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Counter-Rotating Axial Fan - SINDFAN
Counter-Rotating Axial Fan

Contra-Rotating Axial Fans

A contra-rotating fan has two impellers turning in opposite directions. The swirl generated by the first stage is recovered by the second, giving higher pressure and flow for the same diameter, with a short axial length and no guide vanes. It is the workhorse for mine auxiliary ventilation and long-distance air delivery.

SINDFAN contra-rotating units are designed to mine auxiliary fan practice: two motors driving directly on their own shafts, no inter-stage duct, impellers replaceable as assemblies. We can also supply the two impeller stages separately.

Key specifications

Impeller diameterØ400 - Ø1250mm (typically Ø600 / Ø630 / Ø800)
Stage arrangementTwo stages, counter-rotating, e.g. 7+6 blade combination
Motors2 x 18.5kW to 2 x 37kW, direct on shaft
Air volumeapprox. 5 - 12 m³/s depending on model and blade angle
Total pressure3000 - 4000 Pa class depending on model
Blade materialCast aluminium or fabricated steel
Air delivery distanceØ600 ducting approx. 300m (400m maximum); Ø800 ducting approx. 600-800m (1000m maximum)
MountingRail bogie for underground use / fixed base (optional)

Figures above are our standard ranges; the actual supply is per the agreed technical specification. Impeller performance curves describe the bare impeller under standard inlet conditions. Once installed, performance is affected by casing clearance, tip clearance, inlet straightening and guide vanes; tested as a complete fan to GB/T 1236 / AMCA 210 the result typically differs by 2-5%. Site measurement governs and no complete-fan performance warranty is implied.

Typical applications

  • Coal mine development heading ventilation
  • Metal mine and tunnel heading ventilation
  • Long distance forcing ventilation
  • Underground works and shaft ventilation
  • Large basements and utility tunnels
  • High pressure duty where space is limited

Selection notes

  • Pressure is the sum of both stages - when selecting, give the total resistance of the whole duct run including ducting, bends and outlet loss, not just the length.
  • Rule of thumb for delivery distance: Ø800 ducting costs about 330 Pa per 100m, Ø600 ducting about 1400 Pa per 100m - bigger ducting throws further, which is why large diameters suit long runs.
  • Blade angle is adjustable, so one unit can be tuned to different duties. Adjust only with the fan stopped and re-check the fasteners afterwards.
  • For mining projects, mining approval (MA) and explosion-proof motors are required - tell us the certification requirement for your region up front.

FAQ

What does contra-rotating give me over a standard axial fan?

More pressure for the same diameter in a shorter axial length, because the second stage recovers the swirl loss of the first - two stages of work for one compact body.

Can you reach 3000 Pa?

Standard units reach the 3000-4000 Pa total pressure class. Higher pressure requires re-calculating diameter, speed and blade count - send us the duty point.

How far will it deliver air?

Ø800 ducting delivers 600-800m reliably (about 1000m maximum); Ø600 ducting about 300m. Actual performance depends on duct quality, joint leakage and the number of bends, so acceptance testing should use the conservative figure.

Need a selection or a quotation? Send us air volume, total or static pressure (please state which), medium temperature and quantity, and we will reply within 24 hours. Contact details are at the foot of this page.