Installing pipeline across the United States, once a booming business in the 1960s, slowed in the late ’80s and ’90s. Today, thanks to the discovery of shale oil and gas, it’s back — and so is the cradle boring machine. These long-distance jobs often call for about 50 bores stretched over more than 50 miles, which must be fast-tracked so the owner can receive payback on the large investment in infrastructure as quickly as possible.
As a result, cradle boring machines (CBMs), once popular during the heyday of cross-country pipeline installation more than 50 years ago, are making a comeback. But today’s CBMs look and act different than they did in the old days. Modern units are designed with new safety features and the capacity to install hundreds of feet of pipe in a single day.
Cradle Boring Machines
CBMs are designed for open-trench, cross-country pipeline road crossings and can efficiently install large steel casings up to 48 inches in diameter — or even 56 inches, with modifications. They can also install casing sections of up to 140 feet in one pass.
CBMs operate like auger boring machines, by using an on-board engine and gear box to drive an auger that bores a pipe into the earth, but they are vastly different in terms of their design, application and productivity. By using the cradle boring method, pipeline contractors can save time and increase productivity since they do not need to excavate and level large excavations for the boring machines. Instead of using cylinders for thrust, a CBM moves forward via a winch and a block and tackle that is attached to an anchor pipe.
By devoting less time and energy to digging, leveling and shoring trenches and setting up a tracked auger boring unit, contractors can complete more bores per day. For example, contractors have been able to complete seven 120-foot bores in one day — a 700 percent increase in production.
The Cradle Boring Method
Step 1: Prep and excavate
Excavate the dirt at the point of entry to obtain the cover required on the project. At the surface, auger flighting is inserted into each section of a dummy steel casing, and the casings are welded together to form a continuous string.
Step 2: Ready the casing
An anchor pipe is buried crossway over the top of the bore entrance to provide reaction force for a winch, which is used to pull the assembly forward into the bore. Then the dummy steel casing is attached to the cradle boring machine by placing the casing string into a cradle on the front of the machine. The auger flighting is then attached to the machine, and the casing string is secured to the cradle boring machine.
Step 3: Begin the cradle bore
The CBM then begins to turn the auger and advance the pipe into the ground. The entire string of casing to complete the road crossing is installed. If the road bore does not require an installed casing, the machine and casing are withdrawn and product pipe is installed.
Step 4: Install permanent pipe
Once the casing is installed, the cradle boring machine is disconnected and the auger flighting is pulled back through the installed casing to remove any remaining spoil from the dummy pipe. The dummy pipe is extracted, and the permanent pipe is installed using the side boom tractor.
New and improved
Modern cradle boring machines have been re-engineered with improved capabilities that include state-of-the-art safety, productivity and control features.
In new CBMs, a casing is mounted in line with the driveline, instead of underneath the machine, eliminating rotating parts and exposed chains. Also, load-sensing circuits on the latches ensure the CBM pump senses when chains are loose, signaling the machine to automatically tighten them.
New CBMs also include technologically advanced features for operators, such as centrally mounted, fully adjustable seats that provide a clear view of the boring process and easy access to the control console. All new models from McLaughlin include hydraulic clutches that ensure quick driveline shutdown.
For more information on McLaughlin cradle boring solutions, visit mclaughlinunderground.com.