Centrifugal pumps pump impeller

Example 7.15. A centrifugal water pump impeller rotates at 1800r/min see Fig. 7.17. The water enters the blades at a radius of 1 in and leaves the blades at a radius of 6 in. The total flow rate is 100 gal/min. The tangential velocities in and out may be assumed equal to the tangential velocity of the rotor at those radii. What is the steady-state torque exerted on the rotor ... 

TABLE 9-1 Effect of Reducing a Centrifugal Pump s Impeller Diameter... 

Eye of the impeller The inlet nozzle in a centrifugal pump s impeller. 

Centrifugal pump uses impeller to increase tbe liquid s kinetic energy, and then converting the kinetic energy back to pressure at pump outlet. 

T. Dahl and L. Nelik, Computer Aided Design of a Centrifugal Pump Impeller, ASME 85-WA/EE-lO, Washington, D.C., 1985. 

For instaUations in which suspended sohds must be handled with a minimum of solids breakage or degradation, such as pumps feeding filter presses, special attention is required either a low-shear positive-displacement pump or a recessed-impeller centrifugal pump may be called for. 

A centrifugal pump, in its simplest form, consists of an impeller rotating within a casing. The impeller consists of a number of blades,... 

An example of a typical turboexpander is shown in Fig. 29-46. Radial-flow turbines are normally single-stage and have combination impulse-reaction blades, and the rotor resembles a centrifugal-pump impeller. The gas is jetted tangentially into the outer periphery of the rotor and flows radially inward to the eye, from which the gas is jetted backward by the angle of the rotor blades so that it leaves the rotor without spin and flows axially away. 

Centrifugal pumps also rec]uire that the fluid be available to the pump s suction nozzle with sufficient energy. Centrifugal pumps cannot suck or draw the liquid into the pump housing. The principal pumping unit of a centrifugal pump is the volute and impeller. (See Figure 1-3). 

According to Bernoulli s Law, when velocity goes up, pressure goes down. This was explained in Chapter 1. A centrifugal pump works by acceleration and imparting velocity to the liquid in the eye of the impeller. Under the right conditions, the liquid can boil or vaporize in the eye of the impeller. When this happens we say that the pump is suffering from vaporization cavitation. 

Use a double. suction impeller. Convert an end suetion centrifugal pump into a split ease horizontal design. 

This system requires a pump with a best effieieney point (BFP) of 94 feet at 300 gallons per minute. If this is a eonventional industrial centrifugal pump with a BFiP of 94 feet, the shut-off head should be approximately 110 feet. And if the motor is a standard NFMA four pole motor spinning at about 1800 rpm, the diameter of the impeller should be approximately 10.5 inehes. If this pump were bought off the shelf from local distributor stock, it would probably be a 3 x 4 x 12 model end-suction centrifugal back pullout pump with the impeller machined to about 10.5 inches before installing the pump into the. system. And that s the way it is done. 

Milk-of-lime transfer pumps should be of the open impeller centrifugal type. Pumps having an iron body and impeller with bronze trim are suitable for this purpose. Rubber-lined pumps with rubber-covered impellers are also frequently used. Makeup tanks are usually provided ahead of centrifugal pumps to ensure a flooded suction at all times. Plating out of lime is minimized by the use of soft water in the makeup tank and slurry recirculation. Turbine pumps and eductors should be avoided in transferring milk of lime because of scaling problems. 

Iversen, H. W., Rolling, R. E., Carlson, J. J. Volute pressure distribution, radial force on the impeller and volute mixing losses of a radial flow centrifugal pump. Trans. ASME, journal of Engineering for Tower 82 (1.960), pp. 136-144. 

Similar to multistage centrifugal pumps, centrifugal compressors, as shown in Figure 10-9, use a series of rotating impellers to impart velocity... 

Kreisel-pumpe, /. centrifugal pump rotary pump, -rad, n. turbine turbine rotor, turbine impeller, -verdichter, m. turbocompres-sor. 

Figure 3-4. Centrifugal Pump, double suction single-stage impeller. (Courtesy Allls-Chalmers Mfg. Co.)...

The effects of impeller shape for the usual centrifugal process pump performance are given in Figure 3-34. The only part the process designer can play is in the selection... 

The pressure at any point in the suction line must never be reduced to the vapor pressure of the liquid (see Equation 3-6). Both the suction head and the vapor pressure must be expressed in feet of the liquid, and must both be expressed as gauge pressure or absolute pressure. Centrifugal pumps cannot pump any quantity of vapor, except possibly some vapor entrained or absorbed in the liquid, but do not count cm it. The liquid or its gases must not vaporize in the eye/entrance of the impeller. (This is the lowest pressure location in the impeller.)... 

Cavitation of a centrifugal pump, or any pump, develops when there is insufficient NPSH for the liquid to flow into the inlet of the pump, allowing flashing or bubble formation in the suction system and entrance to the pump. Each pump design or family of dimensional features related to the inlet and impeller eye area and entrance pattern requires a specific minimum value of NPSH to operate satisfactorily without flashing, cavitating, and loss of suction flowt... 

The specific speed of a centrifugal pump correlates the basic impeller types as shown in Figure 3-47. 

The general operation of a centrifugal compressor is like a centrifugal pump, except that the fluid is compressible. Theoretically, the head developed by a centrifugal impeller or wheel is the same regardless of the characteristics of the... 

Centrifugal pumps can also be classified by the design of the impeller. Centrifugal pumps may have radial-flow impellers, axial-flow impellers, and mixed-flow impellers (both radial-flow and axial-flow). 

Another centrifugal pump classification is whether the pump is a single-stage pump (the pressure head is developed by a single impeller) or a multistage pump (the pressure head is developed by two or more impellers). 

---