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Maintenance and increasing
the reliability of bearings

Changes in maintenance applications

The periodic vibration analyses have reduced the systematic preventive maintenance for the benefit of a conditional maintenance, that is to say maintenance undertaken only if the machine needs it.

However, these analyses do not, or little, improve the lifetime of the machines, since most of the time, the analyses can only notice the degradation.

With a broadband continuous monitoring (frequency), it is possible to adapt the maintenance applications to keep the machines in their optimum operating conditions, by intervening when a significant change appears. This results in a significant increase in the lifetime by a proactive maintenance.

The feedbacks and the exchanges with our customers show that bearings lubricated with grease have an average lifetime much shorter than bearings lubricated with oil (10 to 20 000 h against 50 to 100 000 h).

With our experience we can assert that monitoring continuously bearings lubricated with grease, you can :

  • Understanding the phenomena that occur within bearings,

  • Better mount them,

  • Better lubricate them,

It results in a longer lifetime and an important improvement of operational safety. A bearing under continuous monitoring may not cause a surprise outage !

Our feedbacks and analyses lead us to question several widespread applications in mechanics :

  • The almost universal use of increased clearance bearings (C3 clearance) while manufacturers recommend to mount their bearings without clearance or even slightly preloaded.

  • The blind application of grease addition rules proposed by bearing manufacturers, regardless of the reservations that are made, (Abacus of additions spacing = f (diameter, type, speed of rotation) and quantity = diameter x witdh / 200)

  • Ignorance of significant performance differences between different formulas of grease. (We are not just talking about the type of thickening agents, but base oils, additives, and possibly manufacturing processes)

We have seen some new bearings were difficult to properly lubricate with grease (acute noise caused by friction manifestly poorly lubricated). Nobody being able to explain the phenomenon and some feedbacks that led us to question the excessive clearance, we have launched and conducted a study financed by TOTAL and performed by the laboratory of mechanical vibration of ENSAM Paris (Ecole Nationale Supérieure d'Arts et Métiers).

The results show clearly that it is virtually impossible to properly lubricate with grease a bearing with an important clearance. The rolling elements stop rolling in the non-loaded area, and must instantly rotate when they are back in the bearing load-area, with transitory phenemona that highly request grease. (See the summary of the study in the journal MECASON-INFOS N°1 (only available in french))