PRIME MOVERS AND POWER PLANT MACHINERY.
of the pulsation from the compressor eliminated before the air is dis-
charged from the receiver into the air line. Receivers also act as
separators for any water condensed from the air in the process of
compression and thus give drier air.
TRANSMISSION OF COMPRESSED AIR.
Compressed air is delivered on the lease through pipe lines from
the compressor plant to the point of consumption. Losses in pressure
are due to lower temperature of the air at the compressor, leaks in
the pipe line, and the friction of the air passing through the pipe line.
Losses due to friction vary directly as the length of the pipe,
directly as the square of the velocity, and inversely as the diameter
of the pipe. Tees, elbows, and scale or dirt in the pipe increase
friction losses. The losses from leaky joints or open seams fre-
quently exceed all other losses. In cold weather water often freezes
in and clogs unprotected air lines.
CHOICE OF COMPRESSOR.
Like steam, oil, or gas engines, the size of a compressor is indicated
by the cylinder diameter and the length of stroke.
The theoretical capacity of free air a minute in cubic feet is the
product of the cylinder area in cubic feet by the piston travel a
minute in feet. If the amount of air of a given pressure required
a minute is known the size of a compressor can be estimated; how-
ever, the pipe-line losses and the altitude above sea level must be
Any compressed-air handbook gives tables showing compressor
capacities, conversion of compressed air into free air, horsepower
requirements, and losses of pressure in transmission.
TYPES IN USE.
All standard makes of reciprocating pumps are used in oil fields
to handle water and oil. Centrifugal pumps are used for water,
but are not suited to the high pressures used in pumping oil through
pipe lines. They are used as boiler feed-water pumps, and water-
line pumps, but very little for the pumping of oil. Rotary pumps
are much used around refineries for pumping blended gasoline and
refined products, but are not adapted to high suction lifts. Single
and duplex reciprocating pumps, also known as vacuum pumps, are
also used for pumping gas from wells, thereby decreasing the gas
18 Lewis, J. O., Methods of increasing the recovery from oil sands: Bull. 148, Bureau of
Mines, 1917, pp. 32-35.
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 September 22, 2014.