Booster Pump: An additional pump and prime mover assembly used to increase the velocity of the material in the pipeline to enhance pumping power and pumping distance.
Dredging: An excavation activity in which materials are recovered from beneath the water’s surface. The purpose is generally to gather bottom sediment and either dispose of it at a different location or use these sediments in various products; e.g., sand and gravel that is used in concrete mixtures.
Dredge Pump: The device that moves the slurry in the pipeline. Slurry enters the casing and is whirled by turning impellers, which force it out of the casing and into the pipeline.
Elevation: The angle at which a pipeline rises as it leads away from a dredge pump. Pipeline elevation can increase material’s friction and decrease its velocity, reducing efficiency. Elevation is typically the measurement from the surface of the water to the final discharge point.
Hydraulic Dredging: The process of excavating and pumping underwater material through a pipeline to a different location using a centrifugal pump.
Mechanical Dredging: The process of removing debris or hardened material that is tightly compacted, using buckets to dig and place the material in barges to transport it to different locations.
Pump Speed: The speed at which the pump’s impellers force the water and material into the pipeline. Pump speed is increased to maintain proper slurry velocity as the dredge moves farther away from the discharge point.
Sediment: Materials that are naturally occurring and broken down by weathering and erosion.
Slurry: A thin mixture of an insoluble substance, such as cement, clay, or coal, combined with a liquid, such as water or oil.
Turbulence: The product of velocity and friction within the pipeline. Turbulence keeps materials suspended so they can travel efficiently through the pipeline.
Velocity: The speed of solids traveling through a pipeline.
Construction Dredging: The process in which dredges are used during construction projects that require the creation of trenches for pipelines and tunnels and for the forming of structural foundations.
Environmental Dredging: A dredging process used to remove contaminated materials from a body of water in order to restore the water to non-contaminated levels.
Mining Dredging: The process used to excavate sand, gravel, precious metals, coal, phosphates and various other minerals from bodies of water.
Navigational Dredging: A process used to deepen channels and waterways as a means to improve navigation. Navigational dredging is most commonly used in ports, harbors and shipping channels as a way to maintain these waterways so that large ships, oil tankers, container ships, barges and naval vessels can pass.
Recreational Dredging: A dredging process is used to maintain, expand and deepen lakes that have progressively become shallow from deposits and overgrown vegetation. If lakes are not dredged periodically, they become too shallow for boats and swimmers to enjoy them.
Restoration Dredging: A process used to restore wetlands, beaches, lakes, streams, coastlines and other land reclamation projects by removing material from one area and placing it in the area that requires restoration.
Specialty Dredging: Unique projects so specialized in nature that they cannot be categorized.
Common Dredge Components
Cutterhead: Consists of a cutter basket mounted on a driveshaft and gearbox to turn the shaft. The cutterhead rotates and loosens the solids to add to the slurry.
Instrumentation: Digital instruments used as display meters or process meters.
Ladder: The framework or boom that extends from the front of the dredge. The ladder is lowered below the water to reach the bottom to excavate the material to be dredged. The ladder is outfitted with a suction pipe and a cutting/digging device.
Spuds: Long stakes that are driven into the floor of the water body and used to hold the dredge in place. Winches with wire cables swing the dredge around one spud in an arc, as it removes material. A second spud can then be lowered to move the dredge to a different position.
Winch: A mechanical device used to wind in or wind out a wire cable. The wire cable winds around a powered drum, which turns to create the winding action. Winches may be used to position a dredge in the water, as well as to raise and lower the ladder.