Piston Vacuum Pumps are positive displacement pumps that have an oscillating motion. A piston, usually powered by a rotating mechanism, moves back and forth in a cylindrical cavity. A seal is located between the cavity wall and the piston which creates a pressure difference when the piston moves. This pressure differential is then used to transfer a fluid or gas through the pump. Different designs can include mounting the piston axially or radially and can even utilize multiple pistons. Axial piston pumps have multiple pistons, all on the same axis, arranged in a circle with each piston protruding out at different times controlling different flows. Radial piston pumps are arranged like spokes on a wheel. A cylinder block rotates eccentrically around the center of the housing moving the pistons along the way. This configuration of a radial pump has a very high efficiency and low noise levels.
Piston pumps can handle significantly high pressures, are able to be used with viscous fluids and also fluids containing solid particles. They are used for hydraulic applications such as car jacks and forklifts. The axial and radial pumps are used in advanced settings where multiple different valves need to be controlled simultaneously. Changing the pressure of the pump has minimal effects on the performance providing a good choice for different applications but generally used for lower flow rates. Because the seal between the piston and wall must be strong, a faster stroke could increase friction and prove to be harmful for the seal.