Flash point lowering

Flash points, lower and upper flammability limits, and autoignition temperatures are the three properties used to indicate safe operating limits of temperature when processing organic materials. Prediction methods are somewhat erratic, but, together with comparisons with reliable experimental values for families or similar compounds, they are valuable in setting a conservative value for each of the properties. The DIPPR compilation includes evaluated values for over 1000 common organics. Detailed examples of most of the methods discussed are available in Danner and Daubert."... 

Flash points, lower and upper flammability limits, and autoignition temperature are important properties for determining safe operating limits when processing organic componnds. As with any property, experimental valnes are preferable to predicted values, and prediction techniques for these properties are only modestly accurate. 

A flammable liquid is generally considered to be one with a flash point below 55°C but above 2rC a highly flammable liquid is one with a flash point above 0°C and below 21°C any liquid with a flash point lower than 0°C and a boiling point lower than 35°C must be labelled extremely flammable. These are the definitions used here but it should be noted that the term extremely flammable is sometimes used for liquids with a flash point below 32°C. 

The toxic symptoms, median lethal doses, carcinogenic potentials if any, flammability, flash points, lower and upper explosive limits, violent reactions, and section numbers in this book where these compounds are described at length are highlighted below in condensed form for 63 common solvents. 

However, small traces of toluene in mixed xylenes cause the mixture to have a flash point lower than the weighted average of its main components and the reproducibility of the test method means that a flash point of at least 24 C is normally required for satisfactory operation. In recovery operations, the effect of -butanol (pure flash point 35 C) and ethyl Cellosolve (pure flash point 40 °C), but which both... 

Aqueous ethanol has a flash point lower than would be expected (Table 16.2) and the 4% of methanol added to convert it to industrial methylated spirits makes it lower still. In the event of a large spillage which might be diluted by adding water the ethanol would tend to form a top layer if it were not agitated. 

Extremely Flammable - liquids with a flash point lower than 0°C and a boiling point lower than or equal to 35°C. 

Database of over 10,000 chemicals and synonyms, including DOT Guide information, and physical properties such as flash point, lower explosion limit, and boiling point, including the information contained in the 1997 NIOSH Pocket Guide to Chemical Hazards, the 2000ERG, and other sources. 

Flash points and autoignition temperatures are given in Table 11. The vapor can travel along the ground to an ignition source. In the event of fire, foam, carbon dioxide, and dry chemical are preferred extinguishers. The lower and upper explosion limits are 1% and 7%. 

Flammability Acrolein is very flammable its flash point is <0° C, but a toxic vapor cloud will develop before a flammable one. The flammable limits in air are 2.8% and 31.0% lower and upper explosive limits, respectively by volume. Acrolein is only partly soluble in water and will cause a floating fire, so alcohol type foam should be used in firefighting. The vapors are heavier than air and can travel along the ground and flash back from an ignition source. 

The relatively low flash points of some acrylates create a fire hazard. Also, the ease of polymerization must be home in mind in ah. operations. The lower and upper explosive limits for methyl acrylate are 2.8 and 25 vol %, respectively. Corresponding limits for ethyl acrylate are 1.8 vol % and saturation, respectively. All possible sources of ignition of monomers must be eliininated. 

Pentane Bp, °C Flash point, °C Ignition temperature, °C Lower Upper... 

Isoprene is classified by the ICC as a flammable Hquid requiring a red label (124). Its flash point is —54°C with a lower explosive limit (LEL) of 1.5%... 

Compound Flash point, °C Flammability limit, vol % Lower Upper Autoignition temperature, °C... 

The lower flammable limit (LEL) or lower explosive limit (LEL) is the minimum concentration of vapor in air below which a flame is not propagated when an ignition source is present (61—64). Below this concentration, the mixture is considered too lean to bum. The lower flammable limit and the flash point of a flammable Hquid are closely related by the Hquid s vapor pressure characteristics. 

