Suction Piping

Because of pipe friction, the suction piping toward a pump constitutes a region of decreasing pressure. If this pressure falls below the vapor pressure of the fluid at the specific temperature/pressure conditions, the fluid will boil, causing cavitation. A centrifugal pump will hurl the liquid portion of this to its periphery, leaving a zone of vapor toward the center of the impeller. Basically. this stalls the pump.

This problem occurs especially with hot fluids (or even with cold refrigerant fluids) near their boiling points. The larger pump suction piping reduces this effect. The 5d straight length helps to prevent turbulence and pressure drop as the fluid approaches the pump. In addition, some pumps incorporate a vane in the suction that prevents the fluid from rotating as it approaches the pump.