Which is a key factor in maintaining efficient operation within a positive displacement pump?

In the context of maintaining efficient operation in a positive displacement pump, relieving pressure prior to starting is crucial because it ensures that the pump can function without excessive load or strain on its components. Positive displacement pumps move fluid by trapping a fixed amount of it and forcing that volume into the discharge pipe; if there is significant back pressure from a closed system, starting the pump can lead to mechanical failure or performance issues.

By relieving pressure, the pump can start under optimal conditions, reducing the risk of cavitation and allowing for a smoother initial operation. This practice is essential for preventing damage and ensuring that the pump operates effectively within its designed capacity.

The other options, while related to pump operation, do not directly contribute to the initial efficiency and safe start-up of a positive displacement pump as effectively as relieving pressure does.