For rolling contact bearings like ball bearings, a condition called elasto-hydrodynamic lubrication occurs. At point of contact, ball deflects and flattens out slightly for a moment under high pressure. When ball rolls on, contact surfaces return to their original shape. However, lubricant is not forced away from point of contact due to dramatic increase in viscosity. When ball has passed, viscosity falls back again.

When grease is used for lubricating ball bearings, they also act as protection against impurities like dust, dirt and water that will cause wear down and corrosion.

More about oils and grease for lubrication could be subject of next topic.

Until next time...

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With large machines that use large amounts of lubrication oil engineer has to determine when to change oil. This is because change can be a very expensive affair.

The correct thing to do is to determine whether oil can still be used without changing. The engineer must know exactly when to change oil. He will take measurements of various parameters to help him decide.

That could be a subject for another coming facworld ezine article.

The contents of this page are part of a page from my e-book "General Engineering Knowledge Notes" that will help candidates prepare for Marine Certificate of Competency Examinations. This e-book is available for FREE downloading at Marine Ebooks