![]() ![]() fine sediment and organics), the material requires less power to pump it. coarse sand and gravel), the more power required to pump it. The specific gravity of the slurry has a direct impact on the critical velocity required to move the dredged sediment through the pipeline. This is done by taking insitu-sediment samples of the dredge area and testing them in a lab. On an environmental dredging project where the dredge cut will have various materials present, a pre-project investigation should be conducted to determine an average expected specific gravity. Since we are trying to avoid a plugged pipeline, the realistic specific gravity of a dredged slurry will vary between 1.0, when pumping only water, to 1.33 (40% density by weight), when the operator takes a big slug of material. For a dredged slurry, the specific gravity will fall between 1.0 (water) and 2.67 (solid stone). Materials that are less dense than water (s.g.<1.0) are buoyant. Materials that are denser than water (s.g. Specific gravity is the measure of how dense a material is compared to water, which has a specific gravity of 1.0. These factors include the specific gravity of the slurry mixture in the pipeline, the flow rate of the slurry, and the internal diameter of the discharge pipeline. There are three important factors that must be considered to achieve the critical velocity of a given slurry mixture. ![]() After all, if a pipeline gets plugged, the dredge must shut down, which means the entire project stops. Plugging the pipeline is the bane of any dredging operation and one of the few things that will set a dredge operator trembling in their boots. Therefore, a dredge operator must understand the importance of critical velocity and how it varies as the material in the dredge cut changes.Ĭritical velocity, in this case, is the minimum speed at which sediment and water (slurry) must be pumped to prevent the sediment from settling and subsequently plugging the dredge pipeline. However, there is a fine balance between maximizing percent solids and surpassing critical velocity to transport dredge slurry. The goal of most dredging projects is to maximize efficiency, which means maximizing the average percent solids in the pipeline. ![]() Brennan Company (Brennan) serves as a success story for hydraulically dredging and pumping sediments over long distances and changing elevations. As a leader in inland waterway dredging, J.F. ![]()
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