Linear Scarifying End-Effector Developed For Wall Cleaning In Underground Storage Tanks

This paper describes the development and performance of a Linear Scarifying End-Effector (LSEE) designed and fabricated for deployment by a remotely operated vehicle. The end-effector was designed to blast or scarify in-grained residual contamination from gunite tank walls using high-pressure water jets after the bulk sludge had been removed from the tanks using an integrated suite of remotely operated tools. Two generations of the LSEE were fabricated, tested, and deployed in the gunite tanks at the Oak Ridge National Laboratory, with varying levels of success. Because the LSEE was designed near the end of a four-year project to clean up the gunite tanks at Oak Ridge, a number of design constraints existed. The end-effector had to utilize pneumatic, hydraulic and electrical interfaces already available at the site; and to be deployable through one of the containment structures already in place for the other remote systems. Another primary design consideration was that the tool had to effectively extend the reach of an existing remotely operated vehicle from six ft. to at least ten ft. to allow cleaning the tank walls from floor to ceiling. In addition, the combined weight and thrust of the LSEE had to be manageable by the manipulator mounted on the vehicle. Finally, the end-effector had to follow an autonomous scarifying path such that the vehicle was only required to reposition the unit at the end of each pass after the mist had cleared from the tank. The prototypes successfully met each of these challenges, but did encounter other difficulties during actual tank operations