What is the difference between vacuum and pressure pneumatic conveying?

In vacuum (pull) conveying a blower draws air through the line, so material is pulled in at open pick-up points and separated at a receiver near the blower - ideal for multiple pick-up sources feeding one destination. In pressure (push) conveying a blower pushes air, so material must be fed into the pressurized line through a sealed feeder such as a rotary airlock, and can be pushed to multiple destinations with diverter valves.

How do you size a dilute-phase conveying line?

Size the line so the superficial air velocity at the pickup meets the material's minimum conveying velocity (about 2,400 ft/min for fine powders up to 4,400 ft/min for coarse or abrasive solids), then compute the air volume from the target solids loading ratio and pick the nearest standard pipe or tube. Because air is compressible, velocity increases along the line as pressure drops.

Is a rotary valve the same size as the conveying line?

No. The conveying line is sized by air velocity while the rotary valve is sized by the volume of solids it must pass - required displacement equals mass rate divided by bulk density, divided by rpm and pocket-fill efficiency. The valve is usually larger than the line and connects through a transition adapter.

Pneumatic Convey Sizer | GQI Dry Bulk Solutions

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Reference Tool

Size a Pneumatic Conveying System

Answer a few plain-language questions about what you're moving and where, and this tool estimates a complete dilute-phase pneumatic conveying system - conveying line size and material spec, air flow, the feeder (rotary valve) or pick-up points, the receiver, and a blower package - for either a vacuum (pull) or pressure (push) layout. It's a first-pass reference to guide the conversation; GQI confirms the final design with your material's conveying-test data.

Mode

1What are you conveying?

Material

Bulk densities from the sizer's built-in reference of common bulk solids. Not listed? Enter density below.

Bulk density

How would you describe it? (sets conveying velocity)

Food, pharma or hygienic (sanitary spec)

Any of these a concern? (optional, sharpens the recommendation)

2How much & how far?

Conveying rate

Conveying distance

ft horiz.ft up

Rough is fine - drives the pressure & blower estimate.

Number of bends (elbows)

3System layout

Conveying method

Sources (inlets)

Destinations (outlets)

Feed method (at each source)

Destination type

Advanced: engineering assumptions (auto-set; edit if you know them)

Conveying velocity (set by material)

ft/min

Solids loading ratio φ (auto by material)

Air temp

°F

Elevation

Rotary valve rpm (auto by material)

Pocket fill efficiency

Conveying duty cycle (batch / dump-valve systems only)

Recommended system

Conveying velocity (in → out)–

Air flow (free air)–

Solids loading ratio φ–

Est. system pressure–

Request this system from GQI →

Reference estimate only - idealized dilute-phase assumptions and generic velocity data. Final sizes, feeder model, and blower package are confirmed by GQI using your material's conveying characteristics (test data).

How this builds your system

Line is sized by air & velocity (superficial pickup velocity meets the material's minimum), then your material picks the spec - sanitary tube, Schedule 40, Schedule 80, or abrasion-lined.
Feeder / pick-up depends on method: a pressure line needs a sealed feeder (rotary airlock sized on its own displacement / rpm / pocket-fill basis - not the line size); a vacuum line uses open pick-up adapters.
Receiver (filter receiver / cyclone / bin-vent) is sized by air volume (air-to-cloth ratio).
Blower package is matched to free-air flow (including a rotary-valve leakage allowance where an airlock is in play) and to the estimated pressure or vacuum class.

Method after D. Mills, Pneumatic Conveying Design Guide: pressure-drop model, velocity margin, vertical-run doubling, loading-ratio definition, dilute ceiling ≈15 and bend accounting. The five minimum conveying velocities and the five loading-ratio defaults are GQI reference values and are not from Mills; they are under engineering review.

Line bore is selected to carry at least a 20% velocity margin above the material minimum where a standard size allows it. The delivered margin is reported with the result, and it is usually larger, because the bore is always rounded down.

This tool is a reference and selection aid only and does not constitute a guaranteed design. Estimates are based on idealized assumptions and generic material data; real performance depends on the specific material's conveying behavior, which must be verified by test. Grand Quest Industries confirms all selections before any equipment is quoted or supplied. © 2026 Grand Quest Industries LLC.

Pneumatic Convey Sizer

Size a Pneumatic Conveying System

1Duty

2Result

3Airflow · bore · velocity