A fan on a coastal roof sees more salt in a week than an inland fan sees in a year, and it is usually the bearing that gives first. 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 | 440C martensitic stainless steel |
| Hardness | 58–60 HRC |
| Temperature ceiling | 250 °C |
| Corrosion / chemical | fresh water, food and mild chemicals; pits in chlorides |
| Relative cost | ≈3× of a standard 52100 bearing |
Salt aerosol settles on the shaft and is drawn into the housing as the fan cools. A chrome steel race rusts in a film thin enough to be invisible, and that film is abrasive — the bearing then wears instead of fatiguing, usually within a season. 440C keeps the same hardness and about 90% of the capacity while resisting that film, which is why it is the usual upgrade for coastal and pool plant.
| Position | Bearing type | Material / finish | Why it works there |
|---|---|---|---|
| Roof extract fan | Ball bearing unit | 440C insert, 2RS, stainless housing option | Salt settles on the shaft; 440C rings do not rust into the seal lip. |
| Cooling tower fan | Deep groove ball | 440C, C3, 2RS | Constant moisture and drift; stainless races outlast coated steel. |
| Pool plant blower | Deep groove ball | 440C, C3, 2RS, H1 grease | Chlorinated air attacks 52100 within a season. |
| Material | Fit here | Choose it when |
|---|---|---|
| 440C | Best fit | Coastal roofs, cooling towers and pool halls where salt or chlorine is in the air. |
| 316 | Workable alternative | Direct spray or brine: immune to chlorides but half the dynamic capacity, so the housing has to take a larger bearing. |
| 100Cr6 / 52100 | Workable alternative | Inland installation with a weatherproof housing — zinc-nickel coating is enough. |
Only if the fan is hard to reach. On a roof unit where a replacement is a two-man job with a crane, the bearing price is noise. On a wall fan at ground level, replace the whole unit instead.
It will show rust in a standard 480 h salt-spray test, unlike 316. Real service is less severe than the test because the bearing is sealed and greased, but do not quote a salt-spray hour figure for 440C.
Zinc-nickel on the outer ring protects the housing seat but not the raceway, so it helps with a rusted housing, not with a rusted bearing.
Hardness, temperature, corrosion and equivalents for 440C stainless.
Read →Typical duty, recommended types and suffixes for fans & hvac.
Read →Standard fan duty — fan and blower shafts in air handling units, cooling towers and roof extract fans.
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.