Liquids flash point determination

Figure 6-3 Cleveland open-cup flash point determination. The test flame applicator is moved back and forth horizontally over the liquid sample.

From the point of view of the potential for a fire, the closed cup flash point determination is usually the most important. In a perfect closed cup test, the vapor pressure is in equilibrium with the liquid at the temperature of the test. At the flash point, the vapor composition is at the lower flammable limit. In fact, the lower flammable limit can be estimated from vapor pressure data (for a pure compound). Open cup flash points are generally higher and, thus less conservative, than closed cup determinations. The value determined in an open cup test is subject to air movement at the open face of the cup and true vapor-liquid equilibrium probably does not occur. 

Combustible liquid flash point (closed cup) 85.5°C (186°F) the vapor forms explosive mixtures with air, the explosive range not determined. 

Flash point (1878). n The lowest temperature at which a combustible liquid will give off a flammable vapor that will momentarily burn when exposed to s small flame. The flash point can be determined by the open cup or the closed cup method. The flash point determined by the open cut method is usually somewhat higher than the closed cup method. Wray HA (ed) (1991) Manual for flash point standards and their use. American Society for Testing and Materials, Philadelphia, PA. 

On the basis of the flash points determined in a closed cup and under consideration of the boiling point flammable liquids are classified according to their hazard qualities. 

Flash point is the lowest temperature, corrected to normal atmospheric pressure (101.3 kPa), at which the application of an ignition somce causes the vapors of a specimen to ignite under the specific conditions of the test. Flash point determination methods are designed to be applied to a pure liquid but, in practice, mixtures are also evaluated. It is important to imderstand limitations of such data. The flash point of a solvent mixture can... 

The equilibrium vapor pressure above a confined liquid depends only on temperature. The fraction of the total pressure exerted by vapor pressure determines the composition of the vapor-air mixture. Thus when the total pressure is reduced, for example at high elevations or in vacuum tmcks, the vapor concentration in air increases. Since flash points are reported at a... 

The flash point represents the minimum temperature at whieh an ignitable mixture exists above a liquid surfaee. By definition, flash points are inapplieable to gases. Some solids, e.g. naphtlialene and eamphor, are easily volatilized on heating so that flammable mixtures develop above the solid surfaee and henee flash points ean be determined. (However, although these substanees ean be ignited, they generally need to be heated above their flash points in order for eombustion to be sustained this is the fire point .)... 

The combustion characteristics of liquid fuels are similarly determined by measures of their ability to sustain a flame. Two measures of the combustion characteristics of liquid fuels especially related to safety are flash point and autoignition temperature. The flash point is the maximum temperature at which a liquid fuel can be maintained in an open vessel exposed to air before which it will sustain a flame... 

The temperature and pressure of a liquid system are important in determining the effects created that result in a fire and explosion hazard. Because this relates to the flash point and flammability limits, see Tables 7-21, 7-22 and Figures 7-48, and 7-49A, and 7-49B [34]. 

Certain properties of a liquid fuel are measured routinely in a laboratory for characterization purposes. Besides density and viscosity, these properties include the pour point, the cloud point, and the flash point. Standard ASTM (American Society for Testing Materials) procedures are available for their determination. 

Flammable liquid A liquid having a closed-cup flash point below 100°F (37.8°C) and having a Reid vapor pressure not exceeding 40 psia (2068.6 mm Hg) at 100°F (37.8°C), as determined by ASTM D 323, Standard Method of Test for Vapor Pressure of Petroleum Products (Reid Method). 

Flash point temperatures are determined using an open-cup apparatus, shown in Figure 6-3. The liquid to be tested is placed in the open cup. The liquid temperature is measured with a thermometer while a Bunsen burner is used to heat the liquid. A small flame is established on the end of a movable wand. During heating, the wand is slowly moved back and forth over the open liquid pool. Eventually a temperature is reached at which the liquid is volatile enough to produce a flammable vapor, and a momentary flashing flame occurs. The temperature at which this first occurs is called the flash point temperature. Note that at the flash point temperature only a momentary flame occurs a higher temperature, called the fire point temperature, is required to produce a continuous flame. 

Liquid Mixtures Flash point temperatures for mixtures of liquids can be estimated if only one component is flammable and the flash point temperature of the flammable component is known. In this case the flash point temperature is estimated by determining the temperature at which the vapor pressure of the flammable component in the mixture is equal to the pure component vapor pressure at its flash point. Estimation of flash point temperatures for mixtures of several flammable components can be done by a similar procedure, but it is recommended that the flash point temperature be measured experimentally. 

The lowest temperature of a flammable liquid at which it gives off sufficient vapor to form an ignitable mixture with the air near the surface of the liquid or within the vessel used. The flash point has been commonly determined by the open cup or closed cup method but recent research has yielded higher and lower flash points dependent on the surface area of the ignition source. Because of this aspect ASTM and other standard test methods have been recently withdrawn. They are under review until an adequate determination of a practical and comprehensive standard is composed and agreed upon. 

Combustible Liquid - A liquid having a flash point at or above 37.8 °C (100 °F) as determined under specified conditions. When the ambient temperature of a combustible liquid is raised above its flash point, it essentially becomes a flammable liquid. 

Tag closed-cup tester analy chem A laboratory device used to determine the flash point of mobile petroleum liquids flashing below 175°F (79.4°C). Also known as Tagliabue closed tester. tag klozd k3p tes-tor tagged molecule chem A molecule having one or more atoms which are either... 

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