ANS:B - low barometric pressure

Cavitation in a centrifugal pump results from low discharge pressure. Here’s an explanation: Cavitation occurs when the pressure of the liquid drops below its vapor pressure, causing the formation of vapor bubbles within the pump. In the context of a centrifugal pump:

• High discharge pressure: High discharge pressure typically prevents cavitation because it keeps the pressure above the vapor pressure of the fluid, preventing the formation of vapor bubbles.
• Low barometric pressure: Barometric pressure, which is the atmospheric pressure, does not directly cause cavitation within the pump. Cavitation occurs within the pump itself due to local pressure drops.
• High discharge velocity: While high discharge velocity is a factor, cavitation is more directly related to pressure. High discharge velocity may contribute to localized pressure drops, but it's not the primary cause.
• High discharge rate: This also contributes to the conditions that can lead to cavitation, but it's not the direct cause. A high discharge rate may lead to lower pressures at the pump inlet or within the impeller, contributing to cavitation.

Therefore, cavitation in a centrifugal pump primarily results from low discharge pressure, where the pressure within the pump drops below the vapor pressure of the fluid, causing vapor bubble formation and subsequent collapse, which can damage pump components and reduce efficiency.