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Fluid Mechanics - Engineering

Q1:

While starting a centrifugal pump, its delivery valve should be kept

A opened.

B closed.

C either opened or closed ; it does not make any difference.

D either opened or closed; depending on the fluid viscosity.

ANS:B - closed.

When starting a centrifugal pump, its delivery valve should typically be closed. Here's why:

  1. Preventing Reverse Flow: Keeping the delivery valve closed prevents the backflow of fluid from the discharge side back into the pump when it is not operating. This helps in maintaining prime (ensuring the pump remains filled with fluid) and prevents potential damage to the pump impeller from reverse rotation or water hammer effects.
  2. Starting Procedure: The recommended procedure for starting a centrifugal pump is to ensure the pump casing is filled with liquid (primed) before starting the pump. Once the pump is started, it begins to create suction and pressure, which will eventually open the delivery valve once the system reaches operational conditions.
  3. Operational Safety: Opening the delivery valve before starting the pump can lead to issues such as loss of prime or damage to the pump due to backflow or sudden pressure surges.
Therefore, to ensure proper operation and safety of the centrifugal pump, the delivery valve should be kept closed while starting the pump.