In a centrifugal pump, Why is the suction line diameter usually larger than the discharge line diameter? 1. To Reduce Friction Losses in Suction a. A larger suction pipe means slower fluid velocity. Lower velocity = less friction loss in the pipe. b. This helps maintain higher pressure at the pump suction. Less friction = higher NPSHa (Net Positive Suction Head Available), which helps prevent cavitation. 2. To Maintain NPSHa Above NPSHr a. Cavitation occurs if pressure at the suction drops below vapor pressure. b. A large diameter reduces pressure drop, helping to keep suction pressure above vapor pressure. c. This is especially critical in high-flow or hot fluid systems. 3. Discharge Side Can Handle Higher Pressure a. On the discharge side, the fluid is already pressurized by the pump. b. Higher pressure = smaller pipe can be used, and the fluid can still flow efficiently. c. Slightly higher velocity on discharge is acceptable (and sometimes even desirable)