Why is it so difficult to dredge and pump viscous sludges and how do their properties differ from conventional materials like sand gravel/silt?
It should be noted that clear water flow is almost turbulent and as such, the Hazen Williams and Darcey Weisback equations are based on this fact. Slurries consisting of silt and sand also fall into this category. However, sludge, even though it is considered a fluid, often exhibits laminar flow, in which the friction losses can be several times higher than that for water. To complicate matters further, sludge of three percent solids by weight behaves more like a “Bingham Plastic”, and the flow of such a material is described by two constants – the yield stress and the coefficient of rigidity. Mud Cat™ horizontal auger dredges with submerged vortex type pumps have pumped these types of solids up to 8% by-weight but with corresponding high friction losses in the pipeline. In some cases the friction losses increase exponentially and extreme care must be exercised. Each type of sludge must be evaluated for pumping characteristics.
Related Questions
- Why is it so difficult to dredge and pump viscous sludges and how do their properties differ from conventional materials like sand gravel/silt?
- What is the difference between silt/clay and sand/gravel in the Tier I Look Up Table?
- Why can a dredge pump fine silt a farther distance than say a coarse sand?
