Positive displacement pump parts include a ____.

• A. Diaphragm and Piston
• B. Impeller and Volute
• C. Shaft and Bearing
• D. Casing and Cover

Answer: (A)

In a positive displacement pump, fluid is moved by trapping a fixed amount in a chamber and then pushing it out. The devices that actually create that trapped volume are moving boundary elements, such as a diaphragm that flexes to expand and contract the chamber or a piston that slides to change the volume. That’s why diaphragm and piston are the components you’d expect to find as the parts that enable displacement in these pumps. Other pump types rely on different mechanisms: a centrifugal pump uses an impeller and a volute to impart energy to the fluid, while shaft and bearing or casing and cover are supporting or enclosing parts rather than the means of displacing the fluid.