Submersible Pumps-immersion depth

View of the Hüdig AST series

The immersion depth of a submersible motor pump such as the AST series from Hüdig plays a decisive role in its performance, especially with regard to the delivery head from the water surface. In this article, we look at how immersion depth affects this key performance indicator.

Calculating the head from the water surface:

The head of a submersible pump looks at the pressure it can generate vertically, under atmospheric conditions. This pressure is often specified in meters of water head, with 10 meters corresponding to approximately 1 bar of pressure. However, the delivery head is only relevant when the water is to be lifted above the water surface. Up to this point, there is a water column above the submersible pump without it having to do anything. Only when the water is to be lifted above the surface is the power of the submersible pump required to push the water higher than the surface. This means that the immersion depth has practically no direct influence on the total delivery head above water.

Influence of the immersion depth on the delivery head:

However, the immersion depth has an indirect influence on the delivery head from the water surface. A greater immersion depth enables the pump to lift the water over a greater vertical distance before it has to support the water column above the surface with its power. This can be particularly important in deep waters, where the pump must first overcome a considerable water column before it can lift the water above the surface.

NPSH value and immersion depth:

As mentioned above, the NPSH (Net Positive Suction Head) value does not play a significant role for fully submerged pumps, as the pump does not have to draw in water. Instead, the NPSH value is crucial for preventing cavitation and maintaining the pump's performance in other operating conditions, such as partial submersion or when using suction lines.

To conclude:

The immersion depth of a submersible pump such as the AST series from Hüdig has no direct influence on the delivery head above the water surface. The performance of the pump is only required when the water is to be lifted above the surface. However, a greater immersion depth can indirectly influence the efficiency of the pump, especially in deep water. When selecting and installing submersible pumps, careful consideration of the immersion depth is therefore essential in order to achieve the desired performance.

Note: In this consideration, arising friction losses in the hoses/pipes are not taken into account!