NPSH is primarily used to evaluate the potential for cavitation in a pump. Which statement best aligns with this concept?

• A. It represents the difference between suction pressure and vapor pressure
• B. It represents the pump's maximum discharge pressure
• C. It represents the normal operating temperature of the liquid
• D. It represents the pump's efficiency

Answer: (A)

Net Positive Suction Head is about having enough pressure on the suction side to keep the liquid from turning into vapor. Cavitation happens when the pressure in the suction area drops to the liquid’s vapor pressure, creating vapor bubbles that can damage the pump. NPSH expresses how much pressure head is available at the suction compared with the liquid’s vapor pressure, usually described as the difference between suction pressure and vapor pressure (in head units). If there’s a healthy margin beyond what the pump needs (NPSHa > NPSHr), cavitation is unlikely. The other statements don’t describe this risk: one talks about maximum discharge pressure, another about temperature, and another about efficiency.