Which of the following best describes a variable displacement pump?

• A. The velocity energy created turns into pressure energy at the input port of the pump.
• B. It has a piston and a piston rod of equal diameters.
• C. It uses centrifugal force to supply energy to the fluid.
• D. They are a workhorse for the pump priming industry.

Answer: (C)

A variable displacement pump is designed to alter its output flow rate based on the demands of the system, which is a key feature that distinguishes it from fixed displacement pumps. These pumps can adjust the size of their internal chamber, allowing for varying volumes of fluid to be pumped, depending on the requirements of the hydraulic system.

The correct choice emphasizes that while centrifugal pumps use the principle of converting velocity energy into pressure energy, a variable displacement pump includes mechanisms such as pistons or vanes that can change the volume of fluid displaced. In this type of pump, the output can be modified without the need for additional mechanical changes, which is beneficial in hydraulic systems requiring precise control.

In contrast, other options do not accurately capture the essence of a variable displacement pump. One refers to piston components that do not define the fundamental operation of the pump itself. Another mentions centrifugal force, which applies to centrifugal pumps rather than variable displacement pumps. The last option discusses pump priming but does not relate directly to the characteristics of variable displacement pumps. Understanding these functions clarifies the crucial role of variable displacement pumps in adaptable hydraulic systems.