TFS · Hydraulic & Fluid Applications · Problem 13PDFSolution in PDF ↓
TFS · Hydraulic & Fluid Applications · Problem 13
Problem & Solution
Video Synthesis
Topic: Pump system — A pump transfer is 100 GPM of water from an open reservoir at atmospheric pressure.
Method: The static suction lift is 5 feet.
Key values: 10 psi, 5 feet, 30 feet and the working pressure at the outlet is 10 psi g
✅ Answer: B
Office Hours
2
Student questions asked in live office hours about this problem
OH 25
Q: Why do we use the 5-foot suction lift for pressure terms in problem 8.13 but the full 100-foot (or 200-foot) elevation for pressure terms in problem 8.11?
A: The key difference is where you establish your datum—in 8.13, the static pressure and elevation changes are treated separately using the pump as reference, whereas in 8.11, when you set the datum at the pump centerline, the discharge head becomes the full 200 feet and you must carefully compare the pressure difference between the two states relative to that datum.
OH 112
Q: When solving problems with a pump driven by a motor, when do you use both efficiencies versus just one, and can you give an example of each?
A: It depends on what you're solving for. Motor efficiency (electrical power to mechanical power) and pump efficiency (mechanical power to hydraulic power) are used together only if you need total system efficiency from electrical input to fluid output. If you're only concerned with what the pump produces given a certain mechanical input, you only need pump efficiency—that's likely why this problem only used pump efficiency.