Question

Define Cloud point and Pour point of a lubricant.

Answer 1

i) CLOUD POINT
When oil is cooled slowly, the temperature at which it become cloudy or hazy in appearance is called its cloud point.
ii)POUR POINT 

After cooling oil the temperature at which it ceases to flow is called its pour point.

Good lubricant should have low POUR POINT. 

Cloud and pour point indicates the suitability of the lubricating oil in cold conditions. Lubricant used in a machine working at low temperature should possess low pour point. Otherwise solidification of the lubricant will cause the jamming of the machine. it has been found that presence of waxes in the oil raises the pour point.

Good lubricating oil should have low cloud and pour point

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