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322 CHAPTER 13 1951 Guide |J s o i& 11 -|i Ikz -gfc. ii GaOa --<Q (3Za o is F< b Erg 83 H(S *8 go 5*3 J=3S ? s| $ 11 s-os i'gg |?f III |f3 hi -gsg j|g I 2-- J*5J3 sa s>afSe lis *o rS a S Si w.2 a s3 .s| Aa-' 3-s" S8-2s|-ai-S0 I^0f3f ->-3j3 102 S** 5 > So S.E* .a O^sse*!* ^sfis Sol's! J3 3r_* * 2 M30< " oo o S**4'TM1 J fSi&-h"feS **2 ti*Si -|5r r "oS si = 3 SS.H D etailed R equirements for F u e l Oil s * z sK > g!S 5s E ^AH &53 hoh *1 lsi <- &O g3CH if s 3 I 3 i 3 . ! * eoH *S lSij a13j .| iSois.sa >.g ii3 s& iss* *"3 ass S"1 3 > 53 ^`1 SS o'S Jl II &if *3.M s Ji 3s itio 0C3 jf Tl toia E* a J$ 2E .SS sf 5* _1 JLsj <1 2 <"cu1S Ia' -1s^" >. =J.S isgsS-j "s-S :-a loS Sgg 2 0 S Sf "I a3 w>U3 ;.s ; Jal*3|! ^ a >& a !5 !5,, *-_S| } O __HH ** O ry 0=5 0 0 5 "tifii'i e j Isah "SSSoS jSSddjslagl Fuels aiid Combustion 323 Table 5- Approximate Gravity and Calorific Value of Standard Grades of Fuel Oil Commebcxu. Standard No. A.PJ.Approximate Gravity Range Calorific Value Btu Pee Gallon 1 35-45 138,800-132,900 2 26-40 144,300-135,800 4 12-25 153,000-145,000 5 10-23 154,600-146,200 6 8-17.5 156,000-149,700 geologic formations. Manufactured gas, as distributed, is usually a com bination of gases produced by two or more processes of disintegration of carbonaceous material such as coal, coke or oil. Liquefied petroleum gases are certain hydrocarbons which are gaseous under normal atmospheric conditions, but cah be liquefied under moderate pressure at normal tempera tures. However, the demand for gaseous fuels in the past few years has so extended the original sources of manufacture and distribution that hardly any city of any size can be said to be supplied with one specific type of gas. During peak load demands for heating in natural gas systems, high Btu oil-gas and high Btu liquefied petroleum-air mixtures are added; while in manufactured gas systems, the supply is augmented by use of reformed natural gas, reformed refinery gas, lower Btu mixtures of liquefied petroleum and air, and use of straight natural gas for increasing heating value of other manufactured gases. Representative properties of gaseous fuels' commonly used in domestic heating are presented in Table 6. Natural gas contains from 75 to 95 percent methane, with smaller per centages of the higher hydrocarbons. In addition, non-inflammable com ponents such as carbon dioxide, nitrogen and helium are often present. The percentages of the different components vary with the area from which the gas is withdrawn, and even the composition from a given well will vary over the life of the well. The heating value varies from 900 to 1400 Btu per cu ft as shown in Table 6, although in the majority of cases is between 1000 and 1050 Btu per cu ft. Table 6 also gives the calorific values of the more common types of manu factured gases. Most states and municipalities have legislation which controls the distribution of gas and establishes a minimum limit to its heat content. The gross or higher calorific value usually ranges between 520 and 545 Btu per cu ft, with an average of 535. There has been a tendency lately in some manufactured gas territories to increase the calorific value of the gas in order to serve more customers with the existing distribution system. A given heat value may be maintained and yet permit considerable latitude in the composition of the gas so that, as distributed, the composi tion is not necessarily the same in different districts nor at successive times in the same district. However, in any community the variations in gas composition are held within suitable limits so that the performance of gas appliances conforming to American Standard Requirements will not be adversely affected. Liquefied petroleum gases, principally propane and butane or mixtures of both, are the richest of the gases, having calorific values of 2500 and 3200 Btu per cu ft, respectively. They are normally supplied as liquids under