Question

A conventional Sucker Rod Pumping (SRP) unit is used to lift 25 API oil from a depth of 5000 ft. During operation, the maximum and minimum values of the polished rod load are recorded as 14300 lbf and 5200 lbf respectively.
The ideal counterbalance load (in lbf) is _________ (answer in integer).

Hint:

The ideal counterbalance load is the arithmetic mean of the peak and minimum polished rod loads.

Answer 1

Correct Answer: 9750

Step 1: List the given data:
Peak Polished Rod Load, PPRL = 14300 lbf
Minimum Polished Rod Load, MPRL = 5200 lbf
Step 2: Recall the concept of ideal counterbalance:
In a sucker rod pumping unit, the counterweights are sized so that the torque the prime mover has to supply is as uniform as possible over the full pumping cycle. This ideal condition is achieved when the counterbalance effect equals the average of the maximum and minimum polished rod loads, since the load on the rod string swings between these two extremes once every stroke.
Step 3: Write the formula for the ideal counterbalance load (ICL):
\[ ICL = \frac{PPRL + MPRL}{2} \]
Step 4: Substitute the given values:
\[ ICL = \frac{14300 + 5200}{2} \]
Step 5: Add the numerator terms:
14300 + 5200 = 19500
Step 6: Divide by 2 to get the ideal counterbalance load:
ICL = 19500 / 2
ICL = 9750 lbf
Final Answer:
\[ \boxed{ICL = 9750 \text{ lbf}} \]