In NFPA 20, what is the primary reason for keeping suction piping short and straight?

In NFPA 20, what is the primary reason for keeping suction piping short and straight?

• A. To minimize noise in the suction line
• B. To reduce the need for maintenance personnel
• C. To simplify installation
• D. To prevent cavitation by maintaining adequate pressure and reducing friction

Answer: (D)

Keeping suction piping short and straight minimizes friction losses and turbulence along the path to the pump. That helps preserve pressure at the pump suction, so the fluid does not drop below its vapor pressure as it travels through the pipe. When suction lines are long or have many bends, friction and velocity changes raise the likelihood that the pump suction will fall below the required pressure, leading to cavitation. Cavitation can damage the impeller and reduce pump performance, so maintaining adequate suction pressure (NPSHA relative to NPSHR) is the primary reason for this piping practice. While noise, ease of installation, or maintenance can be related considerations, they are not the main reason NFPA 20 emphasizes short, straight suction runs.

Keeping suction piping short and straight minimizes friction losses and turbulence along the path to the pump. That helps preserve pressure at the pump suction, so the fluid does not drop below its vapor pressure as it travels through the pipe. When suction lines are long or have many bends, friction and velocity changes raise the likelihood that the pump suction will fall below the required pressure, leading to cavitation. Cavitation can damage the impeller and reduce pump performance, so maintaining adequate suction pressure (NPSHA relative to NPSHR) is the primary reason for this piping practice. While noise, ease of installation, or maintenance can be related considerations, they are not the main reason NFPA 20 emphasizes short, straight suction runs.