Which of the following statements is true about centrifugal pumps?

• A. Discharge pressure increases as flow increases
• B. Discharge pressure decreases as impeller speed increases
• C. Discharge pressure decreases as flow increases
• D. Flow remains constant regardless of discharge pressure

Answer: (C)

Centrifugal pumps operate based on the principles of fluid dynamics, and their performance characteristics are defined by the relationship between flow, pressure, and impeller speed. The correct statement regarding centrifugal pumps is that discharge pressure decreases as flow increases.

This behavior can be understood through the pump's characteristic curve. As the flow rate increases, the pump has to work against the system's resistance, which can lead to a reduction in the available pressure at the discharge. Essentially, when you increase the flow through a centrifugal pump, it typically encounters greater resistance, thereby causing the discharge pressure to drop.

In more practical terms, the system's design and piping also play significant roles in how pressure and flow interact in a pumping scenario. As flow demand increases, the pump can only maintain a certain pressure before it starts to lose efficiency, leading to lower discharge pressure.

The other statements do not accurately reflect the behaviors of centrifugal pumps or these principles. Understanding this relationship is crucial in various applications, such as determining the appropriate pump for a specific system or troubleshooting pump performance in real-world scenarios.