Tips for Houston Electric Motor Bearings Care and ProtectionHouston Electric Motor Bearings
Houston Electric Motor Bearings contamination, or the entry of foreign particles or liquids into the bearing cavity is a leading cause of failure in electric motors. According to failure analysis statistics, about 15% of all motor bearing failures can be directly attributed to contamination. But this figure may underestimate the real problem.
Some contaminants do not leave physical evidence, such as dents, in the bearing raceway. Instead, they degrade the lubricant, reducing its viscosity, and ultimately cause bearing failure. These failures are often classified as lubricant related, although their root cause was contamination. Consequently, the actual number of motor bearing failures attributable to contamination may be as high as 30%.
Houston Electric Motor Bearings contamination can dramatically shorten bearing life and lead to costly downtime. Maintenance professionals should be knowledgeable about the effects of contamination and well-trained in the procedures to prevent it.
Houston Electric Motor Bearings Maintenance
There are five basic ways to maintain bearings and reduce the number of failures caused by contamination.
Identify Signs of Contamination
Many electric motors operate in harsh conditions full of solid or liquid contaminants. Solid contaminants include dirt, lint, dust residue from shaft polishing, or fragments of coal, brick, or cement.
The basic design of electric motors tends to aggravate the problem. Virtually all electric motors contain a cooling fan that draws air, as well as potential contaminants, across the two bearing positions.
Solid contaminants create small dents or fatigue sites in the bearing raceway. This damage is accompanied by an increase in noise as the bearing operates. Gradually, a series of cracks form at the fatigue site. The site then spalls, and metal flakes away from the raceway.
Liquid contaminants have a different, but equally serious, impact on motor bearings. In a recent case, a fan located on a roof was left idle and exposed to heavy rainfall. When the fan was turned on, it ran noisily. An inspection of the bearing components revealed static corrosion which resulted from rainwater mixing with the lubricant. This corrosive mixture etched the raceways at the rolling element locations.
Static Corrosion
Static corrosion can also occur because of excess humidity in the plant. Increasing the frequency of relubrication to purge contaminants and running idle motors periodically help prevent static corrosion.
Water and other liquid contaminants can also damage bearings when they are in operation. Under dynamic conditions, these contaminants degrade the lubricant and reduce its viscosity. The viscosity may drop below the minimum level required for the application, increasing operating temperatures and metal-to-metal contact between rolling surfaces.
Visual inspection of the bearing lubricant can often reveal evidence of contamination. For example, technicians can take a small amount of bearing grease, rub it between their fingers, and feel or see evidence of solid contamination.
Close analysis of a dismounted bearing can also be informative. Grooves or dents in the raceway surface indicates the presence of solid contamination. Etching at ball-spaced intervals along the raceway indicates the probability of liquid contamination.
Lubricate to Purge Contaminants
Although some bearings in specialty motors are oil lubricated, the majority of electric motor bearings use grease. Electric motors usually operate between 140 and 160 F, an ideal temperature range for grease lubrication. Grease provides a thin film of lubricating fluid between a bearing’s rolling and sliding surfaces, minimizing wear and friction. Grease also acts as a barrier against solid and liquid contaminants.
Frequent lubrication is an excellent means of preventing contamination. The process of greasing purges used grease, and any contaminants it may contain, from the bearing and its housing. If contamination is suspected, shorten the lubrication interval.
For example, if lubrication is currently done monthly, increase the frequency to twice a month, but cut the quantity of grease in half. The goal is to reestablish the protective barrier rather than to replenish the grease entirely. Too much grease can cause a condition called churning, which results in excessive heat.
Most electric motors are equipped with a grease fitting and drain plug. Before lubricating, clean the fitting thoroughly to avoid introducing contaminants to the bearing along with fresh grease. Then pump in new grease while allowing the old to exit through the open drain.
Seal Your Houston Electric Motor Bearings
Most electric motor bearings are protected by seals or shields.
Seals provide a superior barrier against small contaminants because, unlike shields, they actually make contact with the bearing inner ring. But this frictional contact results in increased bearing operating temperatures. As electric motor speeds increase and bearing sizes get larger, seals become a less viable option.
Shields are used in the vast majority of electric motor applications, especially high-speed situations. When replacing a bearing, check that the new unit contains the same seal or shield type used in the original. If there are any questions about sealing options, contact the bearing manufacturer.
Here are some of the Value-Added Services we offer.
