1. What is Pump Head Calculation?

The Total Dynamic Head (TDH) calculation determines the total equivalent height that a fluid needs to be pumped, accounting for vertical lift, friction losses, and any additional pressure requirements. It's essential for proper pump selection and system design.

2. Understanding the Components

The TDH equation consists of three main components:

Where:

• Static Head — The vertical distance between the fluid surface and the discharge point (ft)
• Friction Loss — Head loss due to friction in pipes, valves, and fittings (ft)
• Pressure Head — Additional head required to maintain system pressure (ft)

Explanation: The static head is the minimum energy required, while friction loss and pressure head account for system resistance and operational requirements.

3. Example Calculation

Scenario: A water system with:

• Static head: 50 ft
• Friction loss: 12 ft
• Pressure head requirement: 15 ft

Calculation: TDH = 50 ft + 12 ft + 15 ft = 77 ft

Result: You would need a pump capable of providing at least 77 feet of head at your required flow rate.

4. Practical Applications

Details: Accurate TDH calculation is crucial for:

• Selecting the right pump size
• Ensuring proper system performance
• Avoiding energy waste from oversized pumps
• Preventing insufficient flow from undersized pumps

5. Frequently Asked Questions (FAQ)

Q1: How do I determine friction loss?
A: Friction loss can be calculated using the Hazen-Williams equation or Darcy-Weisbach equation, or obtained from pipe friction charts based on pipe material, diameter, length, and flow rate.

Q2: What if my system has no pressure requirement?
A: If you're just pumping to an open tank or similar, the pressure head component can be set to zero.

Q3: How does viscosity affect TDH?
A: Higher viscosity fluids increase friction losses. Special calculations are needed for fluids significantly more viscous than water.

Q4: Should I add a safety factor?
A: It's common practice to add 10-20% to the calculated TDH to account for uncertainties and future system modifications.

Q5: How does TDH relate to pump power requirements?
A: Pump power (HP) = (Q × TDH × SG) / (3960 × η), where Q is flow rate (GPM), SG is specific gravity, and η is pump efficiency.