NWPX Completes First Curved Steel Microtunnel Pipe Installation

A new pipe joint technology has enabled something rarely seen in microtunneling, opening the door to new construction options in constrained environments.

(P&GJ) — NWPX Infrastructure said it has completed the first field installation of its Permalok Radial Bending Joint technology, a new system designed to allow steel casing pipe to be installed along curved alignments during microtunneling operations.

The first installation of the Permalok® Radial Bending Joint featured 72-inch OD casing pipe manufactured by Northwest Pipe Company, providing the flexibility needed to achieve a 5,500-foot-radius curved alignment.

The installation took place as part of an emergency wastewater infrastructure project for the Two Rivers Water Reclamation Authority in New Jersey. The project used approximately 1,290 feet of 72-inch steel casing pipe installed along a 5,500-foot-radius curve beneath Pleasure Bay.

According to NWPX, conventional steel casing pipe used in microtunneling has historically been limited to straight-line installations, often requiring engineers to work around existing utilities, waterways and underground infrastructure. The new joint technology is designed to allow horizontal, vertical and compound curves while maintaining compatibility with existing microtunneling equipment.

The company said the system retains the characteristics of its existing Permalok press-fit connection technology, including weld-free installation and reduced field labor requirements.

"This installation demonstrated that curved steel microtunneling can be successfully executed in the field," CEO Scott Montross said. He added that the technology could expand construction options for projects facing space constraints or challenging underground conditions.

The curved alignment allowed contractors to navigate a limited construction footprint while connecting to an abandoned tunnel associated with the wastewater project.

The project was designed by Hazen and Sawyer and installed by Northeast Remsco Construction.

NWPX said the technology could provide engineers with additional flexibility for future trenchless infrastructure projects where traditional straight-line installations are difficult or impractical.