What is the minimum gauge pressure at the pump suction flange when all pumps are operating at 150% capacity?

What is the minimum gauge pressure at the pump suction flange when all pumps are operating at 150% capacity?

• A. 0 psi
• B. 20 psi
• C. 40 psi
• D. 60 psi

Answer: (A)

Suction pressure is the pressure in the pump’s inlet expressed as gauge pressure relative to atmospheric pressure. When all pumps are pushed to 150% capacity, the flow demand is so high that the suction side cannot maintain any extra pressurized head; the suction line can settle at ambient pressure. That makes the lowest possible reading on the suction flange 0 psi gauge, which means the suction is at atmospheric pressure. Positive readings (like 20, 40, or 60 psi) would imply a pressurized suction source, which isn’t sustained under this high-load condition.

Suction pressure is the pressure in the pump’s inlet expressed as gauge pressure relative to atmospheric pressure. When all pumps are pushed to 150% capacity, the flow demand is so high that the suction side cannot maintain any extra pressurized head; the suction line can settle at ambient pressure. That makes the lowest possible reading on the suction flange 0 psi gauge, which means the suction is at atmospheric pressure. Positive readings (like 20, 40, or 60 psi) would imply a pressurized suction source, which isn’t sustained under this high-load condition.