A submersible pump is a specialty pump that comes with a hermetically sealed motor close-coupled to the pump body. The whole assembly is submerged in the fluid to be pumped. The main advantage of this type of pump is that it prevents pump cavitation, a problem associated with a high elevation difference between the pump and the fluid surface. Its main purpose is to push fluid from a low-lying source up to the surface.
One of the biggest benefits of having a pump completely submerged in a fluid is that it does not need to be primed. This makes submersible pumps more efficient than external pumps because water pressure assists in the movement of fluid into the pump, which requires less energy.
The most common type of submersible pumps are multistage centrifugal pumps operating in a vertical position. Liquids, accelerated by the impeller, lose their kinetic energy in the diffuser, where a conversion of kinetic to pressure energy takes place. This is the main operational mechanism of radial and mixed flow pumps.
On the other hand, horizontal submersible uses a hydraulic motor rather than an electrical motor, and may be closed cycle where power fluid is initially separated from the produced fluid, or open cycle where power fluid is mixed with produced fluid and separated on the surface).
There are also screw-type submersible pumps, there is a steel screw which is used as a working element in them. The screw allows the pump to work in water with a high sand content and other mechanical impurities.
