Flash and Fire Points of Lubricants: Methods and Significance engineering chemsitry notes

Flash Point and Fire Point of Lubricating Oils: Engineering chemistry notes by Mohan

Flash Point and Fire Point of Lubricating Oils

Definition and Theory

Flash Point: The lowest temperature at which an oil gives off vapors that ignite momentarily when a small flame is brought near.

Fire Point: The lowest temperature at which the vapors of the oil ignite and continue to burn for at least five seconds upon exposure to a flame.

    Flash and fire points indicate the fire hazard risks and evaporation losses of petroleum products during high-temperature operation.
  

This method is used for petroleum products with flash points below 175°F and most fuels except those requiring a closed cup.

A brass open cup is filled with the oil sample to a specified level.
The sample is heated at a rate of 9 to 11°F per minute.
At every 5°F rise, a test flame passes over the oil surface.
The temperature at which a flash appears is recorded as the flash point.
Heating and flame application continue until the oil sustains burning for five seconds, which is the fire point.

Limitation: Generally requires that the flash point be above 175°F for validity.

Used for lubricating oils, fuel oils, solvents, and products containing solids (except cut-back asphalt).

The oil sample is placed in a brass cup fitted with a lid that has standard openings.
The cup and sample are heated at a controlled rate while the vapor space is tested with a flame through openings.
Method is preferred for measuring flash points below 100°C as containment prevents vapor loss.

Flash point helps assess flammability hazards and safe storage temperatures.
Fire point indicates the minimum operational temperature that may cause sustained combustion.
Critical for safety regulations, design of storage facilities, and selection of lubricants based on operational environment.