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Lubrication is the life blood of any system consisting of rotating and moving members. Depriving a system of its lifeblood or the lubricant will lead to the death or collapse of the system in a most cruel manner. A bearing is a rotating member consisting of both moving and rotating members; hence lubricant is of prime most importance in a bearing. The lubricant can be a liquid based like lubricating oils or grease. The lubricant provides a very thin layer of film whose thickness is just about a few microns, thus preventing metal to metal contact between the rollers and the raceways of the bearing. Just providing a lubricant doesn’t suffice the lubrication of the bearing. Care needs to be taken in the following aspects
· Ample supply of lubricant to the bearing
· Maintaining an adequate quantity of lubricant to the bearing
· Maintaining the correct viscosity of the lubricant
· Ensuring the correct quality of the lubricant is used
Now let us look how the above points can affect the life of bearing when not adhered to by the designer and the user of the bearing. Bearings which are deprived of the above aspects can be identified by the following phenomena.
1. Discolored raceways and balls (Blue black or silver gold) are the best known indications for a bearing deprived of lubrication. This happens due to the metal to metal contact which leads to increase in temperature and overheating.
2. Excessive wear in the raceway, balls and cages are also indicative for depriving the bearing of lubrication. Click here to see how a lubricant devoid bearing looks like.
This can be prevented by
a) Ensuring a trouble free consistent flow of lubricant to the bearing. If even required ensure a forced lubrication system to the bearing, where the lubricant is supplied continuously by means of a pump to the bearing.
b) In certain cases the bearings tend to work in an elevated temperature, causing the lubricant to loose its property. This also leads to lubrication failure because the viscosity reduces with increase in temperature and does not form a fluid film boundary between contacting surfaces to prevent metal to metal contact. In such cases proper cooling of the bearings or lubricant must be ensured.
We will look into the other types of bearing failures in the next article.
Failure Modes in Rolling Bearings - Part 6
Bearings are normally designed and selected to last for a life time. Any failure occurring in it needs to be identified properly. This article will help you in determining the various causes and the type of failure the causes tend to induce on the bearing.