Cleaning of sludge from the bottom of crude oil storage tanks is expensive and time consuming. Sludge samples from several storage tanks in North America and the Far East were analyzed to characterize the nature of the sludge. A method is described which enables refineries to reduce the volume of tank bottoms material "on line" while crude oil is transferred in and out of active tanks. This practice should reduce the time and cost required to clean storage tanks when they are opened for
inspection and repair. Keywords: sludge reduction, tank bottoms, tank cleaning