Selection of pumps

Centrifugal pumps have a number of good qualities  

They are simple in construction, are inexpensive, are available in a large variety of materials, and have low maintenance cost. 

They operate at high speed so that they can be driven directly by electrical motors. 

They give steady delivery, can handle slurries and take up little floor space. 

Single stage pumps cannot develop high pressures except at very high speeds (10,000 rpm for instance). Multistage pumps for high 

The kind of information needed for the specification of centrifugal, reciprocating and rotary pumps is shown on forms in Appendix B. 

Non-Newtonian characteristics, notably shear-dependent viscosity and yield stress, strongly influence the choice of a suitable pump and its performance. While no deflnite quantitative information is available on this subject, general features of a range of pumps commonly used in industry are briefly described here. In particular, consideration is given to positive-displacement, centrifugal, and screw pumps. 

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Selection of pump for a given appHcation is not a trivial task. Often more than one pump type can accomplish the required job. Thus a final choice on a pump type is often a result of personal experience and usage history. As a rule of thumb, the choice of a kinetic, such as centrifugal, or a positive displacement pump is made on the basis of the specific speed. Whereas specific speed is appHcable primarily for centrifugal but not positive displacement pumps, the US value can be used as a guide. Generally, for calculated values of specific speed, eg, nS > 10 [NS > 500), kinetic-type pumps are usually selected. For nS < 10 [NS < 500), positive displacement pumps are typically appHed. 

Pump Materials of Construction In the (memical industry, the selection of pump materials of construction is dictated by considerations of corrosion, erosion, personnel safety, and liquid contamination. The experience of pump manufacturers is often valuable in selecting materi s. See section on materials. 

Sterling, L., Selection of pump type to match systems. Paper B3, BPMA 5th Tech. Conference., Bath (1977). 

The selection of pumps for liquids is discussed in Chapter 5. Descriptions of most of the types of pumps used in the chemical process industries are given in Volume 1, Chapter 8. Several textbooks and handbooks have also been published on this subject Garay (1997), Karassik (2001) and Parmley (2000). 

Pumps can be either the horizontal or the vertical type. The selection of pump type depends on the water basin, which can be underground or aboveground. An economic evaluation should be made to ascertain which is the more. convenient solution—aboveground basins with horizontal pumps or underground basins with vertical pumps. 

We have discussed only a very small amount of information about pumps. A great deal more detail and practical operating information is available in books dealing with the selection of pumps. Space limitations preclude the inclusion of this detail here. In any specific application the user should consult with the pump vendors for assistance with details regarding materials of construction, installation, operation and maintenance, bearings, seals, valves, couplings, prime movers, and automatic controls. 

It is important that a method be developed to enable the proper selection of pumps to meet specific pumping reqnirements. Thns, before selecting any particular pump, the designer mnst consnlt the characteristics of this pump in order to make an intelligent selection, fii fact, mannfactnrers develop these characteristics for their particnlar pnmp. Thus, pump characteristics are a set of curves that depict the... 

Steffe and Morgan (1986) discussed in detail the selection of pumps and the sizing of pipes for non-Newtonian fluids. Preliminary selection of a pump is based on the volumetric pumping capacity only from data provided by the manufacturers of pumps. 

Selection of pumps for discharge may also be a significant issue with regard to energy input and slurry pumping capability. Crystals that have been carefully grown and are ready for high rate filtration can be reduced in size by pump shear to drastically reduce the filtration rate. This is especially problematic for recycle pumps in filter equipment feed loops. 

By a proper selection of pumping rates, the sample and reagent zones might merge synchronously, that is, completely overlapping each other (as shown) or asynchronously, so that a section of a reagent zone does... 

Several types of pumps are currently in use and are described here. We should emphasize that no system is truly universal, and the choice of an appropriate system depends on the analyst s aims and on the compromises he is ready to make between the advantages and drawbacks we shall discuss. Berry and Karger gave a useful discussion on the selection of pump systems. 

Various types of pumps are to be used in the plant. Confirm that the correct pump has been provided for the required service conditions. The selection of pump, material of constmction of wetted parts depending on the liquid handled, discharge capacity and head, oil seal, water seal, and gland packing should be checked. Direction of rotation of pump and motor must match, and their alignment with each other must be perfect. 

Density and viscosity are important for the process and plant design, especially relating to fluid dynamics calculations for the absorption column, gas-liquid mass transfer resistance and the selection of pumps and packings. The measurement systems were first validated with 30 w1% MEA solutions. As seen in Figure 5, the dynamic viscosity of MEA solutions is significantly increased by the dissolution of CO2 and the measured data agree well with the values predicted from Weiland s correlation [20]. The maximum deviation is less than 3%. 

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