a robotic tank cleaning system is provided , comprising a light - weight , collapsible , and robotically controllable frame having an articulatable washing nozzle for spraying a petroleum - based solvent on a surface to be cleaned . hydraulic power and control units are also provided which allow an operator to control the motion of the frame and washing nozzle from outside the tank , as well as a solvent supply system for delivering solvent to the washing nozzle . a hoisting mechanism is included to allow placement and retrieval of a waste removal pump , and a clearing blade is attached to the frame to assist movement of waste material to the waste removal pump . waste material comprising dislodged oil sludge and expended solvent is collected in waste fractioning tanks where the collected oil sludge is allowed to settle below the expended solvent . the separated solvent in the waste fractioning tanks is redirected through the solvent supply system and is reused for further spraying of the tank interior . a sludge return pipeline delivers settled oil sludge from the waste fractioning tanks back to the refinery for further processing . a method of cleaning hydrocarbon storage tanks is also provided using the robotically controlled frame in conjunction with the waste removal , waste fractioning , and sludge return components .