Fan bearings rarely fail from load — they fail from grease that never formed a film, or from water that got in during shutdown. Fans, Blowers & HVAC duty is light load, condensation during shutdown and noise limits; the material is what decides whether the bearing survives it.
| Industry duty | light load from unbalance and belt pull, a few hundred to 3,000 rpm |
|---|---|
| Typical media | dust, lint, condensate, pool and food washdown |
| Housing temperature | −20 to +80 °C |
| Material and grade | through-hardened chrome steel — 100Cr6 / 52100 |
| Hardness | 59–65 HRC |
| Temperature ceiling | 120 °C (200 °C stabilised) |
| Corrosion / chemical | none — rusts without protection |
| Relative cost | 1.0× of a standard 52100 bearing |
A fan at 900 rpm and 2 kN is nowhere near the rating of a 6205. What limits it is that slow rotation never builds a full elastohydrodynamic film, so the grease does the work, and that a fan housing cools to ambient during shutdown and condenses water onto the rings. 52100 handles both as well as any steel — the specification work is the grease, the fill and the seal.
| Position | Bearing type | Material / finish | Why it works there |
|---|---|---|---|
| Fan shaft, belt driven | Ball bearing unit | 52100 insert, cast housing, 2RS | Self-aligning seat takes frame distortion; the unit bolts straight to the frame. |
| Direct-drive blower | Deep groove ball | 52100, C3, 2Z | Low drag at light load; shields let heat out and keep lint from packing the raceway. |
| Roof extract, vertical shaft | Deep groove ball | 52100, C3, 2RS with rain shield | Seal keeps driven rain out of the grease. |
| Material | Fit here | Choose it when |
|---|---|---|
| 100Cr6 / 52100 | Best fit | Light load, low speed, indoor or sheltered air. The default for a reason. |
| 440C | Workable alternative | Pool plant, kitchen extract and coastal roofs where the housing sees chlorinated or salt air. |
| POM | Workable alternative | Small low-load blowers where a plastic bearing removes relubrication entirely. |
Because load was never the limit. The grease oxidised, or water entered during shutdown, and the bearing ran metal on metal at low speed.
Sealed, unless the housing is above 80 °C or the fan is large enough to justify a lubrication schedule. Relubrication done badly is worse than none.
Slightly, at low speed. If noise is the driver, a C2 or CN with a low-noise grease is better than opening the clearance.
Hardness, temperature, corrosion and equivalents for 52100 chrome steel.
Read →Typical duty, recommended types and suffixes for fans & hvac.
Read →Coastal & pool plant — roof extract fans, cooling tower fans and pool plant blowers in salt or chlorinated air.
Read →Small blowers, quiet duty — small direct-drive blowers, fan trays and appliance fans up to 90 °C.
Read →Send the position, bore size, quantity and the medium it sees. We reply with the material certificate, clearance class, lubricant and price within 30 minutes on working days.