Tall Steel Tanks: Failure, Design, and Repair

Abstract

An organic cohesive material derived from soybeans was stored in a set of five tall unstiffened steel tanks that were equipped with conventional conical hoppers. Stagnant material caused by funnel flow compacted during hot humid weather into solid masses that formed material domes inside the tanks. Collapse of these domes distorted the tank walls and hoppers and compromised their safety; tank collapse was possible. An investigation indicated that a simple repair solution consisted of: (1) Substituting specially designed hoppers for the existing hoppers in order to promote mass rather than funnel flow; and (2) providing a set of vertical stiffeners to each tank shell. Two new steel tanks were also designed that incorporated these features. Stainless steel plates were used for the hopper because their enhanced smoothness promotes mass flow. Since completion of the work in 1982, all tanks have been in continuous operation, and none of the past problems has recurred.