Centrifugal pumps operating ranges

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. 

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 ... 

Tests conducted to operate centrifugal pumps as hydrauhc turbines throughout the head-capacity-speed range show that a good centrifugal pump generally makes an efficient hydraulic turbine. From theoretical considerations it is possible to state that at the same speed... 

A set of curves for h, rj, and P as a function of Q are shown in Figure 8.25 from which it is seen that when die pump is operating near optimum conditions, its efficiency remains reasonably constant over a wide range of flowrates. A more general indication of the variation of efficiency with specific speed is shown in Figure 8.26 for different types of centrifugal pumps. The power developed by a pump is proportional to Qghp ... 

When selecting a centrifugal pump for a given duty, it is important to match the pump characteristic with system curve. The operating point should be as close as is practical to the point of maximum pump efficiency, allowing for the range of flow-rate over which the pump may be required to operate. 

The principal types used and their operating pressures and capacity ranges are summarised in Table 10.17 and Figure 10.63. Centrifugal pumps will normally be the first... 

In a well-designed system, a centrifugal pump will normally operate at or close to its maximum efficiency point. Pump efficiencies, t], are typically in the range 60-80%, larger pumps having the higher efficiencies. 

Centrifugal pumps have a wide range of application for transferring fluids in industrial operations. Centrifugal pumps are reliable and mechanically simple. Many chemical plants and refineries have hundreds of centrifugal pumps of various sizes conveying sundry liquids and slurries. These vital workhorses are used for water, flammable liquids, acids, caustics, and most other fluids. 

Continuous product flows under high-pressure conditions (p > 30 MPa) can only be achieved with hermetic centrifugal pumps. Although the two drive systems that can be used - the permanent magnet coupling and the asynchronous canned motor - have the same mode of operation, they differ in their applications and their safety ranges. 

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