Pump Sizing Calculator
Use this calculator to determine the total dynamic head (TDH), hydraulic power, and brake horsepower required for your pumping application. Accurate pump sizing is crucial for efficient system operation and longevity.
Input Parameters
GPM ft ft ft ft PSI PSI %Calculation Results
Total Dynamic Head (TDH): 0.00 ft
Hydraulic Power (WHP): 0.00 HP
Brake Horsepower (BHP): 0.00 HP
Understanding Pump Sizing
Pump sizing is the process of selecting the correct pump for a specific application to ensure it can deliver the required flow rate against the system's total resistance. An accurately sized pump operates efficiently, consumes less energy, and has a longer lifespan. Oversized pumps lead to wasted energy, cavitation, and premature wear, while undersized pumps fail to meet system demands.
Key Parameters Explained:
- Flow Rate (Q): This is the volume of liquid that needs to be moved per unit of time. It's a fundamental requirement determined by the process or application.
- Static Suction Head (Hs): The vertical distance from the liquid level in the suction tank to the centerline of the pump. If the liquid source is below the pump, it's a positive value (suction lift). If the liquid source is above the pump, it's a negative value (flooded suction).
- Static Discharge Head (Hd): The vertical distance from the pump centerline to the point where the liquid is discharged.
- Suction Pipe Friction Loss (Hf_s) & Discharge Pipe Friction Loss (Hf_d): As liquid flows through pipes, fittings (elbows, valves), and other components, it encounters resistance, leading to a loss of energy, expressed as "head loss due to friction." These losses must be accounted for in both the suction and discharge lines.
- Discharge Pressure (Hp_d) & Suction Pressure (Hp_s): These represent any pressure (positive or negative) acting on the liquid surface at the discharge or suction points, respectively. For open tanks, gauge pressure is typically 0 PSI. If discharging into a pressurized vessel, that pressure must be converted to an equivalent head.
- Fluid Specific Gravity (SG): This is the ratio of the fluid's density to the density of water (which is 1 at standard conditions). While specific gravity affects the power required to pump the fluid, it does not affect the total dynamic head.
- Pump Efficiency (η): This is a measure of how effectively the pump converts the input power (brake horsepower) into hydraulic power (power delivered to the fluid). It's expressed as a percentage and is crucial for calculating the actual power required.
Understanding the Results:
- Total Dynamic Head (TDH): This is the total equivalent height the pump must lift the fluid, including static lift, friction losses in the piping, and any pressure differences. It's the most critical parameter for selecting a pump.
TDH = (Static Discharge Head - Static Suction Head) + (Suction Friction Loss + Discharge Friction Loss) + (Discharge Pressure Head - Suction Pressure Head) - Hydraulic Power (WHP): Also known as Water Horsepower, this is the actual power imparted to the fluid by the pump. It represents the useful work done by the pump.
WHP = (Flow Rate (GPM) * TDH (ft) * Specific Gravity) / 3960 - Brake Horsepower (BHP): This is the actual power required at the pump shaft to achieve the desired flow and head. It accounts for the pump's efficiency. This is the power rating you would look for when selecting a motor for the pump.
BHP = Hydraulic Power / Pump Efficiency
Example Usage:
Imagine you need to pump water (SG=1) at 100 GPM. The suction tank liquid level is 5 ft below the pump centerline (Hs=5 ft), and the discharge point is 50 ft above the pump centerline (Hd=50 ft). You've calculated suction pipe friction loss as 2 ft and discharge pipe friction loss as 8 ft. The discharge is into a tank pressurized at 10 PSI, and the suction tank is open to atmosphere (0 PSI). The pump has an estimated efficiency of 70%.
Using the calculator with these values:
- Flow Rate: 100 GPM
- Static Suction Head: 5 ft
- Static Discharge Head: 50 ft
- Suction Pipe Friction Loss: 2 ft
- Discharge Pipe Friction Loss: 8 ft
- Discharge Pressure: 10 PSI
- Suction Pressure: 0 PSI
- Fluid Specific Gravity: 1
- Pump Efficiency: 70%
The calculator would yield:
- Total Dynamic Head (TDH): 78.10 ft
- Hydraulic Power (WHP): 1.97 HP
- Brake Horsepower (BHP): 2.81 HP
This means you would need a pump capable of delivering 100 GPM at 78.10 ft of head, and its motor should be rated for at least 2.81 HP (often rounded up to the next standard motor size, e.g., 3 HP).