We often talk about the optimum efficiency that a pump should have, in this article we explain what the efficiency of a pump is and how it is calculated.

By efficiency we mean the nominal flow rate, the manometric head and the absorbed power that the pump must have in order to optimise the installation.

Nominal flow rate (Q)

The nominal flow rate is the volume of liquid required in a given time. It is usually expressed in litres/minute or m3/hour.

Total manometric head (Hm)

The manometric head of the installation is the total head of the liquid. The sum of the suction head (Ha) plus the delivery head (Hi) is called the geometric head (Hg). The latter added to the pressure drop is the gauge head (Hm).

Instalación en carga
Instalación en aspiración

Pressure losses

These are the head losses of the liquid due to friction with the pipe. These losses increase with the roughness, length of the pipe and the flow rate through it. And they are reduced if the pipe diameter increases. Obstacles such as reductions, extensions, valves or elbows (singular losses) also contribute to increase the head losses.
It is established that the head losses due to 90º bends are equivalent to 5 linear metres of pipe and those due to valves to 10 metres.
According to the above, it is recommended not to exceed a head loss of 4%. In particular, in order to favour the work of the pump, it is recommended to install pipes of a larger diameter on the suction side.

Pressure drops in fittings

Equivalent length of straight pipe (in metres).
Approximate values, variable depending on the quality of the fittings (valves, elbows, etc.).

Pérdida de carga en accesorios

Pressure drop in cast iron pipe

Diagram to determine pressure drop and fluid velocity as a function of flow rate and pipe bore.

Pérdidas de carga en tubería de hierro fundido

Correction coefficients for other pipelines

Effective for calculations and pump selection that do not require a very high degree of accuracy.

Coeficientes correctores para otras tuberías

Pressure drop abacus

In smooth PVC/PF pipes

Ábaco de pérdidas de carga
Whatsapp 9am - 13pm CET +34 972 588 000
Do you want to receive the latests news from ESPA?