Peripheral electric pumps may generally be regarded as an intermediate category between centrifugal pumps and volumetric pumps. While in the first category, an increase in the head implies a decrease in the flow rate, in the latter the flow rate is not affected by pressure. Instead, the curve of the peripheral pumps follows a trend that is in-between these two categories of pumps.
Peripheral pumps are therefore particularly suitable to meet those needs that could not otherwise be met with small centrifugal pumps, or rather when a high head must be granted even when faced with a low flow rate.
Fields of application range from irrigation to pressurisation, from water supply to washing systems.
Peripheral pumps operate by means of an impeller characterised by a large number of small dual-flow radial blades (with dual input) arranged along its peripheral area. The centrifugal forces inside the rotor generate a circulatory flow between the impeller and the casing channel. The peripheral speed of the fluid and of the impeller are basically the same, whilst the fluid speed within the casing channel is significantly lower. Therefore, the fluid flows from the casing channel to the impeller in a spiral-shaped path, which is repeated several times along the perimeter. More frequently these “vortices” are formed, higher is the transfer of energy and, consequently, the pressure produced. The number of spirals increases when the flow is reduced, thus, the transfer of energy and the power absorbed are higher in case of partial loads.
The main characteristic of peripheral pumps is their ability to grant very high pressure at low flow. The impeller turns very close to the volute of the pump and the pressure difference that is produced between input and output is substantial. That is main reason why peripheral pumps are rather noisy, which is strictly connected to the way they work. Under this point of view, however, peripheral pumps are cheaper if compared to centrifugal pumps and they feature also a high self-priming capability.
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