Page 527 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Applied Process Design 493

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UPPER FLAMMABLE LIMITS
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-10 -10 0 10 '20 30 40 so
This chart is applicable only to flammable liquids or gases in equilibrium in a closed container. Mixtures of vapor and air will be too "rich" to
be flammable at temperatures above and pressures below the values shown by the lines on the chart for any substance. Conditions repre-
sented by points to the right of and below the respective lines are accordingly nonflammable.
Figure 7-498. Variation of upper flammable limits with temperature and pressure. Reprinted by permission from Fire Protection Handbook,
17th Ed. (1991 ), National Fire Protection Association, Quincy, MA 02269 [34].

the "saturated vapor-air-mixture line and to the right of it Ignition of Flammable Mixtures
make up the saturated and unsaturated combustible-oxi-
dant system at a specified pressure" [ 43]. The engineer is Ignition can take place for any flammable mixture
urged to study Reference [ 43] because it deals with many within the concentration ranges for the respective LEL
more important topics of this subject than can be includ- and UEL. The conditions for ignition may vary with the
ed here.
specific mixture, the type of oxidant (usually air or pure
oxygen), the temperature, and pressure of the system.
Figure 7-50 shows the effect of pressure on the limits of Ignition may result from electrical spark, static spark, con-
flammability of an ethane system. tact with hot surfaces (autoignition) (see Figures 7-48,