Paper: Best Method To Balance Torque of A Pumping Unit Gearbox

There are three methods available to the operator to determine the net torque loading of a pumping unit's gearbox. Two dynamic methods determine the instantaneous torque throughout the pumping cycle: method I ) uses measured motor power, motor and drive efficiencies and the pumping unit speed to determine gearbox torque and method 2) Combines the measured surface dynamometer card and calculated torque factors together with measured or calculated counterbalance moments from the crank and weights. Performing a counter balance effect, CBE, test is a direct method of determining net gearbox torque at a specific crank position to estimate the counterbalance moment; this static test is where the cranks and counter weights are held level until no upward or downward movement is noticed when the break is released. Field case studies of applying all three methods to determining gearbox torque are presented in this paper. The pros and cons of using each method are discussed.