When does a hydraulic pump produce a constant flow rate?

A hydraulic pump produces a constant flow rate when it is a fixed displacement pump. This type of pump is designed to deliver a specific volume of fluid with each rotation of its components, regardless of the pressure or load demand on the system. This means that the flow rate is determined solely by factors such as the pump speed and its design, and it remains consistent unless intentionally altered by changing the pump speed or utilizing some other mechanism.

In contrast, variable displacement pumps can adjust their output flow based on the system's requirements, which means the flow rate can change with varying loads. Gear pumps, while they might be fixed displacement types, are not exclusively so, as they can also be designed for variable displacement applications. Therefore, focusing on the fixed displacement nature provides clarity about why this option represents a constant flow rate effectively.