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COVER PAGE |
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IBT |
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IMT |
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MATERIAL HANDLING |
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FLUID POWER |
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GENERAL INDUSTRIAL |
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LEAN SIX SIGMA |
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ELECTRICAL |
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RUBBER |
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ENGINEERING |
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TRAINING |
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SAFETY |
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Overheated Bearings
Overheated bearings have the potential to cause serious and permanent damage. IMT Technicians frequently encounter overheating problems in a wide range of applications. Their first question is usually whether the problem is from ambient conditions or whether the heat comes from within the bearing itself.
When encountering this problem, the technicians look first to what are the most likely causes - and, if correct with their initial diagnosis, they apply the most common remedies.
Electric Motors
The ball bearings used in most electric motors are pre-greased, shielded ball bearings. Normal motor bearing operating temperatures range from 140°F (60°C) to 160°F (71°C).
In electric motor bearings, overheating is generally lubricant related. The three major types of lubricant problems are: low temp lubricant, over-lubrication or the use of incompatible lubes.
Low temp grease is a frequent problem with open bearings. This grease may not provide adequate viscosity at the normal operating temperature. In over-greasing, the user may use too much lubricant, which forces bearing balls to push through excess grease as they rotate. This leads to sharp temperature rises. The third common cause of overheating is when incompatible greases are mixed. This can reduce the consistency of the grease and, possibly, the overall viscosity.
Fans
Commercial fans generally use ball and roller bearings, mounted in cast iron or pressed steel housings. Fans are exposed to a wide variety of ambient conditions, which can range from below zero temperatures (rooftop fans) to extremely high temperatures (fans used in industrial processes.)
Normal bearing operating temperatures may vary, depending on the environment and application. The standard grease in most fan bearings remains effective to an operating temperature of 180°F (82°C).
When steady-state operating temperatures go higher than 180°F (82°C), IMT technicians recommend using grease made with a synthetic base oil. Compared to standard mineral oils, viscosity in synthetic oil does not vary as much with temperature. The rate of oxidation is also much slower. When operating temperatures exceed 200°F (93°C), they frequently recommend the use of circulating oil systems. These systems pump clean, cool oil through the bearings and maintain temperature control and proper lubrication.
Pumps
Normal bearing operating temperatures in pumps range from 100°F (38°C) to 180°F (82°C) depending on application. Most pump bearings run between 140°F (60°C) and 160°F (71°C). Although grease is used in some vertical pumps, oil is the preferred lubricant in the majority of pump applications. Standard bearing oils in pumps remain effective to approximately 180°F (82°C). If normal operating temperatures are higher than 180°F (82°C), use a synthetic oil. If temperatures exceed 200°F (93°C), IMT recommends the use of a circulating oil system.
As in other bearing applications, bearing over lubrication can cause higher-than-normal operating temperatures in pumps. Bearing misalignment or ball skidding within the bearing can also cause overheating. Specially designed bearings are available to eliminate ball skidding. Ideally, bearing temperatures in pumps, especially those in critical applications, should be regularly monitored.
Gear Drives
Bearings in gear drives normally operate at 160°F (71°C) to 180°F (82°C) and are lubricated with static oil systems. As improved technology permits reductions in the size of gear drives, there is a growing trend to transmit more power through a given size drive than ever before. This practice can cause bearings in gear drives to run hotter and may necessitate the use of alternative cooling methods.
If you are having problems with bearings overheating, IMT is always ready, willing and able to provide professional assistance. To learn how IMT may help you, contact Chris Treat.
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To learn more about services available form IMT, contact us today!
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