ENGINEERED FOR THE PROCESS
Rotary Valve Capacity Calculator and Formula
Estimate rotary feeder capacity in kg/h and t/h, then review the operating factors that change real output.
What this calculation can—and cannot—tell you
The formula converts usable rotor displacement into a theoretical mass flow. It is useful for comparing an initial valve size and speed against a required throughput, provided the loose bulk density and expected pocket filling are realistic.
Four inputs used by the calculator
- Usable rotor displacement per revolution—not only the nominal inlet size.
- Rotor speed under the intended operating duty.
- Estimated pocket filling for the actual material behavior.
- Representative loose bulk density at the valve inlet.
Engineering checks still required
- Pressure differential, air leakage and product fallback.
- Starting torque, drive margin and continuous-duty requirements.
- Particle damage, abrasion, buildup and rotor-clearance risks.
- Flange dimensions, available height and maintenance access.
Use the estimate below as a starting point, then confirm the proposed configuration against process data and an approved project drawing.
CAPACITY ESTIMATE
Rotary valve capacity calculator
Enter the usable displacement per revolution, rotor speed, estimated pocket filling and loose bulk density. The result is a theoretical mass flow and should be confirmed with representative material data.
The pre-filled values are an arithmetic example. Replace them with your project data before copying the estimate into an enquiry.
Take this estimate into your enquiry
Copy the calculated inputs and estimate, then paste them into Requirement / notes on the enquiry form. Add your required throughput and real operating conditions; the estimate is not guaranteed performance.
Worked example
For 2.5 L/rev at 20 rpm, 75% filling efficiency and 650 kg/m³ bulk density, the estimate is 1,462.5 kg/h, or about 1.46 t/h.
Why actual capacity changes
- Cohesive, aerated or poorly flowing powders may not fill each rotor pocket completely.
- Pressure differential, air leakage and product fallback can reduce effective throughput.
- Large particles and fragile products may require a lower speed or a different pocket design.
- Drive sizing must consider torque and starting load, not capacity alone.
SIZE FROM REQUIRED THROUGHPUT
How much rotor displacement is required?
Rearrange the capacity formula to estimate the displacement needed for a stated mass flow:
Convert filling efficiency from percent to a fraction: 75% becomes 0.75. Speed, filling fraction and bulk density must all be greater than zero.
Example: a 1,500 kg/h process target
At an assumed 20 rpm, 75% pocket filling and 650 kg/m³ loose bulk density, the arithmetic result is 1500 × 1000 ÷ (20 × 60 × 0.75 × 650) = approximately 2.56 L/rev. These values illustrate the calculation; they are not a recommended operating speed or a guaranteed valve rating.
Check the displacement definition
Ask the supplier for net usable pocket volume per revolution. If a quoted capacity already includes a filling allowance, confirm its assumptions before applying another allowance. Confirm the material behavior, pressure differential and drive requirements with the proposed valve configuration.
Send your target capacity for a sizing review
Include the required kg/h, loose bulk density, material, temperature, pressure conditions and the copied calculation summary.
FROM ESTIMATE TO CONFIGURATION
Choose the product duty after checking capacity
A capacity estimate describes solids flow. The next choice depends on whether the process mainly needs controlled feeding, leakage control across a pressure difference, or both.
Controlled hopper or silo discharge
Review the rotary feeder configuration with your minimum, normal and maximum output. Specify any mass-flow accuracy or weighing requirement separately from the volumetric estimate.
Feeding across a pressure difference
Review the rotary airlock valve configuration with inlet and outlet pressure, temperature and the acceptable leakage requirement. The calculated throughput alone does not establish airlock performance.
Include the copied calculation summary in your enquiry and identify whether the stated displacement is a confirmed supplier value or an assumption requiring review. Use the dimension checklist to confirm that the proposed configuration also fits the installation.
APPLICATION NOTES
Engineering considerations for Rotary Valve Capacity Calculation
The main design objective is estimating realistic throughput instead of relying on nominal rotor volume. Confirm rotor displacement, speed, filling efficiency and bulk density before fixing the valve size, rotor and drive arrangement.
Use conservative filling efficiency for cohesive or poorly aerated powders and verify the result against the process target. Sercan reviews these details against capacity, installation interface and maintenance access before issuing a project drawing.
Recommended project checks
- Provide representative material and bulk density data.
- State normal and maximum temperature and pressure conditions.
- Confirm flange dimensions, available height and drive orientation.
- Define the expected duty cycle and maintenance target.
TECHNICAL FAQ
Questions before selection
How is rotary valve capacity calculated?
Multiply usable rotor displacement by revolutions per minute, 60 minutes per hour, filling efficiency and bulk density. Convert litres to cubic metres by dividing by 1000.
Is the calculator result the guaranteed output?
No. It is a theoretical estimate. Material flowability, pressure differential, air leakage, rotor geometry and operating conditions can change actual throughput.
Which bulk density should be used?
Use representative loose bulk density at the valve inlet. Do not substitute particle density, because it can substantially overstate capacity.