An ESP pump is the multistage centrifugal element of an electrical submersible pumping system. Each stage adds head, so the required total dynamic head is met by stacking stages inside a housing sized for the casing.
How the stages work
Fluid enters the impeller, gains kinetic energy, and passes into the diffuser where velocity converts to pressure. Repeating the pair hundreds of times produces the head an ESP pump delivers at its rated flow.
Selection basics
Pump selection starts from the target rate and the available casing size: the housing outside diameter has to clear the casing drift, and the operating point should sit inside the recommended range of the published curve.