Mark II Geometry Reduces Rod Load and Peak Torque

Mark II Unitorque Pumping UnitLufkin Mark II Unitorque Pumping Units are available in fifty different sizes up to the M-1824D-427-216; a unit with a 216-inch stroke, a polished rod capacity of 42,700 pounds and a 1,824,000 inch-pound double reduction gear box.
The Mark II’s unique UNITORQUE geometry is characterized by three (3) basic configurations that reduce the rod load and peak torque over that of a conventional pumping unit. The design characteristics which make the Mark II unique are:

  • Shifting the gearbox from directly under the equalizer towards the Samson post turning in a preferred direction of rotation, creates an upstroke that occurs in approximately 195° of crank rotation and a downstroke of approximately 165° of crank rotation.
  • Placing the equalizer between the horsehead and the Samson post creates a “push-up” or “Class 3” lever system.
  • The 195° upstroke, coupled with the front mounted geometry, reduces the acceleration at the beginning of the upstroke where the load is greatest, thereby effecting a reduction in polished rod load. Locating the cross-yoke forward of the gear reducer creates a greater mechanical advantage for lifting the heavy load on the upstroke, and a lesser mechanical advantage for the reduced downstroke load (i.e., the maximum upstroke torque factor is reduced while the maximum downstroke torque factor is increased).
  • An angular offset in the crank that produces a more effective counterbalance torque which at the beginning of the upstroke “lags” the well load torque approximately 71⁄2 degrees. Similarly, at the beginning of the downstroke, this same offset condition produces a counter balance torque which “leads” the well load torque approximately 71⁄2 degrees.

markII-chartIndependently these features would not produce a relatively uniform torque, but working together a “unitorque” system is obtained which can reduce the torque on the gearbox up to 35% as well as lowering power costs and often, prime mover size.









Download the Mark II Unitorque Pumping Units Brochure pdf and the Mark II Pumping Units Installation Manual pdf.

Mark II Pumping Units BrochureMark II Pumping Unitis Installation Manual