Hydraulic classification

Pneumatic classification can be partitioned conveniently into coarse, ie, fine products above 95% < 100 pm intermediate, ie, fine products ranging between 95% < 100 and 30 pm and fine, ie, fine products below 95% < 30 pm. Pneumatic classification, like hydraulic classification, balances the force of gravity with drag forces (counter flow) in order to bring about a separation. 

Hydraulic classification The rearrangement of resin particles in an ion-ex- change unit. As the backwash water flows up through the resin bed, the particles are placed in a mobile condition wherein the larger particles settle and the smaller particles rise to the top of the bed. 

Particles with the lowest specific gravity are carried with the water towards the outside wall of the spiral. The spiral separates at its greatest efficiency when used in the size range of 10 to 200 mesh. Some particles will be recovered both above and below these size ranges, but occasionally, ultrafine and very coarse heavies will be lost in the tailings, as will be middlings or unliberated ore particles. The spiral will benefit, therefore, from the use of hydraulic classification as a feed preparation step. 

Two ores, of densities 3700 and 9800 kg/m3 are to be separated in water by a hydraulic classification method. If the particles are all of approximately the same shape and each is sufficiently large for the drag force to be proportional to the square of its velocity in the fluid, calculate the maximum ratio of sizes which can be completely separated if the particles attain their terminal falling velocities. Explain why a wider range of sizes can be... 

The Metcalf Eddy HYDRO-SEP soil washing system is an ex situ, water-based technology that separates contaminants from soil matrices. The HYDRO-SEP modular system uses screening and hydraulic classification processes to separate uncontaminated soil particles from a contaminated mixture. 

Hydraulic classification ensures the highest separating efficiency obtainable by wet-classification means. The amount of hydraulic water is controlled so that in each succeeding compartment the coarsest particles are maintained in hindered-settling condition and the finer fractions pass along for similar treatment. Two compartments will normally capture 90 percent of a two-screen-size fraction. Spigot discharge is controlled by air-actuated valves in the Jet Sizer and motor-driven pincer-type valves in the SuperSorter. Solid fractions... 

Mechanical separations Gravity Centrifugal force Pressure Heterogeneous Sorting (s - s) Dense-media separation (s — 1) Flotation (s — 1 — g) Sedimentation (s — 1) Filtration (s — 1) Pressing (s — 1) Centrifugation (s — 1) Hydrocyclone separation (s — 1) Classification Sieving (s — s) Air classification (s — g) Hydraulic classification (s — 1)... 

A size classification of one material does give the finest particles at the top, and therefore is more easily clogged than if there was a decrease in the size of flow channels downwards through the bed. The proper reclassification is best achieved by using a multi-layer filter. Two or more materials of different densities and sizes make up the bed, so that the hydraulic classification of cleaning places the finer, denser particles below the coarser, less dense particles (with filtration flow downwards). 

Fire-Resistant Hydraulic Fluids. The four classifications of fire-resistant hydrauHc fluids are Hsted below (7). Three of the four groups are fire resistant because they contain a significant amount of water which provides cooling and blanketing of the combustible materials. 

Some U.S. governmental lubricant requirements for nontactical equipment is now acquired as Commercial Item Descriptions (CID), rather than against specific military numbers. A new classification system for shear-stable, high VI hydraulic fluids was balloted by ASTM in 1994. 

Fluids for Hydraulic Transmissions-Fire Resistant Fluids—Classifications, Provisional Recommendation RP7.7H, European Oil HydrauHc and Pneumatic Committee, 1976. 

A series of classification pockets, with decreasing quantities of hydraulic water in each, producing a range of product sizes. 

Filter aids should have a narrow fractional composition. Fine particles increase the hydraulic resistance of the filter aid, whereas coarse particles exhibit poor separation. Desired particle-size distributions are normally prepared by air classification, in which the finer size fractions are removed. 

HydrauUc Design. The numbers 1 through 9 in the third character of the fixed cutter classification code refer to the hydraulic design of the bit (Figure 4-160). 

DRILLING MUD HYDRAULICS Rheological Classification of Drilling Fluids... 

This is the energy source for hydraulic systems. It converts electrical energy into dynamic, hydraulic pressure. In almost all cases, hydraulic systems utilize positive displacement pumps as their primary power source. These are broken down into two primary sub-classifications constant-volume or variable-volume. In the former, the pumps are designed to deliver a fixed output (i.e. both volume and pressure) of hydraulic fluid. In the later, the pump delivers only the volume or pressure required for specific functions of the system or its components. 

Table 52.7 CETOP classifications of fire-resistant hydraulic fluids...

R.L. Augsburger J.K. Lee, Hydraulic Size Classification Facility for Bali Propellants , Rept No TD-128, Olin Corp, New Haven (1974)... 

The classification in Table 2.2, based on the hydraulic diameter of the channel, was suggested by Kandlikar and Grande (2002). 

As representative examples of the various machineries used for classification mention may be made of mechanical classifiers, hydraulic classifiers, and hydrocyclones. Simplified sketches of these have been shown in Figure 2.12 (A-C). 

Clay is the most important component of soil liners because the clay fraction of the soil ensures low hydraulic conductivity. In the United States, however, there is some ambiguity in defining the term clay because two soil classification systems are widely used. One system, published by the American Society for Testing and Materials (ASTM), is used predominantly by civil engineers.18 The other, the U.S. Department of Agriculture s (USDA s) soil classification system, is used primarily by soil scientists, agronomists, and soil physicists.19... 

Perhaps the simplest classification of flow regimes is on the basis of the superficial Reynolds number of each phase. Such a Reynolds number is expressed on the basis of the tube diameter (or an apparent hydraulic radius for noncircular channels), the gas or liquid superficial mass-velocity, and the gas or liquid viscosity. At least four types of flow are then possible, namely liquid in apparent viscous or turbulent flow combined with gas in apparent viscous or turbulent flow. The critical Reynolds number would seem to be a rather uncertain quantity with this definition. In usage, a value of 2000 has been suggested (L6) and widely adopted for this purpose. Other workers (N4, S5) have found that superficial liquid Reynolds numbers of 8000 are required to give turbulent behavior in horizontal or vertical bubble, plug, slug or froth flow. Therefore, although this classification based on superficial Reynolds number is widely used... 

Classification efficiency of the hydroseparator compares with that of the cone classifier and is appreciably lower than that obtained from mechanical or hydraulic units. The chief virtue of the hydroseparator is its ability to receive and slough off great quantities of water at low per-unit-volume cost. 

Jet Sizer and SuperSorteri The Jet Sizer and SuperSorter are multicompartment and, therefore, multiproduct classifiers operating on the basis of hindered settling. The classification pockets are arranged in series for throughflow with parallel pockets to take care of high tonnage size fractions. Each compartment is served with low-pressure hydraulic water. 

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