PRIME MOVERS AND POWER PLANT MACHINERY. 41
supply is too low to run gas engines. The oil engine is economical
of fuel, reliable, and requires no more attention than a gas engine.
However, care should be taken to have the fuel oil free from sand
To decrease the water content and solid matter in suspension, many
oil companies using crude oil as fuel heat and settle it before using it.
Some oil companies feed their oil to the engine through a heat ex-
changer; the oil passes to the engine through a 1-inch pipe within a
3-inch pipe, through which the cooling water leaves the engine
jacket. This arrangement tends to keep the oil at a uniform tem-
perature, decreases its viscosity, and generally increases the efficiency
of the operation of the engine.
One of the manufacturers of oil engines recommends that the fuel
oil used have the following specifications:
SPECIFICATIONS FOR FUEL OIL.
Flash-below 2750 F. (Open-cup test.)
Baumo gravity-not below 26.
Sulphur content-less than J per cent.
Water content-less than J per cent.
Coke--not over 3 per cent.
Fraction which will distill below 360 C.-at least 60 per cent.
Compressors are used in oil fields to compress natural gas to ex-
tract the gasoline content,1' to produce petroleum by the Smith-Dunn
or Marietta compressed-air process,1" to compress air for the air-lift
system of production,12 and to start oil or gas engines. Compressors
are also used to supply compressed air intermittently for small
pumps, for steam engines that pull rods and tubing, and for ma-
chinery at the machine and repair shops.
Compressors are either driven by a belt from a steam, gas, or oil
engine or electric motor, or are direct connected to a gas or steam
engine, the engine or compressor forming one unit on a single bed
plate. The latter type eliminates belts and saves much in floor space
and often on first cost and maintenance.
TYPES OF COMPRESSORS.
Compressors are classified as single stage and multiple stage.
Most compressors are double acting; that is, they compress the air
10 Burrell, George A., Seibert, Frank M., and Oberfell, G. G., The condensation of gaso-
line from natural gas: Bull. 88, Bureau of Mines, 1915, pp. 51. Dykema, W. P., Re-
covery of gasoline from natural gas by compression and refrigeration: Bull. 151, Bureau
of Mines, 1918, p. 80.
11 Lewis, J. O., Methods for increasing the recovery from oil sands: Bull. 148, Bureau
of Mines, 1917, pp. 39 and 41.
12 Arnold, Ralph and Garfias, V. R., Methods of oil recovery in California: Tech. Paper
70, Bureau of Mines, 1914, p. 44.
George, H. C. Surface Machinery and Methods for Oil-Well Pumping. Washington D.C.. UNT Digital Library. http://digital.library.unt.edu/ark:/67531/metadc12407/. Accessed March 8, 2014.