How can you reduce the load when starting an electrically driven centrifugal pump?

How can you reduce the load when starting an electrically driven centrifugal pump?

• A. Close both valves
• B. Open the suction valve and close the discharge valve
• C. Increase the motor speed
• D. Use a smaller pump

Answer: (B)

Opening the suction valve while closing the discharge valve is a method to reduce the load on an electrically driven centrifugal pump during startup. When the discharge valve is closed, it limits the flow of fluid out of the pump, which minimizes the resistance the pump faces. Simultaneously, opening the suction valve allows the pump to draw in fluid more freely without the added load created by having to push out against a closed discharge. This configuration reduces the initial pressure required to start the pump, which can help prevent excessive torque and current draw on the motor. Starting with the discharge closed means that the pump can build up internal pressure without working against the full system head, thereby starting up more smoothly and safely. Other options are less effective or may lead to operational issues. Closing both valves would prevent fluid flow entirely, which can cause the pump to run dry and potentially damage it. Increasing the motor speed is not a safe option during startup, as it could lead to abrupt load changes that can stress the pump and motor. Using a smaller pump might reduce the load, but it doesn’t tackle the issue of managing the startup conditions properly, and it may not be appropriate for the application if the system requires a specific flow rate.

Opening the suction valve while closing the discharge valve is a method to reduce the load on an electrically driven centrifugal pump during startup. When the discharge valve is closed, it limits the flow of fluid out of the pump, which minimizes the resistance the pump faces. Simultaneously, opening the suction valve allows the pump to draw in fluid more freely without the added load created by having to push out against a closed discharge.

This configuration reduces the initial pressure required to start the pump, which can help prevent excessive torque and current draw on the motor. Starting with the discharge closed means that the pump can build up internal pressure without working against the full system head, thereby starting up more smoothly and safely.

Other options are less effective or may lead to operational issues. Closing both valves would prevent fluid flow entirely, which can cause the pump to run dry and potentially damage it. Increasing the motor speed is not a safe option during startup, as it could lead to abrupt load changes that can stress the pump and motor. Using a smaller pump might reduce the load, but it doesn’t tackle the issue of managing the startup conditions properly, and it may not be appropriate for the application if the system requires a specific flow rate.