The choice of the type of pump to be used for a given use is essentially determined by a few, but fundamental elements: the required flow rate, the prevalence and the characteristics of the liquid to be pumped by ceme .
There are also other factors that can influence the choice of a pump, such as the characteristics of the suction line and the economic aspects linked to the investment for the plant. All these aspects must necessarily be taken into account when evaluating the purchase of a pump for a given application.
The choice of the pump to be inserted in a generic lifting system with an assigned flow rate Q measured in litres per minute is not univocal if the type and diameter of the pipes are not assigned a priori: to a smaller diameter correspond losses of higher load and therefore greater prevalence. In practice, however, it is always possible to find the pump capable of supplying the necessary head H measured in meters.
There are different types of pumps, which lend themselves to different uses. There are pumps with a vertical axis configuration, a horizontal axis, as shown in the figure or eccentric.
Elements to be evaluated in the selection of the pump
In general, therefore, for the correct sizing of the pump must be evaluated:
- The flow rate of the liquid volume to be conveyed in the unit of time
- The specific characteristics of the hydraulic circuit (head, pressure drops and accessories plant
- The properties of the liquid type, composition, concentration, temperature and specific weight
Based on this information, it will be possible to choose the pump suitable for a particular application, the right impeller and the correct engine power in relation to the characteristic curve. Now let’s see in more detail how to consider these aspects to proceed with the choice of an industrial pump.
Evaluation of the technical characteristics of the pump and system
Regarding the flow rate and the characteristics of the system, the definition of the pump flow rate in relation to the plant design choice of pipes and other elements is done according to an economy criterion.
We consider the cost of the plant, generically indicated with “Ci” which also affects the type of pump chosen and which will be directly proportional to the diameter of the pipes and the operating cost, “Ce”, which instead is inversely proportional to the diameter of the ducts since smaller ducts involve high-pressure losses and consequently higher operating costs. The search for the optimal diameter of the pipes “De” is obtained by evaluating the plant and operating costs corresponding to a certain number of commercial diameters, thus constructing the cost curve by points and identifying the nearest diameter value on the graph to the theoretical diameter for which the minimum cost occurs.
Among the various types of pumps to be chosen on the market, centrifugal pumps are certainly the most versatile, thanks to a particularly wide range of applicability. In reality, it is necessary to pay close attention to their configuration, which in fact must always be set in relation to the characteristics of the system, to the needs of the pumping and to the individual requests of the user.