A properly specified, installed and maintained bearing will have a long life, even in tough conditions, but bearings continue to fail prematurely in service, resulting in costly downtime.

 

Lubrication

Poor lubrication is the biggest single cause of premature bearing failure, responsible for 36% of early failures. That’s why an effective lubrication programme is central to good bearing maintenance. Lubrication management involves ensuring a specified amount of the correct lubricant is delivered by the best method to reach the right point at the right time. Making that happen in a real production environment requires a detailed action plan that encompasses the whole lubricant supply chain, from selection to delivery, storage, application and disposal at end of life.

Equipment owners no longer have to manage all the complexities of bearing maintenance themselves, however; instead they can now outsource this responsibility to specialist external providers. SKF, for example, has developed complete lubrication management services for customers. This can include an audit of the customer’s needs, followed by the design and implementation of a complete program for the supply of appropriate tools and materials and a schedule of activities. 

Installation and alignment 

Incorrect mounting is the root cause of 16% of early bearing failures. Cold mounting smaller bearings using a hammer and length of pipe, for example, can lead to installation forces being transmitted through the rolling elements rather than the casing, causing damage to the raceways before the bearing has even turned. Proper installation tools, by contrast, are designed to have an interference fit that ensures forces are only applied to the retaining ring of the bearing, which has been designed to cope with them without damage.

Similarly, larger bearings are often heated in an oil bath prior to installation. Unfortunately, this can introduce contamination, shortening the life of the bearing, not to mention the safety hazards associated with handling a hot, slippery component prior to installation. A better approach is the use of dedicated induction heaters, which as well as avoiding contamination or damage due to excessive or uneven heating, also allow the bearing to be heated with greater efficiency, controllability and safety.

Poor shaft alignment is another common installation issue, resulting in increased friction that reduces machine efficiencies and shortens bearing life. Fortunately for installation and maintenance engineers, shaft alignment technologies have evolved dramatically in recent years and the latest systems are much more accurate, robust, user friendly and cost effective than those of the past.

SKF’s latest TKSA 11 alignment tool, for example, connects directly to a smartphone app that guides the engineer step-by-step through the entire alignment process. In addition, the device makes use of robust, accurate and inexpensive inductive proximity sensors, making it suitable for every budget. 

Condition monitoring 

A further two major sources of early bearing failure are contamination, responsible for 16% of failures, and fatigue from overloading, incorrect adjustment or neglect, the root cause of the remaining 34%. Equipment owners can reduce the chance of these sorts of failure by selecting appropriate bearings, housing and seals, and by operating and maintaining equipment within its design parameters. It is a reality of the production environment that unexpected problems can arise, however. The challenge is spotting these issues in a timely fashion and so avoiding unplanned downtime.

Doing this has become easier in recent years thanks to the availability of a wide variety of simple, portable measuring systems that can help operations and maintenance staff build a clearer picture of the performance of a machine in service – allowing them to schedule service interventions when they are needed most. These basic condition monitoring tools include temperature sensors to identify the tell-tale signs of excess friction, hand held tachometers to spot deviations from desired operating speeds, and stethoscopes and vibration sensors to listen for changes that indicate wear or damage in rotating components. Today’s robust, inexpensive endoscopes even allow engineers to look inside equipment without the need to do disassemble or even shut it down.