To achieve guided boring steel casing installations in deep, densely compacted ground and soft rock, Akkerman announces the newest solution in the Guided Boring Machine (GBM) equipment line, the Guide Rod Swivel (GRS-50) family of cutter heads with a universal bearing swivel.
The GRS-50 family contains four sizes of high thrust bearing upsizing tools able to withstand up to 50 tons of continuous thrust loads on guided boring, guided auger boring, and soft rock pilot tube projects.
Akkerman’s GRS-50 is a versatile choice for an incredible range of pilot tube projects. It is used during guided auger boring to upsize from the pilot tube to the steel casing diameters and also follow the Rock Drill Adapter with Tri-Hawk drill bit tooling in weathered rock conditions.
The GRS-50 Cutter Heads meet the outside diameter of common steel casing pipe in 24-in. (610 mm), 30-in. (762 mm), 36-in. (914 mm) and 42-in. (1,067 mm) diameters. The complete assembly is housed in a reusable, casing sleeve to ensure optimum and consistent performance with all manufacturers’ steel casing. On projects with space constraints, the 24-in. and the 30-in. GRS-50 is also compatible with a 4800 Series Jacking Frame with an Auger Boring Adapter for spoil discharge.
The GRS-50 is an economical solution since the 7-in. bearing swivel is universal to all GRS-50 Cutter Heads and securely bolts onto the cutter head collar. Two seals inside the bearing swivel prevent contaminants from entering the main housing.
The guide shaft extends beyond the face of the cutter head and connects to the last length of pilot tube with a 3-in. hex connection to firmly hold the alignment on line and grade. During steel casing installation, the bearing swivel absorbs the rotational torque while the cutter head excavates in a clockwise manner. Excavated spoil enters the cutter head and flows through the auger flighting for removal in the launch shaft.
The durable, carbide gage cutter bit tooling is the same proven design used on Akkerman Tunnel Boring Machines (TBMs). Gage cutter bits along the perimeter of the cutter head create the bore overcut. If an obstacle is encountered, they are situated on collapsible wings that retract into the casing sleeve for pullback. In this event, the guide shaft can quickly reconnect to the hex connection on the pilot tube to resume bore advancement. The gage cutter bit’s round shank allows it to turn as it excavates ground for optimal wear and longevity and if necessary, can be easily replaced.
The complete assembly includes a 24-in., 30-in., 36-in. or 42-in. GRS-50 Cutter Head, a Bearing Swivel, an Auger Drive Adapter for 6- to 5-in. lead auger hex connection and a Casing Sleeve. The assembly is 42-in. (1,067 mm) long from tip of the guide shaft to the rear Auger Drive Adapter.
To upsize from the pilot tubes in ground conditions requiring less jacking force, a single or two-step weld-on reaming head remains the appropriate choice for these circumstances.