Can your tunnel fans run on fire mode at high temperature?
Yes. We build to the smoke-control class you specify, most commonly a 250 °C for 2 hours or 400 °C for 2 hours class. On that build we upgrade the casing to IS 2062 or 16Mo3, fit high-temperature bearing grease and shaft seals, add a heat-slinger or cooling disc where the class requires it, and select bearings for the sustained hot-mode housing temperature so the fan keeps pumping smoke for the full rated hold time. The construction is engineered to the class and the performance is tested in-house to the IS 4894 / ISO 5801 / AMCA 210 method; to be precise, that is a tested-to-standard build, not a third-party smoke-fan certification.
Do these fans reverse, and does reverse flow actually work?
They can, but only if it is engineered. A centrifugal wheel and its volute are drawn for one direction of flow, so a fan reversed by simply swapping rotation loses most of its rated flow, which is a dangerous surprise if the emergency plan assumed full reverse duty. We engineer the reverse point explicitly: the wheel and volute are selected for the required forward-and-reverse performance, the reverse curve is computed and stated on the datasheet, and where the scheme needs equal both-way flow we propose a symmetric or bifurcated configuration rather than a blind rotation swap. Tell us the forward and reverse duty and we state both, not one.
What flow and pressure range do tunnel and metro fans typically sit in?
Tunnel and metro ventilation is high-flow, moderate-static duty. Per fan we typically see 50,000 to 2,25,000 CMH against 200 to 1,200 mmWC of duct, shaft and grille resistance, well inside our 2,25,000 CMH and 2,000 mmWC envelope. The demanding requirement is rarely the flow itself; it is the combination of that flow with a smoke-control heat class, reversibility and a strict noise limit on the same machine. We size the daily point on the best-efficiency region and compute the emergency and reverse points alongside it.
The plant room is next to a platform. What sound levels can you meet?
As standard we design toward a predicted below 85 dB(A) at 1 m, with silencer and enclosure scope selected to your stated site sound limit. Below 80 dB(A) is achievable with inlet and discharge silencers plus an acoustic-lagged casing, and below 75 dB(A) with a custom acoustic enclosure. We favour backward-inclined or airfoil wheels for low aerodynamic tone, and we match the attenuator selection to the measured tunnel or shaft acoustics rather than fitting a generic silencer. Tell us the platform or portal noise limit and where the fan sits, and we predict and engineer to it.
How do you control the fan across daily traffic and the emergency case?
VFD is our default. Daily ventilation demand tracks traffic and congestion, so the fan spends most of its life well below the emergency duty; VFD speed control holds the daily air-change target at low power and low noise, then commands full duty on fire mode. This is far more efficient than throttling a fixed-speed fan with a damper, and it lets one machine cover both the quiet daily case and the emergency case. Inlet dampers remain available for legacy retrofit where the existing motor and starter cannot take a drive.
Are you the fan supplier or the whole ventilation system?
We are the custom-engineering fan manufacturer, and we supply the fan as an engineered sub-package to the tunnel ventilation contractor, metro EPC or building services integrator. You specify the duty and the integration interface — flow and pressure for daily and fire mode, reverse duty, smoke class, flange and orientation, electrical and control interface, and the acoustic limit — and we document it up front and deliver the fan and its accessory scope ready to mate. We name our boundary honestly: we do not supply the dampers, controls or duct that sit outside our battery limit unless it is in the agreed scope.
This is public infrastructure that runs unattended for years. How do you build for reliability?
The location is hard to reach and the duty is continuous, so we design for long unattended service. Bearing life is a design target of L10h at least 40,000 hours continuous, longer on application; the rotor is dynamically balanced to ISO 21940 G6.3 as standard, with G2.5 or G1.0 available where vibration limits are tight; materials and coatings are selected for the damp tunnel or coastal-portal environment; and the fan is performance-tested in-house before dispatch so you receive a proven curve, not a catalogue promise. We build for the day the fan has to work, not just the days it idles.
What about API, CE, ATEX and AMCA claims — what is actually certified?
We state our claims precisely. Performance is tested in-house to the IS 4894 / ISO 5801 / AMCA 210 method on our 200 HP VFD test rig; that is testing to the method, not an AMCA certification, and we are not an AMCA member. CE is self-declared per the relevant EU directives, and ATEX Zone 2/22 is self-declared per 2014/34/EU, Category 3, where the classified area calls for it — those are self-declarations of conformity, not third-party certifications. The smoke-class heat build is engineered and tested to standard, not a third-party smoke-fan certification. Our only third-party certification is ISO 9001:2015. Rotor balance is to ISO 21940 (G6.3 standard, G2.5 / G1.0 on application) and bearing life is a design target of L10h at least 40,000 hours.
