26 SURFACE MACHINERY AND METHODS FOR OIL-WELL PUMPING.
Hot-tube ignition is not advisable in oil fields producing large
quantities of natural gas, as disastrous explosions may result.
Ignition by electric spark is most satisfactory, as it makes prompt
starting and accurate timing possible. The low tension, or " make
and break," and the high tension, or jump spark, are the two types
of electrical ignition. As a source of current the magneto is gen-
erally used; however, the primary battery and the storage battery
are other sources.
In the make-and-break system spark is made by the intermittent
separation of the terminals of a circuit through W"hich a low-voltage
current is flowing. To increase the spark intensity, an induction coil
is usually placed in the circuit. The terminals or contact points are
extended into the clearance space of the engine cylinder. In a com-
mon type, one of the terminals is mounted on a movable shaft to the
outer end of which is attached a coil spring and arm. This arm at
regular intervals engages with a push rod actuated by a cam that
connects with the engine shaft. Where the arm slips off the edge
of the push rod, the coil spring instantly separates the terminals,
thus producing a spark in the cylinder.
In the jump-spark system the voltage of the current is increased
enough to break down the resistance of the spark gap and to jump
from one terminal to the other. The ordinary spark plug supplies
Of the many types of high-tension magnetos the Wico high-tension
igniter is most generally used with gas engines in the oil fields.
It differs from others in that the intensity of the spark is independ-
ent of the engine speed and the motion is reciprocating instead of
rotary. The design is simple, requiring no adjustment; it is with-
out condensers, contact points, or primary windings. The current is
generated by the reciprocating movement of the two soft-iron arma-
tures that in their movement pass through the center of the electric
fields. The upward movement of the armatures is produced by the
movement of the engine, but the downward movement which pro-
duces the spark is caused by the action of a spring. Plate VI at
f shows a Wico magneto.
The installation of the jump-spark system costs more than the
make-and-break system, which in turn costs more than the hot tube.
The three principal systems of lubrication are: Sight, splash, and
The sight-feed system makes use of drip oil cups. Oil cups
should be cleaned frequently with gasoline or kerosene to remove
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.