Pumps are used to transfer liquids from one point to another. They convert mechanical energy from a rotating impeller into pressure energy (head).
The pressure applied to the liquid forces the fluid to flow at the required rate.
This also helps the fluid to overcome friction (or head) losses in piping, valves, fittings, and process equipment.
The pumping system makers are forced to consider fluid properties, determine end use requirements, and understand environmental conditions. These considerations are the pumping applications which include constant or variable flow rate requirements, serving single or networked loads, and consisting of open loops (non-return or liquid delivery) or closed loops (return systems).
Fluid Properties
Pump choice can significantly be affected by the properties of the fluids being pumped
Key considerations include:
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Acidity/alkalinity (pH) and chemical composition.
Corrosive and acidic fluids can degrade pumps. This should be put to consideration when selecting pump materials.
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Operating temperature
With pumped fluids that are hotter than 200°F, pump materials and expansion, mechanical seal components, and packing materials need to be considered.
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Solids concentrations/particle sizes.
When pumping abrasive liquids such as industrial slurries, selecting a pump that will not clog or fail prematurely depends on particle size, hardness, and the volumetric percentage of solids.
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Specific gravity.
The fluid specific gravity is the ratio of the fluid density to that of water under specified conditions. Specific gravity affects the energy required to lift and move the fluid, and must be considered when determining pump power requirements.
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Vapor pressure.
A fluid’s vapor pressure is the force per unit area that a fluid exerts in an effort to change phase from a liquid to a vapor, and depends on the fluid’s chemical and physical properties. Proper consideration of the fluid’s vapor pressure will help to minimize the risk of cavitation.
The viscosity of a fluid is a measure of its resistance to motion. Since kinematic viscosity normally varies directly with temperature, the pumping system designer must know the viscosity of the fluid at the lowest anticipated pumping temperature. High viscosity fluids result in reduced centrifugal pump performance and increased power requirements. It is particularly important to consider pump suction-side line losses when pumping viscous fluids
