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referring to full barrel or "L" referring to liner barrel. The third
letter may be "E" indicating use of an extension shoe and nipple,
"A" indicating stationary barrel with top hold-down, "B" for
stationary barrel with bottom hold-down, or "T" for traveling
barrel.

The Sucker Rod String
Energy is transmitted from the surface equipment to the
pump by means of using of steel sucker rods. Sucker rods are
available in five standard parameters, and the problem of
designing a sucker rod string is essentially problem of determining
the lightest (and therefore the most economical) that can be used
without exceeding the working stress for the rods, maximum
working stress for sucker rods has been the subject of con-able
debate. It depends on the chemical composition and mechanical
forties of the rods and on the nature of the fluid (i.e., whether
corrosive or uncorrosive”). As a rule, it is desirable to keep rod
stresses under 30,000 psi, however, experience in a given area may
indicate a much lower limit. When pumps are set at depths greater
than approximately 3500 feet, it actually desirable to use a tapered
rod string, i.e., a string consisting of different sizes. The smallest-
diameter rod is placed at the bottom 3 string, immediately above
the plunger, since the rod load is least at Joint. At lesser depths,
where rod load is greater, larger rods are used, arrangement results
in a smaller load on the surface equipment than be obtained with
an untapered string, and it represents a distinct decreasing in cost
of sucker rods.

The Surface Pumping Equipment

The surface equipment transfers energy for pumping the well
from prime mover to the sucker rod string. In doing this, it must
change the rotary motion of the prime mover to reciprocating
motion for the sucker rods, and it must reduce the speed of the

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