Basic training for selecting, installing and maintaining bearings.
SKF USA, Inc.
08/05/2019
Maintenance technicians handle a wide range of responsibilities to ensure rotating equipment and machine components operate at peak performance levels. With a generation of seasoned technicians soon ready for retirement, it is imperative to close the knowledge gap. A new crop of up-and-coming employees needs to understand the basics of maintaining rotating equipment and the new technology available to help them troubleshoot machine performance. Bearings play a vital role in rotating equipment performance. Bearing failure can compromise machine health and lead to unexpected downtime and production delays. Fortunately, there are numerous tips for preventative measures that technicians can follow as they gain more on-the-job experience in machine maintenance. As with any maintenance project, the No. 1 tip is to follow the company’s safety procedures when inspecting, maintaining or replacing a bearing.
Understanding Product Designation
One main factor in bearing performance is ensuring the proper bearing is specified for the given application. Each bearing has a unique set of design characteristics and options that may not necessarily be determined simply by looking at, or even handling, the old bearing. Sometimes the right bearing is not used to begin with, further complicating the choice moving forward. In many cases, the best way to identify the critical specifications is by understanding the bearing’s product designation marked on the side faces of the bearing. For example, if a technician only looks at a numeral designation—without the additional suffixes—the selected bearing may be provided with the incorrect design feature such as the improper level of internal clearance.Proper Bearing Installation
Manufacturing facilities collect dust and other contaminants. Despite the surroundings, it is crucial to establish a clean workspace prior to bearing installation. This prevents harmful elements from contacting the bearing before it is commissioned. An oft-forgotten but common-sense tip is to keep the box containing the new bearing closed until it is ready for mounting to avoid any ingress of contaminants. Additionally, technicians should closely monitor the orientation of the bearings during both removal and installation. Bearings that are asymmetrical and mistakenly installed in reverse will not perform as intended, leading to bearing damage and possible machine failure.Seals Are a Bearing’s Best Friend
To achieve maximum service life, bearings require a sealing solution to retain lubricant and prevent the entry of contaminants. Anytime a bearing is replaced, a new seal should also be installed. And, like bearings, there is a wide range of seals for a variety of applications, so it is important to specify the proper seal design. Sometimes, the rotating shaft has deteriorated to a point where the seal is no longer effective. This can be caused by an inadequate surface finish, surface roughness or hardness. Instead of replacing the shaft, consider installing a sleeve over the worn shaft to provide a smoother surface for the seal, giving new life to an older but still productive machine. Some sleeves are designed to slide over the worn area, providing a counter-face surface that is optimized for radial shaft seals.Precision Lubrication
It is critical to use the right amount of lubricant during bearing installation and operation. Not enough lubricant can lead to metal-on-metal contact, which can cause premature wear and reduce the life of the bearing. Conversely, too much lubrication can generate additional friction, causing the machine to overheat. It is also important for machine technicians to use the proper type of lubricant. Oil and grease are most commonly used to lubricate rotating equipment. These lubricants are applied differently and also perform differently. As a liquid, oil is ideal for carrying heat away from bearings in machines that generate a lot of heat. Oil requires routine maintenance through filtration, temperature control, flow rate monitoring and replenishment. After the initial fill, however, grease only requires replenishment after a small amount has left the bearing, has aged or deteriorated. Properly calculating the intervals for replenishment is something many newer technicians overlook. Bearing companies can provide tools to help technicians calculate the proper relubrication intervals for optimal machine health.Working With Sensors
Today’s machinery and digital tools often involve a variety of sensors to collect data. However, it is important to remember the context of the data may not paint a complete picture of machine health. Depending on the situation, data reported from a vibration sensor mounted on a bearing housing may be misleading and result in a technician troubleshooting the wrong problem. For example, a service tech might notice a pump is displaying a higher than normal vibration velocity reading and may contact the manufacturer to help diagnose the problem. Those readings can be misleading if the fluctuation in vibration is attributed to changes in equipment, such as the pump being recently serviced. If the condition of the bearing housing is not up to specification, the vibration sensor may also pick up the difference. Therefore, it is imperative for technicians to access all the necessary machine data and history—including service and maintenance schedules—to accurately assess machine heath.
Image 1. The new generation of employees needs to understand the basics of maintaining rotating equipment and the new technology available to help them. (Image courtesy of SKF USA, Inc.)