The temperature at which vapor above a heated oil sample flashes when a small test flame is passed over it, measured in the Cleveland open cup (ASTM D92) for most lubricants or a closed cup for fuels and diluted oils. Most industrial mineral oils flash somewhere above 180 C. In used-oil analysis a drop of 20 C or more points to fuel or solvent dilution, and flash point also sets fire-code storage rules for the lube room.
Flash point dropped from 220 to 170 on the compressor oil, something light is getting into that sump.
Also heard as
- COC flash
- open cup flash
Related terms
Viscosity
A fluid's resistance to flow, the lubricant property that sets how thick an oil film can build.
Oil analysis
Lab testing of in-service oil samples to judge oil condition, contamination and machine wear.
Turbine oil
Highly refined, lightly additized circulating oil built to last for years in steam, gas and hydro turbines.
Base oil group
Five-group system that sorts base stocks by saturates, sulfur, viscosity index and chemical type.