Keeping vibration analysis happy | Automation.com https://www.automation.com/files/pluginfiles/item_99814/field_376/SMB064---image_reg.jpg
By Chris Johnson, Managing Director of SMB Bearings
Implementing condition monitoring can reduce the frequency and cost of device maintenance. In particular, vibration analysis can provide valuable insights into the machine's condition and identify problems before extensive damage occurs. This article describes the steps that machine builders should take to reduce the likelihood that bearings are the primary cause.
With a large number of rolling elements in industrial machinery, it can be difficult to decipher exactly what is going on in a unit. Condition monitors often use accelerometers to measure the vibration. It is possible to distinguish between vibrations by examining the individual frequencies present in the higher-level vibration signal. These frequencies can then be used to match individual parts or certain malfunctions.
This analysis may indicate errors in time for failure. In the case of bearings, it is possible to detect excessive wear of the rolling element or damage due to poor assembly techniques that allow bearing replacement. The alternative would be to further deteriorate the bearing and possibly fail other components.
Other problems that vibration analysis can detect are misalignment, lubricant problems, or misalignments between shaft and housing. With early detection, it may be possible to overcome these problems long before a costly bearing failure.
As a safety net, a regular vibration analysis can be used to confirm the bearing condition and prevent catastrophic failure. However, if the proper precautions are taken to reduce bearing vibration during machine design and bearing selection, the likelihood of errors is greatly reduced.
From a bearing manufacturing standpoint, a low noise or vibration rating is achieved by taking into account the surface finish of the raceways and balls, their roundness and the choice of the correct cage design.
Finely filtered noise greases can also be used to reduce vibration. These contain fewer, smaller solid particles that can generate noise when passing between balls and raceway.
Unintentional contamination by dirt or dust can also increase levels of noise and vibration, as this inevitably affects the rolling ability of the bearing. End shields or better contact seals are a good solution to this problem.
Choose the Right Lubrication
In order to maintain rollability, it is important that the bearings are adequately lubricated and have a suitable level, depending on the torque, speed and load requirements. Likewise, the type of lubrication should be carefully checked depending on temperature, speed and environmental conditions.
If bearings are found to be insufficiently lubricated or filled with a wrong grease, contact a bearing manufacturer to relubricate bearings.
Pay attention to the radial play
The internal clearance can make a big difference. Choose closer distances for precise travel, but be aware of temperature differences that reduce internal clearances during operation. Select looser distances when using a press fit or when there is a slight misalignment between the shaft and the housing.
As tempting as it may be, end users should avoid using a bearing that is close to their maximum carrying capacity. The load ratings are only guideline values. In reality, bearings should be used at about one tenth of the dynamic load rating when a long life is required. Higher loads can be tolerated, but the life of the bearings is shortened.
When the bearing inner ring is mounted on a shaft by pressing on the outer ring, it transmits the fitting force over the balls and damages the raceways. Heavy impact may occur if the bearing falls on a hard surface, which can also cause damage resulting in excessive vibration.
Condition monitoring is becoming more prevalent and this technology enables the early detection of storage issues. By taking precautions against the occurrence of problems, machine builders can ensure that their bearings are permanently mounted.Did you like this article?
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