A submersible pump consists of pump and submersible motor, and the whole assembly is submerged in the fluid to be pumped. The pump shares the same working principle with common pumps though there are some differences in their structure, but the submersible motor, which is divided into dry type, wet type and canned type, differs a lot from conventional ones.
Dry Submersible Motor
The dry submersible motor is similar to ones used on land, but there are some obvious changes. More specifically, the connection surfaces are sealed with rubber ring or rubber gasket, the motor shaft extension is mechanically sealed, the cable is specifically designed for underwater use and its external conductor shall be sealed by rubber sleeve or rubber ring.
The picture above is a dry submersible pump composed of a dry submersible motor and a centrifugal pump with open impeller, and it is intended for the transference of water that has particles. A dry submersible motor is inferior to wet ones in the aspects of reliability and life span because its performance is affected by mechanical seal as well as sealing conditions at cables and connection surfaces, but it is relatively cheap.
Oil/Water-Filled Submersible Motor
Deep well submersible pumps usually make use of oil-filled or water-filled submersible motor, and these motors have strict requirements for cables, bearings and other components in rust and corrosion resistance. Accordingly, they are pretty expensive.
Canned Submersible Motor
For a canned submersible motor, its stator windings are hermetically encapsulated in stainless steel or plastic housing which is filled with resin. The rotor cavity allows the entrance of water, and the shaft extension doesn’t require sealing. This product exhibits high reliability and long service life, but its manufacturing cost is also high.
As illustrated above, submersible pumps are classified into dry submersible pump, wet submersible pump (which is further divided into water-filled type and oil-filled type) and canned submersible pump.