To maintain this rate of production, however, the dredge must be equipped with very good instrumentation and a suction side stability system such as Twinkle Co’s CONVAC valve. THIRTY percent average density by weight is a more realistic goal given the availability of information, modern instruments, controls and effective diggers.įORTY percent average density by weight should be the goal of aggressive dredgers. Only dredgers with extremely low expectations are satisfied with such a pee-poor rate of production. Even today the unknowing use this piddly rule-of-thumb rate to project dredge production. TWENTY percent average density by weight used to be an acceptable rate of dredge production. For this reason, only percent solids by weight is useful in dredging calculations. Pumping relatively lightweight coal is a vastly different proposition than pumping heavier sand and gravel. In contrast, solid coal weighs about 90 lb. The specific gravity (S.G.) of stone is the ratio of the weights of a cubic foot of stone and a cubic foot of water. A cubic foot of water weighs 62.4 pounds. A cubic foot of the solid stone, the stuff of which sand and gravel is made, weighs about 167 lbs. The density of the solids-their specific gravity-has a tremendous effect on the performance of a centrifugal pump as well as the manner in which they can be expected to flow through a pipeline. Table 1Ĩ4% by weight = Plugged Pipe Notes on Table 1Īs noted above, percent solids by volume is not used when referring to dredge system performance because that reference does not take into account the density of the solids particles. Linear relationships do not exist between these values so they must be calculated. Table 1 lists the values of various densities by weight, by volume and specific gravity. Integrated with velocity to obtain the rate of solids production. Often used to make impossible productivity claims.Of little use if expressed as percent by volume.Useful for dredge calculations only if expressed as percent by weight.Measured using a nuclear density meter.A measure of dredge system productivity.The ratio of the weights of a volume of slurry relative to an identical volume of clear water expressed as a percentage.Useful stuff to know about hydraulic dredging.
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