A cutter refers to the type of excavator head such as a basket cutterhead or bucketwheel on a hydraulic pipeline dredge. The cutter houses the suction intake and is used for cutting or agitating the materials that are being dredged.
Cutters have two basic functions:
Basket cutters vary in shape, size, cutting edge, angle, and method of attachment.
A traditional basket cutter arches at the crown end of each blade back inward and towards the drive hub for support. The basket cutter is designed to draw-in free-flowing materials while protecting the suction inlet from being clogged by oversized objects.
Basket cutters are at work in a wide variety of applications. The size of the cutter is determined or sized to the dredge pump to provide the highest amount of solids capacity to the dredge pumping system.
The Ellicott Series 370 and 670 Dragon dredges typically fitted with a 31.5 inch (800 mm) and a 43-inch (1,090 mm) basket cutter respectively, while the Series 1270 Dragon® dredge is fitted with a 54-inch (1,370 mm) cutter. The cutter size diameter has a specific cutter speed range and cutting force.
Basket cutters may also be equipped with renewable-edge teeth that are mounted on the basket cutter blades for tougher applications. When the teeth wear, they may be easily replaced.
The first custom-designed and patented Ellicott® brand bucketwheel excavator was introduced to the dredging industry in 1976. The bucketwheel is typically sold as a separate customized component and is used mostly for mining applications. More complex bucketwheels consist of a revolving wheel of bottomless buckets attached to a lateral shaft. Debris falls into the inner chamber of the wheel in slurry form, moving directly to the dredge pump by way of a suction mouth that is also located inside the wheel. The bucketwheel is an excellent excavation device for hard materials, excavates evenly in both directions of swing, can handle heavy minerals, and excavates in an even path at depth.
The bucketwheel focuses most of its horsepower (HP) on the short lengths of each individual bucket, allowing the bucket wheel to possess as much as three times the cutting power of a traditional basket cutter. Maintaining a bucketwheel cutter can be very costly and requires operating a sliding spud carriage, which is more costly than a traditional walking spud arrangement. Still, in certain applications, the cost is negated by the dredge’s heightened efficiency.