Caking and Consolidation of Solid Bulk Cargoes
Why bulk cargoes set, bridge and rat-hole in the hold: moisture, pressure and chemical mechanisms, the discharge failures they cause, and the prevention that works.
Caking is the consolidation of a free-flowing bulk cargo into a mass that will not discharge, and it is a discharge failure before it is a quality claim. The mechanisms differ by cargo: moisture migration and recrystallisation at particle contacts, compaction under the weight of the stow, temperature cycling over a voyage, and in some cargoes a chemical set on contact with water.
The full article will cover each mechanism and the cargoes it affects, along with the symptoms as they present at the discharge berth: a hard crust, bridging over a suction point, rat-holing where a channel forms and the surrounding cargo does not flow, and blocks that have to be broken mechanically.
It will also cover the consequences and the prevention. A caked cargo cannot be drawn through a pneumatic or vacuum line at all, so the discharge method fails rather than slows, and grab and bulldozer work substitutes at a cost in time and residue. Prevention runs through weather precautions during loading, hatch cover integrity, hold dryness and, for hygroscopic cargoes, an understanding of what the voyage itself adds.