Air cooler bearing and motor lubrication.

What grease do air cooler bearings and motors ship with?

Most ACHE fan shaft bearings ship with a lithium grease, while Timken ACHE bearings and most air cooler fan motors ship with a polyurea grease. The two soap bases are not something to mix casually, so know which one is in the bearing before you add anything.

Temperature range matters at both ends. An induced draft fan runs its bearings in the hot exit air above the bundle. A forced draft fan on a northern site sees the full winter low. See cold climate notes below and forced versus induced draft.

How often should air cooler fan shaft bearings be greased?

ACHE fan shaft bearings should be re-greased every 30 days with about 10 shots from a standard grease gun, or until grease purges out of the lip seals.

• Don't force the seals. Once grease purges, stop.
• Re-lube with the fan running if it's safe to do so. A turning bearing spreads the new grease and pushes the old grease out.
• Hudson and Timken ACHE bearings ship 100% full from the factory. Other fan shaft bearings should be filled 100% at the start of a project. This applies to fan shaft bearings only, never to motor bearings.

Regular greasing rounds are also inspection rounds. A technician at the bearing every 30 days hears the noise, feels the heat and sees the vibration before it turns into a failure. See fan shaft bearings for vertical service for what usually fails and why.

How much grease goes in an air cooler fan motor bearing?

Air cooler fan motor bearings take about 0.5 oz of grease every 4 months.

Do not over-grease a motor bearing. Excess grease gets into the motor windings and can cause premature motor failure. Motor bearings take far less grease, far less often, than fan shaft bearings.

Every grease gun delivers a different amount per shot, so calibrate yours. For reference, 0.5 oz is about 0.7 cubic inches, 2.5 teaspoons or 0.8 tablespoons. Pump into a measuring spoon and count the shots.

Can you mix greases in ACHE bearings?

Only if the two greases are compatible. Before adding grease to a bearing that already has some in it, check the soap base of what's in there (lithium, polyurea, calcium complex and so on) and confirm compatibility with the grease supplier.

Incompatible greases can soften, separate or harden when they meet, and a bearing that looks well greased can end up running on very little lubricant. This is the most common way a well meant greasing round does harm.

Is there one grease for both motor and fan shaft bearings?

A calcium lithium complex grease can serve both ACHE motor bearings and fan shaft bearings, which removes the risk of the wrong gun going on the wrong bearing.

One example Nick recommends is Paragon 3000 Extreme: NLGI grade 2, rated down to −40°C (−40°F), with a dropping point of 346°C (655°F). It's an example, not the only option. Switching still means confirming compatibility with the grease already in each bearing.

What is solid lube, and when does it make sense?

Solid lube is a polymer matrix saturated with oil that fills the bearing. The oil migrates out as the bearing needs it, so there's no re-lubrication for the life of the bearing.

Dodge calls it Poly-Oil. Other manufacturers call it Solid Oil or Solid Grease. All the major bearing makers offer it.

Does solid lube shorten bearing life?

No. Dodge application engineering confirmed in February 2024 that solid lube does not reduce a bearing's L10 life, which is set by fatigue.

Solid lube suits ACHE fan shaft bearings well because air cooler fans run slowly, typically under 400 rpm.

Where does solid lube fit best?

• Heavy fans that are hard to reach for regular re-lubing.
• Cold northern sites, where monthly greasing rounds on the fan deck are hardest to keep up in winter.

What do grease temperature limits mean on a Canadian site?

On a Canadian site the lower temperature limit of the grease matters as much as the upper one. Several common factory greases are rated only to −15°C to −20°C (5°F to −4°F), which a northern winter goes well past.

• Timken's polyurea (GR-220) and a calcium lithium complex such as Paragon 3000 Extreme are rated to −40°C (−40°F).
• TECO and WEG rate their own motors to −40°C (−40°F).
• For solid lube, the MPI-S700 grade is rated to −45°C (−49°F).
• Forced draft fans sit in the coldest air on the unit. Induced draft fans sit in the hottest. The same site can need both ends of the range.

If you're not sure what's in your bearings or whether it suits your winter, ask us. It's a common question on northern gas transmission and SAGD sites.

Related reading

• Fan shaft bearings for vertical service: tapered roller versus spherical roller, load ratings, and the top floating bearing.
• Air coolers, fans and cooling towers explained.
• Fan parts by brand, including bearings and drives.
• Common questions, including what grease goes in fan shaft bearings.