Each bucket digs its own load, carries it to the surface and, as it rotates over the top tumbler, dumps its load and goes back for another. Bucket dredges are more efficient than dipper or grapple dredges because the work cycle is continuous. The hydraulic dredge is characterized by the continuous removal of bottom material by the suction of a dredge pump, supplemented by mechanical excavators where necessary. The dredge pump discharges the slurry, consisting of water and bottom material, through a pipeline to its ultimate site of disposition, thus combining all elements of the dredging operation into one continuous operation. There are several traditional-type hydraulic dredges available to the mining industry.
Plain suction is the simplest form of hydraulic dredge and utilizes no excavator.
The cutterhead pipeline dredge is the most versatile and widely used marine excavating unit. It is similar to the plain suction dredge but is equipped with a rotating cutter surrounding the intake end of the suction pipe. The cutterhead dredge, because of its versatility, capacity, efficiency and relatively low cost, has become the workhorse of the dredging industry. It does more dredging than all other types of dredges combined and has received the attention of a great deal of development. More recently the industry leaders have developed a bucketwheel excavator for pipeline dredges.