centrifugal station operator Interview Questions and Answers

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Centrifugal Station Operator Interview Questions and Answers

  1. What is a centrifugal pump?

    • Answer: A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure of a fluid. It works by accelerating the fluid outwards from the center of the impeller, converting rotational kinetic energy into the fluid's pressure energy.

  2. Explain the principle of operation of a centrifugal pump.

    • Answer: The impeller's rotation accelerates the fluid, increasing its velocity. This high-velocity fluid then enters the pump casing, where its kinetic energy is converted into pressure energy as the fluid slows down due to the gradually increasing cross-sectional area of the volute or diffuser.

  3. What are the different types of centrifugal pumps?

    • Answer: There are various types, including single-stage and multi-stage pumps, radial flow, mixed flow, and axial flow pumps. The choice depends on the required head (pressure) and flow rate.

  4. What is Net Positive Suction Head (NPSH)?

    • Answer: NPSH is the absolute pressure at the pump suction, minus the vapor pressure of the liquid, expressed in feet or meters of liquid. It represents the available energy to prevent cavitation.

  5. What is cavitation, and how does it affect a centrifugal pump?

    • Answer: Cavitation occurs when the liquid pressure at the pump inlet drops below its vapor pressure, causing vapor bubbles to form. These bubbles collapse violently, causing noise, vibration, erosion of impeller and casing, and reduced pump efficiency.

  6. How do you prevent cavitation?

    • Answer: Cavitation is prevented by ensuring sufficient NPSH available is greater than or equal to the required NPSH of the pump. This involves maintaining proper suction pressure, minimizing fluid temperature, using a larger diameter suction pipe, and ensuring there are no restrictions or leaks in the suction line.

  7. What is the significance of pump curves?

    • Answer: Pump curves graphically represent the relationship between flow rate, head, and efficiency at various operating points. They are essential for selecting the right pump and ensuring optimal operation.

  8. Explain the importance of pump priming.

    • Answer: Priming fills the pump casing with liquid before starting to eliminate air pockets that prevent the pump from developing suction. Most centrifugal pumps need to be primed before operation.

  9. How do you check for leaks in a centrifugal pump system?

    • Answer: Regularly inspect all connections, gaskets, and seals for visible leaks. Listen for unusual noises that might indicate leaks. Use pressure gauges to monitor system pressure for any significant drops indicating leaks.

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