safe method for the installation of pipelines underneath rivers, roads, rail crossings, buildings or other obstacles. After a pilot bore is made from the entry to the exit, an HDD string is then guided along the drill path.
Unfortunately, damage to steel pipelines during the HDD installation is commonplace; often rocks and debris will remain in the pilot bore, subjecting a pipe to abrasion and gouging.
“When a coated steel pipe length is pulled through with a corrosion protection on the outside – usually, an epoxy – the coating is subjected to rock and debris that can create heavy impact, gouge, shearing and abrasion forces to the parent coating and then you can have corrosion issues,” Denso’s national product development manager for pipelines George Wettenhall explains
“Abrasion resistant outer wraps (AROs), or BoreWrap specifically, reduce the risk of coating defects and gouging and abrasion. Bore-Wrap is made up of a patented fibre architecture to protect against a variety of potential pipeline threats caused by the stresses of HDD installations.”
The Bore-Wrap is a field-applied abrasion resistance outer-wrap suitable for joint coatings, mainland coatings and shrink sleeves in trenchless installation and directional drilling. The BoreWrap can be applied easily onsite before drilling and only requires the presence of water. There is no mixing required: it is simply wrapped over the existing pipeline coating and cured with water.
“Each roll is supplied in a foil carrier bag that keeps the Bore-Wrap intact. The roll itself is impregnated with urethanes, so once it is open to air and moisture, it starts curing,” says Wettenhall.
“We wrap that roll around the pipe prior to application, so it will fit a range of pipe sizes. The BoreWrap is moisture-cured, unlike other AROs that use UV curing. UV liners have to be cut to size, require special lighting, and generally have to be prepared offsite. Ours can be applied in-situ with only water.”
Firstly, an operator must prepare the surface by removing any loose scale or foreign matter. Then, they will wet the surface of the pipe where the roll is to be applied. As Bore-Wrap is water activated, it is necessary that the water is continuously sprayed onto the surface and underbelly of the roll as it is being applied.
Wrapping should occur circumferentially to begin, ensuring the leading edge has a minimum of two layers. Once the wrap is completely saturated, immediately begin wrapping the compression film over the wrap with tension applied.
Once fully compressed, use the perforating tool to puncture the film, allowing excess moisture, resin and CO2 from the curing process to escape. The operator should allow for the roll to remain under compression while it cures before removing the film.
The finish will appear seamless and fully fused together, creating an impenetrable outer barrier.
In a recent case study, an ageing pipeline crossing beneath a creek required replacement due to corrosion. The pipe was installed using HDD 50 ft deeper than the original line.
During the pilot drill, the ground was found to contain cobble and rock fragments that could pose a threat to pipeline integrity. The contractor opted to install a Denso Bore-Wrap over the welds to protect them from damage during the pull-in. The remainder of the pipe had only an FBE coating.
Once the pipe was pulled through the bore hole, it was apparent that the mainline of the pipe suffered significant damage to the coating, causing the bare steel to become exposed. By contrast, the welds that were protected by the Bore-Wrap did not endure any damage.
As is characteristic of trenchless applications, the Denso Bore-Wrap minimises the need for costly spot repairs or re-pulling pipe due to damage. Bore-Wrap is a simple, effective and economical solution for guaranteeing asset integrity in abrasive conditions. Contractors have commended this Denso product for its flexibility, ease of application and exceptional protective performance.
Denso will be exhibiting the Bore-Wrap at this year’s No-Dig Down Under convention and exhibition.
For more information visit the Denso website.
This article appeared in the February 2022 issue of Trenchless Australasia. Click here to view the digital edition of the magazine.