The grease life calculations in the interactive tool LubeSelect (www.aptitudexchange.com, see also Evolution 4/01) now follow the same rules as in the new SKF diagrams described here. f4 = Bearing load (0.1 to 1.0) If, however, these bearing types are subjected to negative influences, the effective grease lifetime can be rapidly reduced and bearing damage can occur. Grease service life also degrades with extremely low temperatures, but this cannot be measured with the same test stand configuration. The newly added grease cannot displace the hardened and oxidized lubricant already present, and it makes an exchange of grease impossible. The adjustment for temperature is the same procedure as explained in the SKF General Catalogue for the relubrication interval. In practice, only a few grams of grease are used for lubricating rolling element bearings and this quantity typically lasts a long time. By further analysis of available field data and by running many grease-life tests in the laboratories, SKF engineers have managed to better understand grease-life phenomena and to improve existing models. I use white lithium grease or synthetic wheel bearing grease for that type of stuff if enclosed .i always have both in the garage. For the standard grease (lithium soap and mineral oil), thermal aging increases disproportionately following any increase in temperature above 140°C. By addressing a number of influencing factors, grease service life can be greatly reduced. The task of the thickener is to absorb the oil and release it in small quantities to the bearing element over a long period. As the grease reaches its dropping point, irreversible and spontaneous oil bleeding occurs and the grease loses its properties. ), ceramic components, etc. Be sure you use press or have a bearing heater so you don't ruin the new bearings hammering them on with punch. They can easily achieve grease lifetimes which are 20 times higher than standard greases, depending on the temperature. Extreme bearing temperatures 212°F (100°C) can cause oil evaporation, condensation and stability issues for the grease and the bearing. An important step was made by recognising different grease failures as a function of operating temperature. About 90 percent of all bearings are lubricated in this manner. Dull brown-colored raceways and tracks on the ball or rollers are typical (Figures 9 through 14). \�� +G��� ��+�q��h�ws�c�e��AS��T��h���}����E�A�ˊ���l�wj��H��:mI�K��[�84ӕ�y�&j/Idd����&f.���'3�MU2ϛej��8ᠣy��� Im�q'�����P��_����o���߯��}z�z��OO�ޤ�i���~�����}�>�?N�8�'N�8�۴o � Ԍ3f���� ��/���X����l�(��/��7��N`0`�9P�}y"C��� � A new sophisticated diagram ( diagram 1) was developed for lubricated-for-life deep groove ball bearings using the same model as for the relubrication diagram. A variety of factors drives the interval, but generally this has to do with previous application lifecycle experiences. Advanced grease-life estimates for lubricated-for-life ball bearings can be made with a new diagram that includes operating temperature and grease type. A grease with GPF=2 would give a grease life L10 ≈3,000 hours. Also for the speed parameter A = n x dm, where n is the rotational speed in r/min and dm is the bearing mean diameter in mm, existing grease-life data have been rearranged. Want to learn more about what is driving change in the engineering world? This type of grease has a high dropping point, approximately 470°F, has an ashless structure, excellent water resistance, pumpability and provides superb high temperature bearing life. Practical implication will be introduced through the issue of electric continuity (bearing currents or bearing spark erosion) and the effect on the grease and rolling bearings. The values can easily vary between 0.1 and 1 (no influence), meaning the result of the actual calculation is strongly influenced by the experience level of the person estimating factor values. With normal relubrication intervals, bearing failure is inevitable (Figures 3 through 8). f6 = Type of mounting, centrifugal energy (0.5 to 0.7). Practical experience shows that bearing surfaces will be damaged, even with a minimal load. These methods are effective only when working with direct current (DC) or low-frequency alternate current (AC). Due to the different influences of the centrifugal forces on the grease, the driven race way of a bearing (IR or OR rotating) must be considered. The Portuguese railway rolling stock maintenance operator EMEF is taking delivery of SKF sealed, pre-greased tapered roller bearing units (TBUs) as a, SKF’s climate target 2012–2016 has resulted in some impressive achievements and has helped to lay the foundation for the company’s ambitious new, In air conditioning large buildings and in some industrial processes, chillers make cold water for cooling. Today, the typical diameter of the nearly circular craters present in most common failures ranges from 1 to 4 µm. For kinematically complex bearings (like axial cylindrical roller bearings with high sliding friction) the kf factor can reach values up to 90. ^��xNj0��[`�H#+σog�7 total bearing width [mm] (for tapered roller bearings use T, for thrust bearings use height H) During a running-in period, excess grease in the bearing distributes or escapes. This factor can have values between 0.9 and 10 for kinematically simple ball bearings. hbspt.cta.load(3951034, 'c99217f3-09e7-4751-bc3a-7739dac44a0e', {}); Product Unboxing - Simalube Single-Point Automatic Lubricators, Circulating Oil Systems: What You Should Know. These arcs also lead to a catastrophic oxidation-induced aging of the grease in the rolling contact area, which dramatically shortens grease life (Figures 13 and 14). In a shielded 6302-2Z deep groove ball bearing operating at 15,000 rpm (A=428,000), at C/P=8 and 90 °C, the L10 is estimated at 1,500 hours for a grease with GPF=1 (including a correction factor of 0.5 for the load ( table 2). The actual lubricant for a rolling bearing is oil, which can be a mineral oil, fully synthetic or a blend of the two. Recognizing the environmental influences (f1 and f3) and selecting appropriately reduced lifecycle factors can contribute to overcoming the arc induced stress on the element. The above analysis has resulted in the new relubrication interval diagram in the SKF General Catalogue 5000, which is valid for an operating temperature of 70°C, using good quality lithium thickener/mineral oil greases. However, there is only partial advantage for this increase, as the estimate for the bearing fatigue life under these conditions is L10 ≈ 2,100 hours (calculated with the SKF rating-life method).

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