How does a plunger pump differ from a piston pump?

In engineering, both piston and plunger pumps are types of reciprocating positive displacement pumps that operate by moving a component back and forth within a cylinder to displace fluid.1

The primary difference lies in the location of the seal and the design of the moving part:

• Piston Pumps: The packed seal is carried directly on the piston, which moves within the cylinder to push the fluid out.1
• Plunger Pumps: The plunger moves through a stationary packed seal located in the cylinder wall, rather than carrying the seal itself.1

Both designs function by increasing and decreasing the volume within the cylinder to draw fluid in through an inlet valve and force it out through an outlet valve. While both types are considered expensive, they are recognized for being extremely reliable and durable in industrial applications.1