Screw Pump Flow Rate Calculator

Screw Pump Flow Rate Equation:

\[ Q = \frac{\pi}{4} \times (D^2 - d^2) \times \text{pitch} \times \text{RPM} \times \eta \div 60 \]

Outer Diameter (D):

Root Diameter (d):

Pitch:

RPM:

rev/min

Efficiency (η):

(0-1)

Flow Rate (Q):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Screw Pump Flow Rate?

The screw pump flow rate represents the volumetric throughput capacity of a screw pump, determined by its geometry, rotational speed, and efficiency. It's crucial for proper pump selection and system design in various industrial applications.

2. How Does the Calculator Work?

The calculator uses the screw pump flow rate equation:

\[ Q = \frac{\pi}{4} \times (D^2 - d^2) \times \text{pitch} \times \text{RPM} \times \eta \div 60 \]

Where:

\( Q \) — Flow rate (m³/h)
\( D \) — Outer diameter (m)
\( d \) — Root diameter (m)
pitch — Axial distance between screw threads (m)
RPM — Rotational speed (revolutions per minute)
\( \eta \) — Pump efficiency (0-1)

Explanation: The equation calculates the theoretical displacement volume per revolution, adjusted for efficiency and converted to hourly rate.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate estimation is essential for system design, ensuring the pump meets process requirements while avoiding over-sizing (which increases costs) or under-sizing (which reduces performance).

4. Using the Calculator

Tips: Enter all dimensions in meters, RPM in revolutions per minute, and efficiency as a decimal between 0 and 1 (typically 0.7-0.9 for screw pumps). Ensure outer diameter is greater than root diameter.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between outer and root diameter?
A: Outer diameter is the maximum screw diameter including threads, while root diameter is the central shaft diameter excluding threads.

Q2: How does pitch affect flow rate?
A: Larger pitch increases flow rate proportionally but may reduce pressure capability and efficiency.

Q3: What's a typical efficiency value?
A: Well-designed screw pumps typically have 70-90% efficiency (0.7-0.9), depending on design, viscosity, and operating conditions.

Q4: Can this be used for multi-screw pumps?
A: For twin/triple screw pumps, multiply the result by the number of working screws (e.g., 2 for twin-screw).

Q5: How does viscosity affect the calculation?
A: Viscosity mainly impacts efficiency (η) - higher viscosity typically reduces efficiency and thus flow rate at given RPM.