The type of furnace in which the oil is to be used is an important consideration in making any compari son with other fuels. Assume, for example, a furnace which has an efficiency of 76 per cent when burning coal. If, upon converting this furnace to an oil-burner, it- has an efficiency of 83 per cent, the amount of oil required will be less than the amount indicated by a comparison of the heating values of coal and oil. As a rule such an improvement in efficiency may be ex pected from the conversion of a coal burning to an oil burning furnace, provided the installation is made by a competent oil expert. This is partially due to the higher furnace efficiency inherently attainable with fuel oil. But a more important cause lies in the fact that the average plant using coal as fuel is attended by an un skilled fireman, who can only get the best results from coal by hard work, close attention, and intimate knowl edge of the coal. Often he does not understand the most efficient method of firing the coal or regulating the draft, and as a result a great deal of fuel is wasted. This point is clearly brought out when a coal or boiler expert is brought in to conduct a test ; much higher efficiencies are invariably attained.
Conditions are very different in a plant using oil. The work of firing requires no physical exertion ; a clear eye and common sense is all that is required. The fireman has plenty of time to see that the burner is working properly and that a uniform amount of feed water is being supplied ; and by watching the stack he can prevent some of the fuel losses that take place if smoking is permitted. Also, when using fuel oil a much better class of labor can be secured ; this has been clearly proven on board ocean going steam. ers.
The writer can remember the time when it was almost impossible to secure firemen on a certain steamer, and many that were secured were unfit fJr work during their first watch, three watches being often required to get them in good working condition. It was laborious. hot work as the steamer was run ning to the tropics. The firemen usually made but one voyage and a new crew had to be obtained each trip. This vessel is now using fuel oil, and I have teen informed by the engineers, that they seldom make a change in the fire room crew.
Purchasing Fuel Oil.
With the supply of oil fuel assured, the question of greatest interest to the engineer is how to buy it. The price of the oil must of course be low enough to warrant making the fuel oil installation. And the time
for which this price is guaranteed in the fuel oil con tract should be long enough to enable the consumer to save on his fuel bill at least the cost of making the oil installation.
The analysis of crude and fuel oils varies with the wells or countries from which the oil is obtained. The characteristics required by the purchaser should be embodied in a contract ; a good commercial fuel oil should be of the following specifications : The value of "c" in this equation is based on the coefficient of expansion of the oil and differs for differ ent oils. Generally speaking, the lighter the oil the higher the coefficient and also the value of "c." From determinations made in our laboratories we have arrived at a close approximation to the correct coefficients of expansion for California oils, as follows • For California oil of 10 deg. B. "c." ----- .0033 For California oil of 11 deg. B. "c." = .0033 For California oil of 12 deg. B. "c." ----- .0034 For California oil of 13 deg. B. "c." .0034 For California oil of 14 deg. B. "c." = .0035 For California oil of 15 deg. B. "c." .0036 For California oil of 20 deg. B. "c." = .0039 For California oil of 25 deg. B. "c." = .0042 Many purchasers of road oils use an arbitrary con stant for all oils, but that this is manifestly incorrect is clearly shown by the above table. The constant used by the Los Angeles County, Cal., Highway Com mission and recommended by Prevost Hubbard, Chemist in the Office of Public Roads of the United State Agricultural Department is — "c" = .004 This would be correct for California oils of about 21 deg. B. or 22 deg. B.; but as most road oils are heavier than this the result of the use of this constant is an error in the measurement of all oils delivered at a temperature above or below 60 deg. F.
According to statistics compiled under the super vision of J. D. Northrop of the United States Geo logical Survey, the quantity of petroleum entering the markets of the world in 1914 amounted to 400,483,489 barrels. Of this record-breaking output the United States is credited with 66.36 per cent, representing in quantity a trifle less than double the output of all the other oil-producing countries combined. The fol lowing table shows the marketed production of petro leum in the world in 1914, and for purposes of com parison the corresponding output in 1913, together with the total output from 1857 to 1914 inclusive :