About Rotodynamic Pumps

A rotodynamic pump is a kinetic machine in which energy is continuously imparted to the pumped fluid by means of a rotating impeller, propeller, or rotor. The most common types of rotodynamic pumps are axial flow, mixed flow, and centrifugal pumps (radial flow). Centrifugal pumps are the most common rotodynamic pump used today because they serve a wide range of applications and have a long history of safe and reliable operation. For full details on rotodynamic pumps refer to ANSI/HI 1.1-1.2, 2.1-2.2, 5.1-5.6, and 12.1-12.6.  For more information, visit our Rotodynamic e-learning page.

There are three common pump classifications within the rotodynamic pump family: 

1. Overhung (OH) Pumps

In this group, the impeller(s) is mounted on the end of a shaft that is cantilevered or “overhung” from its bearing supports. These pumps are either close coupled, where the impeller is mounted directly on the driver shaft; or separately coupled, where the impeller is mounted on a separate pump shaft supported by its own bearings.  Types of overhung rotodynamic pumps are described in ANSI/HI 1.1-1.2.  

• Sealless pump is a term used to define a pump that does not utilize a dynamic shaft seal as the method to limit leakage to atmosphere.  This is accomplished by the use of a canned motor or a magnetic coupling.  Sealless pumps are used when there is a need to contain toxic, dangerous, and/or valuable fluids.  Types of sealless rotodynamic pumps are described in ANSI/HI 5.1-5.6.  
  

2. Between Bearings (BB) Pumps

In this group, the impeller(s) is mounted on a shaft with bearings at both ends. The impeller(s) is mounted between these bearings. These pumps may be further identified as one- and two-stage or multistage configurations. Types of between bearing rotodynamic pumps are outlined in ANSI/HI 1.1-1.2.

3. Vertically Suspended (VS) Pumps

Rotodynamic vertical pumps are kinetic machines in which energy is continuously imparted to the pumped fluid by means of an impeller, propeller, or rotor having a vertical axis of rotation. Within these broad types there are many design variations in both horizontal axis and vertical axis configurations.  Historically a particular group within this pump category has been called vertical turbine pumps.  Vertical turbine pumps typically use radial, modified radial or mixed flow impellers. Types of vertically suspended rotodynamic pumps are outlined in ANSI/HI 2.1-2.2.