Design of a Tele-Robotic System for the Maintenance of Boiler Hoppers in Electric Power Plants

The design of a novel tele-operated robotic device for clearing undesirable residues (known as clinkers) from the bottom of boiler hoppers in electric power plants is presented in this article. A key aspect of the problem that drives the design process is the fact that the environment inside the hopper is harsh and unstructured. The part of the device that goes into the boiler through a hatch door must be able to handle high temperatures, highly corrosive ash, and the possibility of large residues falling on the device which could lead to serious structural damage to the device. This has led to a new robot design which has all its sophisticated mechanical and control hardware located outside the boiler hopper access port. The only component that goes into the boiler is an inexpensive pole which is expendable and easily replaceable. Also, it can be pulled out from the hopper even if it is seriously damaged. A special insertion mechanism serves as a prismatic joint for inserting and extracting the pole. Forward (sensing) and inverse (control) kinematics problems that are unique to this new design are also presented. Finally, a discussion of the results from preliminary experimental testing in a laboratory setting is included. An important component of the process of designing the robot was the inclusion of ideas from the currently practiced manual clinker clearing process. This was accomplished via periodic discussions with the plant workers who perform the manual process.