Why buy the whole boiler fan set from one vendor instead of four?
Because a boiler fails at the interfaces, not the fans. When you buy the ID, FD, PA and SA fans from four vendors you inherit four GA drawing languages, four spare kits, four sets of bearings and seals, and — when the furnace hunts or a fan trips — four suppliers each pointing at the others. Supplied as one matched set, the fans share one aerodynamic language, one coordinated control strategy, one QA record and one spares kit, so the boiler is commissioned against a single drawing set and one vendor owns the whole draught-fan island. That is the point of the suite: one set, one vendor, not four arguments.
How do you coordinate the ID and FD fans for balanced draft?
The ID and FD fans have to track each other across every load or the furnace pressure hunts — the ID over-pulls, the FD chases it, and the boiler trips on furnace draft. We size the ID and FD curves as a coordinated pair off the same firing rate, with a common turndown map and matched control response, so the furnace holds target draft, typically -5 to -10 mmWC, steady across the range instead of oscillating. Buying them separately is exactly what makes balanced draft hard; matching them at design is what makes it hold.
Can the whole set turn down together across boiler load?
Yes. A boiler swings from roughly 40% to 100% MCR, and if each fan turns down on its own logic the air/fuel ratio drifts at part-load and the burn goes dirty. We size all four fans to hold their duty from about 40% to 100% MCR on a common VFD-led control strategy, with each duty point engineered onto the stable region of its own curve. VFD is our default because speed control avoids the throttling loss of a damper at part-load; Inlet Guide Vanes or inlet dampers remain available for legacy retrofit.
What is the ID fan's job in the set, and how is it different?
The ID fan sits downstream of the boiler and pulls hot flue gas out, holding the furnace under negative pressure and pushing the gas through the pollution-control train to the stack. It carries the harshest duty of the four: flue gas up to 600 °C, fly ash, and sometimes acid dew-point condensate, so it gets a rugged radial-tipped backward-curved wheel, wear protection and corrosion-resistant metallurgy. The individual Induced Draft (ID) page covers that duty in full.
What is the difference between the FD, PA and SA fans?
The FD fan pushes the bulk of the combustion air into the furnace at positive pressure on the clean, efficient side of the process. The PA fan carries the highest static, typically 1,000 to 1,800 mmWC, to dry the milled fuel and transport it from the pulveriser to the burner, with a combustible fuel-laden discharge. The SA or overfire-air fan supplies and stages the remaining combustion air for a clean, low-NOx burn. Each is engineered to its own regime, then matched across the set on control and spares. The individual FD, PA and SA pages cover each duty in full.
Do all four fans share the same spares, bearings and interfaces?
Wherever the duty allows, yes. We standardise the set on a common bearing, seal and coupling family, a shared spares kit, and common Flexible Connection / Expansion Joint and Isolation / Shut-off Damper interfaces, all built to one L10h design target of at least 40,000 hours continuous. That means one store serves four fans instead of four separate spare inventories. Where a position demands something specific — hard-faced wear parts on the ID and PA wheels, for instance — that is called out on the GA, but the common kit stays common.
Can you supply just part of the set, or match fans we already have?
Yes. The suite is the single-source offer, but a credible single source names its own boundaries: if you already run a serviceable FD fan and only need the ID, PA and SA replaced, we engineer the new fans to match the existing duty point, bearing centres and orientation of the one you keep, so the set still reads as one island. Send the old GA, nameplate and a curve if you have one and we match to it, rather than forcing a nearest-catalogue substitute.
Are the fans built to AMCA, CE, ATEX and ISO requirements?
Every fan in the set is performance-tested in-house to the AMCA 210 / ISO 5801 method on our 200 HP VFD test rig, and balanced to ISO 21940 G6.3 as standard (G2.5 / G1.0 on application) — that is our in-house test method, not an AMCA certification. CE is self-declared per 2006/42/EC and 2014/35/EU, and ATEX Zone 2/22 is self-declared per 2014/34/EU (Category 3), typically on the PA fan where combustible dust and the area classification call for it. To be precise: those are self-declarations of conformity, not third-party certifications. Our only third-party certification is ISO 9001:2015.
