Two impellers in series. Twice the pressure.

A double stage is not a different kind of blower — it is two single stages in series inside one casing. Understanding what the second stage buys you, and what it costs, is the whole selection decision.

One stage · YEBL-1 — Flow-led duty

• Single impeller regenerates the air once around the channel.
• Pressure tops out around 330–460 mbar; vacuum around -340 mbar.
• Lighter, shorter, lower first cost for a given flow.
• Right answer when the process needs air volume more than lift.

Two stages · YEBL-DS — Pressure-led duty

• Second impeller lifts the first stage’s discharge again.
• Pressure to 660 mbar; vacuum to -440 mbar at moderate flow.
• Holds deep-tank aeration and high-lift vacuum a single stage drops.
• Right answer when pressure at flow is the binding constraint.

Start from your duty point, never from horsepower. Fix the airflow your process actually needs at the pressure or vacuum it has to overcome, then scan the table for the first trim that clears both with headroom. Horsepower is the result of that choice, not the input — two YEBL-DS trims at the same flow can differ by a full HP class purely because one holds more pressure.

The range splits into three practical bands. The 1–5 HP trims (YEBL-DS-88 to YEBL-DS-230P) suit compact high-pressure jobs — small deep tanks, single-machine vacuum lift, benchtop conveying — reaching up to 490 mbar. The 5.5–15 HP band (YEBL-DS-320LVP through YEBL-DS-520) is the workhorse for STP aeration and process vacuum, topping out at the 660 mbar of the [YEBL-DS-520]. Above that, the 15–33 HP high-flow trims (YEBL-DS-900 to YEBL-DS-2050P) move up to 2050 m³/hr for large aeration grids and central vacuum.

Pick the double stage when…

• Your tank depth or lift needs 400–660 mbar continuously.
• A single-stage trim only reaches your pressure by over-sizing flow.
• Vacuum duty runs beyond -340 mbar.
• Oil-free air is mandatory and a PD blower is overkill.

Still flow-led and under ~330 mbar? The single-stage YEBL-1 range is the lighter, lower-cost choice.

A double stage runs warmer than a single stage for the same flow, so cooling discipline matters more. Give the motor fan cowl unobstructed air, keep the machine out of a hot enclosed corner, and on long pressure duty consider an after-run so the fan clears residual heat. A correctly sized relief valve is not optional — with two stages compounding pressure, a dead-headed YEBL-DS heats even faster than a single stage.

Everything else mirrors the single stage: rigid flat base, shaft horizontal, a clean inlet filter guarding the tight impeller clearances, flexible pipe connectors to divorce vibration from pipe strain, and no liquid carry-over on vacuum lines. Because the two impellers share one shaft, an overhaul inspects both clearances at once.

Commissioning checklist

• Confirm rotation direction against the housing arrow before load.
• Set the relief valve to the duty pressure, not the max rating.
• Verify filter fitted and line unrestricted; log baseline amps.
• Check inter-stage porting for leaks after first hot run.
• Re-grease / replace motor bearings on the hour schedule.

• Deep-tank aeration — Effluent and STP tanks deeper than a single stage can push against — the 400–660 mbar band feeds diffusers under 5–7 m of water column.
• High-lift process vacuum — Vacuum holding and forming that runs past -340 mbar, where a single stage collapses but a PD pump is unnecessary.
• Central vacuum systems — One large YEBL-DS feeding multiple stations — the high-flow 15–33 HP trims hold system vacuum across a manifold.
• Dense-phase-adjacent conveying — Higher-pressure dilute conveying of heavier granules and longer runs than a single stage manages.
• Thermoforming & CNC hold-down — Deep-draw vacuum forming and large router beds that demand sustained lift across a big platen.
• Fish farming at scale — Large biofloc and RAS aeration grids where oil-free air and continuous 24/7 pressure are both non-negotiable.