A rotary piston pump operates using a rotary mechanism where a piston is housed within a larger cylinder. The piston is typically eccentrically mounted, which means it is not centered within the cylinder. As the piston rotates, it creates expanding and contracting volumes within the cylinder.

Here’s a step-by-step explanation of the process:

1. Intake Stroke: As the piston moves away from the inlet port of the pump, it creates a vacuum. This vacuum causes the inlet valve to open due to the pressure difference, allowing the fluid to enter the pump.
2. Compression Stroke: As the piston continues to rotate, the volume of the fluid chamber decreases. This action compresses the fluid, increasing its pressure.
3. Discharge Stroke: When the fluid pressure exceeds the pressure in the discharge line, the outlet valve opens, and the fluid is forced out of the pump.
4. Return Stroke: After the discharge, the piston continues to rotate back towards the inlet port, and the cycle repeats.

This type of pump is known for its precision and ability to handle a wide range of viscosities, making it useful in applications such as fuel injection, hydraulic systems, and in the chemical industry where precise fluid handling is necessary.