Lubrication Checkup: Cold-Weather Strategies

By Dr. Lube, AKA Ken Bannister

Symptom:  

“We’ve successfully used single-point lubricators on our rooftop fans for several years, changing them every spring and fall. Last winter, they seem to have discharged very little lubricant. The grease reservoirs look full, but some fan bearings are making grinding noises. Could these lubricators have frozen, and are they a good strategy for cold climates?

Diagnosis: 

Single-point lubricators (SPLs) are particularly effective in remote and hard-to-reach areas (inside and outside plants) where it’s not cost-effective to install centralized lubrication systems and/or where it’s difficult to manually grease on a weekly or monthly basis year-round. Such is the case with rooftop fan bearings.

SPLs are self-contained devices that couple to a grease point and continually deliver small amounts of lubricant until the grease reservoir is empty. Depending on its design, the unit is then replaced or its reservoir and battery are replenished. Most SPLs are capable of dispensing lubricant for a year or more.

The typical SPL is a sealed unit, purchased pre-filled with the customer’s specified lubricant brand and grease consistency—with NLGI (National Grease Lubricating Institute) #2 grade grease being a popular choice. This medium-consistency product feels like smooth peanut butter. In cold weather, though, the oil within it tends to thicken, meaning an SPL must work harder to discharge it.

If an SPL gets too cold and can’t overcome the stiffness of the grease to be dispensed, it stalls. Although the device will start working again as the weather warms, bearings that have been starved of lubrication will move in a metal-to-metal or boundary state in which wear rapidly occurs (as the grinding sounds of your bearings would indicate).

Prescription: 

For now, you’ll probably need to replace some fan bearings. Going forward, I recommend in your fall SPL change-out schedule that you replace all #2 grease-filled units with #1 or #0 grease-filled units. NLGI #1 or #0 grease is more suited to outside applications in Northern climates: Their softer consistency won’t over-tax your SPLs. However, always consult your lubricant supplier as to what grease grade(s) are recommended for typical winter temperatures in your area.

SPLs filled with the correct grease for the climate and application—and set correctly to discharge at a valid rate—can be an excellent choice for lubricating bearings in remote locations in cold climates. Good Luck! MT

Ken Bannister of Engtech Industries, Inc., is a Lubrication Management Specialist and author of Lubrication for Industry (Industrial Press), and the 28th Edition Machinery’s Handbook Lubrication section (Industrial Press). For in-house ICML lubrication certification training, Ken can be reached at 519-469 9173 or kbannister@engtechindustries.com.