Beam Pumps
Beam pumps are the most commonly used rod pumps.
For this section, we will only discuss the physics
of the surface system.
The beam bump contains three essential parts
that we will discuss.
1. The Beam: The beam is attached to a center
point and pivots back and forth as the rod pump
cycles. The beam is essential in determining the most
efficient way to operate.
2. The Rods: Rods come in 30 feet sections
and are used to connect the pump located down hole to
the surface components that power the pump. Knowing
the weights of the rods, and the weight of the fluid
being lifted is essential to the proper set up of a
rod pump.
3. Pitman Arm attached to Counter Weights: In
a beam pump, counter weights rotate in a circle motion
to "drive" the rod up and down. The goal is to match
the same amount of torque being applied by the rods,
to the same torque being applied by the pitnam arm. To
achieve this, the counter weights can be adjusted
along the pitman arm (the radius of a circle), to
achieve equal torques.
Using Phyiscs To Put These Concepts to Use
Both the rod and the pitnam arm apply torque
forces to the beam, and the goal is to get these
torques almost equal to each other.
D1*M1*g=D2*M2*g
In this case we will assume that D2 and M2 are the
mass of the rods and well fluid and d is the distance
that the rod is attached to the beam from the pivot
point. Since D2, M2, D1, and g are all fixed numbers,
the only thing we can change is M1, which is where the
adjustable counterweights come in.
Since the design of every beam pump is different, the
equation for determining the position of the
counterweight is different. In general, the
counterweights are adjusted along the crank arms,
relative to the pitman arm.
To see one of these in action, click here.
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