Earlier this year on a job site to do regular PM service to the centrifugal air blowers, the outside temperature was below zero as I asked the operator to start up a blower that hadn't been in operation for at least a few months. It occurred to me that the cold had to be detrimental to the blower. The unit started up and ran fine, but the bearing temperature, measured with my infra-red thermometer, was still less than 30OF after ten minutes of operation!
Operating a blower/motor unit during severe cold weather does require a little more attention. First off, be sure the blower shaft rotates freely before you energize the motor. The steel components of blowers and motors will not freeze until extremely low temperatures, but the cold may cause a certain amount of shrinkage, or shifting of positions that could change the internal clearances. Most often, the shafts don't rotate because the moisture in the blower froze!
Any dirt, rust & corrosion, or other foreign material could very easily "freeze" in a minimal clearance area such as a shaft seal, or impeller bore, and at least slow the rotation of the rotor, if not stop it completely. The grease in the bearings does not freeze at zero degrees, but it will become less "pliable". You don't have to worry about the bearings being adequately lubricated, because the heat generated in the bearing will quickly warm the grease enough to provide adequate lube.
The same holds true for oil lube bearings. The bearing will quickly heat up without enough oil mist, but it should recover to provide enough lube for the bearing. In both cases, there is going to be some shortening of the bearing life due to the cold. Bearing housing oil heaters can be a very good investment for critical machines or units with very large, costly, ball bearings.
Another concern is the fact that cold air is much heavier than warm air, so the motor has to work harder. A motor drawing say 100 amps may only be providing 20 -30% less air to the system than it would at 70O F. To provide the equal amount of air, the motor would have to draw 120-130 amps, which could put the motor at risk of overload.
Most landfill gas blowers have water separators to remove the water from the incoming gas, but they don't always work real well and water gets in the blower. It has been such a major problem that blowers can now be ordered with special insulating wraps and "heat tape" that protect the blower from the cold freezing the water inside the blowers. There are a few aftermarket companies manufacturing the wraps. The company in Buffalo makes a pretty good cover wrap.
In the end, it is preventative maintenance that can make the difference between online making money, or offline losing money. Invest in PM, it will save you money!
