What should you do first when starting a centrifugal pump that is part of a manifold with no check valves?

When starting a centrifugal pump that is part of a manifold with no check valves, the initial focus is on ensuring proper fluid flow and avoiding damage to the system. Opening the suction valve before starting the pump allows the pump to draw fluid into its casing, which is crucial for its operation. If the discharge valve is closed, the pump can build pressure safely without causing back pressure issues that can lead to pump damage or cavitation. Once the pump is started, slowly opening the discharge valve allows for controlled pressurization of the system, minimizing the risk of hydraulic shock and ensuring that fluid can flow smoothly through the system. This sequence effectively ensures that the pump operates correctly and reduces the risk of air entering the system, which can happen if the discharge valve is opened too quickly while the pump is running.