Abstract: The pump-off controller checks for pump-off by calculating the area inside of a figure whose boundaries are the minimum load, two position lines defined by the user and the load at the time the calculation is being made. This area is compared to a user defined limit to determine whether pump-off has occurred. While the well is running the controller also checks the value of the minimum load, and if it is outside of preset boundaries it readjusts the load signal to locate it within the desired range. The position synthesizer cyclically detects the position of the beam or rod during each stroke and generates a waveform whose amplitude and frequency correspond to the motion of the rod with a period corresponding to the time of each stroke. This information is used by the controller to determine the top of the stroke and to check for pump-off.

Abstract: A process and system for distinguishing between actual and false pump off of a well and for shutting in the well only upon the occurrence of actual pump off. The process and system employs the principle that pump off may occur only after a not pumped off condition has been detected.

Abstract: A system for measuring current or load for shutting down a motor of a walking beam type pumping unit in the event that pump-off occurs. The system employs a peak picker which picks either minimum current or maximum load and an integrator coupled to the peak picker for integrating current or load during each stroke cycle. A threshold device coupled to the output of the integrator produces a control signal for shutting down the motor if the integrator output fails to reach a predetermined threshold during each stroke cycle.