Question

Define flash and fire points.

Answer 1

Flash point:- Flash point is defined as the lowest temperature at which the lubricant gives
off enough vapours to cause a momentary flash when a standard test flame is brought near it.

Fire point:- Fire point is the lowest temperature at which the oil vapours catch fires for at least 5 seconds, on being lighted by a test flame.

Fire point is usually 5-40ºC above the flash point. A good lubricant should have flash point at least above the working temperature . This ensures safety against the risk hazards. Thus flash point acts as a guide for the safe storage, transportation and use in machine.
Good lubricant oil should have hiah flash and fire point.