Bearings - 02/06/2010
“There’s always room for improvement.” That goes for the use of bearings too. If specific bearings cause problems and frequently fail, there’s generally a relatively easy way to solve the problem. The best plan is to tackle the issue systematically. NSK has developed just such a systematic approach with its Asset Improvement Programme. The training sessions on offer also help to extend bearings’ lives.
Virtually every works manager will be familiar with the problem of bearings frequently failing at a particular point. If the machinery in question is not critical to the main production process, you can afford to adopt a defensive strategy and replace the bearings more often. However, if the failure could lead to production stoppages or the repairs are costly and time-consuming, a more permanent solution is needed.
The aim: Optimising the use of bearings
NSK launched its AIP scheme for precisely such scenarios and as a means of optimising the use of bearings. AIP stands for ‘Asset Improvement Programme’, which sums up the principle behind the scheme.
The programme starts with an inspection of the production facility by bearings experts with manufacturing expertise in the relevant area. This gives the user an opportunity to point out which bearings tend to fail most frequently. An inspection like this is important because it is impossible to gauge (and optimise) the bearings’ lives without taking the operating environment into account.
95% of failures are linked to contamination
You may be surprised to learn that in 95% of cases, it is contamination that causes a bearing to fail. Of course, this contamination can enter the system during mounting – which is why it is so important to train assembly staff and raise their awareness of this issue.
However, in most cases, the contaminants enter the bearing when the machine or system is operating. Therefore, as part of the AIP scheme NSK engineers often recommend replacing the existing bearings with specially sealed ones.
Many reasons for failure
Industry expertise is important for such analyses because the conditions in which the bearings operate vary widely from sector to sector. For example, in the food production industry, machinery is often cleaned using pressure washers or aggressive detergents. Bearings in the steel industry are exposed to high mechanical loads and the environment is heavily contaminated. In other areas of application, a combination of moisture and heat can cause more frequent failures if conventional bearings are used.
In many cases, the ‘problem bearings’ undergo a precise investigation at NSK’s European Technology Centre (ETC) in Ratingen, Germany. The testing and measuring facilities there enable staff to narrow down the cause of the failure with a high degree of precision. This is a good starting point for minimising failures in the future.
The simple way to reduce maintenance and downtime costs
An inspection of this kind – followed by an analysis and optimisation recommendations – can be of huge benefit. There are many examples of companies using NSK’s AIP scheme and subsequently saving hundreds of thousands of euros because their plant productivity increased and their downtime was slashed.
Take-up of the programme is greatest in the sectors that make particularly high demands of the bearings they use. There is a simple reason for this: their bearings fail most frequently. At the same time, however, the chance of prolonging the bearings’ lives is also higher in such cases. This is because special bearings have been developed for almost every specific operating environment:
– Bearings with Super-TF technology are made from a special steel so that any contamination that enters the system generates less tension in the material. This provides long-term protection from spalling.
– WTFTM technology also prevents water particles from penetrating and thereby triples the bearings’ life in damp conditions.
– The Molded-OilTM series is ideal for bearings in food processing applications which operate in damp conditions as the lubricant is incorporated into a polymer.
– Alternative materials (ceramic, fluoropolymers) and coatings (nickel, hard chrome plating) stop the bearings from corroding.
This has two implications for users: Firstly, they must have an in-depth knowledge of the operating conditions relevant to the choice of bearings. Secondly, they need to be just as familiar with the range of products offered by their chosen bearings manufacturer. This is the only way in which users can choose the ideal bearings for their operating environment.
Training boosts plant productivity
Training forms an important part of the AIP scheme and NSK’s service as a whole. The training sessions are generally conducted at the stockist’s or company’s premises. This ensures that the questions and issues relevant to users are specifically tackled. Even courses on standard issues such as “Hands-on use – mounting bearings” and “Choosing the right bearings” do not follow a set schedule. Instead, the NSK engineers conducting the training sessions ask beforehand which issues particularly interest the participants and produce a tailored agenda. This makes sense because – as mentioned above – the reasons behind failures are just as varied as the applications for which the bearings are used. NSK also offers training sessions for specific applications or sectors, e.g. for companies from the food processing industry, the steel sector and the machine tool building industry.
In practice, mistakes are often made when mounting or dismantling bearings. Contamination is the most common source of malfunction, but by no means the only one. That is why the training sessions for assembly and maintenance staff always include exercises in a mobile training unit which can simulate any bearing fitting and dismantling scenario.
Free of charge yet invaluable
The training sessions are offered free of charge as part of NSK’s service. This offer is open to users, distributors and trade partners, who often book the seminars and invite their customers to attend. Running the sessions pays off as they increase satisfaction among our users, who appreciate the sound, tailored advice. The same applies to the AIP scheme, which generates quantifiable advantages for our clients once the recommendations have been implemented. Here are a few examples:
– A wire manufacturer saves more than €1 million in downtime costs a year simply by following a recommendation to change their bearings lubricant.
– A paper-manufacturing company has replaced its conventional spherical roller bearings with bearings from the Tough & Long Life series developed for high temperatures. This saves €140,000 per annum in downtime costs.
– A dairy now uses Molded-OilTM bearings – where the lubricant is permanently incorporated into a carrier – for its conveyor belts. This prevents contamination of the bearing surface and means the lubricant cannot be washed out. Savings of €40,000 per annum were made as a result.
All of this means that users benefit greatly from the training sessions and the AIP scheme. It does not take long to make use of these services – and it is without doubt time well spent.
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