If the nozzle pressure is 70 psi, friction loss is 15 psi, and elevation head is 5 psi, what should PDP be?

If the nozzle pressure is 70 psi, friction loss is 15 psi, and elevation head is 5 psi, what should PDP be?

• A. 70 psi
• B. 90 psi
• C. 20 psi
• D. 15 psi

Answer: (B)

Pumping discharge pressure must cover what the nozzle needs plus the losses and any elevation difference along the water path. You add the pressure at the nozzle to the friction loss and the elevation head to get the pressure the pump must deliver. So you take 70 psi (nozzle pressure) + 15 psi (friction loss) + 5 psi (elevation head) = 90 psi. The pump discharge pressure should be 90 psi. The other numbers would omit either the losses or part of the elevation requirement, so they don’t meet all the needs of delivering the nozzle pressure.

Pumping discharge pressure must cover what the nozzle needs plus the losses and any elevation difference along the water path. You add the pressure at the nozzle to the friction loss and the elevation head to get the pressure the pump must deliver.

So you take 70 psi (nozzle pressure) + 15 psi (friction loss) + 5 psi (elevation head) = 90 psi. The pump discharge pressure should be 90 psi. The other numbers would omit either the losses or part of the elevation requirement, so they don’t meet all the needs of delivering the nozzle pressure.