Flash Point (ASTMD92). The Cleveland open cup method is most commonly used although the Tag open cup (ASTM D3143) is apphcable to cutbacks. Flash point is an indication of fire hazard and the test is frequendy used to indicate whether a given product has been contaminated with materials of lower dash point. 

Because biphenyl is often transported in the molten state, a moderate fire ha2ard does exist under these circumstances. Biphenyl, with a flash point of 113°C, has a lower flammability limit of about 0.6% (by volume) at the flash point to an upper limit of 5.8% at 166°C (42). Dust explosions are a ha2ard when vapors from a hot Hquid surface condense in air in a confined space. 

Procedures for shipping boric acid esters depend on the particular compound. Aryl borates produce phenols when in contact with water and are therefore subject to shipping regulations governing such materials and must carry a Corrosive Chemical label. Lower alkyl borates are flammable, flash points of methyl, ethyl, and butyl borates are 0, 32, and 94°C, respectively, and must be stored in approved areas. Other compounds are not hazardous, and may be shipped or stored in any convenient manner. Because borate esters are susceptible to hydrolysis, the more sensitive compounds should be stored and transferred in an inert atmosphere, such as nitrogen. 

Flash point, °C Autoignition temperature, °C lower upper... 

Inhibited grades of 1,1,1-trichloroethane are used in hundreds of different industrial cleaning appHcations. 1,1,1-Trichloroethane is preferred over trichloroethylene or tetrachloroethylene because of its lower toxicity. Additional advantages of 1,1,1-trichloroethane include optimum solvency, good evaporation rate, and no fire or flash point as determined by standard test methods. Common uses include cleaning of electrical equipment, motors, electronic components and instmments, missile hardware, paint masks, photographic film, printed ckcuit boards, and various metal and certain plastic components during manufacture (see Metal surface treatments). 

Benzyl chloride [(chloromethyl)henzene, a-chlorotoluene], CgH CH2Cl, is a colorless Hquid with a very pungent odor. Its vapors are irritating to the eyes and mucous membranes, and it is classified as a powerfljl lacrimator. The physical properties of pure benzyl chloride are given in Table 2 (2—7). Benzyl chloride is insoluble in cold water, but decomposes slowly in hot water to benzyl alcohol. It is miscible in all proportions at room temperature with most organic solvents. The flash point of benzyl chloride is 67°C (closed cup) 74°C (open cup) autoignition temperature is 585°C lower flammability limit 1.1% by volume in air. Its volume coefficient of expansion is 9.72 x. ... 

Fig. 1. Effect of temperature on limits of flammabiUty of a pure Hquid fuel ia air, where = lean (or lower) flash point = rich (or upper) flash point ...

An alternate method for flash point prediction is the method of Gmehling and Rasmussen and depends on the lower flammabihty limit (discussed later). Vapor pressure as a function of temperature is also required. The method is generally not as accurate as the preceding method as flammability limit errors are propagated. The authors have also extended the method to defined mixtures of organics. 

The upper and lower flammabihty limits are the boundary-line mixtures of vapor or gas with air, which, if ignited, will just propagate flame and are given in terms of percent by volume of gas or vapor in the air. Each of these limits also has a temperature at ch the flammabihty limits are reached. The temperature corresponding to the lower-hmit partial vapor pressure should equal the flash point. The... 

Chemical compound Flam, limits, lower, % v/v Flam, hmits, upper, % v/v Autoignition temperature. Flash point, closed cup. Flash point, open cup. 

Pressure affects flash point. A decrease in pressure lowers the flash point. With toluene, for example, at two-thirds of an atmosphere the vapor pressure must be only 0.74 kPa (5.6 mm Hg) to equal the LFL of 1.1 percent. (No significant difference in LFL will exist at two-thirds of an atmosphere compared to the published LFL of 1.1 percent at one atmosphere.) This vapor pressure occurs at —3°C, corresponding to a decrease in flash point of about 7.4°C from one atmosphere. Conversely, an increase in pressure raises the flash point. 

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