Flash point is a lowest temperature at which the oil gives off enough vapour that ignite for a moment, when a small flame is brought near it. Fire point is the lowest temperature at which the vapour of the oil burns continuously for at least 5 seconds when a small flame is brought near it. Generally the fire point is 5 to 40 degree C higher than flash point.
A good lubricating oil should have flash and fire points higher than the operating temperature of the machine. A knowledge of flash and fire point is useful in providing protection against fire hazard during transport and storage. Lubricating oils of paraffinic base. Hence the determination of flash and fire points is helpful in identifying the type of lubricating oil.
Flash and fire points can be determined using the same apparatus. An oil is heated at a prescribed rate in an open cup apparatus or closed cup apparatus of standard dimensions. A small test flame is periodically applied over the surface of the oil. The temperature at which a distinct flash is seen is the flash point. The heating and periodical application of test flame are continued. The temperature at which the oil vapour catches fire and burns continuously for 5 seconds is noted as the fire point.
Tuesday, January 19, 2010
Flash And Fire Point
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