Radial piston pump

Note: Information and figures included in this post are copied from Wikipedia with many modifications.

Radial piston pump has the following features:

1.   Comprises a circular pattern of piston-cylinder arrangements. Pistons move in radial direction with respect to the drive shaft

2.    The stroke of each piston is caused by an eccentric drive shaft or an external eccentric ring

3.   Types according to construction: 1. Inside impinged     2. Outside impinged

Advantages:

1.   high efficiency

2.   high pressure (up to 1000 bar)

3.   low flow and pressure ripple (due to the small dead volume in the workspace of the pumping piston)

4.   low noise level

5.   very high load at lowest speed due to the hydro-statically balanced parts possible

6.   no axial internal forces at the drive shaft bearing

7.   high reliability

Disadvantages:

Larger radial dimensions when compared with axial piston pumps

Inside impinged pump:

1.   Pistons and cylinders rotate about the shaft axis

2.   Outer ring is eccentric

3.   Suction and pressure sides are fixed for the same direction of rotation 

Outside impinged pump:

1.   Pistons and cylinders don’t rotate

2.   Rotating shaft is eccentric

3.   Each cylinder needs suction and discharge valves

 Note: all pistons are spring-loaded to make sure that piston follower is always in contact with the eccentric part.