Put simply, head is the height at which a pump can raise fluid up and is measured in metres or feet. We use it when specifying centrifugal pumps because their pumping characteristics tend to be independent of the fluid’s specific gravity, often referred to as relative density.
Head can sometimes be confused with pressure, purely because there is a close relationship between the two parameters but there is one fundamental difference.
Head is fluid independent, that is, regardless of the fluid’s relative density, the pump will lift it to the same height. Therefore, it does not matter whether the fluid is water or heavy sludge.
Pressure, on the other hand, is fluid dependent and is affected by gravity. Therefore, the same head will generate a different pressure depending on the fluid’s relative density.
Suction conditions are also relevant to the pump head. If the suction level is lower, the head measured will be less, and vice versa. The pump’s motor converts electrical energy into mechanical energy, which the pump then imparts into the fluid as pressure. Raising or lowering the suction level therefore adjusts the potential pressure of the liquid. The more pressure the pump delivers, the higher the head will be.
The total head parameter is crucial when buying or renting the right pump for your application. It gives an accurate indication of the pump’s performance, regardless of other contributing factors such as suction level and fluid density.