 Pump Selection
Pump selection involves matching the pump flow rate to the application. Of the many factors that must be considered, the four most important are flow, pressure, materials of construction and type of drive. The application and time required for the task will determine the flow and the pressure, whilst the location of the application will generally determine the type of drive and the liquid being pumped dictating the materials of the wet-end construction and seals.
The output from Cat Pumps’ reciprocating positive displacement triplex pump is determined by the running speed, piston or plunger diameter and crankshaft stroke, and it is virtually unaffected by discharge pressure.
The discharge pressure is not created by the pump, but by restrictions downstream which requires the pump to generate a pressure that is sufficient to overcome these restrictions. It follows, therefore, that the smaller the restriction the higher the pressure generated.
In a given pump frame size, a larger diameter piston or plunger provides more flow at any given speed, but the pressure acting on the larger area transmits more force to the drive end so the allowable working pressure is reduced. Smaller diameter pistons or plungers deliver less flow but allow the pump to operate at high pressures as less force is transmitted to the drive end. Cat Pumps will provide advice on the precise pump build configuration and running speed for any application. Speed-reducing transmissions and variable speed drives are available.
Where it is necessary to control either very low flows, or to match the output flow to a fixed running speed (e.g. a petrol or diesel engine, direct drive electric motor or drive from a machine lay-shaft) a reduced stroke crankshaft can be fitted.
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