Self-unloading vessels can discharge dry-bulk cargo at an unimproved dock without assistance from any shore-side equipment or shore-side personnel. Because they do not require any land-based assistance, these vessels can literally arrive in the middle of the night, discharge their cargo, and depart before daybreak. They are capable of transporting and unloading almost any free-flowing, dry-bulk commodity, including iron ore, coal, limestone, sand, gypsum, and grain. ASC’s self-unloaders range in size from 635 feet to 1,000 feet, transport anywhere from 18,000 to 70,000 tons per trip, and can self-discharge cargo at rates up to 10,000 tons per hour. This not only means that our customers can avoid investing in expensive, shore-side unloading equipment, but that their cargo is discharged in an incredibly short period of time – quickly freeing up our customer’s dock.
The graphic above demonstrates a self-unloader in action. The cargo is unloaded using a system of conveyors built into the ship. The cargo holds are "hopper-sloped", or slanted on their sides, so that the cargo will flow down through gates located at the bottom of the holds. The cargo drops onto a tunnel conveyor belt, which carries the cargo to one end of the ship and transfers it onto a loop or incline conveyor belt system. This system carries the cargo up to the main deck of the ship where it is then transferred onto the boom conveyor belt. The boom conveyor can be lifted and swung hydraulically left or right to position the cargo on the dock or into a receiving hopper as specifically desired by our customer.