Northwest Pipe Company has developed the Permalok Radial Bending Joint (RBJ) that enables steel pipe to be installed in a curved radius in microtunneling applications. This patent-pending technology is a ground-breaking advancement in trenchless microtunneling construction. The Northwest Pipe Company team developed the proprietary joint design to meet a target radius curve of 800 feet during trenchless installation.

Permalok steel pipe is most often used as a casing pipe for utilities and excels in trenchless jacking applications including microtunneling, pipe jacking, auger boring, and pipe ramming. The press-fit machined joints reduce field time by eliminating butt-weld joints and result in a shortened install duration and reduced field costs. To solidify the joint's validity, the Permalok RBJ has undergone Finite Element Analysis at the University of Thessaly Department of Mechanical Engineering.

The Company manufactures Permalok RBJ in pipe diameters varying from 30 to 156 inches. The actual curve radius is dependent on site conditions as well as the pipe diameter and length.