Even though heavy construction equipment such as a crane or backhoe excavator, is used to perform the task of pipe laying in the trench, workers are required to be inside the trench to guide the excavation, pipe laying, and final alignment. Work place safety has become a major concern in the construction industry over the past few decades, and trench cave-ins have caused serious and often fatal injuries to workers in the United States. It has become of crucial importance to implement the use of new technologies to prevent accidents in trench excavation and pipe installation.

The Construction Automation and Robotics Laboratory(CARL) at North Carolina State University has developed an alternative which involves advanced new technology: the prototype robotic excavation and pipe installation system.

            Pipe manipulator mounted                  on the excavator

          Overview of Pipe manipulator

  Layout of the robotic trenching and pipe installation system(Huang & Bernold, 1993)

The main components of the concept are the man-machine interface, actuation system, laser beam and feedback system.The man-machine interface is used to keep the operator in a safe area and allow him to guide the Pipeman intelligently, while the Pipeman works in a hazardous environment. The man-machine interface also in includes manipulation and visualization functions. The operator will have two different joysticks to control 1) the excavator, and 2) the pipe manipulator prototype. The operator will see his/her manipulation status through visualization functions.

1. H.Motor(M_Rot1): A hydraulic motor provides +/- 100 degrees rotation of the pipe in order to line up the pipe.
2. H.Motor(M_Rot2): A hydraulic motor provides a locking mechanism on the back of the pipe manipulator prototype to prevent the pipe manipulator from sliding from the bucket.
3. H.Cylinder(C_Trans): A hydraulic cylinder provides a linear activation of the pipe to joint the new pipe to the pipe already laid.
4. H.Bladders(B_Clamp): Hydraulic bladders provide inflating and deflating mechanisms to clamp the pipe manipulator to the bucket
5. E.Winch(W-Hold): An electric winch is used to attach the pipe with a quick release.

Schematic overview of the Pipeman

The amount of clearance available to insert the bucket is 10.5 inches(26.7 cm)in order to fit the bucket more easily. Bladders(B_Clamp) have been mounted to support the bucket and to prevent it from slipping off in operation. The basic principle of the bladder system is to introduce the hydraulic fluid into the unit trough the bladder intake, causing the bladders to inflate, which clamps the pipe manipulator to the bucket. To eliminate slippage, a rubber plate of 1 inch(2.54 cm) of thickness is also attached both at the bottom of the upper part of the cantilever hook and on the top of the steel plate over the bladders. Additionally, to prevent the pipe manipulator from sliding off the bucket, a locking mechanism on the back of the pipe manipulator has been designed as a mechanical stop. A rotational motor (M-Rot2) will rotate steel bars(backstop) toward the back of the bucket.

A simple joystick and on/off switches are applied for easy manual control and the electro-hydraulic valves are used to activate each actuation function. The beam laser system is also used to align the pipes. Two laser targets are used to make sure that the grade is correct. Micro cameras as feedback system are mounted to improve the machine interface. This system allows the operator to have a real-time visual control for the final alignment of the pipe joint. 

• The greatest advantage of the Pipeman is that it offers a new technological approach to pipe installation which has the potential of improving safety.
• One key item in every project is the cost associated with OSHA(Occupational Safety and Health Administration) to protect workers in an open trench. By removing the need for workers going into the trench, the OSHA regulations do not have to be followed, therefore a major cost factor is eliminated.
• Also, this technology will drastically reduce the number of fatal accidents and lost workdays due to injuries, because the robotic manipulator will reduce or eliminate the exposure of humans to risks such as collapsing trenches, and cave-ins.
• Preliminary evaluations of the economic benefits shows excellent results and monetary savings using conservative assumptions. The evaluation does not include reduction in insurance premiums and possible increases in productivity. Therefore, it is possible to reduce costs and improve safety by implementing this technology.

The prototype robotic excavation and pipe installation system  has been developed by the Construction Automation and Robotics Laboratory(CARL) at North Carolina State University. It is sponsored by the National Institute for Occupational Safety and Health(NIOSH).

Work is continuing on testing the system with different soils and depths. An economic evaluation of the performance will also be performed with statically sound data analysis.

Preliminary evaluation of economic benefits shows excellent results   using the Pipe manipulator