What happens to the suction lift of a pump when the water temperature increases from 150°F to 200°F?

• A. Increases
• B. Decreases
• C. Remains the same
• D. Becomes unstable

Answer: (B)

When the water temperature increases, the density of the water decreases due to thermal expansion. This change in density affects the suction lift of the pump. The suction lift is the vertical distance that the pump can lift the fluid from the source to the pump. As the temperature rises, the vapor pressure of water also increases, which may lead to cavitation issues in the pump if the pump's design is not adequate to handle these conditions.

In this case, the increased vapor pressure combined with the decreased density means that the pump will have a lower effective suction lift. This is because a pump's ability to lift fluid is primarily dependent on the fluid's density and the vapor pressure. Thus, as the temperature rises, the suction lift of the pump decreases, making it more challenging for the pump to create the necessary pressure differential to lift the fluid efficiently.