Lubrication is a basic element of maintenance. A thorough understanding of lubricants enabling optimised lubricant management is not possible without in-depth know-how and expertise. Our editors talked to three experts from Klüber Lubrication about the selection and application of lubricants, also under cost-benefit aspects.

What role does the lubricant play in maintenance?
Dietmar Netuschil: Possibly, a lubricant manufacturer has a slightly different view on lubricants than a maintenance engineer. But there is no doubt about the fact that lubricants do play a decisive role in maintenance. Firstly, because we are generally interested in reducing quantities as stipulated in our law on waste prevention, and secondly, because it is the lubricant's job to optimise the wear characteristics of friction components such that the machine or equipment concerned does not have to be repaired during its specified service life. The advantages of high-performance lubricants become apparent when looking at the cost-benefit analysis.
Dr. Dieter Sohn: With a view to maintenance, the new lubricants offered should guarantee a longer service life than the lubricant used previously and ensure shorter machine downtimes.

Do high-performance lubricants contain special raw materials?
Dr. Dieter Sohn: Yes. In many cases we make use of synthetic base oils which by far outperform mineral oils as far as oxidation stability and temperature resistance are concerned.

If this is so, do mineral oil products have a future at all?
Dr. Dieter Sohn: Mineral oil products do have a future in applications exposed to moderate temperatures - that is, not too cold. For temperatures far below zero as well as at very high temperatures, synthetic lubricants will be more and more in demand.

How do you test the performance of a lubricant?
Dr. Jochen Blume: There are hardly any standardised test procedures, just a few for rolling bearings. I don't know of any lubricant life tests in the gear or chain sectors. This is something of a problem for both the user and the producer of lubricants, but you can imagine that we cannot integrate service life tests, which for today's requirements would take up up to 20,000 hours, in our development work. This would mean we would come up with a new product ten years later. So we have to employ time-accelerating test procedures, in which the lubricants are exposed to higher loads, but in a way that causes the same type of wear patterns, which allows us to reduce testing times.

So service life is an important aspect of lubricant selection. What are the test criteria that allow conclusions on service life?
Dr. Jochen Blume: It is helpful to look at relative measurements. This means, different products are exposed to time-accelerating tests at higher loads and higher temperatures. You observe the behaviour of the different lubricants in these tests, so you can grade them relative to one another. This tells you how they will behave in practice. There are also chemico-physical tests, where evaporation loss is measured to estimate a lubricant's thermal stability.

Today, many maintenance departments are confronted with the task to significantly reduce the range of products used. What can you recommend to avoid mistakes in the reduction of lubricants?
Dietmar Netuschil: It is quite difficult to actually make sure no mistakes are made, since it is hard to compare lubricants with each other. What you can compare are the raw materials used or the composition of the lubricants. Performance, however, is a different story, as Dr. Blume has correctly pointed out. When asked to give an evaluation with regard to maintenance, I would say that environmental management is of utmost importance, which means the focus should be on quantity reduction. To reduce quantities, you need high-performance lubricants. Looking at the differences between standard and special lubricants today, quantity reductions of up to 70 % are very well feasible.
Dr. Dieter Sohn: When reducing the number of lubricants to be used, it makes sense to bear in mind an old sailors' rule: the slowest boat sets the pace for the convoy. Applied to lubricants, this means that if you use a cheap lubricant as the standard product, you will have to put up with limited overall lubricant performance in maintenance. It is usually always a good idea to take a high-quality special lubricant since this allows optimum performance in maintenance for the company.
Dr. Jochen Blume: The biggest problem is the lack of knowledge about lubricants. Your average engineer will know - with luck - that there are oils of different viscosity. He will also know that there are greases as well. But that there are some 2000 different greases with very different properties is simply something that hardly any engineer is aware of. The training of engineers is insufficient under this aspect, although there are now university institutions and seminars dedicated to the subject of "tribology".

"The biggest problem is the lack of knowledge about lubricants."
Dietmar Netuschil: In my opinion, there are two major problems, which are connected with what Dr. Blume has already said. Firstly, the wrong lubricant is used in the wrong application at the wrong time - this is still quite common today. The second problem is that frequently there is no professional lubrication-point or lubricant management, although thanks to simple computer systems like the Klüber Maintenance System 01 it is today no longer a difficult task to manage and document lubrication for maintenance.
Dr. Dieter Sohn: A major contribution the Klüber chemistry department has to offer for maintenance purposes is the analysis of used lubricants and the inspection of machine elements. These examinations have shown that there are two principal causes of component failure. During initial lubrication, these are insufficient cleanliness and incompatibility with the anticorrosion agent. The second cause is the mixing of different lubricants. If compatibility of base oils and thickeners has not been checked, premature failure is likely.

Who can use these Klüber services and what costs are to be reckoned with?
Dr. Dieter Sohn: Basically, every customer can ask for our services. Of course, costs depend on the magnitude of the service. The charge incurred for a normal used-lubricant analysis, which examines for instance the percentage of solid foreign particles, the base oil viscosity and other relevant data such as the neutralisation number of the used lubricant, is just a few hundred marks per sample. Yet, it allows conclusions on recommendable relubrication intervals or a change of lubricant.
Dr. Jochen Blume: To come back to the subject of training I would like to add that Klüber is trying to fill this gap by offering training courses for users working in development, design and - in particular - in maintenance. The users attending these courses are usually surprised to learn about the multitude of lubricants available, the different causes of failure and how the right selection can be made.

When buying lubricants, many companies today simply go for the lowest price. What are the consequences?
Dietmar Netuschil: I'm all in favour of looking at the price when buying lubricants; what I don't like is the term "cheap". If today a company does not employ a price-oriented purchasing policy, this is a severe mistake. What matters to me is that we have to see that there are different types of lubricants and different requirements. There are standard lubricants that can be purchased at fairly low prices. These lubricants meet certain minimum requirements specified in industrial standards. Then there are special lubricants, or niche products, however it is difficult to draw a line between the former and the latter. Naturally, these innovative products have a higher price than the standard lubricants. Now, if you draw up a cost-benefit balance considering environmental aspects, consumption, quantity reduction and performance, you will often find that the more expensive lubricant is actually more cost-efficient. And this is the all-important aspect the user should be aware of. So it may well be the case that a company buying a relatively expensive lubricant does so in fact because they are very much aware of the need for price management.
Dr. Jochen Blume: Technical aspects are also very important for cost-benefit analysis. Today everybody is going on about globalisation - what does that mean for lubricants? On the one hand, it means that lubricants must be available in all major industrialised countries of the world so that the customer can obtain them fast and without lots of red tape. On the other hand, globalisation also has an impact on lubricant performance requirements. A lubricant is expected to work in Norway as well as in Africa. Another problem lies with the continuous increase of equipment and machine outputs. Loads on machines today are much higher than they were only a few years ago. Just think of a frequency converter, for example: you press a button, and it runs 50 % faster. For equipment this means that loads rise not just by 50 % but by 200 %, and the lubricant has to bear them all the same. This is also an important question in the evaluation of a lubricant, namely, does it still have something in reserve or is it already near the upper limit?

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