Flashpoint testing is one of the oldest methods of the ASTM D02 Committee on Petroleum Products and Lubricants, which was formed in 1904. The most prevalent standards are ASTM D56 (Tag Method), D92 (Cleveland Method), and D93 (Pensky-Martens Method).
These classical techniques, commonly referred to as open-cup and closedcup methods, share a common principle: A test flame is lowered into the vapor space at regular intervals so that the ignition can be observed. Depending on the method, 70–75 mL of sample is used for open- and closed-cup flashpoint determination. Naturally the ignition of a larger specimen carries a fire risk, but this risk can be minimized if the flashpoint analysis is monitored by laboratory personnel.
A unique solution to an old problem
ASTM standardization of the classical flashpoint methods has resulted in an increased number of requirements. Flashpoint testing is no longer limited to the refining industry, but is used for other applications and industries, including:
- Analysis of hazardous chemicals for compliance with transportation regulations
- Waste analysis of liquids, used oils, and solids
- Analysis of pharmaceuticals, adhesives, paints, varnishes, and plastics
- Analysis of flavors and fragrances
- Analysis of contamination of fuel oil, lubrication oil, and hydraulic oil by lighter hydrocarbons (e.g., gasoline, diesel on ships, power plants, and construction and mining machinery to protect expensive equipment)
- Analysis of bitumen, asphalt, and tar
- Criminal investigations.
Today, the classical techniques have major drawbacks for most applications:
- Safety regulations prohibit testing with an open flame close to highly flammable liquids. This is even more critical for testing petroleum products in refineries or for analyzing oily wastewater on offshore platforms.
- Flavors, fragrances, and pharmaceuticals usually produce very costly substances. Testing 75 mL for each flashpoint determination may cost a manufacturer thousands of dollars each year.
- Coal tar pitch and bitumen may produce hazardous odors when heated, posing a health risk for employees.
- Forensic analysis typically utilizes trace amounts of fuels and substances, rather than quantities of 75 mL.
- The construction and mining businesses require portable analyzers to test directly in the field if there is no laboratory available.
- Analysis of engine lubrication oil on ship engines necessitates a small, closed analyzer that is fastened securely to reduce the risk of splashes and spills on the open sea. These spills could easily be ignited by the tester’s own ignition source.
- Cleaning is messy and time-consuming.
To improve flashpoint testing, a method was developed that eliminates the above problems. The MINIFLASH TOUCH flashpoint tester (Grabner Instruments, Vienna, Austria) requires only 1–2 mL of sample for highly repeatable flashpoint tests. The flashpoint is tested by an instantaneous pressure increase inside a continuously closed test chamber resulting from an energy-controlled electric arc. By design, the method protects against fire hazards since there are no open flames or noxious fumes in the testing area. The small sample size and use of thermoelectric temperature control allow flashpoint testing in a compact and portable analyzer. The MINIFLASH TOUCH can be used for testing liquids and solids, and the sample cups are extremely easy to clean. The complete flashpoint test is visible via graphical combustion analysis directly on the analyzer; even small contaminants inside of a sample can be analyzed.
The flashpoint tester follows the regulations of ASTM D6450 and ASTM D7094, which the ASTM committee considers equivalent to the Pensky-Martens ASTM D93A Method. Because of statistical equivalence with the Pensky-Martens Method, the U.S. Department of Transportation has granted special permits allowing the flashpoints of volatile organic liquids to be determined by means of a MINIFLASH TOUCH flashpoint analyzer.