Cavitation occurs when which condition is satisfied?

Cavitation occurs when which condition is satisfied?

• A. NPSHA > NPSHR
• B. NPSHA < NPSHR
• C. The pump discharge pressure is very high
• D. The pump speed is zero

Answer: (B)

Cavitation happens when the pressure on the suction side drops low enough that the liquid boils, forming vapor bubbles that collapse inside the pump. In practice this is described by comparing the head available at the suction (NPSHA) with the head the pump requires to avoid cavitation (NPSHR). When the available suction head is less than the required head (NPSHA < NPSHR), the pressure falls below the liquid’s vapor pressure and cavitation occurs. If there’s more suction head than required (NPSHA > NPSHR), cavitation is avoided. The other scenarios don’t trigger cavitation by themselves. Very high discharge pressure doesn’t directly cause cavitation on the suction side, though it can affect overall operating conditions; zero pump speed means there’s no flow and the fast-acting cavitation mechanism isn’t active under pump operation.

Cavitation happens when the pressure on the suction side drops low enough that the liquid boils, forming vapor bubbles that collapse inside the pump. In practice this is described by comparing the head available at the suction (NPSHA) with the head the pump requires to avoid cavitation (NPSHR). When the available suction head is less than the required head (NPSHA < NPSHR), the pressure falls below the liquid’s vapor pressure and cavitation occurs. If there’s more suction head than required (NPSHA > NPSHR), cavitation is avoided.

The other scenarios don’t trigger cavitation by themselves. Very high discharge pressure doesn’t directly cause cavitation on the suction side, though it can affect overall operating conditions; zero pump speed means there’s no flow and the fast-acting cavitation mechanism isn’t active under pump operation.