When is damage most likely to occur in a centrifugal pump with a defective vertical check valve?

Damage in a centrifugal pump with a defective vertical check valve is most likely to occur when starting up an additional pump. During this phase, the system experiences changes in pressure and flow dynamics, which can lead to backflow or reverse flow if the check valve is not functioning properly.

In a typical setup, check valves are designed to prevent backflow and maintain the desired direction of fluid flow. If the check valve is defective, starting another pump can create conditions where fluid is forced back into the pump that has the faulty check valve, potentially causing cavitation, increased wear, or mechanical failure.

During idle times, the pump is not actively moving fluid, which minimizes the risk of damage related to flow reversal. Maintenance checks generally involve shutting down and isolating the pump, reducing the likelihood of mechanical harm. Running at maximum capacity poses a risk in terms of wear and tear under normal operating conditions but does not specifically relate to the issues caused by a defective check valve during sudden changes in system operation like starting another pump. Thus, the scenario when starting up an additional pump is where the defective check valve issue becomes critical, making it the most likely time for damage to occur.