Pneumatic conveying moves bulk solids — powders, granules, pellets — through pipe using air. Whether a blower can do the job, and which one, comes down to two choices: dilute phase or dense phase, and the pressure the distance and material demand. Get those right and the line runs for years; get them wrong and you either bury the pipe in settled material or stall the blower. This guide explains the two conveying modes, how to size, and — honestly — where a regenerative or centrifugal blower is the right tool and where a positive-displacement roots blower takes over.
Dilute phase vs dense phase
The fundamental split in conveying:
| Dilute phase | Dense phase | |
|---|---|---|
| How it moves | Material suspended in a fast air stream | Material pushed as slugs at low velocity |
| Air volume | High | Low |
| Pressure | Low to medium | High |
| Material | Most powders and granules, non-fragile | Fragile, abrasive or high-rate materials |
| Typical machine | Regenerative / centrifugal / roots blower | Positive-displacement / dense-phase compressor system |
Dilute phase is the common, forgiving mode: keep the air velocity high enough to hold material in suspension and it flows. It is a blower duty — volume to carry the material, pressure to overcome the pipe. Most day-to-day conveying of flour, sugar, plastic granules, sand and light powders is dilute phase.
Dense phase pushes material as dense slugs at low velocity, which is gentler on fragile product and abrasive on the pipe but needs high pressure — usually beyond what a regenerative or centrifugal blower holds, into positive-displacement or dedicated dense-phase territory.
How distance and material set the pressure
For a dilute-phase line, the pressure the blower must hold is the sum of:
- Pipe friction — longer runs and more bends cost more pressure.
- Lift — raising material vertically adds to the load.
- Material loading — the more solids per unit of air, the more pressure to keep them moving.
- Acceleration and pickup — getting material moving at the pickup point.
The practical rule: fix the pressure from the pipe and material first, then add the air volume to keep velocity up. Sizing on volume alone is the classic error — it produces a blower that moves plenty of air until material loads the line, then stalls.
Matching Yash families to conveying duty
Short-to-medium dilute-phase runs with modest lift suit the High Pressure Series. The YEBL-HP-DS-120 reaches around 820 mbar and the YEBL-HP-TS-175 around 1,040 mbar — enough pressure for real material loading over a working distance.
Continuous medium-pressure conveying and fluidisation suit the Double Stage Turbine Blower; the YEBL-DS-320P at 10 HP gives around 570 mbar at good volume.
High-volume, lower-pressure dilute transport — light, bulky material over a short hop — can suit a High Pressure Centrifugal Blower where the YBCB-HP-919-11 develops around 7,000 Pa at large flow.
Where roots blowers take over
We will always be straight about this: when the conveying distance is long, the material loading is heavy, or the mode is dense phase, the pressure requirement exceeds what a regenerative or centrifugal blower can hold continuously. That is positive-displacement roots blower territory, and forcing a side-channel machine into it just burns the motor and stalls the line. Our ring blower vs roots blower post lays out the crossover honestly — if your duty is past the line, we will tell you.
Sizing checklist
- Choose the mode. Fragile or abrasive material, or very high rate → consider dense phase. Otherwise dilute phase.
- Fix the pressure. Sum friction, lift, loading and pickup for a dilute line. This eliminates undersized machines.
- Add the volume to hold conveying velocity, with margin for filter and valve losses.
- Check continuous duty and abrasion. Conveying often runs 24/7 with abrasive material — protect the inlet and size for round-the-clock service.
- Know the ceiling. If the pressure demand is past regenerative/centrifugal capability, specify a positive-displacement machine.
Related duties
Cement, food powders and textile waste are all conveying duties with their own notes — see cement plant applications for the pressure-led powder case, and the dust collection guide for where conveying meets extraction. The full duty list is on our pneumatic conveying application page.
Pressure-conveying vs vacuum-conveying
There is a second choice alongside dilute-vs-dense: whether the blower pushes the material (pressure conveying) or pulls it (vacuum conveying). Both are common dilute-phase methods and a regenerative blower serves either, because the same machine works in pressure or vacuum mode.
| Pressure conveying | Vacuum conveying | |
|---|---|---|
| Blower position | Pushes air into the line | Pulls air through the line |
| Best for | One pickup, several drops | Several pickups, one drop |
| Leak behaviour | Blows dust out at a leak | Draws air in at a leak (cleaner) |
| Material entry | Rotary valve feeds pressurised line | Simple suction nozzle |
Vacuum conveying is often chosen for cleanliness — a leak pulls in rather than puffs product out — and for gathering material from several points to one receiver. Pressure conveying suits pushing from one source to several destinations.
A worked example: dilute-phase powder over a short run
Take a plastic-granule transfer, one pickup to one silo, a modest horizontal run with a short vertical lift:
- Mode. Non-fragile granule, short run → dilute phase, pressure conveying.
- Pressure. Sum pipe friction, the lift, material loading and pickup acceleration. This gives your required discharge pressure.
- Volume. Add enough air to hold conveying velocity above the material's settling point, plus margin.
- Model. A YEBL-HP-DS-120 (~820 mbar) suits a run like this; a longer, more heavily loaded line steps up to the YEBL-HP-TS-175 (~1,040 mbar).
Frequently asked questions
How do I know if I need dense phase? If the material is fragile (breaks in a fast air stream), very abrasive (wears the pipe at high velocity), or you need very high rates, consider dense phase — which is usually beyond blower pressure and into positive-displacement territory.
Why does my line plug intermittently? Usually conveying velocity dropping below the material's settling point — often from an undersized blower sagging under load, or a duct sized too large. Fix the velocity, not just the volume.
Can one blower feed pickup and a filter? The conveying blower moves the material; the receiving vessel needs its own filter and vent. Do not expect one machine to convey and extract.
Keeping a conveying line reliable
A well-sized conveying blower still needs a sound install to run for years:
- Hold conveying velocity. The line plugs the moment velocity drops below the material's settling point — do not oversize the duct, and do not let an undersized blower sag under load.
- Protect against abrasion. Abrasive material and grit shorten impeller life; keep the blower on the clean side where possible and run a maintained inlet filter.
- Fit a relief valve. A conveying line that can dead-head — a closed valve, a blocked pipe — needs a pressure relief valve to protect the machine.
- Size for 24/7 thermal load. Conveying often runs continuously; leave margin so the blower is not permanently at the edge of its curve heat-soaking.
- Vent the receiver. The receiving vessel needs its own filter and vent — the conveying blower moves material, it does not also do the receiver's extraction.
Match the mode to the material, fix the pressure from the pipe, add the volume to hold velocity, and protect the machine — and a dilute-phase line runs quietly in the background for years.
Get your conveying line sized
Send us your material, conveying distance, lift and throughput rate, and our engineers will size a dilute-phase blower — or advise a positive-displacement machine where that is genuinely the right tool. WhatsApp +91 9311693322 or email sales@yashblowers.org for a quote in 24 hours.