Paper: Pumping Unit Torque Factors

When a load is applied to the well end of a pumping unit it results in a torque around the speed reducer crankshaft. This resultant torque is a function of the geometrical design of the unit and the crank angle. Under constant load conditions the torque is constantly changing since it varies with the crank angle. Under static conditions and when considering only the applied load and the unit geometry (not considering the weight of each component part of the unit, the counterbalance being used, or the inertia effects) the torque around the crankshaft is the result of the applied load times a built-in multiplication factor. This multiplication factor is commonly known as the torque factor. Since the torque factors vary with the crank angle there is an infinite number of them. To simplify their use the American Petroleum Institute has devised a form for recording the torque factors at only every 15 degrees.