What is the most likely cause if a centrifugal pump is losing its prime after being started?

Losing prime in a centrifugal pump is a common issue that can hinder its performance and lead to system failures. One primary cause of this problem is an air leak through the stuffing box. The stuffing box is where the pump shaft enters the casing and provides sealing to prevent fluid from leaking out. If there is wear or damage to the packing or seals in this area, air can be drawn into the pump. This influx of air disrupts the balance of liquids within the pump and can lead to a loss of prime.

Additionally, when a centrifugal pump is operating, a stable, fully-filled casing ensures that the impeller can generate the necessary suction to move the fluid. If air enters the casing because of a leak, the pump cannot establish the required pressure differential, resulting in a loss of prime. Therefore, addressing air leaks in the stuffing box is critical to maintaining proper pump operation and preventing this issue from recurring.

Other potential causes, while possible, are less likely to produce results as quickly or evidently as an air leak through the stuffing box. For instance, a clogged inlet screen might restrict flow but would not typically cause a loss of prime immediately after starting. Similarly, a faulty check valve might allow backflow but would not directly introduce air into the pump