What feature allows positive-displacement pumps to operate effectively?

Positive-displacement pumps operate effectively due to their design, which includes seals against the casing. This design is essential for creating a specific volume of fluid that is moved with each cycle of the pump. The seals prevent fluid from leaking back into the inlet side, ensuring that the full volume intended to be pumped is indeed delivered.

The functionality of positive-displacement pumps revolves around trapping a fixed amount of liquid and then moving it through the discharge. The tight seals maintain the pressure necessary for the pump to operate efficiently, especially in applications where a steady flow is critical. This feature allows for effective performance even at varying system pressures, making them ideal for scenarios where consistent flow rates are required regardless of the pressure levels.

Other features such as variable speed control, while useful in controlling flow rates or adapting to different system needs, do not specifically define the operational effectiveness of positive-displacement pumps. Similarly, constant pressure flow is a characteristic related more to system requirements than to the inherent function of the pump itself. Vane adjustments pertain to a different category of pumps and are not applicable to the functioning principles of positive-displacement types.