Self indexing elbow

Abstract

Apparatus is disclosed for assisting in the unloading of a difficult to unload lading from a vessel. An accumulator is mounted adjacent the vessel. A first conduit connects the accumulator with a valve for periodic discharge of the accumulator. A self-indexing elbow is rotatably mounted on the vessel and extends within the vessel. A second conduit connects the valve with the elbow. The elbow includes an elbow conduit portion in fluid communication with the second conduit. The elbow conduit portion has a center line defining an axis about which the elbow is rotatable. The elbow also includes an elbow portion having an elbow center line passing therethrough. The elbow portion has a discharge end having a discharge opening through which the elbow center line passes. At the discharge end the elbow center line is offset with respect to the axis so as to define a moment arm between the elbow portion and the axis. The accumulator is pressurized with gas sufficient to dislodge bridged or clogged lading in the vessel and sufficient to cause said elbow to rotate relative to the axis. A bearing assembly is mounted between the elbow conduit portion and the vessel, having a frictional force sufficient to limit rotation of said elbow with respect to the vessel, such that rotation ceases at a new angular position relative to the axis prior to the next discharge of pressurized gas from the accumulator. The elbow may be attached so that the frictional force can be adjusted to vary the extent of elbow rotation after each blast of gas is discharged from the elbow. A check valve may be applied to the discharge end of the elbow to prevent lading from entering the elbow. Lading clearing openings in addition to the discharge opening may be provided in the elbow portion to facilitate removal of lading or other material which may tend to hold the elbow in place and prevent the same from rotating as a blast of gas is discharged from the discharge opening.