Bucket Dredge

a floating excavation machine with a bucket device for scooping up soil from under the water; one of the ships of the technical fleet. Bucket dredges are used mainly for dredging operations, the creation of submerged trenches, and the extraction of minerals. The bucket dredges used for mining are equipped with concentrators and are called drags. Modern bucket dredge types include single-bucket dipper dredges, grab dredges, and chain-and-bucket dredges. Grab (grapple) dredges (equipped with a hold for the soil) and seagoing chain-and-bucket dredges are usually self-propelled.

A single-bucket dipper dredge is a floating mechanical shovel with a bucket capacity of 12 cu m; it is sometimes equipped with a rock-crushing device. It is intended primarily for rocky (heavy) and debris-littered bottoms. It is moved by means of lifting piles. The dredged soil is dumped directly onto the waste pile or loaded into a hopper barge (dump scow).

Grab (grapple) dredges have one to four slewing bucket cranes. Double-hinged (clamshell) or four-hinge grab buckets with a capacity of 1–4 cu m are used depending on the properties of the bottom to be dredged and on the load-lifting capacity of the cranes. Grab dredges are suited mainly for dredging work in moorages; they move along cables by means of boat hoists. The dredged soil is dumped into the grab dredge’s own hold or into a hopper barge.

A chain-and-bucket dredge is a continuous-operation machine that excavates the bottom with buckets with a capacity of 1.2 cu m, connected in a closed loop; the loop passes around two drums, the upper of which has the drive. The dredge is moved by means of boat hoists. Modern chain-and-bucket dredges have capacities of up to 1,500 cu m per hour for light bottom work and up to 750 cu m per hour for heavy bottom work. The dredged soil is transported by hopper barges, soil pumps, or conveyers.