Rotary Airlock Valve Capacity Calculator

Enter the rate of conveying, product density, valve efficiency, and rotor speed into the calculator to determine the Rotary Airlock Valve Capacity.

Rotary Airlock Valve Capacity Formula

This calculator estimates the rotary airlock valve capacity needed from the conveying rate, product density, valve efficiency, and rotor speed. It is useful for feeder sizing, throughput checks, and comparing whether a valve can support the required material flow under actual operating conditions.

C = \frac{R}{D \cdot \left(\frac{E}{100}\right) \cdot S}

In this equation, the calculated value represents the effective capacity term required by the sizing method used in the calculator. For reliable results, keep all inputs on a consistent basis and use operating bulk density rather than idealized material density.

Variable	Meaning	Typical Input Basis
C	Rotary airlock valve capacity	Equivalent valve capacity or displacement basis used for sizing
R	Rate of conveying	Material flow rate entered into the calculator
D	Product density	Operating bulk density of the conveyed material
E	Valve efficiency	Percent efficiency from 0 to 100
S	Rotor speed	Revolutions per minute

Rearranged Equations

If you know four values and need to solve for the fifth, these forms are useful:

R = C \cdot D \cdot \left(\frac{E}{100}\right) \cdot S

D = \frac{R}{C \cdot \left(\frac{E}{100}\right) \cdot S}

E = \frac{100R}{C \cdot D \cdot S}

S = \frac{R}{C \cdot D \cdot \left(\frac{E}{100}\right)}

How to Calculate Rotary Airlock Valve Capacity

Determine the required conveying rate for the process.
Measure or estimate the material’s bulk density at operating conditions.
Enter the valve efficiency as a percentage. Lower efficiency means more capacity is required to achieve the same throughput.
Enter the actual rotor speed in RPM.
Calculate the capacity and compare it to the valve’s available rotor pocket volume or rated handling capability.

The most important part of the calculation is using realistic plant values. Density should reflect the material as it flows, not the true solid density of the particles. Efficiency should reflect fill quality, leakage, air bypass, and slip under the expected pressure differential.

Example

Suppose the conveying rate is 100, the product density is 5, the valve efficiency is 75%, and the rotor speed is 200 RPM.

C = \frac{100}{5 \cdot \left(\frac{75}{100}\right) \cdot 200} = 0.1333

Under those assumptions, the valve must provide an effective capacity of approximately 0.1333 on the same unit basis used in the calculation.

What Affects Rotary Airlock Valve Capacity?

Bulk density: Lighter materials generally require more valve volume to move the same amount of product.
Valve efficiency: Pocket fill losses, internal leakage, and air blowback reduce effective capacity.
Rotor speed: Higher RPM can increase throughput, but excessive speed may reduce fill efficiency and increase wear.
Material flow behavior: Cohesive, aerated, fragile, or abrasive products often perform differently than free-flowing granular materials.
Pressure differential: Larger pressure drops across the valve can increase leakage and reduce real-world performance.
Rotor geometry: Pocket count, pocket depth, rotor diameter, and tip clearance all influence achievable capacity.

Practical Sizing Notes

Use bulk density, not true particle density.
Use the actual operating RPM, not only the motor nameplate speed.
Enter efficiency as a percent, so 75 means 75%, not 0.75.
If the calculated efficiency would exceed 100%, the inputs are not physically consistent.
If the required capacity is too high for the selected valve, increase valve size, improve efficiency, or adjust rotor speed.

Common Input Mistakes

Mixing unit systems between flow rate, density, and capacity.
Using laboratory density values instead of in-process bulk density.
Ignoring efficiency losses caused by pressure, wear, or poor rotor fill.
Assuming a higher RPM always improves performance without checking fill quality and product damage.
Comparing calculated capacity to a vendor rating that was developed under different material conditions.

When used correctly, this calculator gives a fast estimate for feeder sizing and performance checks, helping determine whether a rotary airlock valve can support the desired conveying rate with the available speed and efficiency.