OIL FUEL ON SHIPS branch of industry in which the benefits of oil fuel arc most conspicuously observable is that of shipping. In the first place, the space occupied by oil is less than that of coal, one ton of oil occupying only 37 cu. ft. compared with 44 cu. ft. for one ton of coal. Moreover, oil can be stored in a ship where coal cannot be carried, thus the fuel capacity is increased.
It has been proved that by substituting oil for coal an increase in radius of action is attained of 50 per cent on equal bunker weight and 80 per cent on equal bunker space. The effect of this on the per ton mileage of a vessel is, therefore, obvious, and equally so is the economy of space resulting from the substitution. A statement made by a high authority on the subject some time back showed that over a series of years a 7,700 ton vessel consumed about 22i tons of oil a day, compared with from 32 to 33 tons of Welsh coal. This implies a saving in weight of fuel consumption of 33 per cent. With coal of inferior grade the economy would naturally be considerably greater. Furthermore, the vessel referred to was enabled to carry from 150 to 200 tons more cargo. Another way of expressing this fact is by comparing the i.h.p. consumption under oil and under coal, the generally accepted figures being, in regard to the former, 1.02 lb. to •95 lb., and for the latter from 1.51b. to 1.61b. i.h.p. One of the most valuable aspects of oil fuel running from a commercial point of view is the shortening of the duration of the journey. This is an economic factor of far reaching influence zind is not sufficiently considered by shipping companies, though one would imagine it would appeal very weightily to them. Such an advantage. with its many concomitant items of economy, could readily convert a loss into a profit in the earning capacity of a vessel. For instance, in one well-known case a round voyage, which, under coal occupied 186 days, was reduced under oil to 161 days, which, taking into consideration all the ecomonies effected, resulted in an additional revenue of over The next important claim is the increase in thermal efficiency. In the case of oil, working experience has shown that this may be as high as 83 per cent, compared with 60 per cent when coal is employed as fuel. In tests carried out in America recently the ther mal efficiency of boilers using coal varied between 66-6 to 68 per cent, whilst in burning oil the thermal efficiency stood at from 80.6 per cent to 81.5 per cent. Efficiencies as high as 8-1.5 per cent had been secured, under marine type boilers, using Mexican fuel oil with the pressure system of oil burning. In order to arrive at a fair
conclusion, the quality of coal used should be taken into account, and should, of course, be stated where comparisons are made, for, while there is always a sub stantial balance in favour of oil, a low-grade coal will cause the comparison to appear much more favourable than as against a high-grade coal. The following instance may be quoted as illustrating this point : In the conversion of certain boilers from coal to fuel-oil firing, the water evaporation per lb. of coal, with a calorific value of 11,451 B.T.U.. was 7-22 lbs. ; whereas, when working with the pressure system of oil burning, using an oil having a calorific value of 18,750, the evaporation per lb. of oil reached 14.44 lbs. The quantity of water evaporated to the square foot of heating surface on coal was 3.3 lbs., whereas oil showed over 7 lbs., thereby increasing the boiler rating by over 100 per cent. With a higher grade coal, this disparity would not, of course, be so marked.
The progress which has been made in oil-fuel practice during the last thirty years is well indicated by figures relative to the evaporation per lb. of petroleum. On a gunboat belonging to the French Navy the water evaporated per lb. of oil is stated to have been from 1156 to 11.58 lbs. ; on a French torpedo boat in 1890 the quantity of water evaporated was 11.36 lbs., while it was regarded as quite an achievement when this factor attained the figure of 13.25 lbs. Twenty-three years later in the results obtained on a Chilian battleship fitted with a Kermode oil-fuel installation the quantity of water evaporated varied between the average of 12.12 lbs and 15.72 lbs in tests of two hours duration ; while in later tests under marine boilers, with which the Kermode pressure jet system was used, the evapor ative efficiency rose as high as 16-16.74 lbs. per lb. of petroleum. Similarly, in regard to the consumption of oil i.h.p. The figures given for this item on an Italian battleship some twenty years ago were 1.25 lbs. of oil compared with 2.13 lbs. of coal, while at the present time, as already stated, the consumption of oil ranges from .95 to 1-02 lbs. of oil i.h.p., and for coal from 1.5 to 1.6 lbs., showing that in both liquid and solid fuel practice great advances have been made. These figures are an excellent indication of what has been achieved in bringing oil fuel appliances to a high standard and of the progress made by both engineer and chemist in the science of oil fuel burning.