Comparing Class I Class III Varying Pumping Unit Geometries

This paper presents the advantages and disadvantages of the class I and class III lever system varying geometry pumping units. By significantly modifying the lengths of the 5bar linkage systern that controls the geometric motion of the polish rod, varying geometries have been achieved in class I units. Varying geometry is achieved when the upstroke of the pumping unit is accomplished in greater than 180 degrees of crank-arm rotation and the downstroke in less than 180 degrees. Previously varying geometries were generally limited to the class III lever system design pumping units. This paper will discuss and compare class I and class III lever system varying geometries.