Centrifugal pumps, operating

FIG. 10-28 Characteristic curve of a centrifugal pump operating at a constant speed of. 3450 r/min. To convert gallons per minute to cubic meters per hour, multiply hy 0.2271 to convert feet to meters, multiply hy 0..3048 to convert horsepower to kilowatts, multiply hy 0.746 and to convert inches to centimeters, multiply hy 2.54. 

FIG. 29-52 Generalized curves showing hydraulic behavior of centrifugal pumps operating as power-recovery turbines. 

Brake horsepower, centrifugal pumps, 200 Driver horsepower, 201 Burst pressure, 405, 456 Cartridge filters, 274-278 Capture mechanism, 279 Edge filler, 278 Filter media, table, 278 Micron ratings, 277 Reusable elements, 281 Sintered metal, 280 Types, 276, 277, 279 Wound vs. pleated, 276, 277 Centrifugal pumps, operating characteristics, 177-180 Calculations, see hydraulic performance Capacity, 180... 

If the characteristic performance curves are available for a centrifugal pump operating at a given rotation speed, equations 4.28 to 4.30 enable the characteristic performance curves to be plotted for other operating speeds and for other slightly different impeller diameters. 

A centrifugal pump operates in this particular system with a total head against mean velocity curve represented by the equation... 

The centrifugal pump operates over a very wide range of flows and pressures. For low heads but high flows the axial pump is best suited. Both the centrifugal and axial flow pumps impart energy to the fluid Iw the rotational speed of the impeller and the velocity it imparts to the fluid. 

A pump curve has two general areas. These are the flat portion on the curve and the steep portion of the curve. We normally design and operate a pump to run toward the end of the flat portion of its curve. A centrifugal pump, operating on the flat portion of its curve, loses only a small portion of its discharge pressure, when flow is increased. This is a desirable operating characteristic. 

The versatile drive system of the asynchronous canned motor has set fresh yardsticks for centrifugal pumps operating under high-pressure conditions. The operating limits for pressure, temperature and toxicity of the flow product have been extended by some orders of magnitude. This is the logical result of the response to heightened safety environment requirements, and means that technical processes can now be implemented for the manufacture of new products. 

Using Equation 6-69, Figure 6-3 shows typical characteristic curves for a 6-inch centrifugal pump operating at 1750 rpm. Equation 6-69 gives... 

NPSH requirement [m] = rpm/(5400 volumetric flowrate [L/s]) Centrifugal pumps operate on their operating head-capacity curve. Head capacity curves are independent of the fluid although the curve drops slightly at higher... 

In most pumps, the speed is generally not varied. Characteristic curves for a typical single-stage centrifugal pump operating at a constant speed are given in Fig. 3.3-2. Most pumps are usually rated on the basis of head and capacity at the point of peak efficiency. The efficiency reaches a peak at about 50 gal/min flow rate. As the discharge rate in gal/min increases, the developed head drops. The brake hp increases, as expected, with flow rate. 

Every centrifugal pump operates on a predetermined "pump curve", as shown in Figure 25-1. The pump curve indicates the fixed relationship between total head and volumetric flow rate. The range and shape of the pump curve is determined by ... 

Centrifugal pump operation should conform to the pump curve supplied by the manufacturer. A sample pump curve is shown in Figure 11-3. 

For a given centrifugal pump operating at a constant speed, the flow rate through the pump is dependent upon the differential pressure or head developed by the pump. The lower the pump head, the higher the flow rate. A vendor manual for a specific pump usually contains a curve of pump flow rate versus pump head called a pump characteristic curve. After a pump is installed in a system, it is usually tested to ensure that the flow rate and head of the pump are within the required specifications. A typical centrifugal pump characteristic curve is shown in Figure 21.3. 

Shutoff head is the maximum head that can be developed by a centrifugal pump operating at a set speed. 

The greater the head against which a centrifugal pump operates, the lower the flow rate through the pump. The relationship between pump flow rate and head is illustrated by the characteristic curve for the pump. 

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