PRIME MOVERS AND POWER PLANT MACHINERY.
shown in Plate VIII, A, at a, or attached by a steel rod to the ec-
centric disk of a central pumping power, as shown in Plate IX, A, at
a, or attached to a jack operated by a central pumping power, as
shown in Plate IX, B, at a. There are many ingenious variations of
type, but those shown are typical. Tail pumps are designed to use
existing power installations.
The pump shown in Plate VIII, A, at a is moving oil from the
production tank to the storage tank. The well to which this tail
pump is attached is situated near the production tank, and the con-
necting pipe line to the storage tank is placed so that the power
available at the beam of the well can be used.
The tail pump shown in Plate VIII, A, is single acting. It pumps
the oil on the upstroke of the plunger. The pump cylinder is shown
at b, a check valve at c, and an oil-pressure gage at d. The plunger of
the pump is attached by a steel rod to the power arm of the walking
beam at e. As the pump does its work on the upstroke, it acts as
a counterbalance to the well being pumped. Some manufactured
types of tail pumps work as shown in Plate VIII, A.
Some types of tail pumps attached to the beam, as shown in Plate
VIII, A, are double acting, pumping oil with both strokes by use of
a piston instead of a plunger with a valve. This type has pipe
connections to the intake and discharge lines at both the top and
the bottom of the pump cylinder. In each of these pipe connec-
tions is a check valve so placed that with the upstroke of the piston
the check valve is open at the lower intake, closed at the lower dis-
charge, open at the upper discharge, and closed at the upper intake.
With the downstroke the valves formerly open are closed, and the
valves formerly closed are open.
With this type of tail pump the downstroke of the piston adds to
the load at the well, and usually necessitates a counterbalance. Some
tail pumps instead of being attached to the beam, as shown in Plate
VIII, A, are attached to a timber extension of the power arm of the
beam, similar to some types of counterbalance.
At times when the tail pump is not being used to pump oil it
should be detached from the beam, not only to save in wear on the
pump, but also to prevent the risk of fire. Disastrous fires have re-
sulted from operating the tail pump dry. Tail pumps are oper-
ated under maximum pressures of 200 pounds to the square inch.
Plate IX, A, shows a tail pump connected to a central power.
The piston of the pump, a, is attached to a rocker arm, b, which in
turn is made to oscillate by a rod connection, c, to the eccentric disk
of the power. The tail pump can not always be placed near the
pumping power, but the type shown in Plate IX, A, can be erected
at any convenient point and operated by means of a shackle-line
connection from the power, attached to the pump at d, and provided
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 December 4, 2013.