The Flash Point of an industrial lubricant is an important test to determine if light-end hydrocarbons are getting into the oil through seal leaks or other means. It is an effective way to monitor seal performance in light end hydro-carbon compressors. Low Flash Points pose a safety hazard in the event of component failure than can generate heat above the flash point of the oil, such as bearing failure. The Flash Point of most ISO VG 32 R&O mineral oils is in the 370 – 390° F range. Generally, the more viscous and the more additives in the oil, the higher the Flash Point. A typical automotive or diesel engine oil will have a Flash Point in the 425 to 460° F range.
A Flash Point test is conducted by slowly heating a sample of lubricant. Directly above the sample container is an ignition source, either an open flame or spark source. As the sample heats, the light-ends boil off and form flammable gases. When there is enough gas built-up to be ignited by the ignition source, the gases will flash. The temperature at which the oil was heated to when this occurs is called the Flash Point. It is reported in ° F or ° C.
If you continue to heat the sample after the flash point has been reached, eventually the oil will sustain a flame. This is known as the Fire Point and again reported as ° F or ° C. The Fire Point is generally 10 or 20 ° F above the Flash Point.
If you remove the ignition source and heat the lubricant, eventually it will auto-ignite. This is called, you guessed it, the auto-ignition point. These are generally in the 750 to over 1000° F. range.